0001485003-22-000033 | 10-K | XBRL Viewer

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CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 162,636	$ 52,389
Accounts receivables	21,011	0
Other receivables	3,482	0
Prepaid expenses and other current assets	18,476	7,478
Restricted Cash	0	3,000
Total current assets	205,605	62,867
Non-current assets:
Restricted cash	20	20
Property and equipment, net	43	123
Intangible assets	14,700	46,400
Goodwill	13,064	13,064
Long term prepaid expenses	7,192	0
Other assets	123	349
Total non-current assets	35,142	59,956
Total Assets	240,747	122,823
Current liabilities:
Accounts payable	2,853	3,102
Accrued expenses	8,255	3,973
Deferred revenue	0	1,500
Contingent consideration	0	8,985
Other current liabilities	460	489
Total current liabilities	11,568	18,049
Non-current liabilities:
Contingent consideration, net of current portion	52,000	99,855
Deferred tax liability	3,969	12,528
Deferred revenue, net of current portion	1,500	1,500
Other non-current liabilities	0	118
Total non-current liabilities	57,469	114,001
Total Liabilities	69,037	132,050
Stockholders’ Equity (Deficit):
Preferred stock, $0.001 par value per share; 5,000,000 shares authorized at December 31, 2021 and 2020; no shares issued and outstanding at December 31, 2021 and 2020	0	0
Common stock, $0.001 par value per share; 400,000,000 and 200,000,000 shares authorized at December 31, 2021 and 2020; 199,463,645 and 140,449,647 shares issued and outstanding at December 31, 2021 and 2020, respectively	199	140
Additional paid-in capital	487,768	306,554
Accumulated deficit	(316,257)	(315,921)
Total Stockholders’ Equity (Deficit)	171,710	(9,227)
Total Liabilities and Stockholders’ Equity	$ 240,747	$ 122,823

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	400,000,000	200,000,000
Common stock, shares issued (in shares)	199,463,645	140,449,647
Common stock, shares outstanding (in shares)	199,463,645	140,449,647

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Total Revenue	$ 26,544	$ 11,236	$ 0
Operating expenses:
Research and development	25,312	29,191	24,663
General and administrative	29,393	14,302	12,208
Restructuring charge	5,528	0	0
Intangibles impairment charge	31,700	0	0
Change in fair value of contingent consideration	(56,840)	(11,180)	71,620
Total operating expenses	35,093	32,313	108,491
Loss from Operations	(8,549)	(21,077)	(108,491)
Other (expense) income, net	(60)	125	991
Loss Before Taxes	(8,609)	(20,952)	(107,500)
Benefit (provision) from income taxes	8,273	(1,445)	0
Net Loss After Taxes	(336)	(22,397)	(107,500)
Comprehensive Loss After Taxes	(336)	(22,397)	(107,500)
Deemed dividend on adjustment of exercise price of certain warrants	0	(147)	0
Net loss attributable to common stockholders - basic	(336)	(22,544)	(107,500)
Net loss attributable to common stockholders - diluted	$ (336)	$ (22,544)	$ (107,500)
Net loss per common share - basic (in dollars per share)	$ 0	$ (0.19)	$ (1.18)
Net loss per common share - diluted (in dollars per share)	$ 0	$ (0.19)	$ (1.18)
Weighted-average common shares outstanding - basic (in shares)	182,323	118,221	90,929
Weighted-average common shares outstanding for diluted (in shares)	182,323	118,221	90,929
License and related revenue
Total Revenue	$ 26,544	$ 11,236	$ 0

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	ATM Facility	Common Stock	Common Stock ATM Facility	Additional Paid-in Capital	Additional Paid-in Capital ATM Facility	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018			77,456,180
Beginning balance at Dec. 31, 2018	$ 44,207		$ 77		$ 230,154		$ (186,024)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(107,500)						(107,500)
Share-based compensation	$ 1,237				1,237
Exercise of stock awards and vesting of restricted stock awards (in shares)	90,000		89,812
Exercises of stock options and vesting of RSAs	$ 98				98
Sales of common stock under 2014 ESPP (in shares)			10,283
Sales of common stock under 2014 ESPP	8				8
Exercise of common stock warrants (in shares)			6,772,928
Exercise of common stock warrants	5,481		$ 7		5,474
Issuance of common stock and common stock warrants, net of issuance costs (in shares)			20,410,000	2,062,206
Issuance of common stock and common stock warrants, net of issuance costs	27,833	$ 1,936	$ 21	$ 2	27,812	$ 1,934
Ending balance (in shares) at Dec. 31, 2019			106,801,409
Ending balance at Dec. 31, 2019	(26,700)		$ 107		266,717		(293,524)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(22,397)						(22,397)
Share-based compensation	$ 1,757				1,757
Exercise of stock awards and vesting of restricted stock awards (in shares)	12,000		12,000
Exercises of stock options and vesting of RSAs	$ 13				13
Sales of common stock under 2014 ESPP (in shares)			28,186
Sales of common stock under 2014 ESPP	11				11
Exercise of common stock warrants (in shares)			238,110
Exercise of common stock warrants	131				131
Issuance of common stock and common stock warrants, net of issuance costs (in shares)				33,369,942
Issuance of common stock and common stock warrants, net of issuance costs		37,958		$ 33		37,925
Ending balance (in shares) at Dec. 31, 2020			140,449,647
Ending balance at Dec. 31, 2020	(9,227)		$ 140		306,554		(315,921)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(336)						(336)
Share-based compensation	$ 5,143				5,143
Exercise of stock awards and vesting of restricted stock awards (in shares)	34,000		33,610
Exercises of stock options and vesting of RSAs	$ 42				42
Exercise of common stock warrants (in shares)	2,048,000		2,048,059
Exercise of common stock warrants	$ 1,126		$ 2		1,124
Issuance of common stock and common stock warrants, net of issuance costs (in shares)				56,932,329
Issuance of common stock and common stock warrants, net of issuance costs		$ 174,962		$ 57		$ 174,905
Ending balance (in shares) at Dec. 31, 2021			199,463,645
Ending balance at Dec. 31, 2021	$ 171,710		$ 199		$ 487,768		$ (316,257)

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY (DEFICIT) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Issuance costs	$ 5.4	$ 1.2	$ 2.2
ATM Facility
Issuance costs			$ 0.2

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash Flows from Operating Activities:
Net loss	$ (336)	$ (22,397)	$ (107,500)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	85	122	219
Share-based compensation	5,143	1,757	1,237
Change in fair value of contingent consideration	(56,840)	(11,180)	71,620
Intangibles impairment charge	31,700	0	0
Changes in operating assets and liabilities:
Accounts receivable (net)	(24,493)	0	0
Prepaid expenses and other assets	(17,964)	(1,304)	(5,188)
Accounts payable	(249)	1,200	535
Accrued expenses and other liabilities	(4,424)	(2,035)	1,556
Deferred revenue	(1,500)	3,000	0
Net cash used in operating activities	(68,878)	(30,837)	(37,521)
Cash Flows from Investing Activities:
Purchases of equipment	(4)	(8)	(136)
Net cash used in investing activities	(4)	(8)	(136)
Cash Flows from Financing Activities:
Proceeds from issuance of common stock and common stock warrants, net of issuance costs	0	0	27,833
Proceeds from exercises of common stock warrants	1,126	131	5,481
Proceeds from issuance of common stock under ATM Offering, net of issuance costs	174,962	37,958	1,936
Proceeds from exercises of stock options	42	13	98
Proceeds from sale of common stock pursuant to ESPP	0	11	8
Net cash provided by financing activities	176,129	38,113	35,356
Net increase (decrease) in cash, cash equivalents and restricted cash	107,247	7,268	(2,301)
Cash, cash equivalents and restricted cash - beginning of period	55,409	48,141	50,442
Cash, cash equivalents and restricted cash - end of period	162,656	55,409	48,141
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	162,636	52,389	48,121
Short term restricted cash	0	3,000	0
Long term restricted cash	20	20	20
Total cash, cash equivalents and restricted cash	162,656	55,409	48,141
Supplemental cash flow disclosure:
Cash paid for amounts included in the measurement of lease liabilities	174	154	153
Supplemental disclosure of non-cash operating activities:
Right-of-use assets related to the adoption of ASC 842	0	0	236
Right-of-use assets obtained in exchange for lease obligations	0	290	0
Supplemental disclosure of non-cash financing activities:
Deemed Dividend on adjustment of exercise price on certain warrants	$ 0	$ 147	$ 0

DESCRIPTION OF BUSINESS	12 Months Ended
DESCRIPTION OF BUSINESS	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
DESCRIPTION OF BUSINESS	DESCRIPTION OF BUSINESS Sesen Bio, Inc. ("Sesen" or the “Company”), a Delaware corporation formed in February 2008, is a late-stage clinical company advancing targeted fusion protein therapeutics ("TFPTs") for the treatment of patients with cancer. The Company’s most advanced product candidate, VicineumTM, also known as VB4-845, is a locally-administered targeted fusion protein composed of an anti-epithelial cell adhesion molecule ("EpCAM") antibody fragment tethered to a truncated form of Pseudomonas exotoxin A for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with bacillus Calmette-Guérin ("BCG"). The Company has an ongoing single-arm, multi-center, open-label Phase 3 VISTA clinical trial of Vicineum as a monotherapy in patients with BCG-unresponsive NMIBC (the "VISTA Trial"). The VISTA Trial completed enrollment in April 2018 with a total of 133 patients. On December 18, 2020, the Company submitted its completed Biologics License Application (the "BLA") for Vicineum for the treatment of BCG-unresponsive NMIBC to the United States Food and Drug Administration ("FDA"). On February 12, 2021, the FDA notified the Company that it has accepted for filing the BLA. The FDA also granted Priority Review for the BLA and set a target Prescription Drug User Fee Act ("PDUFA") date for a decision on the BLA of August 18, 2021. On July 13, 2021, the Company participated in a productive Late-Cycle Meeting with the FDA regarding the BLA for Vicineum for the treatment of BCG-unresponsive NMIBC. In the meeting, the FDA confirmed that there was no Advisory Committee meeting planned at that time, and that no post-marketing requirements, including a confirmatory trial, had been identified at that time. Also in the meeting, the Company and the FDA discussed remaining questions related to manufacturing facilities inspection, product quality information requests and additional information related to chemistry, manufacturing and controls (“CMC”), and a timeline to submit additional supporting information was agreed upon. On August 13, 2021, the Company received a complete response letter (“CRL”) from the FDA indicating that the FDA had determined that it could not approve the BLA for Vicineum in its present form and provided recommendations specific to additional clinical/statistical data and analyses in addition to CMC issues pertaining to a recent pre-approval inspection and product quality. The Company participated in Type A Meetings with the FDA on October 29, 2021 and December 8, 2021 to discuss questions related to CMC and clinical issues raised in the CRL. Both meetings helped the Company determine the appropriate path forward for Vicineum. Any changes in these assumptions and estimates or other information obtained, may have a significant impact on the remeasurement of the contingent consideration liability in the future. The Company believes it has a clear understanding of what additional information regarding CMC is required for resubmission of a BLA. Additionally, although not an issue raised in the CRL, the FDA confirmed that Vicineum manufactured using the proposed commercial process is comparable to Vicineum used in prior clinical trials. The FDA also confirmed that the Company can utilize Vicineum manufactured during process validation for any future clinical trials needed to address issues raised in the CRL, and that these potential trials can proceed while addressing CMC issues. Viventia Acquisition In September 2016, the Company entered into a Share Purchase Agreement with Viventia Bio, Inc., a corporation incorporated under the laws of the Province of Ontario, Canada ("Viventia"), the shareholders of Viventia named therein (the “Selling Shareholders”) and, solely in its capacity as seller representative, Clairmark Investments Ltd., a corporation incorporated under the laws of the Province of Ontario, Canada (“Clairmark”) (the “Share Purchase Agreement”), pursuant to which the Company agreed to and simultaneously completed the acquisition of all of the outstanding capital stock of Viventia from the Selling Shareholders (the “Viventia Acquisition”). In connection with the closing of the Viventia Acquisition, the Company issued 4.0 million shares of its common stock to the Selling Shareholders, which at that time represented approximately 19.9% of the voting power of the Company as of immediately prior to the issuance of such shares. Clairmark is an affiliate of Leslie L. Dan, a director of the Company until his retirement in July 2019. In addition, under the Share Purchase Agreement, the Company is obligated to pay to the Selling Shareholders certain post-closing contingent cash payments upon the achievement of specified milestones and based upon net sales, in each case subject to the terms and conditions set forth in the Share Purchase Agreement, including: (i) a one-time milestone payment of $12.5 million payable upon the first sale of Vicineum (the “Purchased Product”), in the United States; (ii) a one-time milestone payment of $7.0 million payable upon the first sale of the Purchased Product in any one of certain specified European countries; (iii) a one-time milestone payment of $3.0 million payable upon the first sale of the Purchased Product in Japan; and (iv) quarterly earn-out payments equal to 2% of net sales of the Purchased Product during specified earn-out periods. Such earn-out payments are payable with respect to net sales in a country beginning on the date of the first sale in such country and ending on the earlier of (i) December 31, 2033, and (ii) fifteen years after the date of such sale, subject to early termination in certain circumstances if a biosimilar product is on the market in the applicable country. Under the Share Purchase Agreement, the Company, its affiliates, licensees and subcontractors are required to use commercially reasonable efforts, for the first seven years following the closing of the Viventia Acquisition, to achieve marketing authorizations throughout the world and, during the applicable earn-out period, to commercialize the Purchased Product in the United States, France, Germany, Italy, Spain, United Kingdom, Japan, China and Canada. Certain of these payments are payable to individuals or affiliates of individuals that became employees or members of the Company's board of directors. However, as of December 31, 2021, none of these individuals are active employees or members of the Company's board of directors. Liquidity and Capital Resources As of December 31, 2021, the Company had cash and cash equivalents of $162.6 million and an accumulated deficit of $316.3 million. The Company incurred negative cash flows from operating activities of $68.9 million, $30.8 million and $37.5 million for the years ended December 31, 2021, 2020 and 2019, respectively. Since the Company’s inception, it has received no revenue from sales of its products, and the Company anticipates that operating losses will continue for the foreseeable future as it seeks to address the issues raised in the CRL it received for a BLA for Vicineum for the treatment of BCG unresponsive NMIBC and the concerns identified in the EMA Withdrawal Assessment Report, complete the follow-up stage of the ongoing Phase 3 VISTA Trial of Vicineum for the treatment of BCG-unresponsive NMIBC, complete any additional clinical trials for Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG, and seek marketing approval from the FDA and the European Commission and, if approved, commercialize Vicineum. The Company has financed its operations to date primarily through private placements of its common stock, preferred stock, common stock warrants and convertible bridge notes, venture debt borrowings, its initial public offering ("IPO"), follow-on public offerings, sales effected in "at-the-market" ("ATM") offerings, commercialization partnership and out-license agreements. See “Note 12. Stockholders’ Equity” below for information regarding the Company’s recently completed equity financings. Management believes that the Company’s cash and cash equivalents as of December 31, 2021 will be sufficient to fund the Company's current operating plan for at least the next twelve months from the date these consolidated financial statements were issued. Funding Requirements The Company’s future success is dependent on its ability to develop, and if approved, commercialize its product candidates, including Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG, and ultimately upon its ability to attain profitable operations. In order to commercialize its product candidates, including Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG, the Company needs to complete clinical development and comply with comprehensive regulatory requirements. The Company is subject to a number of risks similar to other late-stage clinical companies, including, but not limited to, successful discovery and development of its product candidates, raising additional capital, development and commercialization by its competitors of new technological innovations, protection of proprietary technology and market acceptance of its products. The successful discovery, development and, if approved, commercialization of product candidates, including Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG, requires substantial working capital, and the Company expects to seek additional funds through equity or debt financings or through additional outside of United States (“OUS”) business development partnerships, collaborations, licensing transactions or other sources. The Company may be unable to obtain equity or debt financings or enter into additional OUS business development partnerships, collaborations or licensing transactions at favorable terms, or at all, and, if necessary, may be required to implement cost reduction strategies. The Company will incur substantial expenses if and as it: •addresses the issues identified in the CRL it received from the FDA for its BLA for Vicineum for the treatment of BCG-unresponsive NMIBC and the concerns identified in the European Medicines Agency’s (“EMA”) Withdrawal Assessment Report, which the Company expects will include the completion of an additional Phase 3 clinical trial; •seeks marketing approvals for Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG; •establishes and implement sales, marketing and distribution capabilities and scale up and validate external manufacturing capabilities to commercialize Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG, if approved; •maintains, expands and protects its intellectual property portfolio; •hires additional clinical, regulatory, quality control, scientific and management personnel; •expands its operational, financial and management systems and personnel; •conducts research and pre-clinical and clinical development of Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG, and its other product candidates; •seeks to discover and develop additional product candidates; and •in-licenses or acquires the rights to other products, product candidates or technologies. The Company's future capital requirements will depend on many factors, including: •the scope, initiation, progress, timing, costs and results of laboratory testing and clinical trials for Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG and its other product candidates; •the ongoing COVID-19 pandemic and its impact on the Company’s business; •the Company’s ability to establish additional OUS business development partnerships, collaborations or licensing arrangements on favorable terms, if at all, particularly manufacturing, marketing and distribution arrangements for its product candidates; •the costs and timing of the implementation of commercial-scale manufacturing activities, including those associated with the manufacturing process and technology transfer to third-party manufacturers to facilitate such commercial-scale manufacturing of Vicineum; •the costs and timing of establishing and implementing sales, marketing and distribution capabilities for Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG, if approved; •the costs and timing of preparing, filing and prosecuting patent applications, maintaining and enforcing its intellectual property rights and defending any intellectual property-related claims; •the Company’s obligation to make milestone, royalty and other payments to third-party licensors under its licensing agreements; •the extent to which the Company in-licenses or acquires rights to other products, product candidates or technologies; •the outcome, timing and cost of regulatory review by the FDA, EMA and comparable non-US regulatory authorities for Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG, including the potential for the FDA, EMA or comparable non-US regulatory authorities to require that the Company perform more studies or clinical trials than those that it currently expects to perform; •the Company’s ability to achieve certain future regulatory, development and commercialization milestones under its out-license and OUS business development partnership agreements •the effect of competing technological and market developments; and •the revenue, if any, received from commercial sales of Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG, if approved. Until such time, if ever, as the Company can generate substantial product revenues from commercial sales, the Company expects to finance its cash needs through a combination of equity offerings, debt financings, government or other third-party funding, strategic collaborations, OUS business development partnership agreements, partnerships, alliances, and licensing arrangements. The Company does not have any committed external source of funds other than the amounts payable under the license agreement with F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc. (collectively, “Roche”) and the license agreement with Qilu Pharmaceutical, Co., Ltd. (“Qilu”). To the extent the Company raises additional capital through the sale of equity or convertible debt securities, the ownership interests of existing stockholders will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect the rights of existing stockholders. Debt financing, if available, may involve agreements that include liens or other restrictive covenants limiting the Company’s ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends. If the Company raises additional funds through government or other third-party funding, strategic OUS business development partnerships, collaborations, alliances or licensing arrangements, the Company may have to relinquish valuable rights to its technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable to the Company. If the Company is unable to raise additional funds when needed, the Company may be required to delay, limit, reduce or terminate its product development or future commercialization efforts or grant rights to develop and market products or product candidates that the Company would otherwise prefer to develop and market itself. The COVID-19 pandemic has negatively impacted the global economy, disrupted business operations and created significant volatility and disruption to financial markets. Significant uncertainty remains as to the potential impact of the COVID-19 pandemic on the Company’s operations, and on the global economy as a whole. The extent and duration of the pandemic could continue to disrupt global markets and may affect the Company’s ability to raise additional capital in the future.

