0001485003-22-000063 | 10-Q | XBRL Viewer

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Cover - shares	3 Months Ended
Cover - shares	Mar. 31, 2022	May 02, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2022
Document Transition Report	false
Entity File Number	001-36296
Entity Registrant Name	Sesen Bio, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-2025616
Entity Address, Address Line One	245 First Street
Entity Address, Address Line Two	Suite 1800
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
City Area Code	617
Local Phone Number	444-8550
Title of 12(b) Security	Common Stock, $0.001 par value
Trading Symbol	SESN
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		199,463,645
Entity Central Index Key	0001485003
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 169,790	$ 162,636
Accounts receivables	1,011	21,011
Other receivables	1,041	3,482
Prepaid expenses and other current assets	8,795	18,476
Total current assets	180,637	205,605
Non-current assets:
Restricted cash	20	20
Property and equipment, net	33	43
Intangible assets	14,700	14,700
Goodwill	13,064	13,064
Long term prepaid expenses	17,301	7,192
Other assets	85	123
Total non-current assets	45,203	35,142
Total Assets	225,840	240,747
Current liabilities:
Accounts payable	666	2,853
Accrued expenses	7,278	8,255
Other current liabilities	530	460
Total current liabilities	8,474	11,568
Non-current liabilities:
Contingent consideration	39,100	52,000
Deferred tax liability	3,969	3,969
Deferred revenue	1,500	1,500
Total non-current liabilities	44,569	57,469
Total Liabilities	53,043	69,037
Stockholders’ Equity:
Preferred stock, $0.001 par value per share; 5,000,000 shares authorized at March 31, 2022 and December 31, 2021; no shares issued and outstanding at March 31, 2022 and December 31, 2021	0	0
Common stock, $0.001 par value per share; 400,000,000 shares authorized at March 31, 2022 and December 31, 2021; 199,463,645 shares issued and outstanding at March 31, 2022 and December 31, 2021	199	199
Additional paid-in capital	489,662	487,768
Accumulated deficit	(317,064)	(316,257)
Total Stockholders’ Equity	172,797	171,710
Total Liabilities and Stockholders’ Equity	$ 225,840	$ 240,747

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2022	Dec. 31, 2021	May 03, 2021	May 02, 2021
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	400,000,000	400,000,000	200,000,000
Common stock, shares issued (in shares)	199,463,645	199,463,645
Common stock, shares outstanding (in shares)	199,463,645	199,463,645

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Total Revenue	$ 0	$ 4,310
Operating expenses:
Research and development	4,760	6,078
General and administrative	8,975	5,293
Change in fair value of contingent consideration	(12,900)	48,160
Total operating expenses	835	59,531
Loss from Operations	(835)	(55,221)
Other income (expense), net	28	(3)
Loss Before Taxes	(807)	(55,224)
Provision for income taxes	0	(288)
Net Loss After Taxes	(807)	(55,512)
Comprehensive Loss After Taxes	(807)	(55,512)
Net loss attributable to common stockholders - basic	(807)	(55,512)
Net loss attributable to common stockholders - diluted	$ (807)	$ (55,512)
Net loss per common share - basic (in dollars per share)	$ (0.00)	$ (0.35)
Net loss per common share - diluted (in dollars per share)	$ (0.00)	$ (0.35)
Weighted-average common shares outstanding - basic (in shares)	199,464	157,033
Weighted-average common shares outstanding - diluted (in shares)	199,464	157,033
License and related revenue
Total Revenue	$ 0	$ 4,310

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY - 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, 2020			140,449,647
Beginning balance at Dec. 31, 2020	$ (9,227)		$ 140		$ 306,554		$ (315,921)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(55,512)						(55,512)
Share-based compensation	958				958
Exercise of stock options (in shares)			30,610
Exercises of stock options	39				39
Exercise of common stock warrants (in shares)			852,840
Exercises of common stock warrants	469		$ 1		468
Issuance of common stock under ATM Offering, net of issuance costs of $2.2 million (in shares)				30,645,702
Issuance of common stock under ATM Offering, net of issuance costs of $2.2 million		$ 72,543		$ 31		$ 72,512
Ending balance (in shares) at Mar. 31, 2021			171,978,799
Ending balance at Mar. 31, 2021	9,270		$ 172		380,531		(371,433)
Beginning balance (in shares) at Dec. 31, 2021			199,463,645
Beginning balance at Dec. 31, 2021	171,710		$ 199		487,768		(316,257)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(807)						(807)
Share-based compensation	$ 1,894				1,894
Exercise of stock options (in shares)	0
Exercise of common stock warrants (in shares)	0
Ending balance (in shares) at Mar. 31, 2022			199,463,645
Ending balance at Mar. 31, 2022	$ 172,797		$ 199		$ 489,662		$ (317,064)