BASIS OF PRESENTATION	12 Months Ended
BASIS OF PRESENTATION	Dec. 31, 2021
Accounting Policies [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATIONThe accompanying financial statements have been prepared in accordance with United States generally accepted accounting principles ("GAAP"). Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the ASC and Accounting Standards Updates ("ASUs"), promulgated by the Financial Accounting Standards Board ("FASB"). Use of Estimates The preparation of financial statements in accordance with GAAP and the rules and regulations of the SEC requires the use of estimates and assumptions, based on judgments considered reasonable, which affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The Company bases its estimates and assumptions on historical experience, known trends and events and various other factors that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Although management believes its estimates and assumptions are reasonable when made, they are based upon information available at the time they are made. Management evaluates the estimates and assumptions on an ongoing basis and, if necessary, makes adjustments. Due to the risks and uncertainties involved in the Company’s business and evolving market conditions, and given the subjective element of the estimates and assumptions made, actual results may differ from estimated results. The most significant estimates and judgments impact the fair value of intangible assets, goodwill and contingent consideration; income taxes (including the valuation allowance for deferred tax assets); research and development expenses; and going concern considerations. Principles of Consolidation The Company’s consolidated financial statements include the accounts of the Company, its wholly owned subsidiary Viventia and its indirect subsidiaries, Viventia Bio USA Inc. and Viventia Biotech (EU) Limited. All intercompany transactions and balances have been eliminated in consolidation. Foreign Currency Translation The functional currency of the Company and each of its subsidiaries is the US dollar.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	Dec. 31, 2021
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Cash, Cash Equivalents, Restricted Cash and Concentration of Credit Risk The Company's cash is held on deposit in demand accounts at a large financial institution in amounts in excess of the Federal Deposit Insurance Corporation ("FDIC") insurance coverage limit of $250,000 per depositor, per FDIC-insured bank, per ownership category. Restricted cash represents cash held by the Company's primary commercial bank to collateralize a letter of credit issued related to a license agreement and the credit limit on the Company's corporate credit card, and are classified as short term and long term, respectively. The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Financial instruments that potentially subject the Company to credit risk principally consists of cash equivalents and accounts receivable. As of December 31, 2021 and 2020, the Company limited its credit risk associated with cash equivalents by placing investments in highly-rated money market funds. Property and Equipment Property and equipment are recorded at cost. Maintenance and repairs are charged to expense as incurred, and costs of improvements and renewals are capitalized. Depreciation is recognized using the straight-line method over the estimated useful lives of the relative assets. The Company uses an estimated useful life of five years for lab equipment, four years for furniture and fixtures, three years for computer equipment and software and the lesser of five years or the remaining lease term for leasehold improvements. Indefinite-Lived Intangible Assets The Company’s intangible assets consist of indefinite-lived, acquired in-process research and development ("IPR&D") worldwide product rights to Vicineum as a result of the acquisition of Viventia in 2016. IPR&D assets acquired in a business combination are considered indefinite-lived until the completion or abandonment of the associated research and development efforts. Amortization over the estimated useful life will commence at the time of Vicineum's commercial launch in the respective markets, if approved. If regulatory approval to market Vicineum for the treatment of BCG-unresponsive NMIBC is not obtained, the Company will immediately expense the related capitalized cost. Indefinite-lived intangible assets are quantitatively tested for impairment at least annually during the fourth quarter of the fiscal year, or more often if indicators of impairment are present. Impairment testing of indefinite-lived intangible assets requires management to estimate the future discounted cash flows of an asset using assumptions believed to be reasonable, but which are unpredictable and inherently uncertain. Actual future cash flows may differ from the estimates used in impairment testing. The Company recognizes an impairment loss when and to the extent that the estimated fair value of an intangible asset is less than its carrying value. In addition, on a quarterly basis, the Company performs a qualitative review of its business operations to determine whether events or changes in circumstances have occurred which could indicate that the carrying value of its intangible assets was not recoverable. If an impairment indicator is identified, an interim impairment assessment is performed. In August 2021, the Company received a CRL from the FDA regarding its BLA for Vicineum for the treatment of NMIBC, its lead product candidate. In the CRL, the FDA determined that it could not approve the BLA for Vicineum in its present form and provided recommendations specific to additional clinical/statistical data and analyses in addition to CMC issues pertaining to a recent pre-approval inspection and product quality. Given the inherent uncertainty in the development plans for Vicineum (and Vysyneum in the EMA) as a result of the CRL and the withdrawal of the Company's marketing authorization application (“MAA”), an interim impairment analysis was conducted in the third quarter of 2021, which concluded that the carrying value of the Company’s intangible asset of Vicineum US rights was fully impaired as of September 30, 2021. The $31.7 million of impairment charges were due to delays in the expected start of commercialization and lower probabilities of success, combined with higher operating expenses expected to be incurred prior to commercialization, resulting in lower expected future cash flows estimated in the US market. However, while similar delays in timelines and reduced probabilities of success also affected the estimated fair value of the Company's intangible asset of Vicineum EU rights, this asset was not impaired as of September 30, 2021. At that time, management assessed that the carrying value of the Vicineum EU rights is not at significant risk of impairment in the future within the current range of commercialization timelines and probability of clinical and regulatory success (“POS”) assumptions. This is primarily due to the fact that the Company expects the Vicineum sales outside of the US to be two to three times the expected sales volume in the US, based on management’s reassessment of the total addressable global market for high-risk NMIBC during the quarter ended June 30, 2019, wherein management determined that both the global market size and the estimated potential Vicineum commercial sales within the global market were likely higher than the Company's previous estimate. In addition, the EU asset is burdened with significantly less expense than the US asset, as the Company’s strategic operating plan is to sublicense Vicineum to business development partners in all regions outside the US, including the EU, with it earning a potential combination of upfront, milestone, and royalty payments, and the business development partner bearing the majority of regulatory and commercialization costs. The Company participated in Type A Meetings with the FDA on October 29, 2021 and December 8, 2021 to discuss questions related to CMC and clinical issues raised in the CRL. Both meetings helped the Company determine the appropriate path forward for Vicineum. Based upon the outcome of these meetings, the Company plans to conduct an additional Phase 3 clinical trial. Also, during the Clinical Type A Meeting, the Company aligned with FDA to include patients with less than adequate BCG into its new clinical trial. The Company performed the annual impairment test, which incorporated the impact of the CRL and the subsequent Type A Meetings in the fourth quarter of 2021 and concluded that the carrying value of the Company's intangible asset of Vicineum EU rights was not impaired as of December 31, 2021. The Company did not recognize any impairment charges during the year ended December 31, 2020. Goodwill Goodwill on the Company's consolidated balance sheets is the result of the Company’s acquisition of Viventia in September 2016 and represents the difference between the purchase price and the fair value of the identifiable tangible and intangible net assets acquired under the acquisition method of accounting. Goodwill is not amortized; rather than recording periodic amortization, goodwill is quantitatively tested for impairment at least annually during the fourth quarter of the fiscal year, or more often if indicators of impairment are present. Impairment testing of goodwill requires management to estimate the future discounted cash flows of a reporting unit using assumptions believed to be reasonable, but which are unpredictable and inherently uncertain. Actual future cash flows may differ from the estimates used in impairment testing. If the fair value of the equity of a reporting unit exceeds the reporting unit’s carrying value, including goodwill, then goodwill is considered not to be impaired. The Company recognizes a goodwill impairment when and to the extent that the fair value of the equity of a reporting unit is less than the reporting unit's carrying value, including goodwill. The Company has only one reporting unit. In addition, on a quarterly basis, the Company performs a qualitative review of its business operations to determine whether events or changes in circumstances have occurred which could have a material adverse effect on the estimated fair value of each reporting unit and thus indicate a potential impairment of the goodwill carrying value. If an impairment indicator is identified, an interim impairment assessment is performed. Given the inherent uncertainty in the development plans for Vicineum as a result of the CRL and the Company’s withdrawal of its MAA, an impairment analysis was conducted in the third quarter of 2021. While an impairment was recognized in one of the Company’s intangible assets, Vicineum US Rights, the Company concluded that the carrying value of its goodwill of $13.1 million was not impaired as of September 30, 2021. In October and December 2021, we participated in a CMC Type A Meeting and a Clinical Type A Meeting, respectively, with the FDA to discuss issues raised in the CRL and to discuss design elements of an additional Phase 3 clinical trial for Vicineum, which the FDA confirmed will be required for a potential resubmission of a BLA. Following these Type A Meetings, we believe we have greater clarity of the requirements for potential resubmission of a BLA. We have a Type C Meeting scheduled with the FDA for March 28, 2022, in which we expect to discuss the study protocol for the additional Phase 3 clinical trial that we plan to conduct for potential resubmission of our a BLA for Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG. The Company performed the annual impairment test, which incorporated the impact of the CRL and the subsequent Type A Meetings in the fourth quarter of 2021 and concluded that there was no goodwill impairment as of December 31, 2021. Management believes the Company has sufficient future cash flows from additional geographic regions outside the US to support the value of its goodwill. The Company projects future cash flows based on various timeline assumptions and applies a probability to each outcome based on management’s best estimate. In addition, probabilities of success in achieving certain clinical and regulatory success can also have a material effect on the estimated fair value of the equity of its reporting unit as of the impairment assessment date. The Company will continue to evaluate timelines for commercialization and probability of success of development of Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG. Based on the annual testing and quarterly reviews performed, the Company concluded that there was no goodwill impairment during the year ended December 31, 2020. Contingent Consideration The Company uses a discounted cash flow model to estimate the fair value of the contingent consideration liability each reporting period, which represents the present value of projected future cash flows associated with regulatory approval milestones and royalties on net sales due to the selling shareholders of Viventia Bio Inc. as a result of the Viventia Acquisition in September 2016. See "Note 1. Description of Business" for additional information. Contingent consideration is measured at its estimated fair value on a recurring basis at each reporting period, with fluctuations in value resulting in a non-cash charge to earnings (or loss) during the period. The estimated fair value measurement is based on significant unobservable inputs (Level 3 within the fair value hierarchy), including internally developed financial forecasts, probabilities of success and timing of certain milestone events and achievements, which are inherently uncertain. Actual future cash flows may differ from the assumptions used to estimate the fair value of contingent consideration. The valuation of contingent consideration requires the use of significant assumptions and judgments, which management believes are consistent with those that would be made by a market participant. Management reviews its assumptions and judgments on an ongoing basis as additional market and other data is obtained, and any future changes in the assumptions and judgments utilized by management may cause the estimated fair value of contingent consideration to fluctuate materially, resulting in earnings volatility. In October and December 2021, we participated in a CMC Type A Meeting and a Clinical Type A Meeting, respectively, with the FDA to discuss issues raised in the CRL and to discuss design elements of an additional Phase 3 clinical trial for Vicineum, which the FDA confirmed will be required for a potential resubmission of a BLA. Following these Type A Meetings, we believe we have greater clarity of the requirements for potential resubmission of a BLA. We have a Type C Meeting scheduled with the FDA for March 28, 2022, in which we expect to discuss the study protocol for the additional Phase 3 clinical trial that we plan to conduct for potential resubmission of our a BLA for Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG. The Company reassessed the underlying assumptions used to develop the revenue projections upon which the fair value of its contingent consideration is based. The most significant and impactful assumptions in the Company's revenue projection models are timing of product launch and probabilities of clinical and regulatory success ("POS"); the Company expects delays in the start of commercialization and estimates lower POS as a direct result of the CRL. The Company plans to conduct an additional clinical trial, which will lead to delays in the start of commercialization globally. The Company has assessed a range of commercialization timeline assumptions and applied a probability to each outcome based on management’s best estimate. In addition, the Company now assumes a lower POS in achieving certain clinical and regulatory milestones in the range of approximately 45% to 55% globally. Any changes in these assumptions and estimates, or other information obtained, may have a significant impact on the remeasurement of the contingent consideration liability in the future. The fair value of the Company’s contingent consideration is determined based on the present value of projected future cash flows associated with sales-based milestones and earnouts on net sales and is heavily dependent on discount rates to estimate the fair value at each reporting period. Earnouts are determined using an earnout rate of 2% on all commercial net sales of Vicineum through December 2033. The discount rate applied to the 2% earnout is derived from the Company’s estimated weighted-average cost of capital (“WACC”), which has fluctuated from 8.8% as of December 31, 2020, to 7.8% as of March 31, 2021, 6.8% as of June 30, 2021, 8.6% as of September 30, 2021, and 9.3% as of December 31, 2021. Milestone payments constitute debt-like obligations, and therefore a high-yield debt index rate is applied to the milestones in order to determine the estimated fair value. This index rate changed from 8.4% as of December 31, 2020, to 7.4% as of March 31, 2021, 6.6% as of June 30, 2021, 7.5% as of September 30, 2021, and 8.0% as of December 31, 2021. Leases Effective January 1, 2019, the Company adopted ASC Topic 842, Leases (“ASC 842”) using the optional transition method outlined in ASU No. 2018-11, Leases (Topic 842), Targeted Improvements. The adoption of ASC 842 represents a change in accounting principle that aims to increase transparency and comparability among organizations by requiring the recognition of right-of-use assets and lease liabilities on the balance sheet for both operating and finance leases. In addition, the standard requires enhanced disclosures that meet the objective of enabling financial statement users to assess the amount, timing and uncertainty of cash flows arising from leases. The reported results for the year ended December 31, 2021, 2020 and 2019 reflect the application of ASC 842 guidance, while the reported results for priors were prepared in accordance with the previous ASC Topic 840, Leases ("ASC 840") guidance. The adoption of ASC 842 resulted in the recognition of operating lease right-of-use assets and corresponding lease liabilities of $0.2 million on the Company’s consolidated balance sheet as of January 1, 2019. The adoption of this guidance did not have a material impact on the Company’s financial condition, results of operations or cash flows; however, the adoption did result in significant changes to the Company’s financial statement disclosures. As part of the adoption of ASC 842, the Company utilized certain practical expedients outlined in the guidance. These practical expedients include: •Accounting policy election to use the short-term lease exception by asset class; •Election of the practical expedient package during transition, which includes: - An entity need not reassess whether any expired or existing contracts are or contain leases; - An entity need not reassess the classification for any expired or existing leases. As a result, all leases that were classified as operating leases in accordance with ASC 840 are classified as operating leases under ASC 842, and all leases that were classified as capital leases in accordance with ASC 840 are classified as finance leases under ASC 842; and - An entity need not reassess initial direct costs for any existing leases. The Company’s lease portfolio as of the adoption date and as of December 31, 2021 includes: a property lease for manufacturing, laboratory, warehouse and office space in Winnipeg, Manitoba, a property lease for its headquarters in Cambridge, MA, and a property lease for office space in Philadelphia, PA. The Company determines if an arrangement is a lease at the inception of the contract and has made a policy election to not separate out non-lease components from lease components, for all classes of underlying assets. The asset components of the Company’s operating leases are recorded as operating lease right-of-use assets and reported within other assets on the Company's consolidated balance sheet. The short-term and long-term liability components are recorded in other current liabilities and other liabilities, respectively, on the Company’s consolidated balance sheet. As of December 31, 2021, the Company did not have any finance leases. Right-of-use assets and operating lease liabilities are recognized based on the present value of lease payments over the lease term at the commencement date. Existing leases in the Company’s lease portfolio as of the adoption date were valued as of January 1, 2019. The Company uses an incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments, if an implicit rate of return is not provided with the lease contract. Operating lease right-of-use assets are adjusted for incentives received. Operating lease costs are recognized on a straight-line basis over the lease term, in accordance with ASC 842, and also include variable operating costs incurred during the period. Lease costs also include amounts related to short-term leases. Research and Development Costs Research and development activities are expensed in the period incurred. Research and development expenses consist of both internal and external costs associated with all basic research activities, clinical development activities and technical efforts required to develop a product candidate. Internal research and development consist primarily of personnel costs, including salaries, benefits and share-based compensation, facilities leases, research-related overhead, pre-approval regulatory and clinical trial costs, manufacturing and other contracted services, license fees and other external costs. In certain circumstances, the Company is required to make advance payments to vendors for goods or services that will be received in the future for use in research and development activities. In such circumstances, the advance payments are recorded as prepaid assets and expensed when the activity has been performed or when the goods have been received. Share-Based Compensation The Company recognizes the grant-date fair value of share-based awards granted as compensation as expense on a straight-line basis over the requisite service period, which is generally the vesting period of the award. To date, the Company has not issued awards where vesting is subject to market conditions. From time to time, the Company has granted to its executives' stock option awards which contain both performance-based and service-based vesting criteria. Performance milestone events are specific to the Company’s corporate goals, including certain clinical development objectives related to the new clinical trial, regulatory and financial objectives. Share-based compensation expense associated with performance-based vesting criteria is recognized using the accelerated attribution method if the performance condition is considered probable of achievement in management’s judgment. The fair value of stock options is estimated at the time of grant using the Black-Scholes option pricing model, which requires the use of inputs and assumptions such as the fair value of the underlying stock, exercise price of the option, expected term, risk-free interest rate, expected volatility and dividend yield. The fair value of each grant of options during the years ended December 31, 2021, 2020 and 2019 was determined using the following methods and assumptions: •Expected Term. Due to the lack of historical exercise data and given the plain vanilla nature of the options granted by the Company, the expected term is determined using the “simplified" method, as prescribed in SEC Staff Accounting Bulletin ("SAB") No. 107 ("SAB 107"), whereby the expected life equals the arithmetic average of the vesting term (generally four years) and the original contractual term (ten years) of the option, taking into consideration multiple vesting tranches. •Risk-Free Interest Rate. The risk-free rate is based on the interest rate payable on United States Treasury securities in effect at the time of grant for a period that is commensurate with the assumed expected term. •Expected Volatility. The expected volatility is based on historical volatilities of a representative group of publicly traded biopharmaceutical companies, including the Company's own volatility, which were commensurate with the assumed expected term, as prescribed in SAB 107. •Dividend Yield. The dividend yield is 0% because the Company has never declared or paid, and for the foreseeable future does not expect to declare or pay, a dividend on its common stock. Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and net operating loss ("NOL") and research and development credit ("R&D credit") carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in operations in the period that includes the enactment date. A valuation allowance is recorded to the extent it is more likely than not that some portion or all of the deferred tax assets will not be realized. Unrecognized income tax benefits represent income tax positions taken on income tax returns that have not been recognized in the financial statements. The Company recognizes the benefit of an income tax position only if it is more likely than not (greater than 50%) that the tax position will be sustained upon tax examination, based solely on the technical merits of the tax position. Otherwise, no benefit is recognized. The tax benefits recognized are measured based on the largest benefit that has a greater than 50% likelihood of being realized upon ultimate settlement. The Company recognizes accrued interest and penalties related to uncertain tax positions as income tax expense in its consolidated statements of operations. As of December 31, 2021 and 2020, the Company did not have any uncertain tax positions. Revenue Recognition The Company records revenue from out-license agreements and OUS business development partnership agreements, including the License Agreement with Roche and its OUS partnerships. Under each of these agreements, the Company granted the counterparty an exclusive license to develop and commercialize the underlying licensed product. These agreements contain up-front license fees, development and regulatory milestone payments, sales-based milestone payments, and sales-based royalty payments. The Company determines whether the out-license agreements and OUS business development partnership agreements are in scope of ASC 606, which it adopted as of January 1, 2018. Under ASC 606, in determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under these agreements, management performs the following steps: 1) Identification of the contract; 2) Determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; 3) Measurement of the transaction price, including the constraint on variable consideration; 4) Allocation of the transaction price to the performance obligations; and 5) Recognition of revenue when or as the Company satisfies each performance obligation. Development and Regulatory Milestones and Other Payments At the inception of an arrangement that includes development milestone payments, management evaluates whether the development milestones are considered probable of being reached and estimate the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated development milestone value is included in the transaction price. Development milestone payments that are not within the Company's control or the licensee's control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. For payments pursuant to sales milestones and royalty payments, the Company will not recognize revenue until the subsequent sale of a licensed product occurs. For arrangements with one than one performance obligations, the milestones are generally allocated entirely to the license performance obligation, as (1) the terms of milestone and royalty payments relate specifically to the license and (2) allocating milestones and royalties to the license performance obligation is consistent with the overall allocation objective, because management’s estimate of milestones and royalties approximates the standalone selling price of the license. In December 2021, a $20 million milestone was achieved due to Roche initiating a Phase II clinical trial. The Company invoiced Roche $20 million with payment terms of 30 days following the achievement of the corresponding milestone event, pursuant to the Roche License Agreement. Management evaluated the transaction under ASC 606 and determined it is probable that a significant revenue reversal will not occur in future periods, which was not the case in the previous quarter. Accordingly, the Company recorded $20 million as license revenue and accounts receivables in the fourth quarter of 2021. In January 2022, the payment of $20 million was received. The Company recognized $26.5 million of license revenue related to the Roche, Qilu and MENA License Agreements during the year ended December 31, 2021 and $11.2 million of license revenue related to the Qilu License Agreement during the year ended December 31, 2020.

RECENT ACCOUNTING PRONOUNCEMENTS	12 Months Ended
RECENT ACCOUNTING PRONOUNCEMENTS	Dec. 31, 2021
Accounting Standards Update and Change in Accounting Principle [Abstract]
RECENT ACCOUNTING PRONOUNCEMENTS	RECENT ACCOUNTING PRONOUNCEMENTS Adopted in 2021 In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes ("ASU 2019-12"). ASU 2019-12 simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The amendments in ASU 2019-12 also improve consistent application of and simplify GAAP for other areas of Topic 740 by clarifying and amending existing guidance. ASU 2019-12 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. Early adoption is permitted. The method with which the amendments in this ASU are to be applied varies depending on the nature of the tax item impacted by amendment. The Company adopted this guidance effective January 1, 2021, and it did not have a material impact on its financial position, results of operations or cash flows.

- Definition

The entire disclosure for change in accounting principle. Includes, but is not limited to, nature, reason, and method of adopting amendment to accounting standards or other change in accounting principle.

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-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22499-107794

Reference 32: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 848
-SubTopic 10
-Section 65
-Paragraph 1
-Subparagraph (e)(1)
-URI http://asc.fasb.org/extlink&oid=122150657&loc=SL122150809-237846

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 65
-Paragraph 8
-Subparagraph (e)(3)
-URI http://asc.fasb.org/extlink&oid=123459177&loc=SL121830611-158277

Reference 34: http://www.xbrl.org/2003/role/disclosureRef
-Topic 848
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Publisher FASB
-Subparagraph (c)

+ Details

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS

The carrying values of cash and cash equivalents, restricted cash, prepaid expenses and other current assets, and accounts payable on the Company’s consolidated balance sheets approximated their fair values as of December 31, 2021 and 2020 due to their short-term nature.

Certain of the Company’s financial instruments are measured at fair value using a three-level hierarchy that prioritizes the inputs used to measure fair value. This fair value hierarchy prioritizes the use of observable inputs and minimizes the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows:

Level 1: Inputs are quoted prices for identical instruments in active markets,

Level 2: Inputs are quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; or model-derived valuations whose inputs are observable or whose significant value drivers are observable.

Level 3: Inputs are unobservable and reflect the Company’s own assumptions, based on the best information available, including the Company’s own data.

The following tables set forth the carrying amounts and fair values of the Company's financial instruments measured at fair value on a recurring basis as of December 31, 2021 and 2020 (in thousands):


	December 31, 2021
					Fair Value Measurement Based on
	Carrying Amount		Fair Value		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Money market funds (cash equivalents)	$	16,382	$	16,382	$	16,382	$	—	$	—
Liabilities:
Contingent consideration - short term	—		$	—	$	—	$	—	$	—
Contingent consideration - long term	$	52,000	$	52,000	$	—	$	—	$	52,000


	December 31, 2020
					Fair Value Measurement Based on
	Carrying Amount		Fair Value		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Money market funds (cash equivalents)	$	16,374	$	16,374	$	16,374	$	—	$	—
Liabilities:
Contingent consideration, current portion	8,985		$	8,985	$	—	$	—	$	8,985
Contingent consideration, net of current portion	$	99,855	$	99,855	$	—	$	—	$	99,855

The Company evaluates transfers between fair value levels at the end of each reporting period. There were no transfers of assets or liabilities between fair value levels during the year ended December 31, 2021.

Contingent Consideration

The estimated fair value of the Company’s contingent consideration was determined using probabilities of successful achievement of regulatory milestones and commercial sales, the period in which these milestones and sales are expected to be achieved ranging from 2025 to 2033, the level of commercial sales of Vicineum forecasted for the US, Europe, Japan, China and other potential markets and discount rates ranging from 8.0% to 9.3% as of December 31, 2021 and 8.4% to 8.8% as of December 31, 2020. There have been no changes to the valuation methods utilized during the year ended December 31, 2021.

The following table sets forth a summary by quarter of the change in the fair value of the Company's contingent consideration liability, measured on a recurring basis at each reporting period, for the year ended December 31, 2021 (in thousands):


Balance at December 31, 2020	$	108,840
Change in fair value included in loss	48,160
Balance at March 31, 2021	157,000
Change in fair value included in loss	13,600
Balance at June 30, 2021	170,600
Change in fair value included in loss	(114,000)
Balance at September 30, 2021	56,600
Change in fair value included in loss	(4,600)
Balance at December 31, 2021	$	52,000

Balance at December 31, 2021, current portion	$	—
Balance at December 31, 2021, net of current portion	$	52,000

The following table sets forth a summary of the change in the fair value of the Company's total contingent consideration liability, measured on a recurring basis at each reporting period, for the year ended December 31, 2021.


Balance at December 31, 2020	$108,840
Change in fair value of contingent consideration - short term	(8,985)
Change in fair value of contingent consideration - long term	(47,855)
Balance at December 31, 2021	$	52,000

The fair value of the Company’s contingent consideration is determined based on the present value of projected future cash flows associated with sales-based milestones and earnouts on net sales and is heavily dependent on discount rates to estimate the fair value at each reporting period. Earnouts are determined using an earnout rate of 2% on all commercial net sales of Vicineum through December 2033. The discount rate applied to the 2% earnout is derived from the Company’s WACC, which has fluctuated from 8.8% as of December 31, 2020, to 7.8% as of March 31, 2021, 6.8% as of June 30, 2021, 8.6% as of September 30, 2021, and 9.3% as of December 31, 2021. Milestone payments constitute debt-like obligations, and therefore a high-yield debt index rate is applied to the milestones in order to determine the estimated fair value. This index rate changed from 8.4% as of December 31, 2020, to 7.4% as of March 31, 2021, 6.6% as of June 30, 2021, 7.5% as of September 30, 2021, and 8.0% as of December 31, 2021. The decrease in the fair value of contingent consideration of $56.8 million for the year ended December 31, 2021 was driven by the receipt of the CRL from the FDA, in which the FDA determined that it could not approve the BLA for Vicineum in its present form, and the Company’s withdrawal of its MAA with EMA. In October and December 2021, we participated in a CMC Type A Meeting and a Clinical Type A Meeting, respectively, with the FDA to discuss issues raised in the CRL and to discuss design elements of an additional Phase 3 clinical trial for Vicineum, which the FDA confirmed will be required for a potential resubmission of a BLA. Following these Type A Meetings, we believe we have greater clarity of the requirements for potential resubmission of a BLA. We have a Type C Meeting scheduled with the FDA for March 28, 2022, in which we expect to discuss the study protocol for the additional Phase 3 clinical trial that we plan to conduct for potential resubmission of our a BLA for Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG. Incorporating the impact of the CRL and the subsequent Type A Meetings in the fourth quarter of 2021, the Company reassessed the underlying assumptions used to develop the revenue projections upon which the fair value of its contingent consideration is based. The most significant and impactful assumptions in the Company’s revenue projection models are timing of commercial product launch and probabilities of clinical and regulatory success; the Company expects delays in the start of commercialization and estimates lower POS as a direct result of the CRL and the Company’s withdrawal of its MAA. The Company plans to conduct an additional Phase 3 clinical trial in order to resubmit a BLA for Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG, which will lead to delays in the start of commercialization globally. The Company has assessed a commercialization timeline assumption and applied a probability to each outcome based on management’s best estimate. In addition, the Company now assumes a lower POS in achieving certain clinical and regulatory milestones in the range of approximately 45% to 55% globally.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

RECEIVABLES	12 Months Ended
RECEIVABLES	Dec. 31, 2021
Receivables [Abstract]
RECEIVABLES	RECEIVABLES The accounts receivable balance as of December 31, 2021 is $21.0 million, comprised primarily of a $20 million milestone achieved in December 2021 due to Roche initiating a Phase II clinical trial. The Company invoiced Roche $20 million with payment terms of 30 days following the achievement of the corresponding milestone event, pursuant to the Roche License Agreement. In January 2022 the payment of $20 million was received. Additionally, in June 2021, the Qilu License Agreement was recognized by Shandong Province, Bureau of Science and Technology as a "Technology Transfer". As such, the Company recorded $0.9 million of revenue and accounts receivable for the additional purchase price resulting from Qilu's obligation to pay Sesen an amount equal to its recovery of VAT. The Company will not be subject to VAT on future potential milestone payments from Qilu. The other receivable balance as of December 31, 2021 is $3.5 million. The Company recorded $3.4 million to other receivables in the fourth quarter of 2021 for German VAT recovery related to drug substance sent to Baxter. The Company received a payment for $1.8 million in January 2022 and expects to collect the remaining balance. The accounts receivable and other receivable balances as of December 31, 2020 were de minims.

PROPERTY AND EQUIPMENT

12 Months Ended

Dec. 31, 2021

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT

The following table sets forth the composition of property and equipment, net as of December 31, 2021 and 2020 (in thousands):


	December 31,
	2021		2020
Lab equipment	$	569	$	570
Furniture and fixtures	16		16
Computer equipment	99		97
Software	32		28
Leasehold improvements	293		293
Property and equipment, gross	1,009		1,004
Less: accumulated depreciation	(966)		(881)
Total Property and Equipment, Net	$	43	$	123

Depreciation expense was $0.1 million, $0.1 million and $0.2 million for the years ended December 31, 2021, 2020 and 2019, respectively.

INTANGIBLES AND GOODWILL

12 Months Ended

Dec. 31, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

INTANGIBLES AND GOODWILL

Intangibles

Intangible assets on the Company's consolidated balance sheet are the result of the Viventia Acquisition in September 2016. The following table sets forth the composition of intangible assets as of December 31, 2021 and 2020 (in thousands):


	December 31,
	2021		2020
IPR&D intangible assets:
Vicineum United States rights	$	—	$	31,700
Vicineum European Union rights	14,700		14,700
Total Intangibles	$	14,700	$	46,400

The fair value of the acquired intangible assets for the US and EU rights of Vicineum is determined using a risk-adjusted discounted cash flow approach, which includes probability adjustments for projected revenues and operating expenses based on the success rates assigned to each stage of development for each geographical region; as well as discount rates applied to the projected cash flows. In August 2021, the Company received a CRL from the FDA regarding its BLA for Vicineum for the

treatment of NMIBC, the Company’s lead product candidate. In the CRL, the FDA determined that it could not approve the BLA for Vicineum in its present form and provided recommendations specific to additional clinical/statistical data and analyses in addition to CMC issues pertaining to a recent pre-approval inspection and product quality. Given the inherent uncertainty in the development plans for Vicineum as a result of the CRL and the Company’s withdrawal of its MAA, an impairment analysis was conducted in the third quarter of 2021, which concluded that the carrying value of the Company’s intangible asset of Vicineum United States rights was fully impaired as of September 30, 2021. The $31.7 million of impairment charges as of September 30, 2021 are due to delays in the expected start of commercialization and lower probabilities of success, combined with higher operating expenses expected to be incurred prior to commercialization, resulting in lower expected future cash flows estimated in the US market. At this time, management has assessed that the carrying value of the Vicineum EU rights is not at significant risk of impairment in the future within the current range of commercialization timelines and POS assumptions. This is primarily due to the fact that the Company expects the Vicineum sales outside of the US to be two to three times the expected sales volume in the US, based on management’s reassessment of the total addressable global market for high-risk NMIBC during the quarter ended June 30, 2019, wherein management determined that both the global market size and the estimated potential Vicineum commercial sales within the global market were likely higher than the Company's previous estimate. In addition, the EU asset is burdened with significantly less expense than the US asset, as the Company’s strategic operating plan is to sublicense Vicineum to business development partners in all regions outside the US, including the EU, with it earning a potential combination of upfront, milestone, and royalty payments, and the business development partner bearing the majority of regulatory and commercialization costs.

The Company performed the annual impairment test, which incorporated the impact of the CRL and the subsequent Type A Meetings in the fourth quarter of 2021 and concluded that the carrying value of the Company's intangible asset of Vicineum EU rights was not impaired as of December 31, 2021.

The Company did not recognize any impairment charges during the year ended December 31, 2020.

Goodwill

Goodwill on the Company's consolidated balance sheet is the result of the Viventia Acquisition in September 2016. Goodwill had a carrying value of $13.1 million as of December 31, 2021 and 2020. Given the inherent uncertainty in the development plans for Vicineum as a result of the CRL and the Company's withdrawal of its MAA, a quantitative impairment analysis was conducted during the third quarter of 2021, in advance of the Company's typical annual assessment date of October 1. While an impairment was recognized in one of its intangible assets, Vicineum US Rights, the Company concluded that the carrying value of its goodwill of $13.1 million was not impaired as of September 30, 2021, with the fair value of equity of the reporting unit exceeding the estimated carrying value of the reporting unit by approximately 45%.

In October and December 2021, we participated in a CMC Type A Meeting and a Clinical Type A Meeting, respectively, with the FDA to discuss issues raised in the CRL and to discuss design elements of an additional Phase 3 clinical trial for Vicineum, which the FDA confirmed will be required for a potential resubmission of a BLA. Following these Type A Meetings, we believe we have greater clarity of the requirements for potential resubmission of a BLA. We have a Type C Meeting scheduled with the FDA for March 28, 2022, in which we expect to discuss the study protocol for the additional Phase 3 clinical trial that we plan to conduct for potential resubmission of our a BLA for Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG. The Company performed the annual impairment test, which incorporated the impact of the CRL and the subsequent Type A Meetings in the fourth quarter of 2021 and concluded that there was no goodwill impairment as of December 31, 2021. The Company believes it has sufficient future cash flows from additional geographic regions outside the US to support the value of its goodwill. The Company projects future cash flows based on various timeline assumptions and applies a probability to each outcome based on management’s best estimate. In addition, probabilities of success in achieving certain clinical and regulatory success in the Company's current development profile (ranging from 45% to 55% globally) also have a material effect on the estimated fair value of its reporting unit as of the impairment assessment date. The Company will continue to evaluate its timelines for commercialization and probability of success of development of Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG.

Based on the annual testing and quarterly reviews performed, the Company concluded that there was no goodwill impairment during the year ended

ACCRUED EXPENSES

12 Months Ended

Dec. 31, 2021

Payables and Accruals [Abstract]

ACCRUED EXPENSES

The following table sets forth the composition of accrued expenses as of December 31, 2021 and 2020 (in thousands):


	December 31,
	2021		2020
Research and development	$	1,841	$	1,372
Payroll-related expenses	2,967		1,892
Restructuring charge related	1,497		—
Professional fees	1,941		684
Other	9		25
Total Accrued Expenses	$	8,255	$	3,973

COMMITMENTS AND CONTINGENCIES	12 Months Ended
COMMITMENTS AND CONTINGENCIES	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Legal Proceedings From time to time, the Company may become subject to legal proceedings, claims, and litigation arising in the ordinary course of business. When the Company becomes aware of a claim or potential claim, it assesses the likelihood of any loss or exposure. In accordance with authoritative guidance, the Company records loss contingencies in its financial statements only for matters in which losses are probable and can be reasonably estimated. Where a range of loss can be reasonably estimated with no best estimate in the range, the Company records the minimum estimated liability. If the loss is not probable or the amount of the loss cannot be reasonably estimated, the Company discloses the nature of the specific claim if the likelihood of a potential loss is reasonably possible, and the amount involved is material. The Company continuously assesses the potential liability related to the Company’s pending litigation and revises its estimates when additional information becomes available. The Company is not currently a party to any material legal proceedings, other than as described below. On August 19, 2021, August 31, 2021, and October 7, 2021, three substantially identical securities class action lawsuits captioned Bibb v. Sesen Bio, Inc., et. al., Case No. 1:21-cv-07025, Cizek v. Sesen Bio, Inc., et. al., Case No. 1:21-cv-07309, and Markman v. Sesen Bio, Inc. et al., Case No. 1:21-cv-08308 were filed against the Company and certain of its officers in the US District Court for the Southern District of New York. The three complaints allege violations of Sections 10(b) and 20(a) of the Exchange Act and Rule 10b-5 promulgated thereunder based on statements made by the Company concerning its BLA for Vicineum for the treatment of BCG-unresponsive NMIBC. The three complaints seek compensatory damages and costs and expenses, including attorneys’ fees. On October 29, 2021, the court consolidated the three cases under the caption In re Sesen Bio, Inc. Securities Litigation, Master File No. 1:21-cv-07025-AKH (the “Securities Litigation”), and appointed Ryan Bibb, Rodney Samaan, Lionel Dreshaj and Benjamin Dreshaj (“Lead Plaintiffs”) collectively as the lead plaintiffs under the Private Securities Litigation Reform Act. On November 1, 2021, two stockholders filed motions to reconsider asking the court to appoint a different lead plaintiff. The court has not ruled on those motions at this time. On November 24, 2021, defendants filed a motion to transfer venue to the US District Court for the District of Massachusetts. That motion was fully briefed as of December 13, 2021, but the court has not yet ruled on that motion. On December 6, 2021, the Lead Plaintiffs filed an amended class action complaint (the “Amended Complaint”). The Amended Complaint alleges the same violations of Sections 10(b) and 20(a) of the Exchange Act and Rule 10b-5 promulgated thereunder on the same theory as the prior complaints. Defendants’ response to the Amended Complaint is due to be filed on March 7, 2022. On September 20, 2021 and September 24, 2021, two substantially similar derivative lawsuits captioned Myers v. Sesen Bio, Inc., et. al., Case No. 1:21-cv-11538 and D’Arcy v. Sesen Bio, Inc., et. al., Case No. 1:21-cv-11577 were filed against the Company’s board of directors and certain of its officers in the US District Court for the District of Massachusetts, with the Company named as a nominal defendant. On January 12, 2022, a third derivative complaint captioned Tang v. Sesen Bio, Inc., et al., was filed in Superior Court in Massachusetts against the Company’s board of directors and certain of its officers in the US District Court for the District of Massachusetts, with the Company named as nominal defendant, but no defendant has yet been served. The three derivative complaints allege breach of fiduciary duties, waste of corporate assets, and violations of federal securities laws based on statements made by the Company concerning its BLA for Vicineum for the treatment of BCG-unresponsive NMIBC. The D’Arcy complaint further alleges unjust enrichment, abuse of control, gross mismanagement and aiding and abetting thereof. The three derivative complaints seek unspecified damages, restitution and disgorgement of profits, benefits and compensation obtained by the defendants and costs and expenses, including attorneys’ fees. On October 18, 2021, the court consolidated the two federal cases under the caption In re Sesen Bio, Inc. Derivative Litigation, Lead Case No. 1:21-cv-11538 (the “Federal Derivative Litigation”). On December 22, 2021, the court entered a joint stipulation among the parties to stay the Federal Derivative Litigation until after a ruling on any motion to dismiss filed by defendants in the Securities Litigation. Defendants intend to seek a similar stay of the state court derivative litigation in the event any defendant is served. The Company believes that these lawsuits are without merit and intends to vigorously defend against them. The lawsuits are in the early stages and, at this time, no assessment can be made as to the likely outcome or whether the outcome will be material to the Company. Executive Employment Agreements The Company has entered into employment agreements and offer letters with certain of its key executives, providing for separation payments and benefits in certain circumstances, as defined in the agreements.

LEASES

12 Months Ended

Dec. 31, 2021

Leases [Abstract]

LEASES

The Company accounts for operating leases under ASC Topic 842, Leases. The Company's lease portfolio includes an operating lease for its 31,100 square foot facility in Winnipeg, Manitoba which consists of manufacturing, laboratory, warehouse and office space. In September 2020, the Company entered into an extension of this lease for an additional two years, through September 2022, with a right to extend the lease for one subsequent three-year term. The minimum monthly rent under this lease is CAD $18,100 (approximately $14,300 at exchange rates in effect on December 31, 2021). In addition to rent expense, the Company expects to incur CAD $18,200 per month related to operating expenses (approximately $14,300 at exchange rates in effect on December 31, 2021). Operating lease cost under this lease, including the related operating costs, were $0.3 million and $0.3 million for the year ended December 31, 2021 and $0.3 million and $0.3 million for the year ended December 31, 2020, respectively.

The asset component of the Company’s operating leases is recorded as operating lease right-of-use assets and reported within other assets on the Company's consolidated balance sheets. The short-term lease liability is recorded in other current liabilities and the long-term lease liability is recorded in other liabilities on the Company’s consolidated balance sheets. Operating lease cost is recognized on a straight-line basis over the term of the lease.

In addition, the Company has short-term property leases for modular office space for 1) its corporate headquarters in Cambridge, MA and 2) office space in Philadelphia, PA. The short-term leases renew every three months to six months and currently extend through June 2022 and May 2022, respectively. The minimum monthly rent for these office spaces is $2,100 and $18,400, respectively, which is subject to change if and as the Company adds space to or deducts space from the leases.

The components of lease cost for the years ended December 31, 2021 and 2020 is as follows (in thousands):


	Year Ended December 31, 2021		Year Ended December 31, 2020
Lease Cost:
Operating lease (including related operating costs)	$	327	$	301
Short term property leases	262		261
Total lease costs	$	589	$	562


Supplemental Information:	Year Ended December 31, 2021		Year Ended December 31, 2020
Weighted-average remaining lease term (years)	0.75		1.75
Weighted-average discount rate - operating leases	12	%	12	%

The following table sets forth the Company's future minimum lease payments under non-cancelable leases as of December 31, 2021 (in thousands):


Minimum Lease Payments:	Year Ended December 31, 2021
Total future minimum lease payments (2022)	$	129
Less: Amounts representing present value adjustment	(5)
Operating lease liabilities, net of current portion	$	124

STOCKHOLDERS' EQUITY DEFICIT

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

STOCKHOLDERS' EQUITY DEFICIT

Equity Financings

ATM Offering

In November 2019, the Company entered into an Open Market Sale Agreement SM (the "Sale Agreement") with Jefferies LLC ("Jefferies"), under which the Company may issue and sell shares of its common stock, par value $0.001 per share, from time to time (the “ATM Offering”) for an aggregate sales price of up to $35 million through Jefferies. In October 2020 and February 2021, the Company entered into Amendments No. 1 and No. 2 to the Sale Agreement, respectively. Amendments No. 1 and No. 2 modified the Sale Agreement to reflect that the Company may issue and sell shares of its common stock from time to time for an aggregate sales price of up to an additional $50.0 million and $34.5 million, respectively. In June 2021, the Company entered into Amendment No. 3 to the Sale Agreement, which modified the Sale Agreement to remove the maximum dollar amount of shares of common stock that may be sold pursuant to the Sale Agreement. In June and July 2021, the Company filed prospectus supplements with the SEC in connection with the offer and sale of up to an aggregate of $200 million of common stock pursuant to the Sale Agreement. Sales are made by any method that is deemed to be an ATM offering as defined in Rule 415(a)(4) of the Securities Act of 1933, as amended, including but not limited to sales made directly on or through the Nasdaq Global Market or any other existing trading market for the Company's common stock. The Company may sell shares of its common stock efficiently from time to time but has no obligation to sell any of its common stock and may at any time suspend offers under the Sale Agreement or terminate the Sale Agreement. Subject to the terms and conditions of the Sale Agreement, Jefferies will use its commercially reasonable efforts to sell common stock from time to time, as the sales agent, based upon the Company’s instructions, which include a prohibition on sales below a minimum price set by the Company from time to time. The Company has provided Jefferies with customary indemnification rights, and Jefferies is entitled to a commission at a fixed rate equal to 3.0% of the gross proceeds for each sale of common stock under the Sale Agreement. The Company raised $175.0 million of net proceeds from the sale of 56.9 million shares of common stock at a weighted-average price of $3.17 per share during the year ended December 31, 2021, compared to $38.0 million of net proceeds from the sale of 33.4 million shares of common stock at a weighted-average price of $1.17 per share during the year ended December 31, 2020. Share issuance costs, including sales agent commissions, related to the ATM Offering totaled $5.4 million and $1.2 million during the year ended December 31, 2021 and 2020, respectively.

June 2019 Financing

In June 2019, the Company raised $27.8 million of net proceeds from the sale of 20.4 million shares of common stock and accompanying warrants to purchase an additional 20.4 million shares of common stock in an underwritten public offering (the "June 2019 Financing"). The combined purchase price for each share of common stock and accompanying warrant was $1.47. Subject to certain ownership limitations, the warrants issued in the June 2019 Financing were exercisable immediately upon issuance at an exercise price of $1.47 per share, subject to adjustments as provided under the terms of such warrants, and had a one-year term that expired on June 21, 2020.

Preferred Stock

Pursuant to its Amended and Restated Certificate of Incorporation (the "Certificate of Incorporation"), the Company is authorized to issue 5.0 million shares of "blank check" preferred stock, $0.001 par value per share, which enables its board of directors, from time to time, to create one or more series of preferred stock. Each series of preferred stock issued shall have the rights, preferences, privileges and restrictions as designated by the board of directors. The issuance of any series of preferred stock could affect, among other things, the dividend, voting and liquidation rights of the Company's common stock. The Company had no preferred stock issued and outstanding as of December 31, 2021 and 2020.

Common Stock

Following approval by the Company’s stockholders on May 3, 2021, an amendment became effective to the Certificate of Incorporation that increased the number of authorized shares of common stock from 200 million to 400 million, of which 199 million and 140 million shares were issued and outstanding as of December 31, 2021 and 2020, respectively. In addition, the Company had reserved for issuance the following amounts of shares of its common stock for the purposes described below as of December 31, 2021 and 2020 (in thousands):


	December 31,
	2021	2020
Shares of common stock issued	199,464	140,450
Shares of common stock reserved for issuance for:
Warrants	199	2,247
Stock options	15,703	10,147
RSUs	3,041	—
Shares available for grant under 2014 Stock Incentive Plan	8,933	4,863
Shares available for sale under 2014 Employee Stock Purchase Plan	2,300	—
Total shares of common stock issued and reserved for issuance	229,640	157,707

The voting, dividend and liquidation rights of holders of shares of common stock are subject to and qualified by the rights, powers and preferences of holders of shares of preferred stock. Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company's stockholders; provided, however, that, except as otherwise required by law, holders of common stock shall not be entitled to vote on any amendment to the Company’s Certificate of Incorporation that relates solely to the terms of one or more outstanding series of preferred stock if the holders of such affected series are entitled, either separately or together as a class with the holders of one or more such series, to vote thereon. There shall be no cumulative voting.