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY (Parenthetical) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)
Statement of Stockholders' Equity [Abstract]
Issuance costs	$ 2.2

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash Flows from Operating Activities:
Net loss	$ (807)	$ (55,512)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	10	30
Share-based compensation	1,894	958
Change in fair value of contingent consideration	(12,900)	48,160
Changes in operating assets and liabilities:
Accounts receivable (net)	20,000	(2,886)
Other receivables	2,441	0
Prepaid expenses and other current assets	9,682	(6,250)
Long term prepaid expenses	(10,109)	0
Other assets	38	91
Accounts payable	(2,187)	(1,098)
Accrued expenses and other liabilities	(908)	(468)
Deferred revenue	0	(1,500)
Net cash provided (used in) operating activities	7,154	(18,475)
Cash Flows from Investing Activities:
Net cash used in investing activities	0	0
Cash Flows from Financing Activities:
Proceeds from exercises of common stock warrants	0	469
Proceeds from issuance of common stock under ATM Offering, net of issuance costs	0	72,543
Proceeds from exercises of stock options	0	39
Net cash provided by financing activities	0	73,051
Net increase in cash, cash equivalents and restricted cash	7,154	54,576
Cash, cash equivalents and restricted cash - beginning of period	162,656	55,409
Cash, cash equivalents and restricted cash - end of period	169,810	109,985
Supplemental cash flow disclosure:
Cash paid for amounts included in the measurement of lease liabilities	$ 43	$ 43

DESCRIPTION OF BUSINESS	3 Months Ended
DESCRIPTION OF BUSINESS	Mar. 31, 2022
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 bladder cancer (“NMIBC”). The Company is in the follow-up stage of its single-arm, multi-center, open-label Phase 3 clinical trial of Vicineum as a monotherapy in patients with bacillus Calmette-Guérin ("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 had accepted the BLA file. 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 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 chemistry, manufacturing and controls (“CMC”) issues pertaining to a recent pre-approval inspection and product quality. In October 2021 and December 2021, the Company 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 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. In March 2022, the Company participated in a Type C meeting with the FDA. During the Type C meeting, the FDA agreed to a majority of the Company’s proposed protocol and statistical analysis plan design elements for an additional Phase 3 clinical trial for potential resubmission of a BLA for Vicineum for the treatment of NMIBC. The Company plans to further engage the FDA in the coming months to align on the remaining outstanding items related to the additional Phase 3 clinical trial. 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. 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 March 31, 2022, none of these individuals are active employees or members of the Company's board of directors.

BASIS OF PRESENTATION	3 Months Ended
BASIS OF PRESENTATION	Mar. 31, 2022
Accounting Policies [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATION The 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 Accounting Standards Codification (“ASC”) and Accounting Standards Updates ("ASUs"), promulgated by the Financial Accounting Standards Board ("FASB"). Interim Financial Statements The accompanying unaudited interim condensed consolidated financial statements have been prepared from the books and records of the Company in accordance with GAAP for interim financial information and Rule 10-01 of Regulation S-X promulgated by the United States Securities and Exchange Commission (“SEC”), which permit reduced disclosures for interim periods. All adjustments, consisting only of normal recurring adjustments, which are, in the opinion of management, necessary for a fair presentation of the accompanying condensed consolidated balance sheets and statements of operations and comprehensive (loss) income, stockholders’ equity (deficit) and cash flows have been made. Although these interim financial statements do not include all of the information and footnotes required for complete annual financial statements, management believes the disclosures are adequate to make the information presented not misleading. These unaudited interim results of operations and cash flows for the three months ended March 31, 2022 are not necessarily indicative of the results that may be expected for the full year. These unaudited interim condensed consolidated financial statements and footnotes should be read in conjunction with the Company’s audited annual consolidated financial statements and footnotes included in its Annual Report on Form 10-K, as filed with the SEC on February 28, 2022, wherein a more complete discussion of significant accounting policies and certain other information can be found. 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); and research and development expenses. Principles of Consolidation The Company’s condensed 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	3 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	Mar. 31, 2022
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIESThe Company's complete summary of significant accounting policies can be found in "Item 15. Exhibits and Financial Statement Schedules - Note 3. Summary of Significant Accounting Policies" in the audited annual consolidated financial statements included in its Annual Report on Form 10-K for the year ended December 31, 2021.