Dividends may be declared and paid on the common stock from funds lawfully available thereof as and when determined by the board of directors and subject to any preferential dividend or other rights of any then-outstanding preferred stock. The Company has never declared or paid, and for the foreseeable future does not expect to declare or pay, dividends on its common stock.

Upon the dissolution or liquidation of the Company, whether voluntary or involuntary, holders of common stock will be entitled to receive all assets of the Company available for distribution to its stockholders, subject to any preferential or other rights of any then-outstanding preferred stock.

Warrants

All of the Company’s outstanding warrants are non-tradeable and equity-classified because they meet the derivative scope exception under ASC Topic 815-40, Derivatives and Hedging - Contracts in Entity’s Own Equity ("ASC 815-40"). The following table sets forth the Company's warrant activity for the year ended December 31, 2021 (in thousands):


Issued	Exercise Price	Expiration	December 31, 2020	Issued	(Exercised)	(Cancelled)	December 31, 2021
Jun-2019	$1.47	Jun-2020	—	—	—	—	—
Mar-2018	$0.55*	Mar-2023	1,705	—	(1,573)	—	132
Nov-2017	$0.55*	Nov-2022	487	—	(475)	—	12
May-2015	$11.83	Nov-2024	28	—	—	—	28
Nov-2014	$11.04	Nov-2024	27	—	—	—	27
			2,247	—	(2,048)	—	199

* Exercise price shown (i) reflects modification described below and (ii) subject to further adjustment based on down round provision added by amendment described below.

During the year ended December 31, 2021, the Company received proceeds of $1.1 million from the exercises of 1.6 million 2018 Warrants and 0.5 million 2017 Warrants.

Warrant Modifications

In October 2019, the Company entered into transactions with holders of its outstanding 2018 Warrants and 2017 Warrants to purchase the Company's common stock. At such time, the 2018 Warrants and 2017 Warrants utilized the same form of warrant, which contained a prohibition on variable rate transactions (as defined therein). Warrant holders agreed to waive such

prohibition in exchange for certain concessions from the Company. Management evaluated the warrants after modifications and determined that they continued to be equity-classified under the derivative scope exception of ASC 815-40. The warrants were revalued immediately before and immediately after the modifications to calculate the $1.1 million incremental value of the modified warrants. The Company considers this incremental value to be akin to an offering cost since the modifications were directly related to enabling the ATM Offering and would not have otherwise been incurred. Therefore, in the fourth quarter of 2019, management initially capitalized the $1.1 million to deferred financing cost asset, with an offsetting credit to additional paid-in capital, and then reclassified the deferred financing cost asset to reduce the ATM Offering proceeds within equity as proceeds were received from sales of common stock under the ATM Offering.

2018 Warrants

In October 2019, the Company entered into transactions with the holders of its outstanding 2018 Warrants pursuant to which such holders either (i) exercised their warrants pursuant to a Warrant Exercise Agreement (the "2018 Warrant Exercise Agreements") or (ii) amended their warrants pursuant to a Warrant Amendment Agreement (the "2018 Warrant Amendment Agreements"). As consideration for those holders executing the 2018 Warrant Exercise Agreements, the Company reduced the exercise price of the warrants from $1.20 to $0.60 per share of the Company's common stock, resulting in proceeds of $2.0 million from the exercise of 3.4 million warrants. Pursuant to the 2018 Warrant Amendment Agreements, the prohibition on certain variable rate transactions included in the 2018 Warrants was amended to exclude ATM offerings and the exercise price of the warrants was reduced from $1.20 to the lesser of (a) $0.95 per share of common stock and (b) the exercise price as determined from time to time pursuant to the anti-dilution provisions in the 2018 Warrant Amendment Agreements. During the second quarter of 2020, the anti-dilution provision was triggered to lower the exercise price of the warrants to $0.55; as such, the Company recognized a deemed dividend of approximately $0.1 million which reduced the income available to common stockholders. As the Company has an accumulated deficit balance, there is no overall impact to additional paid-in capital, as the deemed dividend is recorded as offsetting debit and credit entries to additional paid-in capital. Therefore, the amounts were not presented on the Statement of Stockholders' (Deficit) Equity.

In connection with the 2018 Warrant Exercise Agreements and 2018 Warrant Amendment Agreements, the Company entered into an amendment to the Securities Purchase Agreement dated March 21, 2018 related to the March 2018 Financing, by and among the Company and each purchaser identified on the signature pages thereto, with certain holders representing greater than 50.1% of the securities issued based on initial subscription amounts, pursuant to which the prohibition on variable rate transactions, including ATM offerings, was deleted in its entirety.

2017 Warrants

In October 2019, the Company entered into transactions with the holders of its outstanding 2017 Warrants pursuant to which such holders either (i) exercised their warrants pursuant to a Warrant Exercise Agreement (the "2017 Warrant Exercise Agreements") or (ii) amended their warrants pursuant to a Warrant Amendment Agreement (the "2017 Warrant Amendment Agreements"). As consideration for those holders executing the 2017 Warrant Exercise Agreements, the Company reduced the exercise price of the warrants from $0.80 to $0.55 per share of the Company's common stock. Pursuant to the 2017 Warrant Amendment Agreements, the prohibition on certain variable rate transactions, including ATM offerings, included in the 2017 Warrants was deleted in its entirety and the exercise price of the warrants was reduced from $0.80 to the lesser of (a) $0.55 per share of common stock and (b) the exercise price as determined from time to time pursuant to the anti-dilution provisions in the 2017 Warrant Amendment Agreements. As of December 31, 2021, there has been no adjustment to the exercise price of these warrants.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496171-112644

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496189-112644

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
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-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-URI http://asc.fasb.org/topic&trid=2208762

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
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-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496189-112644

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section 50
-Paragraph 18
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496189-112644

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 16
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496180-112644

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

EARNINGS (LOSS) PER SHARE

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

EARNINGS (LOSS) PER SHARE

A net loss cannot be diluted. Therefore, when the Company is in a net loss position, basic and diluted loss per common share are the same. If the Company achieves profitability, the denominator of a diluted earnings per common share calculation includes both the weighted-average number of shares outstanding and the number of common stock equivalents, if the inclusion of such common stock equivalents would be dilutive. Dilutive common stock equivalents potentially include warrants, stock options and non-vested restricted stock awards and units using the treasury stock method, along with the effect, if any, from outstanding convertible securities. The majority of the Company’s outstanding warrants to purchase common stock have participation rights to any dividends that may be declared in the future and are therefore considered to be participating securities. Participating securities have the effect of diluting both basic and diluted earnings per share during periods of income. During periods of loss, no loss is allocated to the participating securities since the holders have no contractual obligation to share in the losses of the Company.

Additionally, an entity that presents earnings per share shall recognize the value of the effect of an anti-dilution provision in an equity-classified freestanding financial instrument in the period the anti-dilution provision is triggered. That effect shall be treated as a deemed dividend and as a reduction of income available to common stockholders in basic earnings per share. The

deemed dividend is added back to income available to common stockholders when applying the treasury stock method for diluted earnings per share.

For periods with net income, diluted net earnings per share is calculated by either (i) adjusting the weighted-average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period as determined using the treasury stock method or (ii) the two-class method considering common stock equivalents, whichever is more dilutive. The two-class method is an earnings allocation formula that treats a participating security as having rights to earnings that otherwise would have been available to common stockholders.

The two-class method was not applied for the twelve months ended December 31, 2021, 2020 and 2019 as the Company’s participating securities do not have any obligation to absorb net losses.

For purposes of the diluted net loss per share calculation, common stock equivalents are excluded from the calculation if their effect would be anti-dilutive.

The following potentially dilutive securities outstanding as of December 31, 2021, 2020 and 2019 have been excluded from the denominator of the diluted loss per share of common stock outstanding calculation (in thousands):


	December 31,
	2021	2020	2019
Warrants	199	2,247	22,895
Stock options	15,703	10,147	6,236
Total	15,902	12,394	29,131

SHARE-BASED COMPENSATION

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

SHARE-BASED COMPENSATION

The following table sets forth the amount of share-based compensation expense recognized by the Company by line item on its Consolidated Statements of Operations and Comprehensive Loss for the years ended December 31, 2021, 2020 and 2019 (in thousands):


	Year ended December 31,
	2021		2020		2019
Research and development	$	973	$	350	$	188
General and administrative	4,170		1,407		1,049
Total Share Based Compensation	$	5,143	$	1,757	$	1,237

2014 Stock Incentive Plan

The Company's 2014 Stock Incentive Plan, as amended (the "2014 Plan"), was adopted by its board of directors in December 2013 and subsequently approved by its stockholders in January 2014. The 2014 Plan became effective immediately prior to the closing of the Company's IPO in February 2014 and provides for the grant of incentive and non-qualified stock options, restricted stock awards and restricted stock units, stock appreciation rights and other stock-based awards, with amounts and terms of grants determined by the Company's board of directors at the time of grant, to the Company's employees, officers, directors, consultants and advisors.

At the Annual Meeting of the Company's stockholders in June 2019, the Company's stockholders approved an amendment to the 2014 Plan that (i) increased by 7.9 million the number of shares of common stock reserved for issuance under the 2014 Plan and (ii) eliminated the “evergreen” or automatic replenishment provision of the 2014 Plan, pursuant to which the number of shares of common stock authorized for issuance under the 2014 Plan was automatically increased on an annual basis. At the Annual Meeting of the Company’s stockholders in May 2021, the Company’s stockholders approved an amendment to the 2014 Plan that increased by 12 million the number of shares of common stock reserved for issuance under the 2014 Plan. There were approximately 8.9 million shares of common stock available for issuance under the 2014 Plan as of December 31, 2021.

Stock options outstanding under the 2014 Plan generally vest over a four-year period at the rate of 25% of the grant vesting on the first anniversary of the date of grant and 6.25% of the grant vesting at the end of each successive three-month period thereafter. Stock options granted under the 2014 Plan are exercisable for a period of ten years from the date of grant. There were approximately 12.8 million stock options outstanding under the 2014 Plan as of December 31, 2021.

On September 9, 2021, the Board of Directors and the Compensation Committee of the Company approved a retention program for all current employees, except for the Chief Executive Officer, pursuant to which the Company will provide certain incentives designed to retain such employees (the “Retention Program”). Pursuant to the Retention Program and effective as of October 1, 2021, the Company’s non-executive employees received a combination of a cash bonus award and a one-time restricted stock unit (“RSU”) award which vests in full on September 30, 2022, subject to continued employment through September 30, 2022. Each RSU represents a contingent right to receive one share of the Company’s common stock. The Company recorded an expense of $0.5 million for retention-related RSUs for the year ended December 31, 2021. Additionally, the Company expensed $0.6 million in relation to the cash bonus portion of the retention program.

Also pursuant to the Retention Program and effective as of October 1, 2021, the Company’s executive officers, except for the Chief Executive Officer, were granted a one-time performance-based restricted stock unit (“PSU”) award equal to the value of approximately fifty percent of current base salary. Each PSU represents a contingent right to receive one share of the Company’s common stock upon the satisfaction of pre-determined performance criteria. Subject to continued employment, such awards vest on September 30, 2023 upon the determination by the Compensation Committee of the level of achievement of certain key milestones consisting of a clinical trial milestone, an employee retention milestone and cash management milestones. As none of the retention milestones were met in the year ended December 31, 2021 and achievement was deemed not probable, the Company did not record expenses for retention-related PSUs. As of December 31, 2021, the unrecognized compensation expense for the retention-related PSUs, granted on October 1, 2021, was $0.4 million.

A summary of the status of restricted stock units is presented below:


			Restricted Stock Units (in thousands)
Unvested at December 31, 2020			—
Granted RSU			2,482
Granted PSU			559
Unvested at December 31, 2021			3,041

The weighted average remaining contractual life of unvested RSUs and PSUs as of December 31, 2021 is 9.75 years. The Company did not grant restricted stock units during the years ended December 31, 2020 and 2019.

2009 Stock Incentive Plan

The Company maintains a 2009 Stock Incentive Plan, as amended and restated (the "2009 Plan"), which provided for the grant of incentive and non-qualified stock options and restricted stock awards and restricted stock units, with amounts and terms of grants determined by the Company's board of directors at the time of grant, to its employees, officers, directors, consultants and advisors. Upon the closing of its IPO in February 2014, the Company ceased granting awards under the 2009 Plan and all shares (i) available for issuance under the 2009 Plan at such time and (ii) subject to outstanding awards under the 2009 Plan that expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased without having been fully exercised or resulting in any common stock being issued were carried over to the 2014 Plan. Stock options granted under the 2009 Plan are exercisable for a period of ten years from the date of grant. There were approximately 0.1 million fully vested stock options outstanding under the 2009 Plan as of December 31, 2021.

Out-of-Plan Inducement Grants

From time to time, the Company has granted equity awards to its newly hired employees, including executives, in accordance with the Nasdaq Stock Market LLC ("Nasdaq") employment inducement grant exemption (Nasdaq Listing Rule 5635(c)(4)). Such grants are made outside of the 2014 Plan and act as an inducement material to the employee's acceptance of employment with the Company. There were approximately 2.8 million stock options outstanding which were granted as employment inducement awards outside of the 2014 Plan as of December 31, 2021.

Stock Options

The following table sets forth a summary of the Company’s total stock option activity, including awards granted under the 2014 Plan and 2009 Plan and inducement grants made outside of stockholder approved plans, for the years ended December 31, 2021, 2020 and 2019:


	Number of Shares under Option (in thousands)	Weighted-Average Exercise Price	Weighted-Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2018	3,942	$2.12	9.14	$	57
Granted	3,986	$1.02
Exercised	(90)	$1.10
Canceled or forfeited	(1,602)	$1.78
Outstanding at December 31, 2019	6,236	$1.52	8.83	$	358
Granted	4,044	$0.87
Exercised	(12)	$1.13
Canceled or forfeited	(121)	$1.04
Outstanding at December 31, 2020	10,147	$1.26	8.50	$	3,160
Granted	8,273	$3.32
Exercised	(34)	$1.23
Canceled or forfeited	(2,683)	$3.70
Outstanding at December 31, 2021	15,703	$1.93	8.03	$	82
Exercisable at December 31, 2021	7,562	$1.65	7.41	$	59

The Company recognized share-based compensation expense of $5.1 million for the year ended 2021. The stock option related expenses were $4.6 million, $1.8 million and $1.2 million for the years ended December 31, 2021, 2020 and 2019, respectively. The RSU related expense was $0.5 million for the year ended December 31, 2021. The Company did not record RSU related expenses for the years ended December 31, 2020 and 2019. As of December 31, 2021, there was $10.4 million of total unrecognized compensation cost related to non-vested stock options which the Company expects to recognize over a weighted-average period of 2.7 years. The weighted-average grant-date fair value of stock options granted during the year ended December 31, 2021, 2020 and 2019 were $2.16, $0.56 and $1.02, respectively. The total intrinsic value of stock options exercised for the years ended December 31, 2021, 2020 and 2019 was de minimis.

For the years ended December 31, 2021, 2020 and 2019, the grant-date fair value of stock options was determined using the following weighted-average inputs and assumptions in the Black-Scholes option pricing model:


	Year ended December 31,
	2021	2020	2019
Fair market value	$3.32	$0.87	$1.02
Grant exercise price	$3.32	$0.87	$1.02
Expected term (in years)	6.0	6.1	6.0
Risk-free interest rate	0.9%	1.3%	2.1%
Expected volatility	74.6%	71.5%	78.1%
Dividend yield	—%	—%	—%

EMPLOYEE BENEFIT PLANS	12 Months Ended
EMPLOYEE BENEFIT PLANS	Dec. 31, 2021
Retirement Benefits [Abstract]
EMPLOYEE BENEFIT PLANS	EMPLOYEE BENEFIT PLANS 2014 Employee Stock Purchase Plan The Company's 2014 Employee Stock Purchase Plan ("2014 ESPP") was adopted by its board of directors in December 2013 and subsequently approved by its stockholders in January 2014. The 2014 ESPP became effective immediately prior to the closing of the Company's IPO in February 2014 and established an initial reserve of 0.2 million shares of the Company's common stock for issuance to participating employees. At the Annual Meeting of the Company's stockholders in May 2021, the Company's stockholders approved an amendment to the 2014 ESPP that increased by 2.3 million the number of shares of common stock reserved for issuance under the 2014 ESPP. The purpose of the 2014 ESPP is to enhance employee interest in the success and progress of the Company by encouraging employee ownership of common stock of the Company. The 2014 ESPP provides employees with the opportunity to purchase shares of common stock at a 15% discount to the market price through payroll deductions or lump sum cash investments. The Company estimates the number of shares to be issued at the end of an offering period and recognizes expense over the requisite service period. Shares of the common stock issued and sold pursuant to the 2014 ESPP are shown on the consolidated statements of changes in stockholders' equity (deficit). As of December 31, 2021, there were 2.3 million shares of common stock available for sale under the 2014 ESPP. The Company sold a de minimis number of shares under the ESPP for the years ended December 31, 2021, 2020 and 2019, respectively. Defined Contribution Plans United States - 401(k) Plan The Company maintains a 401(k) defined contribution retirement plan which covers all of its US employees. Employees are eligible to participate on the first of the month following their date of hire. Under the 401(k) plan, participating employees may defer up to 100% of their pre-tax salary, subject to certain statutory limitations. Employee contributions vest immediately. The plan allows for a discretionary match per participating employee up to a maximum of $4,000 per year. The Company contributed a de minimis amount for each of the three years ended December 31, 2021, 2020 and 2019, respectively. Canada - Defined Contribution Plan The Company maintains a defined contribution plan for its Canadian employees. Participants may contribute a percentage of their annual compensation to this plan, subject to statutory limitations. The Company contributes up to the first 4% of eligible compensation for its Canadian-based employees to the retirement plan. The Company contributed a de minimis amount for each of the three years ended December 31, 2021, 2020 and 2019, respectively.

INCOME TAXES

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

INCOME TAXES

The following table sets forth the components of the Company's loss before income taxes by country (in thousands):


	Year Ended December 31,
	2021		2020		2019
Country
United States	$	(32,757)	$	(35,529)	$	(27,468)
Canada	24,148		14,577		(80,032)
Total Loss Before Income Taxes	$	(8,609)	$	(20,952)	$	(107,500)

The Company's tax benefit (provision) is comprised of the following components (in thousands):


	Year Ended December 31,
	2021		2020		2019
Current Tax Provision
Federal	$	—	$	—	$	—
State	—		—		—
Foreign	(286)		(1,445)		—
Total current (provision)	$	(286)	$	(1,445)	$	—
Deferred tax provision
Federal	$	—	$	—	$	—
State	—		—		—
Foreign	8,559		—		—
Total deferred benefit (provision)	$	8,559	$	—	$	—

Total Tax Benefit (Provision)	$	8,273	$	(1,445)	$	—

The Company did not record current or deferred income tax or benefit for the year ended December 31, 2019.

The following table sets forth a reconciliation of the statutory United States federal income tax rate to the Company’s effective income tax rate:


	Year ended December 31,
	2021		2020		2019
United States federal statutory income tax rate	21.0	%	21.0	%	21.0	%
Impact of foreign rate differential	(15.9)		(4.2)		4.4
State taxes, net of federal benefit	2.3		2.0		0.6
Stock option cancellations	(1.1)		(0.2)		—
Contingent consideration	178.2		14.4		(18.0)
General business credits and other credits	2.4		6.6		0.4
Permanent differences	(1.4)		0.2		—
Other	(13.8)		(2.1)		(0.5)
Foreign taxes	(3.3)		(6.9)		—
Change in valuation allowance	(72.3)		(37.7)		(7.9)
Effective Income Tax Rate	96.1	%	(6.9)	%	—	%

The following table sets forth the tax effects of temporary differences that gave rise to significant portions of the Company's deferred tax assets and liabilities (in thousands):


	December 31,
	2021		2020		2019
Deferred tax assets:
NOL carryforwards	$	63,381	$	57,935	$	50,727
R&D credit carryforwards	4,316		3,787		4,385
Accruals and other	4,058		3,811		2,464
Capitalized start-up costs	53		70		91
Other	41		28		57
Gross deferred tax assets	71,849		65,631		57,724
Deferred tax liabilities:
IPR&D	(3,969)		(12,528)		(12,528)

Gross deferred tax liabilities	(3,969)		(12,528)		(12,528)
Valuation allowance	(71,849)		(65,631)		(57,724)
Net Deferred Tax Liability	$	(3,969)	$	(12,528)	$	(12,528)

In assessing the realizability of the Company's deferred tax assets, management considers all relevant positive and negative evidence in determining whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The realization of deferred tax assets is dependent on several factors, including the generation of sufficient taxable income prior to the expiration of the NOL and R&D credit carryforwards. The Company has generated NOLs since its inception, and management believes that it is more likely than not that the Company's deferred tax assets will not be realized. As a result, valuation allowances of $71.8 million, $65.6 million and $57.7 million have been established as of December 31, 2021, 2020 and 2019, respectively. The $6.2 million increase in the valuation allowance was attributable to the NOL for the year ended December 31, 2021.

The net deferred tax liability of $4.0 million primarily relates to the potential future impairments or amortization associated with IPR&D intangible assets, which is not deductible for tax purposes and cannot be considered as a source of income to realize deferred tax assets. As a result, the Company recorded the deferred tax liability with an offset to goodwill.