RECENT ACCOUNTING PRONOUNCEMENTS	3 Months Ended
RECENT ACCOUNTING PRONOUNCEMENTS	Mar. 31, 2022
Accounting Standards Update and Change in Accounting Principle [Abstract]
RECENT ACCOUNTING PRONOUNCEMENTS	RECENT ACCOUNTING PRONOUNCEMENTS Adopted in 2022 In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity ("ASU 2020-06"). ASU 2020-06 simplifies the complexity associated with applying US GAAP for certain financial instruments with characteristics of both liability and equity. More specifically, the amendments focus on the guidance for convertible instruments and derivative scope exception for contracts in an entity’s own equity. The ASU also amends the diluted earnings per share (EPS) guidance, including the requirement to use the if-converted method for all convertible instruments. ASU 2020-06 is effective for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2021, and should be applied on a full or modified retrospective basis. The Company adopted this guidance on a modified retrospective basis effective January 1, 2022 and it did not have an impact on the Company's financial position, results of operations including per-share amounts, or cash flows. In May 2021, the FASB issued ASU No. 2021-04, Earnings Per Share (Topic 260), Debt—Modifications and Extinguishments (Subtopic 470-50), Compensation—Stock Compensation (Topic 718), and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Issuer’s Accounting for Certain Modifications or Exchanges of Freestanding Equity-Classified Written Call Options ("ASU 2021-04"). ASU 2021-04 clarifies and reduces diversity in an issuer’s accounting for modifications or exchanges of freestanding equity-classified written call options (for example, warrants) that remain equity classified after modification or exchange. ASU 2021-04 is effective for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2021, and should be applied on a prospective basis. The Company adopted this guidance effective January 1, 2022 and it did not have an impact on the Company's financial position, results of operations including per-share amounts, or cash flows. Other recent accounting pronouncements issued, but not yet effective, are not expected to be applicable to the Company or have a material effect on the consolidated financial statements upon future adoption.

- 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=122640432&loc=SL121648383-210437

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22499-107794

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=124501264&loc=SL117420844-207641

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (e)(2)
-URI http://asc.fasb.org/extlink&oid=122640432&loc=SL121648383-210437

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-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

3 Months Ended

Mar. 31, 2022

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 condensed consolidated balance sheets approximated their fair values as of March 31, 2022 and December 31, 2021 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 March 31, 2022 and December 31, 2021 (in thousands):


	March 31, 2022
					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)	$	16,378	$	16,378	$	16,378	$	—	$	—
Liabilities:

Contingent consideration	$	39,100	$	39,100	$	—	$	—	$	39,100


	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	$	52,000	$	52,000	$	—	$	—	$	52,000

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 quarter ended March 31, 2022.

Contingent Consideration

On September 20, 2016, the Company acquired Viventia through the issuance of shares of common stock plus contingent consideration, pursuant to the terms of a Share Purchase Agreement. The Company recorded the acquired assets and liabilities based on their estimated fair values as of the acquisition date and finalized its purchase accounting for the Viventia Acquisition during the third quarter of 2017. The contingent consideration relates to amounts potentially payable to the former shareholders of Viventia under the Share Purchase Agreement. Contingent consideration is measured at its estimated fair value 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 inputs, including internally developed financial forecasts, probabilities of success, and the timing of certain milestone events and achievements, which are not observable in the market, representing a Level 3 measurement within the fair value hierarchy. 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.

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 through 2033, the level of commercial sales of Vicineum forecasted for the US, Europe, Japan, China and other potential markets and discount rates ranging from 9.0% to 9.7% as of March 31, 2022 and 8.0% to 9.3% as of December 31, 2021. There have been no changes to the valuation methods utilized during the three months ended March 31, 2022.

The following table sets forth a summary 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 quarter ended March 31, 2022, (in thousands).


Balance at December 31, 2021	$	52,000

Change in fair value of contingent consideration	(12,900)
Balance at March 31, 2022	$	39,100

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 weighted-average cost of capital (“WACC”), which has fluctuated from 9.3% as of December 31, 2021 to 9.0% as of March 31, 2022. 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 8.0% as of December 31, 2021 to 9.7% as of March 31, 2022. The decrease in the fair value of contingent consideration of $12.9 million for the three months ended March 31, 2022 was driven by changes in underlying assumptions used to develop the revenue projections.

In March 2022, the Company participated in a Type C meeting with the FDA. During the Type C meeting, the FDA agreed to a majority of the Company's proposed protocol and statistical analysis plan design elements for an additional Phase 3 clinical trial for potential resubmission of a BLA for Vicineum for the treatment of NMIBC. The Company also learned during the meeting that the FDA is trending away from accepting single arm trials across therapeutic areas, including NMIBC, and has a strong preference for randomized controlled trials. The Company plans to further engage the FDA in the coming months to align on the remaining outstanding items related to the additional Phase 3 clinical trial. Incorporating the FDA feedback from the Type C meeting, plans for further discussions with the FDA prior to initiation of the additional Phase 3 clinical trial, as well as updates to the competitive landscape, 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 potential commercial product launch, probabilities of clinical and regulatory success, and market share. The Company anticipates further delays in the start of commercialization due to the likelihood of the requirement to conduct a randomized controlled trial which will require more patients to be enrolled, lengthen the duration of the study, and increase study costs. The company is also projecting lower estimated market share as a result of recent clinical and regulatory progress made by competitors. The Company has assessed a commercialization timeline assumption and applied a probability to each outcome based on management’s best estimate. The Company continues to assume a 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.

- 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	3 Months Ended
RECEIVABLES	Mar. 31, 2022
Receivables [Abstract]
RECEIVABLES	RECEIVABLES The accounts receivable balance as of March 31, 2022 is $1.0 million compared to $21.0 million as of December 31, 2021. The decrease is driven by the receipt of the $20.0 million milestone from F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc. (collectively, “Roche”) for the initiation of a Phase II clinical trial in the fourth quarter of 2021. The other receivable balance as of March 31, 2022 is $1.0 million compared to $3.5 million as of December 31, 2021. The decrease is driven primarily by the receipt of $1.8 million for German VAT recovery related to drug substance sent to Baxter in 2020 and 2019.

INTANGIBLES AND GOODWILL

3 Months Ended

Mar. 31, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

INTANGIBLES AND GOODWILL

Intangibles

Intangible assets on the Company's condensed 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 March 31, 2022 and December 31, 2021 (in thousands):


	March 31, 2022		December 31, 2021
IPR&D intangible assets:

Vicineum European Union rights	$	14,700	$	14,700
Total Intangibles	$	14,700	$	14,700

The fair value of the acquired intangible assets for the 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 BCG-unresponsive 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. Also in August 2021, the Company withdrew its MAA to the EMA for Vysyneum for the treatment of BCG-unresponsive NMIBC in order to pause its plans to pursue regulatory approval of Vysyneum in the EU until there is more clarity from the FDA on next steps for Vicineum in the United States. 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 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. At that time, management assessed that the carrying value of the Vicineum EU rights was not at significant risk of impairment in the future within the

current range of commercialization timelines and POS assumptions. This was primarily due to the fact that 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.

In March 2022, the Company participated in a Type C meeting with the FDA. During the Type C meeting, the FDA agreed to a majority of the Company's proposed protocol and statistical analysis plan design elements for an additional Phase 3 clinical trial for potential resubmission of a BLA for Vicineum for the treatment of NMIBC. The Company also learned during the meeting that the FDA is trending away from accepting single arm trials across therapeutic areas, including NMIBC, and has a strong preference for randomized controlled trials. The Company plans to further engage the FDA in the coming months to align on the remaining outstanding items related to the additional Phase 3 clinical trial. Based on the outcome of the Type C meeting as well as updates to the competitive landscape, the Company reassessed the underlying assumptions used to develop its revenue projections, which were then used as significant inputs to determine the fair value of the indefinite-lived intangible asset. Management updated the revenue forecast models based on further launch delays in both US and OUS regions as well as slightly lower market share. The Company anticipates further delays in the start of commercialization due to the likelihood of the requirement to conduct a randomized controlled trial which will require more patients to be enrolled, lengthen the duration of the study, and increase study costs. The company is also projecting lower estimated market share as a result of recent clinical and regulatory progress made by competitors. Accordingly, the Company identified this as a potential impairment indicator and performed an interim quantitative impairment assessment during the first quarter of 2022. The Company concluded that the carrying value of the Company's intangible asset of Vicineum EU rights was not impaired as of March 31, 2022.