The following table summarizes the Company's NOL and R&D and other credit carryforwards in the United States and Canada as of December 31, 2021 (in millions):


	Amount		Expiration Beginning in	Through
United States:
Federal NOL carryforwards - indefinite	$	101.1	None	None
Federal NOL carryforwards	$	118.9	2030	2038
State NOL carryforwards	$	138.4	2030	2040
Federal R&D credit carryforwards	$	2.5	2027	2040
State R&D credit carryforwards	$	0.8	2027	2040
Canada:
Federal non-capital loss carryforwards	$	31.2	2035	2040
Federal scientific research and experimental development expense carryforwards	$	5.1	2032	2040
Federal and provincial investment tax credit carryforwards	$	1.2	2032	2040

Under the Tax Reform Act of 1986 (the "Act'), NOL and R&D credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service, and there are similar provisions in certain state and non-US tax laws. NOL and R&D credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interests of significant shareholders over a three-year period in excess of 50 percent, as defined in Sections 382 and 383 of the Internal Revenue Code, respectively. This could limit the amount of tax attributes that can be utilized to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. Management completed a Section 382 study through March 31, 2016 and determined that it is more likely than not that the Company's NOL carryforwards are subject to a material limitation. Accordingly, the Company reduced its NOL carryforward by $0.8 million. The Company has continued to raise additional equity capital since March 2016 but has not done any additional analysis to determine whether or not ownership changes, as defined in the Act, have occurred, which would result in additional limitations. There could be additional ownership changes in the future that could further limit the amount of NOL carryforwards that the Company can utilize. The Company has not yet conducted a study of its R&D credit carryforwards. Such a study may result in an adjustment to the Company’s R&D credit carryforwards; however, until a study is completed and any adjustment is known, no amount is being presented as an uncertain tax position. A full valuation allowance has been provided against the Company’s R&D credit carryforwards, and, if an adjustment is required, it would be offset by an adjustment to the valuation allowance.

We assess the impact of various tax reform proposals and modifications to existing tax treaties in all jurisdictions where we have operations to determine the potential effect on our business and any assumptions we have made about our future taxable income. We cannot predict whether any specific proposals will be enacted, the terms of any such proposals or what effect, if any, such proposals would have on our business if they were to be enacted. Beginning in 2022, the Tax Cuts and Jobs Act of 2017 eliminates the currently available option to deduct research and development expenditures and requires taxpayers to amortize them over five years. The U.S. Congress is considering legislation that would defer the amortization requirement to future periods, however, we have no assurance that the provision will be repealed or otherwise modified.

As of December 31, 2021, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company's consolidated statements of operations. Due to NOL and R&D credit carryforwards that remain unutilized, income tax returns filed in the United States, certain states within the United States and Canadian tax jurisdictions from the Company's inception through 2020 remain subject to examination by the taxing jurisdictions. There are currently no audits in process in any of the Company's tax filing jurisdictions.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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-Subparagraph (SX 210.4-08(h)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

LICENSE AGREEMENTS	12 Months Ended
LICENSE AGREEMENTS	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
LICENSE AGREEMENTS	LICENSE AGREEMENTS In-License Agreements License Agreement with Zurich The Company has a license agreement with the University of Zurich ("Zurich") which grants the Company exclusive license rights, with the right to sublicense, to make, have made, use and sell under certain patents primarily directed to the Company's targeting agent, including an EpCAM chimera and related immunoconjugates and methods of use and manufacture of the same (the “Zurich License Agreement”). These patents cover some key aspects of Vicineum. Upon the Company's receipt of the CRL regarding the BLA for Vicineum for the treatment of BCG-unresponsive NMIBC, the Company became obligated to pay $0.5 million in a milestone payment to Zurich. The Company is also obligated to pay up to a 4% royalty on the net product sales for products covered by or manufactured using a method covered by a valid claim in the Zurich patent rights. Royalties owed to Zurich will be reduced if the total royalty rate owed by the Company to Zurich and any other third party is 10% or greater, provided that the royalty rate to Zurich may not be less than 2% of net sales. The obligation to pay royalties in a particular country expires upon the expiration or termination of the last of the Zurich patent rights that covers the manufacture, use or sale of a product. There is no obligation to pay royalties in a country if there is no valid claim that covers the product or a method of manufacturing the product. The Company recorded an expense of $0.5 million and $0.3 million related to achievement of a development milestone, (the submission of the Company’s BLA with the FDA in December 2020), in the year ended December 31, 2021 and 2020, respectively, and a regulatory milestone, (the Company’s receipt of the CRL from the FDA in August 2021), in the twelve months ended December 31, 2021, respectively. License Agreement with Micromet The Company has a License Agreement with Micromet AG ("Micromet"), now part of Amgen, Inc., which grants it nonexclusive rights, with certain sublicense rights, for know-how and patents allowing exploitation of certain single chain antibody products (the “Micromet License Agreement”). These patents cover some key aspects of Vicineum. Under the terms of the Micromet License Agreement, as of December 31, 2021, the Company may be obligated to pay up to €2.4 million in milestone payments for the first product candidate that achieves applicable regulatory and sales-based development milestones (approximately $2.7 million at exchange rates in effect on December 31, 2021). The Company is also required to pay up to a 3.5% royalty on the net sales for products covered by the agreement, which includes Vicineum. The royalty rate owed to Micromet in a particular country will be reduced to 1.5% if there are no valid claims covering the product in that country. The obligation to pay royalties in a particular country expires upon the later of the expiration date of the last valid claim covering the product and the tenth anniversary of the first commercial sale of the product in such country. Finally, the Company is required to pay to Micromet an annual license maintenance fee of €50,000 (approximately $56,625 at exchange rates in effect as of December 31, 2021), which can be credited towards any royalty payment the Company owes to Micromet. The Company recorded an expense of €0.7 million ($0.9 million) related to achievement of a development milestone in the three months ended December 31, 2020, due to the submission of the Company's BLA for Vicineum with the FDA in December 2020. The Company recorded an expense of €0.5 million ($0.6 million) related to the submission of the MAA to the EMA for Vysyneum™ in the first quarter of 2021. Vysyneum is the proprietary brand name that was conditionally approved by the EMA for oportuzumab monatox in the European Union. License Agreement with XOMA The Company has a license agreement with XOMA Ireland Limited ("XOMA") which grants it non-exclusive rights to certain XOMA patent rights and know-how related to certain expression technology, including plasmids, expression strains, plasmid maps and production systems (the “XOMA License Agreement”). These patents and related know-how cover some key aspects of Vicineum. Under the terms of the XOMA License Agreement, the Company is required to pay up to $0.25 million in milestone payments for a product candidate that incorporates know-how under the license and achieves applicable clinical development milestones. Based on current clinical status, the Company anticipates that these milestones may be triggered by Vicineum’s clinical development pathway. The Company is also required to pay a 2.5% royalty on the net sales for products incorporating XOMA’s technology, which includes Vicineum. The Company has the right to reduce the amount of royalties owed to XOMA on a country-by-country basis by the amount of royalties paid to other third parties, provided that the royalty rate to XOMA may not be less than 1.75% of net sales. In addition, the foregoing royalty rates are reduced by 50% with respect to products that are not covered by a valid patent claim in the country of sale. The obligation to pay royalties in a particular country expires upon the later of the expiration date of the last valid claim covering the product and the tenth anniversary of the first commercial sale of the product in such country. Out-License Agreements Roche License Agreement In June 2016, the Company entered into the license agreement with Roche (the “Roche License Agreement”), pursuant to which the Company granted Roche an exclusive, worldwide license, including the right to sublicense, to its patent rights and know-how related to the Company’s monoclonal antibody EBI-031 and all other IL-6 anti-IL-6 antagonist monoclonal antibody technology owned by the Company (collectively, the "Roche Licensed Intellectual Property"). Under the Roche License Agreement, Roche is required to continue developing, at its cost, EBI-031 and any other product made from the Roche Licensed Intellectual Property that contains an IL-6 antagonist anti-IL monoclonal antibody (“Roche Licensed Product”) and pursue ongoing patent prosecution, at its cost. Financial Terms The Company received from Roche an upfront license fee of $7.5 million in August 2016 upon the effectiveness of the Roche License Agreement following approval by the Company's stockholders, and Roche agreed to pay up to an additional $262.5 million upon the achievement of specified regulatory, development and commercialization milestones with respect to up to two unrelated indications. Specifically, an aggregate amount of up to $197.5 million is payable to the Company for the achievement of specified milestones with respect to the first indication, consisting of (i) $72.5 million in development milestones, the next of which is $30 million for initiation of the first Phase III clinical trial, (ii) $50 million in regulatory milestones and (iii) $75 million in commercialization milestones. Additional amounts of up to $65 million are payable upon the achievement of specified development and regulatory milestones in a second indication. In September 2016, Roche paid the Company the first development milestone of $22.5 million as a result of the Investigational New Drug application for EBI-031 becoming effective on or before September 15, 2016. In December 2021, a $20 million milestone was achieved due to Roche initiating a Phase II clinical trial. Management evaluated the milestone under ASC 606 and determined it is probable that a significant revenue reversal will not occur in future periods, which was not the case in the previous quarter. Accordingly, the Company invoiced Roche $20 million with payment terms of 30 days following the achievement of the corresponding milestone event, pursuant to the Roche License Agreement and $20 million was recorded as license revenue and accounts receivables in the fourth quarter of 2021. In January 2022, the payment of $20 million was received. In addition, the Company is entitled to receive royalty payments in accordance with a tiered royalty rate scale, with rates ranging from 7.5% to 15% of net sales of potential future products containing EBI-031 and up to 50% of these rates for net sales of potential future products containing other IL-6 compounds, with each of the royalties subject to reduction under certain circumstances and to the buy-out options of Roche. Buy-Out Options The Roche License Agreement provides for two “option periods” during which Roche may elect to make a one-time payment to the Company and, in turn, terminate its diligence, milestone and royalty payment obligations under the Roche License Agreement. Specifically, (i) Roche may exercise a buy-out option following the first dosing (“Initiation”) in the first Phase 2 study for a Roche Licensed Product until the day before Initiation of the first Phase 3 study for a Roche Licensed Product, in which case Roche is required to pay the Company $135 million within 30 days after Roche's exercise of such buy-out option and receipt of an invoice from the Company, or (ii) Roche may exercise a buy-out option following the day after Initiation of the first Phase 3 study for a Roche Licensed Product until the day before the acceptance for review by the FDA or other regulatory authority of a BLA or similar application for marketing approval for a Roche Licensed Product in either the United States or in the EU, in which case Roche is required to pay the Company, within 30 days after Roche’s exercise of such buy-out option and receipt of an invoice from the Company, $265 million, which amount would be reduced to $220 million if none of the Company’s patent rights containing a composition of matter claim covering any compound or Roche Licensed Product has issued in the EU. Termination Either the Company or Roche may each terminate the Roche License Agreement if the other party breaches any of its material obligations under the agreement and does not cure such breach within a specified cure period. Roche may terminate the Roche License Agreement following effectiveness by providing advance written notice to the Company or by providing written notice if the Company is debarred, disqualified, suspended, excluded, or otherwise declared ineligible from certain federal or state agencies or programs. The Company may terminate the Roche License Agreement if, prior to the first filing of a BLA for a Roche Licensed Product, there is a period of twelve months where Roche is not conducting sufficient development activities with respect to the products made from the Roche Licensed Intellectual Property. OUS Business Development Partnership Agreements Qilu License Agreement On July 30, 2020, the Company and its a wholly-owned subsidiary, Viventia Bio, Inc., entered into an exclusive license agreement with Qilu (the “Qilu License Agreement”) pursuant to which the Company granted Qilu an exclusive, sublicensable, royalty-bearing license, under certain intellectual property owned or exclusively licensed by the Company, to develop, manufacture and commercialize Vicineum (the “Qilu Licensed Product”) for the treatment of NMIBC and other types of cancer (the “Field”) in China, Hong Kong, Macau and Taiwan ("Greater China”). The Company also granted Qilu a non-exclusive, sublicensable, royalty-bearing sublicense, under certain other intellectual property licensed by the Company to develop, manufacture and commercialize the Qilu Licensed Product in Greater China. The Company retains (i) development, and commercialization rights in the rest of the world excluding Greater China, the Middle East and North Africa region ("MENA”) and Turkey and (ii) manufacturing rights with respect to Vicineum in the rest of the world excluding China. In consideration for the rights granted by the Company, Qilu agreed to pay to the Company a one-time upfront cash payment of $12 million, and milestone payments totaling up to $23 million upon the achievement of certain technology transfer, development and regulatory milestones. All payments were to be inclusive of value-added tax ("VAT"), which can be withheld by Qilu upon payment, and for which future recovery of such taxes may be available. Qilu also agreed to pay the Company a 12% royalty based upon annual net sales of Qilu Licensed Products in Greater China. The royalties are payable on a Qilu Licensed Product-by-Licensed Product and region-by-region basis commencing on the first commercial sale of a Licensed Product in a region and continuing until the latest of (i) twelve years after the first commercial sale of such Qilu Licensed Product in such region, (ii) the expiration of the last valid patent claim covering or claiming the composition of matter, method of treatment, or method of manufacture of such Qilu Licensed Product in such region, and (iii) the expiration of regulatory or data exclusivity for such Qilu Licensed Product in such region (collectively, the “Royalty Terms”). The royalty rate is subject to reduction under certain circumstances, including when there is no valid claim of a licensed patent that covers a Qilu Licensed Product in a particular region or no data or regulatory exclusivity of a Qilu Licensed Product in a particular region. Qilu is responsible for all costs related to developing, obtaining regulatory approval of and commercializing the Qilu Licensed Products in the Field in Greater China. Qilu is required to use commercially reasonable efforts to develop, seek regulatory approval for, and commercialize at least one Qilu Licensed Product in the Field in Greater China. A joint development committee was established between the Company and Qilu to coordinate and review the development, manufacturing and commercialization plans with respect to the Qilu Licensed Products in Greater China. The Company and Qilu also executed the terms and conditions of a supply agreement and related quality agreement pursuant to which the Company will manufacture or have manufactured and supply Qilu with all quantities of the Qilu Licensed Product necessary for Qilu to develop and commercialize the Qilu Licensed Product in the Field in Greater China until the Company has completed manufacturing technology transfer to Qilu and approval of a Qilu manufactured product by the National Medical Products Administration in China ("NMPA") for the Qilu Licensed Product has been obtained. The Qilu License Agreement will expire on a Qilu Licensed Product-by-Licensed Product and region-by-region basis on the date of the expiration of all applicable Royalty Terms. Either party may terminate the Qilu License Agreement for the other party’s material breach following a cure period or upon certain insolvency events. Qilu has the right to receive a refund of all amounts paid to the Company in the event the Qilu License Agreement is terminated under certain circumstances. The Qilu License Agreement includes customary representations and warranties, covenants and indemnification obligations for a transaction of this nature. The Qilu License Agreement is subject to the provisions of Accounting Standards Codification 606, Revenue from Contracts with Customers ("ASC 606"), which was adopted effective January 1, 2018. In 2020, the initial transaction price was estimated to be $11.2 million and was based on the up-front fixed consideration of $12 million less amounts withheld for VAT. The Company concluded that its agreements under the Qilu License Agreement represented one bundled performance obligation that had been achieved as of September 30, 2020. As such, $11.2 million of the total $11.2 million transaction price was considered earned and the Company recorded $11.2 million of revenue during the three-month period ended September 30, 2020. The Investigational New Drug application for Vicineum submitted by Qilu to the Center for Drug Evaluation of the NMPA was accepted for review in January 2021 and approved in March 2021, resulting in a $3 million milestone payment from Qilu, the first milestone payment out of the $23 million in potential milestone payments. The Company recorded $2.8 million (net of VAT) as license revenue during the three-month period ended March 31, 2021. The Company received the payment in 2021. In June 2021, the Qilu License Agreement was recognized by Shandong Province, Bureau of Science and Technology as a "Technology Transfer". An agreement that is designated as a Technology Transfer shall be entitled to a tax incentive of VAT recovery. As such, the Company recorded $0.9 million of revenue during the three months ended June 30, 2021 for additional purchase price resulting from Qilu's obligation to pay Sesen an amount equal to its recovery of VAT. The Company will not be subject to VAT on future potential milestone payments from Qilu. MENA License Agreement On November 30, 2020, the Company entered into a license agreement with a third party pursuant to which the Company granted an exclusive, sublicensable, royalty-bearing license, under certain intellectual property owned or exclusively licensed by the Company, to commercialize Vicineum in the MENA region, ("MENA License Agreement"). The Company retains development and commercialization rights in the rest of the world excluding Greater China, Turkey and MENA. In consideration for the rights granted by the Company, the counterparty to the MENA License Agreement agreed to pay to the Company an upfront payment of $3 million, which would be subject to certain tax withholdings. In addition, the counterparty agreed to pay to the Company milestone payments upon the achievement of certain sales-based milestones as well as a royalty based upon annual net sales in the MENA region for the term of the MENA License Agreement. The MENA License Agreement is subject to the provisions of ASC 606. The initial transaction price was estimated by management as $1.5 million as of December 31, 2020 and was based on 50% of the upfront payment, or the amount not subject to a refund if certain regulatory approvals in MENA are not obtained. The remaining upfront payment ($1.5 million) is subject to a refund if certain regulatory approvals in MENA are not obtained and recorded as long-term deferred revenue as of December 31, 2021. The Company also concluded that its agreements under the MENA License Agreement represented two distinct performance obligations, the first of which is a bundled performance obligation related to the delivery of the license, associated know-how and certain documentation. The second performance obligation relates to the delivery of manufactured product. The first performance obligation (delivery of the license, associated know-how and certain documentation) was achieved during the quarter ended March 31, 2021; as such, revenue of $1.5 million has been recognized. Additional variable consideration, determined to be allocated entirely to the bundled license performance obligation, to be paid to the Company based upon future sales levels will be recognized as revenue when the underlying sales of the licensed product occurs. In addition, variable consideration related to any future delivery of product will be recognized in future periods as the product is delivered. As of December 31, 2021, none of these additional amounts were reasonably certain to be achieved due to the nature and timing of the underlying activities. EIP License Agreement On August 5, 2021, the Company entered into an exclusive license agreement with EİP Eczacıbaşı İlaç Pazarlama A.Ş., (“EIP”) pursuant to which it granted EIP an exclusive license to register and commercialize Vicineum for the treatment of BCG-unresponsive NMIBC in Turkey and Northern Cyprus (the “EIP License Agreement). Under the terms of the License Agreement, the Company is entitled to receive an upfront payment of $1.5 million. The Company is in the process of amending the license agreement to defer payment of the upfront payment to coincide with the potential FDA approval of Vicineum. The Company is eligible to receive additional regulatory and commercial milestone payments of $2.0 million and is also entitled to receive a 30% royalty on net sales in Turkey and Northern Cyprus. The EIP License Agreement is subject to the provisions of ASC 606 and as of December 31, 2021, none of these amounts have been received by the Company. No initial transaction price was estimated by management as of December 31, 2021, as the upfront payment is subject to a refund if certain regulatory approvals in the US are not obtained. The Company also concluded that its promises under the EIP License Agreement represented two distinct performance obligations, the first of which is a bundled performance obligation related to the delivery of the license and associated know-how. The second performance obligation relates to the delivery of manufactured product. Additional variable consideration, determined to be allocated entirely to the bundled license performance obligation, to be paid to the Company based upon future regulatory milestones will be recognized as achievement of those milestones. In addition, variable consideration related to any future delivery of product will be recognized in future periods as the product is delivered. As of December 31, 2021, none of these additional amounts were reasonably certain to be achieved due to the nature and timing of the underlying activities.

RELATED-PARTY TRANSACTIONS	12 Months Ended
RELATED-PARTY TRANSACTIONS	Dec. 31, 2021
Related Party Transactions [Abstract]
RELATED-PARTY TRANSACTIONS	RELATED-PARTY TRANSACTIONS The Company leases its facility in Winnipeg, Manitoba from an affiliate of Leslie L. Dan, a director of the Company until his retirement in July 2019. For each of the years ended December 31, 2021, 2020 and 2019, the Company paid $0.3 million of rent, which includes the related operating expenses. The Company pays fees under an intellectual property license agreement to Protoden Technologies Inc. ("Protoden"), a company owned by Clairmark, an affiliate of Mr. Dan. Pursuant to the agreement, the Company has an exclusive, perpetual, irrevocable and non-royalty bearing license, with the right to sublicense, to certain patents and technology to make, use and sell products that utilize such patents and technology. The annual fee is $0.1 million. Upon expiration of the term on December 31, 2024, the licenses granted to the Company will require no further payments to Protoden. For each of the years ended December 31, 2021, 2020 and 2019, the Company paid $0.1 million under this license agreement. Due to his retirement in July 2019, Mr. Dan was not deemed a related party during the twelve-month period ended December 31, 2020 and 2021; as such, only payments made through the nine month period ended September 30, 2019 are considered payments to a related party.

RESTRUCTURING AND RELATED ACTIVITIES

12 Months Ended

Dec. 31, 2021

Restructuring and Related Activities [Abstract]

RESTRUCTURING AND RELATED ACTIVITIES

On August 30, 2021, the Company approved a restructuring plan to reduce operating expenses and better align its workforce with the needs of its business following receipt of the CRL from the FDA regarding the BLA for Vicineum for the treatment of BCG-unresponsive NMIBC (the “Restructuring Plan”).

The Restructuring Plan included a reduction in the Company’s workforce by 18 positions (or approximately 35% of the Company’s workforce as of the date of the Restructuring Plan), as well as additional cost-saving initiatives intended to preserve capital while the Company continues development of Vicineum. The following is a summary of accrued restructuring costs related to the Restructuring Plan:


	December 31, 2021
	(in thousands)
Severance and benefits costs	$	2,792
Contract termination costs	2,736
Other restructuring costs	—
Total restructuring costs	$	5,528
Cash payments	(4,031)
Balance at December 31, 2021	$	1,497

Restructuring costs related to the Restructuring Plan were recorded in operating expenses in the Company’s Consolidated Statements of Operations and Comprehensive Loss in the year ended December 31, 2021. The Company expects that substantially all of the accrued restructuring costs as of December 31, 2021 will be paid in cash by the end of September 2022.

SUBSEQUENT EVENTS	12 Months Ended
SUBSEQUENT EVENTS	Dec. 31, 2021
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS On January 7, 2022, the FDA granted the Company’s request for a Type C Meeting (“Type C Meeting”) to discuss the study protocol for an additional Phase 3 clinical trial that the Company plans to conduct for potential resubmission of a BLA for Vicineum™ for the treatment of BCG-unresponsive NMIBC. The Type C Meeting has been scheduled for March 28, 2022. On January 24, 2022, the Company received written notice (the “Notice”) from Nasdaq indicating that the Company is not in compliance with the $1.00 minimum bid price requirement for continued listing on The Nasdaq Global Market, as set forth in Nasdaq Listing Rule 5450(a)(1). The Notice has no effect at this time on the listing of the Company’s common stock (the “Common Stock”), which continues to trade on The Nasdaq Global Market under the symbol “SESN”. In accordance with Nasdaq Listing Rule 5810(c)(3)(A), the Company has a period of 180 calendar days, or until July 25, 2022, to regain compliance with the minimum bid price requirement. To regain compliance, the closing bid price of the Company’s Common Stock must meet or exceed $1.00 per share for a minimum of ten consecutive business days during this 180-day period. If the Company is not in compliance by July 25, 2022, the Company may qualify for a second 180 calendar day compliance period. If the Company does not qualify for, or fail to regain, compliance during the second compliance period, then Nasdaq will notify the Company of its determination to delist the Company’s common stock, at which point the Company would have an opportunity to appeal the delisting determination to a Nasdaq hearings panel. The Company intends to actively monitor the closing bid price of the Company’s common stock and may, if appropriate, consider implementing available options to regain compliance with the minimum bid price requirement under the Nasdaq Listing Rules. As previously announced, the Company’s Board of Directors (the “Board”) initiated an independent internal review conducted by outside counsel with the assistance of subject matter experts focusing on the conduct of, and data generated from, the clinical trials of Vicineum for the treatment of BCG-unresponsive NMIBC, and the overall safety of Vicineum (the “Review”). The Review took place over the course of five months, involved full cooperation from the Company’s management team, a review of more than 600,000 documents, and 39 interviews of current and former employees and consultants. It is now complete. As a result of the Review, the Board continues to fully support the Company’s current management team and believes no changes or amendments relating to the Company’s prior disclosures to the SEC or the FDA relating to Vicineum, the Phase 3 VISTA trial for Vicineum for the treatment of BCG-unresponsive NMIBC, or the BLA for Vicineum are warranted. The Company intends to work cooperatively with the FDA in preparing for an additional Phase 3 clinical trial for Vicineum.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Dec. 31, 2021
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in accordance with GAAP and the rules and regulations of the SEC requires the use of estimates and assumptions, based on judgments considered reasonable, which affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The Company bases its estimates and assumptions on historical experience, known trends and events and various other factors that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Although management believes its estimates and assumptions are reasonable when made, they are based upon information available at the time they are made. Management evaluates the estimates and assumptions on an ongoing basis and, if necessary, makes adjustments. Due to the risks and uncertainties involved in the Company’s business and evolving market conditions, and given the subjective element of the estimates and assumptions made, actual results may differ from estimated results. The most significant estimates and judgments impact the fair value of intangible assets, goodwill and contingent consideration; income taxes (including the valuation allowance for deferred tax assets); research and development expenses; and going concern considerations.
Principles of Consolidation	Principles of Consolidation The Company’s consolidated financial statements include the accounts of the Company, its wholly owned subsidiary Viventia and its indirect subsidiaries, Viventia Bio USA Inc. and Viventia Biotech (EU) Limited. All intercompany transactions and balances have been eliminated in consolidation.
Foreign Currency Translation	Foreign Currency Translation The functional currency of the Company and each of its subsidiaries is the US dollar.
Cash, Cash Equivalents, Restricted Cash and Concentration of Credit Risk	Cash, Cash Equivalents, Restricted Cash and Concentration of Credit RiskThe Company's cash is held on deposit in demand accounts at a large financial institution in amounts in excess of the Federal Deposit Insurance Corporation ("FDIC") insurance coverage limit of $250,000 per depositor, per FDIC-insured bank, per ownership category. Restricted cash represents cash held by the Company's primary commercial bank to collateralize a letter of credit issued related to a license agreement and the credit limit on the Company's corporate credit card, and are classified as short term and long term, respectively. The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Financial instruments that potentially subject the Company to credit risk principally consists of cash equivalents and accounts receivable. As of December 31, 2021 and 2020, the Company limited its credit risk associated with cash equivalents by placing investments in highly-rated money market funds.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost. Maintenance and repairs are charged to expense as incurred, and costs of improvements and renewals are capitalized. Depreciation is recognized using the straight-line method over the estimated useful lives of the relative assets. The Company uses an estimated useful life of five years for lab equipment, four years for furniture and fixtures, three years for computer equipment and software and the lesser of five years or the remaining lease term for leasehold improvements.
Indefinite-Lived Intangible Assets	Indefinite-Lived Intangible Assets The Company’s intangible assets consist of indefinite-lived, acquired in-process research and development ("IPR&D") worldwide product rights to Vicineum as a result of the acquisition of Viventia in 2016. IPR&D assets acquired in a business combination are considered indefinite-lived until the completion or abandonment of the associated research and development efforts. Amortization over the estimated useful life will commence at the time of Vicineum's commercial launch in the respective markets, if approved. If regulatory approval to market Vicineum for the treatment of BCG-unresponsive NMIBC is not obtained, the Company will immediately expense the related capitalized cost. Indefinite-lived intangible assets are quantitatively tested for impairment at least annually during the fourth quarter of the fiscal year, or more often if indicators of impairment are present. Impairment testing of indefinite-lived intangible assets requires management to estimate the future discounted cash flows of an asset using assumptions believed to be reasonable, but which are unpredictable and inherently uncertain. Actual future cash flows may differ from the estimates used in impairment testing. The Company recognizes an impairment loss when and to the extent that the estimated fair value of an intangible asset is less than its carrying value. In addition, on a quarterly basis, the Company performs a qualitative review of its business operations to determine whether events or changes in circumstances have occurred which could indicate that the carrying value of its intangible assets was not recoverable. If an impairment indicator is identified, an interim impairment assessment is performed. In August 2021, the Company received a CRL from the FDA regarding its BLA for Vicineum for the treatment of NMIBC, its lead product candidate. In the CRL, the FDA determined that it could not approve the BLA for Vicineum in its present form and provided recommendations specific to additional clinical/statistical data and analyses in addition to CMC issues pertaining to a recent pre-approval inspection and product quality. Given the inherent uncertainty in the development plans for Vicineum (and Vysyneum in the EMA) as a result of the CRL and the withdrawal of the Company's marketing authorization application (“MAA”), an interim impairment analysis was conducted in the third quarter of 2021, which concluded that the carrying value of the Company’s intangible asset of Vicineum US rights was fully impaired as of September 30, 2021. The $31.7 million of impairment charges were due to delays in the expected start of commercialization and lower probabilities of success, combined with higher operating expenses expected to be incurred prior to commercialization, resulting in lower expected future cash flows estimated in the US market. However, while similar delays in timelines and reduced probabilities of success also affected the estimated fair value of the Company's intangible asset of Vicineum EU rights, this asset was not impaired as of September 30, 2021. At that time, management assessed that the carrying value of the Vicineum EU rights is not at significant risk of impairment in the future within the current range of commercialization timelines and probability of clinical and regulatory success (“POS”) assumptions. This is primarily due to the fact that the Company expects the Vicineum sales outside of the US to be two to three times the expected sales volume in the US, based on management’s reassessment of the total addressable global market for high-risk NMIBC during the quarter ended June 30, 2019, wherein management determined that both the global market size and the estimated potential Vicineum commercial sales within the global market were likely higher than the Company's previous estimate. In addition, the EU asset is burdened with significantly less expense than the US asset, as the Company’s strategic operating plan is to sublicense Vicineum to business development partners in all regions outside the US, including the EU, with it earning a potential combination of upfront, milestone, and royalty payments, and the business development partner bearing the majority of regulatory and commercialization costs. The Company participated in Type A Meetings with the FDA on October 29, 2021 and December 8, 2021 to discuss questions related to CMC and clinical issues raised in the CRL. Both meetings helped the Company determine the appropriate path forward for Vicineum. Based upon the outcome of these meetings, the Company plans to conduct an additional Phase 3 clinical trial. Also, during the Clinical Type A Meeting, the Company aligned with FDA to include patients with less than adequate BCG into its new clinical trial. The Company performed the annual impairment test, which incorporated the impact of the CRL and the subsequent Type A Meetings in the fourth quarter of 2021 and concluded that the carrying value of the Company's intangible asset of Vicineum EU rights was not impaired as of December 31, 2021.
Goodwill	Goodwill Goodwill on the Company's consolidated balance sheets is the result of the Company’s acquisition of Viventia in September 2016 and represents the difference between the purchase price and the fair value of the identifiable tangible and intangible net assets acquired under the acquisition method of accounting. Goodwill is not amortized; rather than recording periodic amortization, goodwill is quantitatively tested for impairment at least annually during the fourth quarter of the fiscal year, or more often if indicators of impairment are present. Impairment testing of goodwill requires management to estimate the future discounted cash flows of a reporting unit using assumptions believed to be reasonable, but which are unpredictable and inherently uncertain. Actual future cash flows may differ from the estimates used in impairment testing. If the fair value of the equity of a reporting unit exceeds the reporting unit’s carrying value, including goodwill, then goodwill is considered not to be impaired. The Company recognizes a goodwill impairment when and to the extent that the fair value of the equity of a reporting unit is less than the reporting unit's carrying value, including goodwill. The Company has only one reporting unit. In addition, on a quarterly basis, the Company performs a qualitative review of its business operations to determine whether events or changes in circumstances have occurred which could have a material adverse effect on the estimated fair value of each reporting unit and thus indicate a potential impairment of the goodwill carrying value. If an impairment indicator is identified, an interim impairment assessment is performed. Given the inherent uncertainty in the development plans for Vicineum as a result of the CRL and the Company’s withdrawal of its MAA, an impairment analysis was conducted in the third quarter of 2021. While an impairment was recognized in one of the Company’s intangible assets, Vicineum US Rights, the Company concluded that the carrying value of its goodwill of $13.1 million was not impaired as of September 30, 2021. In October and December 2021, we participated in a CMC Type A Meeting and a Clinical Type A Meeting, respectively, with the FDA to discuss issues raised in the CRL and to discuss design elements of an additional Phase 3 clinical trial for Vicineum, which the FDA confirmed will be required for a potential resubmission of a BLA. Following these Type A Meetings, we believe we have greater clarity of the requirements for potential resubmission of a BLA. We have a Type C Meeting scheduled with the FDA for March 28, 2022, in which we expect to discuss the study protocol for the additional Phase 3 clinical trial that we plan to conduct for potential resubmission of our a BLA for Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG. The Company performed the annual impairment test, which incorporated the impact of the CRL and the subsequent Type A Meetings in the fourth quarter of 2021 and concluded that there was no goodwill impairment as of December 31, 2021. Management believes the Company has sufficient future cash flows from additional geographic regions outside the US to support the value of its goodwill. The Company projects future cash flows based on various timeline assumptions and applies a probability to each outcome based on management’s best estimate. In addition, probabilities of success in achieving certain clinical and regulatory success can also have a material effect on the estimated fair value of the equity of its reporting unit as of the impairment assessment date. The Company will continue to evaluate timelines for commercialization and probability of success of development of Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG. Based on the annual testing and quarterly reviews performed, the Company concluded that there was no goodwill impairment during the year ended December 31, 2020.
Contingent Consideration	Contingent Consideration The Company uses a discounted cash flow model to estimate the fair value of the contingent consideration liability each reporting period, which represents the present value of projected future cash flows associated with regulatory approval milestones and royalties on net sales due to the selling shareholders of Viventia Bio Inc. as a result of the Viventia Acquisition in September 2016. See "Note 1. Description of Business" for additional information. Contingent consideration is measured at its estimated fair value on a recurring basis at each reporting period, with fluctuations in value resulting in a non-cash charge to earnings (or loss) during the period. The estimated fair value measurement is based on significant unobservable inputs (Level 3 within the fair value hierarchy), including internally developed financial forecasts, probabilities of success and timing of certain milestone events and achievements, which are inherently uncertain. Actual future cash flows may differ from the assumptions used to estimate the fair value of contingent consideration. The valuation of contingent consideration requires the use of significant assumptions and judgments, which management believes are consistent with those that would be made by a market participant. Management reviews its assumptions and judgments on an ongoing basis as additional market and other data is obtained, and any future changes in the assumptions and judgments utilized by management may cause the estimated fair value of contingent consideration to fluctuate materially, resulting in earnings volatility. In October and December 2021, we participated in a CMC Type A Meeting and a Clinical Type A Meeting, respectively, with the FDA to discuss issues raised in the CRL and to discuss design elements of an additional Phase 3 clinical trial for Vicineum, which the FDA confirmed will be required for a potential resubmission of a BLA. Following these Type A Meetings, we believe we have greater clarity of the requirements for potential resubmission of a BLA. We have a Type C Meeting scheduled with the FDA for March 28, 2022, in which we expect to discuss the study protocol for the additional Phase 3 clinical trial that we plan to conduct for potential resubmission of our a BLA for Vicineum for the treatment of non-muscle invasive CIS of the bladder in patients previously treated with adequate or less than adequate BCG. The Company reassessed the underlying assumptions used to develop the revenue projections upon which the fair value of its contingent consideration is based. The most significant and impactful assumptions in the Company's revenue projection models are timing of product launch and probabilities of clinical and regulatory success ("POS"); the Company expects delays in the start of commercialization and estimates lower POS as a direct result of the CRL. The Company plans to conduct an additional clinical trial, which will lead to delays in the start of commercialization globally. The Company has assessed a range of commercialization timeline assumptions and applied a probability to each outcome based on management’s best estimate. In addition, the Company now assumes a lower POS in achieving certain clinical and regulatory milestones in the range of approximately 45% to 55% globally. Any changes in these assumptions and estimates, or other information obtained, may have a significant impact on the remeasurement of the contingent consideration liability in the future. The fair value of the Company’s contingent consideration is determined based on the present value of projected future cash flows associated with sales-based milestones and earnouts on net sales and is heavily dependent on discount rates to estimate the fair value at each reporting period. Earnouts are determined using an earnout rate of 2% on all commercial net sales of Vicineum through December 2033. The discount rate applied to the 2% earnout is derived from the Company’s estimated weighted-average cost of capital (“WACC”), which has fluctuated from 8.8% as of December 31, 2020, to 7.8% as of March 31, 2021, 6.8% as of June 30, 2021, 8.6% as of September 30, 2021, and 9.3% as of December 31, 2021. Milestone payments constitute debt-like obligations, and therefore a high-yield debt index rate is applied to the milestones in order to determine the estimated fair value. This index rate changed from 8.4% as of December 31, 2020, to 7.4% as of March 31, 2021, 6.6% as of June 30, 2021, 7.5% as of September 30, 2021, and 8.0% as of December 31, 2021.
Leases	Leases Effective January 1, 2019, the Company adopted ASC Topic 842, Leases (“ASC 842”) using the optional transition method outlined in ASU No. 2018-11, Leases (Topic 842), Targeted Improvements. The adoption of ASC 842 represents a change in accounting principle that aims to increase transparency and comparability among organizations by requiring the recognition of right-of-use assets and lease liabilities on the balance sheet for both operating and finance leases. In addition, the standard requires enhanced disclosures that meet the objective of enabling financial statement users to assess the amount, timing and uncertainty of cash flows arising from leases. The reported results for the year ended December 31, 2021, 2020 and 2019 reflect the application of ASC 842 guidance, while the reported results for priors were prepared in accordance with the previous ASC Topic 840, Leases ("ASC 840") guidance. The adoption of ASC 842 resulted in the recognition of operating lease right-of-use assets and corresponding lease liabilities of $0.2 million on the Company’s consolidated balance sheet as of January 1, 2019. The adoption of this guidance did not have a material impact on the Company’s financial condition, results of operations or cash flows; however, the adoption did result in significant changes to the Company’s financial statement disclosures. As part of the adoption of ASC 842, the Company utilized certain practical expedients outlined in the guidance. These practical expedients include: •Accounting policy election to use the short-term lease exception by asset class; •Election of the practical expedient package during transition, which includes: - An entity need not reassess whether any expired or existing contracts are or contain leases; - An entity need not reassess the classification for any expired or existing leases. As a result, all leases that were classified as operating leases in accordance with ASC 840 are classified as operating leases under ASC 842, and all leases that were classified as capital leases in accordance with ASC 840 are classified as finance leases under ASC 842; and - An entity need not reassess initial direct costs for any existing leases. The Company’s lease portfolio as of the adoption date and as of December 31, 2021 includes: a property lease for manufacturing, laboratory, warehouse and office space in Winnipeg, Manitoba, a property lease for its headquarters in Cambridge, MA, and a property lease for office space in Philadelphia, PA. The Company determines if an arrangement is a lease at the inception of the contract and has made a policy election to not separate out non-lease components from lease components, for all classes of underlying assets. The asset components of the Company’s operating leases are recorded as operating lease right-of-use assets and reported within other assets on the Company's consolidated balance sheet. The short-term and long-term liability components are recorded in other current liabilities and other liabilities, respectively, on the Company’s consolidated balance sheet. As of December 31, 2021, the Company did not have any finance leases. Right-of-use assets and operating lease liabilities are recognized based on the present value of lease payments over the lease term at the commencement date. Existing leases in the Company’s lease portfolio as of the adoption date were valued as of January 1, 2019. The Company uses an incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments, if an implicit rate of return is not provided with the lease contract. Operating lease right-of-use assets are adjusted for incentives received. Operating lease costs are recognized on a straight-line basis over the lease term, in accordance with ASC 842, and also include variable operating costs incurred during the period. Lease costs also include amounts related to short-term leases.
Research and Development Costs	Research and Development Costs Research and development activities are expensed in the period incurred. Research and development expenses consist of both internal and external costs associated with all basic research activities, clinical development activities and technical efforts required to develop a product candidate. Internal research and development consist primarily of personnel costs, including salaries, benefits and share-based compensation, facilities leases, research-related overhead, pre-approval regulatory and clinical trial costs, manufacturing and other contracted services, license fees and other external costs. In certain circumstances, the Company is required to make advance payments to vendors for goods or services that will be received in the future for use in research and development activities. In such circumstances, the advance payments are recorded as prepaid assets and expensed when the activity has been performed or when the goods have been received.
Stock-Based Compensation	Share-Based Compensation The Company recognizes the grant-date fair value of share-based awards granted as compensation as expense on a straight-line basis over the requisite service period, which is generally the vesting period of the award. To date, the Company has not issued awards where vesting is subject to market conditions. From time to time, the Company has granted to its executives' stock option awards which contain both performance-based and service-based vesting criteria. Performance milestone events are specific to the Company’s corporate goals, including certain clinical development objectives related to the new clinical trial, regulatory and financial objectives. Share-based compensation expense associated with performance-based vesting criteria is recognized using the accelerated attribution method if the performance condition is considered probable of achievement in management’s judgment. The fair value of stock options is estimated at the time of grant using the Black-Scholes option pricing model, which requires the use of inputs and assumptions such as the fair value of the underlying stock, exercise price of the option, expected term, risk-free interest rate, expected volatility and dividend yield. The fair value of each grant of options during the years ended December 31, 2021, 2020 and 2019 was determined using the following methods and assumptions: •Expected Term. Due to the lack of historical exercise data and given the plain vanilla nature of the options granted by the Company, the expected term is determined using the “simplified" method, as prescribed in SEC Staff Accounting Bulletin ("SAB") No. 107 ("SAB 107"), whereby the expected life equals the arithmetic average of the vesting term (generally four years) and the original contractual term (ten years) of the option, taking into consideration multiple vesting tranches. •Risk-Free Interest Rate. The risk-free rate is based on the interest rate payable on United States Treasury securities in effect at the time of grant for a period that is commensurate with the assumed expected term. •Expected Volatility. The expected volatility is based on historical volatilities of a representative group of publicly traded biopharmaceutical companies, including the Company's own volatility, which were commensurate with the assumed expected term, as prescribed in SAB 107. •Dividend Yield. The dividend yield is 0% because the Company has never declared or paid, and for the foreseeable future does not expect to declare or pay, a dividend on its common stock.
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and net operating loss ("NOL") and research and development credit ("R&D credit") carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in operations in the period that includes the enactment date. A valuation allowance is recorded to the extent it is more likely than not that some portion or all of the deferred tax assets will not be realized. Unrecognized income tax benefits represent income tax positions taken on income tax returns that have not been recognized in the financial statements. The Company recognizes the benefit of an income tax position only if it is more likely than not (greater than 50%) that the tax position will be sustained upon tax examination, based solely on the technical merits of the tax position. Otherwise, no benefit is recognized. The tax benefits recognized are measured based on the largest benefit that has a greater than 50% likelihood of being realized upon ultimate settlement. The Company recognizes accrued interest and penalties related to uncertain tax positions as income tax expense in its consolidated statements of operations. As of December 31, 2021 and 2020, the Company did not have any uncertain tax positions.
Revenue Recognition	Revenue Recognition The Company records revenue from out-license agreements and OUS business development partnership agreements, including the License Agreement with Roche and its OUS partnerships. Under each of these agreements, the Company granted the counterparty an exclusive license to develop and commercialize the underlying licensed product. These agreements contain up-front license fees, development and regulatory milestone payments, sales-based milestone payments, and sales-based royalty payments. The Company determines whether the out-license agreements and OUS business development partnership agreements are in scope of ASC 606, which it adopted as of January 1, 2018. Under ASC 606, in determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under these agreements, management performs the following steps: 1) Identification of the contract; 2) Determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; 3) Measurement of the transaction price, including the constraint on variable consideration; 4) Allocation of the transaction price to the performance obligations; and 5) Recognition of revenue when or as the Company satisfies each performance obligation. Development and Regulatory Milestones and Other Payments At the inception of an arrangement that includes development milestone payments, management evaluates whether the development milestones are considered probable of being reached and estimate the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated development milestone value is included in the transaction price. Development milestone payments that are not within the Company's control or the licensee's control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. For payments pursuant to sales milestones and royalty payments, the Company will not recognize revenue until the subsequent sale of a licensed product occurs. For arrangements with one than one performance obligations, the milestones are generally allocated entirely to the license performance obligation, as (1) the terms of milestone and royalty payments relate specifically to the license and (2) allocating milestones and royalties to the license performance obligation is consistent with the overall allocation objective, because management’s estimate of milestones and royalties approximates the standalone selling price of the license.
Recent Accounting Pronouncements	Adopted in 2021 In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes ("ASU 2019-12"). ASU 2019-12 simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The amendments in ASU 2019-12 also improve consistent application of and simplify GAAP for other areas of Topic 740 by clarifying and amending existing guidance. ASU 2019-12 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. Early adoption is permitted. The method with which the amendments in this ASU are to be applied varies depending on the nature of the tax item impacted by amendment. The Company adopted this guidance effective January 1, 2021, and it did not have a material impact on its financial position, results of operations or cash flows.
Fair Value Measurement	The carrying values of cash and cash equivalents, restricted cash, prepaid expenses and other current assets, and accounts payable on the Company’s consolidated balance sheets approximated their fair values as of December 31, 2021 and 2020 due to their short-term nature. Certain of the Company’s financial instruments are measured at fair value using a three-level hierarchy that prioritizes the inputs used to measure fair value. This fair value hierarchy prioritizes the use of observable inputs and minimizes the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows: Level 1: Inputs are quoted prices for identical instruments in active markets, Level 2: Inputs are quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; or model-derived valuations whose inputs are observable or whose significant value drivers are observable. Level 3: Inputs are unobservable and reflect the Company’s own assumptions, based on the best information available, including the Company’s own data.