Goodwill

Goodwill on the Company's condensed consolidated balance sheet is the result of the Viventia Acquisition in September 2016. Goodwill had a carrying value of $13.1 million as of March 31, 2022 and December 31, 2021. Based on the outcome of the Type C meeting as well as updates to the competitive landscape, the Company reassessed the underlying assumptions used to develop its revenue projections, which were then used as significant inputs to determine the fair value of equity. Management updated its revenue forecast models based on further launch delays in both US and OUS regions as well as slightly lower market share. Accordingly, the Company identified these changes to the revenue forecast, as well as the decline in the Company’s stock price and market capitalization during the first quarter of 2022, as potential impairment indicators and performed a quantitative impairment analysis during the first quarter of 2022, in advance of the Company's typical annual assessment date of October 1. The Company concluded that the carrying value of its goodwill of $13.1 million was not impaired as of March 31, 2022, with the fair value of equity of the reporting unit exceeding the estimated carrying value of the reporting unit by approximately 29%.

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) and underlying discount rates 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 NMIBC. Further reductions to probabilities of success, decrease in market share, additional development and commercial launch delays, increases in underlying discount rates, or any decision to undertake any strategic alternative as a result of the review process that the Company has initiated, have the potential to result in future goodwill impairment.

ACCRUED EXPENSES

3 Months Ended

Mar. 31, 2022

Payables and Accruals [Abstract]

ACCRUED EXPENSES

The following table sets forth the composition of accrued expenses as of March 31, 2022 and December 31, 2021 (in thousands):


	March 31, 2022		December 31, 2021
Research and development	$	981	$	1,841
Payroll-related expenses	2,675		2,967
Restructuring charge related	990		1,497
Professional fees	2,582		1,941
Other	50		9
Total Accrued Expenses	$	7,278	$	8,255

COMMITMENTS AND CONTINGENCIES	3 Months Ended
COMMITMENTS AND CONTINGENCIES	Mar. 31, 2022
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 alleged 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 sought 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. The defendants moved to dismiss the Amended Complaint on March 7, 2022. The plaintiffs filed their opposition to that motion on April 6, 2022 and Defendants filed their reply in further support of the motion to dismiss on May 6, 2022. The court has not yet ruled on the motion. 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. 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 court 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. On May 1, 2022, the plaintiffs filed a verified consolidated shareholder derivative complaint in the Federal Derivative Litigation. Defendants intend to seek a similar stay of the state court derivative litigation. 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 or offer letters with certain of its key executives, providing for separation payments and benefits in certain circumstances, as defined in the agreements.

LEASES	3 Months Ended
LEASES	Mar. 31, 2022
Leases [Abstract]
LEASES	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 $14,500 at exchange rates in effect on March 31, 2022). In addition to rent expense, the Company expects to incur CAD $18,200 per month related to operating expenses (approximately $14,500 at exchange rates in effect on March 31, 2022). Operating lease cost under this lease, including the related operating costs, were $0.1 million for the three months ended March 31, 2022 and March 31, 2021. 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 condensed consolidated balance sheets. The right of use asset total was $0.1 million as of March 31, 2022 and December 31, 2021. 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 condensed consolidated balance sheets. The short-term lease liability was $0.1 million as of March 31, 2022 and December 31, 2021. There was no long-term operating lease liability as of March 31, 2022 or December 31, 2021. 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 six to twelve months and currently extend through June 2023 and May 2023, 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.

STOCKHOLDERS' EQUITY

3 Months Ended

Mar. 31, 2022

Equity [Abstract]

STOCKHOLDERS' EQUITY

Equity Financings

ATM Offering

The Company has entered into an Open Market Sale Agreement SM with Jefferies LLC ("Jefferies"), dated November 29, 2019, as amended by Amendment No. 1 dated October 30, 2020, Amendment No. 2 dated February 17, 2021 and Amendment No. 3, dated June 1, 2021 (as amended, the "Sale Agreement"), under which the Company may issue and sell shares of its common stock, par value $0.001 per share, from time to time through Jefferies (the “ATM Offering”). 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 of which $97.8 million of common stock remain available for future issuance as of March 31, 2022. Sales of common stock under the Sale Agreement 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 did not sell any shares of common stock pursuant to the Sale Agreement during the three months ended March 31, 2022. The Company raised $72.6 million of net proceeds from the sale of 30.6 million shares

of common stock at a weighted-average price of $2.44 per share during the three months ended March 31, 2021. Share issuance costs, including sales agent commissions, related to the ATM Offering totaled $2.2 million during the three months ended March 31, 2021.