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Summary of Carrying Amounts and Fair Values of Financial Instruments Measured

The following tables set forth the carrying amounts and fair values of the Company's financial instruments measured at fair value on a recurring basis as of December 31, 2021 and 2020 (in thousands):


	December 31, 2021
					Fair Value Measurement Based on
	Carrying Amount		Fair Value		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Money market funds (cash equivalents)	$	16,382	$	16,382	$	16,382	$	—	$	—
Liabilities:
Contingent consideration - short term	—		$	—	$	—	$	—	$	—
Contingent consideration - long term	$	52,000	$	52,000	$	—	$	—	$	52,000


	December 31, 2020
					Fair Value Measurement Based on
	Carrying Amount		Fair Value		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Money market funds (cash equivalents)	$	16,374	$	16,374	$	16,374	$	—	$	—
Liabilities:
Contingent consideration, current portion	8,985		$	8,985	$	—	$	—	$	8,985
Contingent consideration, net of current portion	$	99,855	$	99,855	$	—	$	—	$	99,855

Summary of Contingent Consideration Liability


Balance at December 31, 2020	$	108,840
Change in fair value included in loss	48,160
Balance at March 31, 2021	157,000
Change in fair value included in loss	13,600
Balance at June 30, 2021	170,600
Change in fair value included in loss	(114,000)
Balance at September 30, 2021	56,600
Change in fair value included in loss	(4,600)
Balance at December 31, 2021	$	52,000

Balance at December 31, 2021, current portion	$	—
Balance at December 31, 2021, net of current portion	$	52,000


Balance at December 31, 2020	$108,840
Change in fair value of contingent consideration - short term	(8,985)
Change in fair value of contingent consideration - long term	(47,855)
Balance at December 31, 2021	$	52,000

PROPERTY AND EQUIPMENT (Tables)

12 Months Ended

Dec. 31, 2021

Property, Plant and Equipment [Abstract]

Schedule of Composition of Property and Equipment

The following table sets forth the composition of property and equipment, net as of December 31, 2021 and 2020 (in thousands):


	December 31,
	2021		2020
Lab equipment	$	569	$	570
Furniture and fixtures	16		16
Computer equipment	99		97
Software	32		28
Leasehold improvements	293		293
Property and equipment, gross	1,009		1,004
Less: accumulated depreciation	(966)		(881)
Total Property and Equipment, Net	$	43	$	123

INTANGIBLES AND GOODWILL (Tables)

12 Months Ended

Dec. 31, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Composition of Intangible Assets

The following table sets forth the composition of intangible assets as of December 31, 2021 and 2020 (in thousands):


	December 31,
	2021		2020
IPR&D intangible assets:
Vicineum United States rights	$	—	$	31,700
Vicineum European Union rights	14,700		14,700
Total Intangibles	$	14,700	$	46,400

ACCRUED EXPENSES (Tables)

12 Months Ended

Dec. 31, 2021

Payables and Accruals [Abstract]

Components of Accrued Expenses

The following table sets forth the composition of accrued expenses as of December 31, 2021 and 2020 (in thousands):


	December 31,
	2021		2020
Research and development	$	1,841	$	1,372
Payroll-related expenses	2,967		1,892
Restructuring charge related	1,497		—
Professional fees	1,941		684
Other	9		25
Total Accrued Expenses	$	8,255	$	3,973

LEASES (Tables)

12 Months Ended

Dec. 31, 2021

Leases [Abstract]

Schedule of Lease Cost

The components of lease cost for the years ended December 31, 2021 and 2020 is as follows (in thousands):


	Year Ended December 31, 2021		Year Ended December 31, 2020
Lease Cost:
Operating lease (including related operating costs)	$	327	$	301
Short term property leases	262		261
Total lease costs	$	589	$	562


Supplemental Information:	Year Ended December 31, 2021		Year Ended December 31, 2020
Weighted-average remaining lease term (years)	0.75		1.75
Weighted-average discount rate - operating leases	12	%	12	%

Schedule of Future Minimum Lease Payments Under Non-Cancelable Operating Leases

The following table sets forth the Company's future minimum lease payments under non-cancelable leases as of December 31, 2021 (in thousands):


Minimum Lease Payments:	Year Ended December 31, 2021
Total future minimum lease payments (2022)	$	129
Less: Amounts representing present value adjustment	(5)
Operating lease liabilities, net of current portion	$	124

STOCKHOLDERS' EQUITY DEFICIT (Tables)

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Summary of Common Stock

In addition, the Company had reserved for issuance the following amounts of shares of its common stock for the purposes described below as of December 31, 2021 and 2020 (in thousands):


	December 31,
	2021	2020
Shares of common stock issued	199,464	140,450
Shares of common stock reserved for issuance for:
Warrants	199	2,247
Stock options	15,703	10,147
RSUs	3,041	—
Shares available for grant under 2014 Stock Incentive Plan	8,933	4,863
Shares available for sale under 2014 Employee Stock Purchase Plan	2,300	—
Total shares of common stock issued and reserved for issuance	229,640	157,707

Summary of Warrants Outstanding and Warrant Activity

The following table sets forth the Company's warrant activity for the year ended December 31, 2021 (in thousands):


Issued	Exercise Price	Expiration	December 31, 2020	Issued	(Exercised)	(Cancelled)	December 31, 2021
Jun-2019	$1.47	Jun-2020	—	—	—	—	—
Mar-2018	$0.55*	Mar-2023	1,705	—	(1,573)	—	132
Nov-2017	$0.55*	Nov-2022	487	—	(475)	—	12
May-2015	$11.83	Nov-2024	28	—	—	—	28
Nov-2014	$11.04	Nov-2024	27	—	—	—	27
			2,247	—	(2,048)	—	199

* Exercise price shown (i) reflects modification described below and (ii) subject to further adjustment based on down round provision added by amendment described below.

- Definition

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65888546&loc=d3e21300-112643

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
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+ Details

EARNINGS (LOSS) PER SHARE (Tables)

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Schedule of Potentially Dilutive Securities


	December 31,
	2021	2020	2019
Warrants	199	2,247	22,895
Stock options	15,703	10,147	6,236
Total	15,902	12,394	29,131

SHARE-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Schedule of Share-Based Compensation Expense


	Year ended December 31,
	2021		2020		2019
Research and development	$	973	$	350	$	188
General and administrative	4,170		1,407		1,049
Total Share Based Compensation	$	5,143	$	1,757	$	1,237

Schedule of the Status of Restricted Stock Units

A summary of the status of restricted stock units is presented below:


			Restricted Stock Units (in thousands)
Unvested at December 31, 2020			—
Granted RSU			2,482
Granted PSU			559
Unvested at December 31, 2021			3,041

Schedule of Stock Option Activity


	Number of Shares under Option (in thousands)	Weighted-Average Exercise Price	Weighted-Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2018	3,942	$2.12	9.14	$	57
Granted	3,986	$1.02
Exercised	(90)	$1.10
Canceled or forfeited	(1,602)	$1.78
Outstanding at December 31, 2019	6,236	$1.52	8.83	$	358
Granted	4,044	$0.87
Exercised	(12)	$1.13
Canceled or forfeited	(121)	$1.04
Outstanding at December 31, 2020	10,147	$1.26	8.50	$	3,160
Granted	8,273	$3.32
Exercised	(34)	$1.23
Canceled or forfeited	(2,683)	$3.70
Outstanding at December 31, 2021	15,703	$1.93	8.03	$	82
Exercisable at December 31, 2021	7,562	$1.65	7.41	$	59

Schedule of Weighted-Average Inputs and Assumptions in Black-Scholes Option


	Year ended December 31,
	2021	2020	2019
Fair market value	$3.32	$0.87	$1.02
Grant exercise price	$3.32	$0.87	$1.02
Expected term (in years)	6.0	6.1	6.0
Risk-free interest rate	0.9%	1.3%	2.1%
Expected volatility	74.6%	71.5%	78.1%
Dividend yield	—%	—%	—%

INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Components of Pre-tax Income (Loss)

The following table sets forth the components of the Company's loss before income taxes by country (in thousands):


	Year Ended December 31,
	2021		2020		2019
Country
United States	$	(32,757)	$	(35,529)	$	(27,468)
Canada	24,148		14,577		(80,032)
Total Loss Before Income Taxes	$	(8,609)	$	(20,952)	$	(107,500)

Components of Income Tax Benefit (Provision)

The Company's tax benefit (provision) is comprised of the following components (in thousands):


	Year Ended December 31,
	2021		2020		2019
Current Tax Provision
Federal	$	—	$	—	$	—
State	—		—		—
Foreign	(286)		(1,445)		—
Total current (provision)	$	(286)	$	(1,445)	$	—
Deferred tax provision
Federal	$	—	$	—	$	—
State	—		—		—
Foreign	8,559		—		—
Total deferred benefit (provision)	$	8,559	$	—	$	—

Total Tax Benefit (Provision)	$	8,273	$	(1,445)	$	—

Reconciliation of Expected Income Tax Expense

The following table sets forth a reconciliation of the statutory United States federal income tax rate to the Company’s effective income tax rate:


	Year ended December 31,
	2021		2020		2019
United States federal statutory income tax rate	21.0	%	21.0	%	21.0	%
Impact of foreign rate differential	(15.9)		(4.2)		4.4
State taxes, net of federal benefit	2.3		2.0		0.6
Stock option cancellations	(1.1)		(0.2)		—
Contingent consideration	178.2		14.4		(18.0)
General business credits and other credits	2.4		6.6		0.4
Permanent differences	(1.4)		0.2		—
Other	(13.8)		(2.1)		(0.5)
Foreign taxes	(3.3)		(6.9)		—
Change in valuation allowance	(72.3)		(37.7)		(7.9)
Effective Income Tax Rate	96.1	%	(6.9)	%	—	%

Components of Deferred Tax Assets and Liabilities

The following table sets forth the tax effects of temporary differences that gave rise to significant portions of the Company's deferred tax assets and liabilities (in thousands):


	December 31,
	2021		2020		2019
Deferred tax assets:
NOL carryforwards	$	63,381	$	57,935	$	50,727
R&D credit carryforwards	4,316		3,787		4,385
Accruals and other	4,058		3,811		2,464
Capitalized start-up costs	53		70		91
Other	41		28		57
Gross deferred tax assets	71,849		65,631		57,724
Deferred tax liabilities:
IPR&D	(3,969)		(12,528)		(12,528)

Gross deferred tax liabilities	(3,969)		(12,528)		(12,528)
Valuation allowance	(71,849)		(65,631)		(57,724)
Net Deferred Tax Liability	$	(3,969)	$	(12,528)	$	(12,528)

Schedule of Credit Carryforwards

The following table summarizes the Company's NOL and R&D and other credit carryforwards in the United States and Canada as of December 31, 2021 (in millions):


	Amount		Expiration Beginning in	Through
United States:
Federal NOL carryforwards - indefinite	$	101.1	None	None
Federal NOL carryforwards	$	118.9	2030	2038
State NOL carryforwards	$	138.4	2030	2040
Federal R&D credit carryforwards	$	2.5	2027	2040
State R&D credit carryforwards	$	0.8	2027	2040
Canada:
Federal non-capital loss carryforwards	$	31.2	2035	2040
Federal scientific research and experimental development expense carryforwards	$	5.1	2032	2040
Federal and provincial investment tax credit carryforwards	$	1.2	2032	2040

RESTRUCTURING AND RELATED ACTIVITIES (Tables)

12 Months Ended

Dec. 31, 2021

Restructuring and Related Activities [Abstract]

Schedule of Restructuring Reserve by Type of Cost

The following is a summary of accrued restructuring costs related to the Restructuring Plan:


	December 31, 2021
	(in thousands)
Severance and benefits costs	$	2,792
Contract termination costs	2,736
Other restructuring costs	—
Total restructuring costs	$	5,528
Cash payments	(4,031)
Balance at December 31, 2021	$	1,497

DESCRIPTION OF BUSINESS (Details) $ in Thousands, shares in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($) shares	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Apr. 30, 2018 patient
Variable Interest Entity [Line Items]
Number of patients \| patient					133
Cash and cash equivalents		$ 162,636	$ 52,389	$ 48,121
Accumulated deficit		316,257	315,921
Negative cash flows from operating activities incurred		$ 68,878	$ 30,837	$ 37,521
Viventia Bio Inc.
Variable Interest Entity [Line Items]
Shares of common stock issued to the selling shareholders (in shares) \| shares	4.0
Percentage of voting interests acquired	19.90%
Period during which quarterly earn-outs are payable after date of net sales	15 years
Period in which acquiree is to use commercially reasonable efforts to achieve marketing authorizations	7 years
Viventia Bio Inc. \| Vicinium \| Collaborative Arrangement, Revenue based on Specified Milestone
Variable Interest Entity [Line Items]
Percentage of net sales of quarterly earn-out payments during earn-out periods	2.00%
Viventia Bio Inc. \| Vicinium \| Collaborative Arrangement, Revenue based on Specified Milestone \| United States
Variable Interest Entity [Line Items]
One-time milestone payment upon first sale of product	$ 12,500
Viventia Bio Inc. \| Vicinium \| Collaborative Arrangement, Revenue based on Specified Milestone \| Europe
Variable Interest Entity [Line Items]
One-time milestone payment upon first sale of product	7,000
Viventia Bio Inc. \| Vicinium \| Collaborative Arrangement, Revenue based on Specified Milestone \| Japan
Variable Interest Entity [Line Items]
One-time milestone payment upon first sale of product	$ 3,000

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)	1 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended
	Jan. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($) unit	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2021	Mar. 31, 2021	Jan. 01, 2019 USD ($)
Property, Plant and Equipment [Line Items]
Insurance coverage limit		$ 250,000	$ 250,000		$ 250,000
Intangibles impairment charge				$ 31,700,000	$ 31,700,000	$ 0	$ 0
Impairment of intangible assets						0
Number of reporting units \| unit					1
Goodwill		$ 13,064,000	$ 13,064,000	$ 13,100,000	$ 13,064,000	13,064,000
Goodwill impairment					$ 0	$ 0
License agreement, royalty rate		2.00%	2.00%		2.00%
Index rate, high-yield		0.080	0.080	0.075	0.080	0.084		0.066	0.074
Lease liability		$ 124,000	$ 124,000		$ 124,000
Dividend yield					0.00%
License and related revenue					$ 26,544,000	$ 11,236,000	$ 0
Discount Rate
Property, Plant and Equipment [Line Items]
Weighted-average cost of capital		9.30%	9.30%	8.60%	9.30%	8.80%		6.80%	7.80%
Minimum
Property, Plant and Equipment [Line Items]
Probability of achieving clinical and regulatory milestones		45.00%	45.00%		45.00%
Maximum
Property, Plant and Equipment [Line Items]
Probability of achieving clinical and regulatory milestones		55.00%	55.00%		55.00%
Cumulative Effect, Period of Adoption, Adjustment
Property, Plant and Equipment [Line Items]
Right-of-use asset										$ 200,000
Lease liability										$ 200,000
Roche \| Subsequent Event
Property, Plant and Equipment [Line Items]
Proceeds from milestone achieved	$ 20,000,000
Performance-Based Awards
Property, Plant and Equipment [Line Items]
Award vesting period					4 years
Expected term					10 years
Licensing Agreements \| Roche
Property, Plant and Equipment [Line Items]
Milestone payment		$ 20,000,000
Milestone payment term		30 days
Vicinium \| United States \| IPR&D intangible assets:
Property, Plant and Equipment [Line Items]
Intangibles impairment charge					$ 31,700,000
EBI-031 \| Roche
Property, Plant and Equipment [Line Items]
License and related revenue			$ 20,000,000
EBI-031 \| Roche \| Subsequent Event
Property, Plant and Equipment [Line Items]
Proceeds from milestone achieved	$ 20,000,000
EBI-031 \| Roche \| Minimum
Property, Plant and Equipment [Line Items]
License agreement, royalty rate		7.50%	7.50%		7.50%
EBI-031 \| Roche \| Maximum
Property, Plant and Equipment [Line Items]
License agreement, royalty rate		15.00%	15.00%		15.00%
Lab equipment
Property, Plant and Equipment [Line Items]
Estimated useful life					5 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Estimated useful life					4 years
Computer equipment
Property, Plant and Equipment [Line Items]
Estimated useful life					3 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful life					5 years

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Liabilities:
Contingent consideration - short term	$ 0	$ 8,985
Contingent consideration - long term	52,000	99,855
Recurring \| Quoted Prices in Active Markets (Level 1)
Assets:
Money market funds (cash equivalents)	16,382	16,374
Liabilities:
Contingent consideration - short term	0	0
Contingent consideration - long term	0	0
Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Money market funds (cash equivalents)	0	0
Liabilities:
Contingent consideration - short term	0	0
Contingent consideration - long term	0	0
Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Money market funds (cash equivalents)	0	0
Liabilities:
Contingent consideration - short term	0	8,985
Contingent consideration - long term	52,000	99,855
Carrying Amount \| Recurring
Assets:
Money market funds (cash equivalents)	16,382	16,374
Liabilities:
Contingent consideration - short term	0	8,985
Contingent consideration - long term	52,000	99,855
Fair Value \| Recurring
Assets:
Money market funds (cash equivalents)	16,382	16,374
Liabilities:
Contingent consideration - short term	0	8,985
Contingent consideration - long term	$ 52,000	$ 99,855

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Option, Quantitative Disclosures [Line Items]
Contingent consideration liability, measurement input	0.080	0.075	0.066	0.074	0.080	0.084
License agreement, royalty rate	2.00%				2.00%
Change in fair value of contingent consideration	$ (4,600)	$ (114,000)	$ 13,600	$ 48,160	$ (56,840)	$ (11,180)	$ 71,620
Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Probability of achieving clinical and regulatory milestones	45.00%				45.00%
Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Probability of achieving clinical and regulatory milestones	55.00%				55.00%
Discount Rate
Fair Value, Option, Quantitative Disclosures [Line Items]
Weighted-average cost of capital	9.30%	8.60%	6.80%	7.80%	9.30%	8.80%
Discount Rate \| Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Contingent consideration liability, measurement input	0.080				0.080	0.084
Discount Rate \| Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Contingent consideration liability, measurement input	0.093				0.093	0.088

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS - Summary of Changes in Fair Value of Contingent Consideration (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 56,600	$ 170,600	$ 157,000	$ 108,840	$ 108,840
Change in fair value included in loss	(4,600)	(114,000)	13,600	48,160	(56,840)	$ (11,180)	$ 71,620
Ending balance	52,000	$ 56,600	$ 170,600	$ 157,000	52,000	108,840
Contingent consideration - short term	0				0	8,985
Contingent consideration, net of current portion	$ 52,000				$ 52,000	$ 99,855

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS - Summary of Changes in Fair Value of Company's Total Contingent Consideration (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 108,840
Ending balance	52,000
Significant Unobservable Inputs (Level 3)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	108,840
Change in fair value of contingent consideration - short term	(8,985)
Change in fair value of contingent consideration - long term	(47,855)
Ending balance	$ 52,000

RECEIVABLES (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended
RECEIVABLES (Details) - USD ($) $ in Thousands	Jan. 31, 2022	Dec. 31, 2021	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivables		$ 21,011	$ 21,011		$ 0
Other receivables		3,482	3,482		$ 0
Increase in other receivables			3,400
Roche
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivables		21,000	21,000
Milestone achieved		$ 20,000	$ 20,000
Payment terms		30 days
Qilu Pharmaceutical Co., Ltd.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivables				$ 900
Subsequent Event
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from value added tax recovery	$ 1,800
Subsequent Event \| Roche
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from milestone achieved	$ 20,000

PROPERTY AND EQUIPMENT - Property and Equipment and Related Accumulated Depreciation (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,009	$ 1,004
Less: accumulated depreciation	(966)	(881)
Total Property and Equipment, Net	43	123
Lab equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	569	570
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	16	16
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	99	97
Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	32	28
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 293	$ 293

PROPERTY AND EQUIPMENT - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 85	$ 122	$ 219

INTANGIBLES AND GOODWILL - Composition of Intangible Assets (Details) - IPR&D intangible assets: - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Total Intangibles	$ 14,700	$ 46,400
United States \| Vicinium
Finite-Lived Intangible Assets [Line Items]
Total Intangibles	0	31,700
European Union \| Vicinium
Finite-Lived Intangible Assets [Line Items]
Total Intangibles	$ 14,700	$ 14,700

INTANGIBLES AND GOODWILL - Narrative (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Intangibles impairment charge	$ 31,700,000	$ 31,700,000	$ 0	$ 0
Goodwill	$ 13,100,000	13,064,000	13,064,000
Percentage of fair value in excess of carrying amount	45.00%
Goodwill impairment		$ 0	$ 0
Minimum
Finite-Lived Intangible Assets [Line Items]
Percentage of fair value in excess of carrying amount	45.00%
Maximum
Finite-Lived Intangible Assets [Line Items]
Percentage of fair value in excess of carrying amount		55.00%

ACCRUED EXPENSES - Components of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Research and development	$ 1,841	$ 1,372
Payroll-related expenses	2,967	1,892
Restructuring charge related	1,497	0
Professional fees	1,941	684
Other	9	25
Total Accrued Expenses	$ 8,255	$ 3,973

COMMITMENTS AND CONTINGENCIES - Additional Information (Details)	Dec. 31, 2021 lawsuit
Commitments and Contingencies Disclosure [Abstract]
Number of lawsuits	3

LEASES - Narrative (Details)	12 Months Ended
LEASES - Narrative (Details)	Dec. 31, 2021 USD ($) ft² term	Dec. 31, 2021 CAD ($) ft² term	Dec. 31, 2020 USD ($)
Lessee, Lease, Description [Line Items]
Short term property leases	$ 262,000		$ 261,000
Operating lease cost, including related operating cost	$ 327,000		$ 301,000
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets	Other assets
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities	Other current liabilities	Other current liabilities
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other non-current liabilities	Other non-current liabilities	Other non-current liabilities
Canada
Lessee, Lease, Description [Line Items]
Office space (in square feet) \| ft²	31,100	31,100
Lease term	2 years	2 years
Renewal option \| term	1	1
Renewal term	3 years	3 years
Monthly rent	$ 14,300	$ 18,100
Related operating expenses	$ 14,300	$ 18,200
Massachusetts And Pennsylvania \| Minimum
Lessee, Lease, Description [Line Items]
Renewal term	3 months	3 months
Massachusetts And Pennsylvania \| Maximum
Lessee, Lease, Description [Line Items]
Renewal term	6 months	6 months
Massachusetts
Lessee, Lease, Description [Line Items]
Monthly rent	$ 2,100
Pennsylvania
Lessee, Lease, Description [Line Items]
Monthly rent	$ 18,400

LEASES - Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
LEASES - Lease Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Lease Cost:
Operating lease (including related operating costs)	$ 327	$ 301
Short term property leases	262	261
Total lease costs	$ 589	$ 562
Supplemental Information:
Weighted-average remaining lease term (years)	9 months	1 year 9 months
Weighted-average discount rate - operating leases	12.00%	12.00%

LEASES - Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2021 USD ($)
Minimum Lease Payments:
Total future minimum lease payments (2022)	$ 129
Less: Amounts representing present value adjustment	(5)
Operating lease liabilities, net of current portion	$ 124

STOCKHOLDERS' EQUITY DEFICIT - Equity Financing (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended				2 Months Ended	12 Months Ended
	Feb. 28, 2021	Oct. 31, 2020	Nov. 30, 2019	Jun. 30, 2019	Jul. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Common stock, par value (in dollars per share)						$ 0.001	$ 0.001
Aggregate sales price					$ 200.0
Proceeds from sale of stock				$ 27.8
Sale of stock, number of units issued (in shares)				20.4
Number of warrants (in shares)				20.4
Stock and warrants price per share (in dollars per share)				$ 1.47
Exercise price per warrant (in dollars per share)				$ 1.47
Expected term				1 year
ATM Facility
Class of Stock [Line Items]
Common stock, par value (in dollars per share)			$ 0.001
Aggregate sales price			$ 35.0
Additional shares to be issued	$ 34.5	$ 50.0
Commission fixed rate			3.00%
Proceeds from sale of stock						$ 175.0	$ 38.0
Sale of stock, number of units issued (in shares)						56.9	33.4
Weighted-average stock price per share (in dollars per share)						$ 3.17	$ 1.17
Issuance of common stock, issuance cost						$ 5.4	$ 1.2

STOCKHOLDERS' EQUITY DEFICIT - Preferred Stock (Details) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Equity [Abstract]
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0

STOCKHOLDERS' EQUITY DEFICIT - Common Stock (Details)	12 Months Ended
STOCKHOLDERS' EQUITY DEFICIT - Common Stock (Details)	Dec. 31, 2021 vote shares	Dec. 31, 2020 shares
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	400,000,000	200,000,000
Common stock, shares issued (in shares)	199,463,645	140,449,647
Common stock, shares outstanding (in shares)	199,463,645	140,449,647
Common Stock
Class of Stock [Line Items]
Number of votes \| vote	1

STOCKHOLDERS' EQUITY DEFICIT - Summary of Common Stock Issued and Reserved for Issuance (Details) - shares	Dec. 31, 2021	Dec. 31, 2020
Class of Warrant or Right [Line Items]
Common stock, shares issued (in shares)	199,463,645	140,449,647
Shares of common stock reserved for issuance for:
Total shares of common stock issued and reserved for issuance (in shares)	229,640,000	157,707,000
Warrants
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance (in shares)	199,000	2,247,000
Stock options
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance (in shares)	15,703,000
RSUs
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance (in shares)	3,041,000	0
Shares available for grant under 2014 Stock Incentive Plan
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance (in shares)	8,933,000	4,863,000
Shares available for sale under 2014 Employee Stock Purchase Plan
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance (in shares)	2,300,000	0

STOCKHOLDERS' EQUITY DEFICIT - Warrants (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2021	Jun. 30, 2019
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)		$ 1.47
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	2,247
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	(2,048)
Warrants Cancelled (in shares)	0
Warrants outstanding, ending balance (in shares)	199
Warrants, Expiring June 2020
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)	$ 1.47
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	0
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Cancelled (in shares)	0
Warrants outstanding, ending balance (in shares)	0
Warrants, Expiring March 2023
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)	$ 0.55
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	1,705
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	(1,573)
Warrants Cancelled (in shares)	0
Warrants outstanding, ending balance (in shares)	132
Warrants, Expiring November 2022
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)	$ 0.55
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	487
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	(475)
Warrants Cancelled (in shares)	0
Warrants outstanding, ending balance (in shares)	12
Warrants, Expiring November 2024, Issued May 2015
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)	$ 11.83
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	28
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Cancelled (in shares)	0
Warrants outstanding, ending balance (in shares)	28
Warrants, Expiring November 2024, Issued November 2014
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)	$ 11.04
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	27
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Cancelled (in shares)	0
Warrants outstanding, ending balance (in shares)	27

STOCKHOLDERS' EQUITY DEFICIT - Warrants Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	6 Months Ended	12 Months Ended
	Oct. 31, 2019	Jun. 30, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019
Class of Warrant or Right [Line Items]
Proceeds from exercises of common stock warrants			$ 1,126	$ 131	$ 5,481
Exercise of common stock warrants (in shares)			2,048,000
Increase in warrant value			$ 1,100
Exercise price per warrant (in dollars per share)							$ 1.47
Deemed dividend		$ 100
Common Stock
Class of Warrant or Right [Line Items]
Exercise of common stock warrants (in shares)			2,048,059	238,110	6,772,928
2018 Warrants
Class of Warrant or Right [Line Items]
Exercise of common stock warrants (in shares)			1,573,000
Exercise price per warrant (in dollars per share)			$ 0.55
2018 Warrants \| Common Stock
Class of Warrant or Right [Line Items]
Proceeds from exercises of common stock warrants	$ 2,000
Exercise of common stock warrants (in shares)	3,400,000
Exercise price per warrant (in dollars per share)	$ 0.60	$ 0.55				$ 1.20
2017 Warrants
Class of Warrant or Right [Line Items]
Exercise of common stock warrants (in shares)			475,000
Exercise price per warrant (in dollars per share)			$ 0.55
2017 Warrants \| Common Stock
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)	$ 0.55					0.80
2018 Warrant Amendment, Amendment to Securities Purchase Agreement
Class of Warrant or Right [Line Items]
Minimum percentage of securities issued	50.10%
2018 Warrant Amendment, Amendment to Securities Purchase Agreement \| Common Stock
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)	$ 0.95					$ 1.20

EARNINGS (LOSS) PER SHARE (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from calculation of diluted net (loss) income per share (in shares)	15,902	12,394	29,131
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from calculation of diluted net (loss) income per share (in shares)	199	2,247	22,895
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from calculation of diluted net (loss) income per share (in shares)	15,703	10,147	6,236

SHARE-BASED COMPENSATION - Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share Based Compensation	$ 5,143	$ 1,757	$ 1,237
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share Based Compensation	973	350	188
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share Based Compensation	$ 4,170	$ 1,407	$ 1,049

SHARE-BASED COMPENSATION - Narrative (Details) - USD ($)	1 Months Ended		12 Months Ended
	May 31, 2021	Jun. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares)			15,703,000	10,147,000	6,236,000	3,942,000
Share-based compensation expense			$ 5,143,000	$ 1,757,000	$ 1,237,000
Unrecognized compensation cost, non-vested stock options			$ 10,400,000
Weighted average period unvested stock to be recognized			2 years 8 months 12 days
Weighted-average grant-date fair value of stock options granted (in dollars per share)			$ 2.16	$ 0.56	$ 1.02
Share-based Payment Arrangement, Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares)			2,800,000
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)			15,703,000
Share-based compensation expense			$ 4,600,000	$ 1,800,000	$ 1,200,000
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)			3,041,000	0
Unvested weighted average remaining contractual life			9 years 9 months
Unvested grant restricted stock units (in shares)			2,482,000	0	0
Performance-Based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
Unrecognized compensation expense			$ 400,000
Unvested weighted average remaining contractual life			9 years 9 months
Unvested grant restricted stock units (in shares)			559,000
2014 Stock Incentive Plan \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares reserved for issuance (in shares)	12,000,000	7,900,000
Shares reserved for future issuance (in shares)			8,900,000
Award vesting period			4 years
Expected term			10 years
Options outstanding (in shares)			12,800,000
Retention Program \| RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares received per award (in shares)			1
Share-based compensation expense			$ 500,000	$ 0	$ 0
Expense related to cash bonus			$ 600,000
Retention Program \| Performance-Based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares received per award (in shares)			1
Percent of base salary			50.00%
Stock Incentive Plan 2009 \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term			10 years
Vested stock options outstanding (in shares)			100,000
Vesting on the First Anniversary of Date of Grant \| 2014 Stock Incentive Plan \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of original number of shares subject to the option vesting			25.00%
Vesting at End of Each Successive Three-Month Period Thereafter \| 2014 Stock Incentive Plan \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of original number of shares subject to the option vesting			6.25%

SHARE-BASED COMPENSATION - Summary of Status and Changes of Unvested Restricted Stock (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
RSUs
Number of Shares
Unvested, beginning balance (in shares)	0
Granted (in shares)	2,482,000	0	0
Unvested, ending balance (in shares)	3,041,000	0
Performance-Based Awards
Number of Shares
Granted (in shares)	559,000

SHARE-BASED COMPENSATION - Stock Options (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares under Option (in thousands)
Outstanding at beginning of period (in shares)	10,147	6,236	3,942
Granted (in shares)	8,273	4,044	3,986
Exercised (in shares)	(34)	(12)	(90)
Canceled or forfeited (in shares)	(2,683)	(121)	(1,602)
Outstanding at end of period (in shares)	15,703	10,147	6,236	3,942
Exercisable at end of period (in shares)	7,562
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 1.26	$ 1.52	$ 2.12
Granted (in dollars per share)	3.32	0.87	1.02
Exercised (in dollars per share)	1.23	1.13	1.10
Cancelled or forfeited (in dollars per share)	3.70	1.04	1.78
Outstanding at end of period (in dollars per share)	1.93	$ 1.26	$ 1.52	$ 2.12
Exercisable at end of period (in dollars per share)	$ 1.65
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-average Remaining Contractual Life (in years), Outstanding	8 years 10 days	8 years 6 months	8 years 9 months 29 days	9 years 1 month 20 days
Weighted-average Remaining Contractual Life (in years), Exercisable	7 years 4 months 28 days
Aggregate Intrinsic Value, Outstanding	$ 82	$ 3,160	$ 358	$ 57
Aggregate Intrinsic Value, Exercisable	$ 59

SHARE-BASED COMPENSATION - Weighted-Average Inputs and Assumptions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair market value (in dollars per share)	$ 3.32	$ 0.87	$ 1.02
Grant exercise price (in dollars per share)	$ 3.32	$ 0.87	$ 1.02
Expected term (in years)	6 years	6 years 1 month 6 days	6 years
Risk-free interest rate	0.90%	1.30%	2.10%
Expected volatility	74.60%	71.50%	78.10%
Dividend yield	0.00%	0.00%	0.00%

EMPLOYEE BENEFIT PLANS (Details) - USD ($) shares in Millions	1 Months Ended	12 Months Ended
	May 31, 2021	Dec. 31, 2021	Feb. 28, 2014
United States
Defined Benefit Plan Disclosure [Line Items]
Defined contribution retirement plan, maximum employee contribution deferred		100.00%
Discretionary match per participating employee, maximum		$ 4,000
Canada
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution, percent of employees' eligible compensation		4.00%
2014 Employee Stock Purchase Plan
Defined Benefit Plan Disclosure [Line Items]
Shares of common stock reserved for issuance (in shares)			0.2
Number of additional shares authorized (in shares)	2.3
Common stock purchase price, discount rate		15.00%
Common stock available for sale (in shares)		2.3

INCOME TAXES - Components of Pre-tax Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Line Items]
Total Loss Before Income Taxes	$ (8,609)	$ (20,952)	$ (107,500)
United States
Income Taxes [Line Items]
Pre-tax income (loss) U.S.	(32,757)	(35,529)	(27,468)
Canada
Income Taxes [Line Items]
Pre-tax income (loss) Canada	$ 24,148	$ 14,577	$ (80,032)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123384075&loc=d3e41242-110953

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(10))
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(8))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-URI http://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(15))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

INCOME TAXES - Components of Income Tax Provisions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current Tax Provision
Federal	$ 0	$ 0	$ 0
State	0	0	0
Foreign	(286)	(1,445)	0
Total current (provision)	(286)	(1,445)	0
Deferred tax provision
Federal	0	0	0
State	0	0	0
Foreign	8,559	0	0
Total deferred benefit (provision)	8,559	0	0
Benefit (provision) from income taxes	$ 8,273	$ (1,445)	$ 0

INCOME TAXES - Reconciliation of Expected Income Tax Expense (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Effective Income Tax Rate Reconciliation:
United States federal statutory income tax rate	21.00%	21.00%	21.00%
Impact of foreign rate differential	(15.90%)	(4.20%)	4.40%
State taxes, net of federal benefit	2.30%	2.00%	0.60%
Stock option cancellations	(1.10%)	(0.20%)	0.00%
Contingent consideration	178.20%	14.40%	(18.00%)
General business credits and other credits	2.40%	6.60%	0.40%
Permanent differences	(1.40%)	0.20%	0.00%
Other	(13.80%)	(2.10%)	(0.50%)
Foreign taxes	(3.30%)	(6.90%)	0.00%
Change in valuation allowance	(72.30%)	(37.70%)	(7.90%)
Effective Income Tax Rate	96.10%	(6.90%)	0.00%

INCOME TAXES - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
NOL carryforwards	$ 63,381	$ 57,935	$ 50,727
R&D credit carryforwards	4,316	3,787	4,385
Accruals and other	4,058	3,811	2,464
Capitalized start-up costs	53	70	91
Other	41	28	57
Gross deferred tax assets	71,849	65,631	57,724
Deferred tax liabilities:
IPR&D	(3,969)	(12,528)	(12,528)
Gross deferred tax liabilities	(3,969)	(12,528)	(12,528)
Valuation allowance	(71,849)	(65,631)	(57,724)
Net Deferred Tax Liability	$ (3,969)	$ (12,528)	$ (12,528)

INCOME TAXES - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
INCOME TAXES - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Valuation allowance	$ 71,849	$ 65,631	$ 57,724
Valuation allowance change	6,200
Deferred tax liability	3,969	$ 12,528
NOL carryforward reduced amount	$ 800

INCOME TAXES - Schedule of Credit Carryforwards (Details) $ in Millions	Dec. 31, 2021 USD ($)
United States: \| Federal
Income Taxes [Line Items]
NOL carryforwards	$ 118.9
United States: \| State
Income Taxes [Line Items]
NOL carryforwards	138.4
Indefinite \| United States: \| Federal
Income Taxes [Line Items]
NOL carryforwards	101.1
R&D credit carryforwards \| United States: \| Federal
Income Taxes [Line Items]
Tax credit carryforwards	2.5
R&D credit carryforwards \| United States: \| State
Income Taxes [Line Items]
Tax credit carryforwards	0.8
R&D credit carryforwards \| Canada
Income Taxes [Line Items]
Tax credit carryforwards	5.1
Non-capital loss carryforwards \| Canada
Income Taxes [Line Items]
Tax credit carryforwards	31.2
Investment tax credit carryforwards \| Canada
Income Taxes [Line Items]
Tax credit carryforwards	$ 1.2

LICENSE AGREEMENTS - Narrative (Details) € in Thousands				1 Months Ended					3 Months Ended							12 Months Ended
LICENSE AGREEMENTS - Narrative (Details) € in Thousands	Aug. 05, 2021 USD ($)	Nov. 30, 2020 USD ($)	Jul. 30, 2020 USD ($)	Jan. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2016 USD ($)	Aug. 31, 2016 USD ($)	Jun. 30, 2016 USD ($) period	Dec. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2021 EUR (€)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 EUR (€)	Sep. 30, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 EUR (€)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Organization And Basis Of Presentation [Line Items]
License and related revenue																$ 26,544,000		$ 11,236,000	$ 0
License agreement, royalty rate					2.00%				2.00%							2.00%
Transaction price													$ 11,200,000		$ 11,200,000			11,200,000
Qilu Pharmaceutical Co., Ltd. \| Licensing Agreements
Organization And Basis Of Presentation [Line Items]
Potential milestone payments											$ 23,000,000
License and related revenue										$ 900,000	2,800,000				$ 11,200,000
Upfront payment			$ 12,000,000															12,000,000
Total milestone payments			$ 23,000,000
Royalty payment, percentage			12.00%
Business combination, milestone payments											3,000,000
University of Zurich
Organization And Basis Of Presentation [Line Items]
Royalty payment obligation, percent																4.00%	4.00%
Third party maximum ownership, percent																10.00%	10.00%
Third party minimum ownership, percent																2.00%	2.00%
Expenses related to achievement of development milestone																$ 500,000		300,000
University of Zurich \| Collaborative Arrangement, Revenue Based on Clinical Development Milestone
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone																$ 500,000
Micromet AG
Organization And Basis Of Presentation [Line Items]
Royalty payment obligation, percent																3.50%	3.50%
Expenses related to achievement of development milestone											600,000	€ 500	900,000	€ 700
Potential milestone payments																$ 2,700,000	€ 2,400
License agreement, royalty payment, reduction, conditions not met																1.50%	1.50%
License maintenance fees																$ 56,625	€ 50
XOMA Ireland Limited
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone																$ 250,000
Royalty payment obligation, percent																2.50%	2.50%
Third party maximum ownership, percent																50.00%	50.00%
Third party minimum ownership, percent																1.75%	1.75%
Roche
Organization And Basis Of Presentation [Line Items]
License agreement, up-front fee							$ 7,500,000
License agreement, additional up-front fee							262,500,000
Milestone achieved					$ 20,000,000				$ 20,000,000							$ 20,000,000
Payment terms					30 days
License agreement, option periods \| period								2
License agreement, buyout amount under first option period								$ 135,000,000
License agreement, period to pay buyout option once exercised								30 days
License agreement, buyout amount under second option period								$ 265,000,000
Buyout amount under second option period								$ 220,000,000
Roche \| Subsequent Event
Organization And Basis Of Presentation [Line Items]
Proceeds from milestone achieved				$ 20,000,000
Roche \| EBI-031
Organization And Basis Of Presentation [Line Items]
Milestone achieved					$ 20,000,000				20,000,000							$ 20,000,000
Payment terms																30 days	30 days
License and related revenue									$ 20,000,000
Roche \| EBI-031 \| Minimum
Organization And Basis Of Presentation [Line Items]
License agreement, royalty rate					7.50%				7.50%							7.50%
Roche \| EBI-031 \| Maximum
Organization And Basis Of Presentation [Line Items]
License agreement, royalty rate					15.00%				15.00%							15.00%
Roche \| EBI-031 \| Subsequent Event
Organization And Basis Of Presentation [Line Items]
Proceeds from milestone achieved				$ 20,000,000
Roche \| IL-6
Organization And Basis Of Presentation [Line Items]
License agreement, royalty rate					50.00%				50.00%							50.00%
Roche \| First Indication
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone							197,500,000
Roche \| Collaborative arrangement, revenue based on development milestone
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone							72,500,000
Roche \| Collaborative arrangement, revenue based on development milestone \| EBI-031
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone						$ 22,500,000
Roche \| Collaborative Arrangement, Revenue Based on Development Milestone, Phase II
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone							30,000,000
Roche \| Collaborative arrangement, revenue based on regulatory milestone
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone							50,000,000
Roche \| Collaborative arrangement, revenue based on commercialization milestone
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone							$ 75,000,000
Roche \| Second Indication
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone																$ 65,000,000
MENA License Agreement \| Licensing Agreements
Organization And Basis Of Presentation [Line Items]
License and related revenue											$ 1,500,000
Upfront payment		$ 3,000,000
Transaction price					$ 1,500,000				$ 1,500,000				$ 1,500,000			$ 1,500,000		$ 1,500,000
Royalty revenue, percentage													0.50					0.50
Eczacibasi Pharmaceuticals Marketing Agreement
Organization And Basis Of Presentation [Line Items]
Potential milestone payments	$ 2,000,000
Transaction price	$ 1,500,000
Eczacibasi Pharmaceuticals Marketing Agreement \| TURKEY
Organization And Basis Of Presentation [Line Items]
Royalty revenue, percentage	0.30

RELATED-PARTY TRANSACTIONS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Majority Shareholder \| Facility in Winnipeg, Manitola
Related Party Transaction [Line Items]
Rent expense in related party transaction	$ 0.3	$ 0.3	$ 0.3
Protoden \| Intellectual Property
Related Party Transaction [Line Items]
Rent expense in related party transaction	0.1	$ 0.1	$ 0.1
Annual fee for remaining term of lease	$ 0.1

RESTRUCTURING AND RELATED ACTIVITIES - Narrative (Details)	Aug. 30, 2021 position
Restructuring and Related Activities [Abstract]
Number of positions eliminated	18
Number of positions eliminated, period percent	35.00%

RESTRUCTURING AND RELATED ACTIVITIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring charge	$ 5,528	$ 0	$ 0
Cash payments	(4,031)
Restructuring Reserve	1,497
Severance and benefits costs
Restructuring Cost and Reserve [Line Items]
Restructuring charge	2,792
Contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charge	2,736
Other restructuring costs
Restructuring Cost and Reserve [Line Items]
Restructuring charge	$ 0

SUBSEQUENT EVENTS (Details) - Subsequent Event	2 Months Ended
SUBSEQUENT EVENTS (Details) - Subsequent Event	Feb. 28, 2022 document interview
Subsequent Event [Line Items]
Review period	5 months
Number of documents reviewed \| document	600,000
Number of interviews \| interview	39