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 March 31, 2022 and 2021.

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 shares were issued and outstanding as of March 31, 2022 and December 31, 2021. In addition, the Company had reserved for issuance the following amounts of shares of its common stock for the purposes described below as of March 31, 2022 and December 31, 2021 (in thousands):


	March 31, 2022	December 31, 2021
Shares of common stock issued	199,464	199,464
Shares of common stock reserved for issuance for:
Warrants	199	199
Stock options	16,783	15,703
Restricted stock units	4,965	3,041
Shares available for grant under 2014 Stock Incentive Plan	3,564	8,933
Shares available for sale under 2014 Employee Stock Purchase Plan	2,300	2,300
Total shares of common stock issued and reserved for issuance	227,275	229,640

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 three months ended March 31, 2022 (in thousands):


Issued	Exercise Price	Expiration	December 31, 2021	Issued	(Exercised)	(Cancelled)	March 31, 2022
Mar-2018	$0.55*	Mar-2023	132	—	—	—	132
Nov-2017	$0.55*	Nov-2022	12	—	—	—	12
May-2015	$11.83	Nov-2024	28	—	—	—	28
Nov-2014	$11.04	Nov-2024	27	—	—	—	27
			199	—	—	—	199

* Exercise price shown (i) reflects modification and (ii) is subject to further adjustment based on down round provision added by amendment described in “Item 15. Exhibits and Financial Statement Schedules - Note. 12 Stockholders’ Equity (Deficit)” in the audited annual consolidated financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2021.

- 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
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-Section 50
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-Subparagraph (b)
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496171-112644

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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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
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-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)
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section 50
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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
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-Topic 505
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-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
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-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
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+ Details

EARNINGS (LOSS) PER SHARE

3 Months Ended

Mar. 31, 2022

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 unvested 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.

The following potentially dilutive securities outstanding as of March 31, 2022 and 2021 have been excluded from the denominator of the diluted loss per share of common stock outstanding calculation (in thousands):


	March 31,
	2022	2021
Warrants	199	1,394
Stock options	16,783	14,380
RSUs and PSUs	6,555	—
Total	23,537	15,774

SHARE-BASED COMPENSATION

3 Months Ended

Mar. 31, 2022

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 Condensed Consolidated Statements of Operations and Comprehensive Loss for three months ended March 31, 2022 and 2021 (in thousands):


	Three Months Ended March 31,
	2022		2021
Research and development	$	502	$	178
General and administrative	1,392		780
Total Share Based Compensation	$	1,894	$	958

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, restricted stock units ("RSU"), 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 3.6 million shares of common stock available for issuance under the 2014 Plan as of March 31, 2022.

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 13.2 million stock options outstanding under the 2014 Plan as of March 31, 2022.

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 RSU award which will vest 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.

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 of March 31, 2022 achievement was deemed probable for only the cash management milestone, representing 20% of the PSU awards.

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 March 31, 2022.

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 3.5 million stock options outstanding which were granted as employment inducement awards outside of the 2014 Plan as of March 31, 2022.

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 three months ended March 31, 2022:


	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, 2021	15,703	$1.93	8.03	$	82
Granted	1,080	$0.71
Exercised	—	—
Canceled or forfeited	—	—
Outstanding at March 31, 2022	16,783	$1.85	7.92	$	1
Exercisable at March 31, 2022	8,513	$1.68	7.26	$	1

The Company recognized share-based compensation expense of $1.9 million for the three months ended March 31, 2022. The stock option related expenses were $1.3 million and $1.0 million for the three months ended March 31, 2022 and 2021, respectively. As of March 31, 2022, there was $9.6 million of total unrecognized compensation cost related to unvested stock options which the Company expects to recognize over a weighted-average period of 2.56 years. The weighted-average grant-date fair value of stock options granted during the three months ended March 31, 2022 and 2021 were $0.45 and $2.05, respectively. No stock options were exercised during the three months ended March 31, 2022. The total intrinsic value of stock options exercised for the three months ended March 31, 2021 was de minimis.

For the three months ended March 31, 2022 and 2021, 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:


	Three Months Ended March 31,
	2022	2021
Fair market value	$0.71	$3.15
Grant exercise price	$0.71	$3.15
Expected term (in years)	6.0	6.0
Risk-free interest rate	1.7%	0.8%
Expected volatility	71.9%	75.0%
Dividend yield	—%	—%

Restricted Stock Units and Performance Stock Units

The following table sets forth a summary of the Company's RSU and PSU activity for the three months ended March 31, 2022:


	Restricted Stock Units (in thousands)	Weighted Average Grant Date Fair Value
Unvested at December 31, 2021	3,041	$0.80
Granted RSU	3,960	$0.67
Granted PSU	1,004	$0.67
Unvested at March 31, 2022	8,005	$0.72

The Company did not grant any RSUs or PSUs during the three months ended March 31, 2021.

The share-based compensation expense related to RSUs and PSUs for the three months ended March 31, 2022 was $0.6 million. There was no shared-based compensation expense related to RSUs and PSUs for the three months ended March 31, 2021. As of March 31, 2022, there was $5.0 million of total unrecognized compensation cost related to unvested RSUs and PSUs which the Company expects to recognize over a weighted-average period of 2.94 years.

EMPLOYEE BENEFIT PLANS	3 Months Ended
EMPLOYEE BENEFIT PLANS	Mar. 31, 2022
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 condensed consolidated statements of changes in stockholders' equity (deficit). As of March 31, 2022, there were 2.3 million shares of common stock available for sale under the 2014 ESPP. The Company did not sell any shares under the ESPP for the three months ended March 31, 2022 and 2021. 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 expenses incurred for the periods presented were de minimis amount for each of the three months ended March 31, 2022 and 2021, 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 expenses incurred for the periods presented were de minimis amount for each of the three months ended March 31, 2022 and 2021, respectively.

LICENSE AGREEMENTS	3 Months Ended
LICENSE AGREEMENTS	Mar. 31, 2022
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. The Company's receipt of the CRL regarding the BLA for Vicineum for the treatment of BCG-unresponsive NMIBC triggered a $0.5 million milestone payment to Zurich. Under the Zurich License Agreement, 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, which includes Vicineum. 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 $0.3 million and $0.5 million related to meeting a development milestone, (the submission of the Company’s BLA with the FDA in December 2020), in the fourth quarter of 2020, and a regulatory milestone, (the Company’s receipt of the CRL from the FDA in August 2021), in the third quarter of 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 March 31, 2022, 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 March 31, 2022). 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 $55,559 at exchange rates in effect as of March 31, 2022), that 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 the provisions of Accounting Standards Codification 606, Revenue from Contracts with Customers ("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 ASC 606. 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 deferred revenue. 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 March 31, 2022, 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 EIP License Agreement, the Company is entitled to receive an upfront payment of $1.5 million. The Company and EIP have amended the license agreement to defer EIP's 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 March 31, 2022, none of these amounts have been received by the Company. No initial transaction price was estimated by management, therefore no revenue was recorded as of March 31, 2022. 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 March 31, 2022, none of these additional amounts were reasonably certain to be achieved due to the nature and timing of the underlying activities.

RESTRUCTURING AND RELATED ACTIVITIES

3 Months Ended

Mar. 31, 2022

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, (in thousands):


Balance as of December 31, 2021	$	1,497
Cash payments	(507)
Balance at March 31, 2022	$	990

The Company expects that substantially all of the accrued restructuring costs as of March 31, 2022 will be paid in cash by the end of September 2022.

SUBSEQUENT EVENTS	3 Months Ended
SUBSEQUENT EVENTS	Mar. 31, 2022
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTSOn May 3, 2022, Sesen Bio, Inc., (the “Company”) announced that it has initiated a process to review strategic alternatives with the goal of maximizing shareholder value. Potential strategic alternatives to be explored and evaluated during the review process may include the sale of the Company, a merger, acquisition or other business combination, a strategic partnership with one or more parties, or the licensing, sale or divestiture of some of the Company’s proprietary technologies. The Company is actively working with an investment bank in this process. Pending any decision to undertake any strategic alternative, the Company is continuing its development activities in accordance with its existing business strategy.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Mar. 31, 2022
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); and research and development expenses.
Principles of Consolidation	Principles of Consolidation The Company’s condensed 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.
Recent Accounting Pronouncements	Adopted in 2022 In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity ("ASU 2020-06"). ASU 2020-06 simplifies the complexity associated with applying US GAAP for certain financial instruments with characteristics of both liability and equity. More specifically, the amendments focus on the guidance for convertible instruments and derivative scope exception for contracts in an entity’s own equity. The ASU also amends the diluted earnings per share (EPS) guidance, including the requirement to use the if-converted method for all convertible instruments. ASU 2020-06 is effective for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2021, and should be applied on a full or modified retrospective basis. The Company adopted this guidance on a modified retrospective basis effective January 1, 2022 and it did not have an impact on the Company's financial position, results of operations including per-share amounts, or cash flows. In May 2021, the FASB issued ASU No. 2021-04, Earnings Per Share (Topic 260), Debt—Modifications and Extinguishments (Subtopic 470-50), Compensation—Stock Compensation (Topic 718), and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Issuer’s Accounting for Certain Modifications or Exchanges of Freestanding Equity-Classified Written Call Options ("ASU 2021-04"). ASU 2021-04 clarifies and reduces diversity in an issuer’s accounting for modifications or exchanges of freestanding equity-classified written call options (for example, warrants) that remain equity classified after modification or exchange. ASU 2021-04 is effective for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2021, and should be applied on a prospective basis. The Company adopted this guidance effective January 1, 2022 and it did not have an impact on the Company's financial position, results of operations including per-share amounts, or cash flows. Other recent accounting pronouncements issued, but not yet effective, are not expected to be applicable to the Company or have a material effect on the consolidated financial statements upon future adoption.
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 condensed consolidated balance sheets approximated their fair values as of March 31, 2022 and December 31, 2021 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)

3 Months Ended

Mar. 31, 2022

Fair Value Disclosures [Abstract]

Summary of Carrying Amounts and Fair Values of Financial Instruments Measured


	March 31, 2022
					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)	$	16,378	$	16,378	$	16,378	$	—	$	—
Liabilities:

Contingent consideration	$	39,100	$	39,100	$	—	$	—	$	39,100


	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	$	52,000	$	52,000	$	—	$	—	$	52,000

Summary of Contingent Consideration Liability


Balance at December 31, 2021	$	52,000

Change in fair value of contingent consideration	(12,900)
Balance at March 31, 2022	$	39,100

INTANGIBLES AND GOODWILL (Tables)

3 Months Ended

Mar. 31, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Composition of Intangible Assets

The following table sets forth the composition of intangible assets as of March 31, 2022 and December 31, 2021 (in thousands):


	March 31, 2022		December 31, 2021
IPR&D intangible assets:

Vicineum European Union rights	$	14,700	$	14,700
Total Intangibles	$	14,700	$	14,700

ACCRUED EXPENSES (Tables)

3 Months Ended

Mar. 31, 2022

Payables and Accruals [Abstract]

Components of Accrued Expenses

The following table sets forth the composition of accrued expenses as of March 31, 2022 and December 31, 2021 (in thousands):


	March 31, 2022		December 31, 2021
Research and development	$	981	$	1,841
Payroll-related expenses	2,675		2,967
Restructuring charge related	990		1,497
Professional fees	2,582		1,941
Other	50		9
Total Accrued Expenses	$	7,278	$	8,255

STOCKHOLDERS' EQUITY (Tables)

3 Months Ended

Mar. 31, 2022

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 March 31, 2022 and December 31, 2021 (in thousands):


	March 31, 2022	December 31, 2021
Shares of common stock issued	199,464	199,464
Shares of common stock reserved for issuance for:
Warrants	199	199
Stock options	16,783	15,703
Restricted stock units	4,965	3,041
Shares available for grant under 2014 Stock Incentive Plan	3,564	8,933
Shares available for sale under 2014 Employee Stock Purchase Plan	2,300	2,300
Total shares of common stock issued and reserved for issuance	227,275	229,640

Summary of Warrants Outstanding and Warrant Activity

The following table sets forth the Company's warrant activity for the three months ended March 31, 2022 (in thousands):


Issued	Exercise Price	Expiration	December 31, 2021	Issued	(Exercised)	(Cancelled)	March 31, 2022
Mar-2018	$0.55*	Mar-2023	132	—	—	—	132
Nov-2017	$0.55*	Nov-2022	12	—	—	—	12
May-2015	$11.83	Nov-2024	28	—	—	—	28
Nov-2014	$11.04	Nov-2024	27	—	—	—	27
			199	—	—	—	199

- 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

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+ Details

EARNINGS (LOSS) PER SHARE (Tables)

3 Months Ended

Mar. 31, 2022

Earnings Per Share [Abstract]

Schedule of Potentially Dilutive Securities


	March 31,
	2022	2021
Warrants	199	1,394
Stock options	16,783	14,380
RSUs and PSUs	6,555	—
Total	23,537	15,774

SHARE-BASED COMPENSATION (Tables)

3 Months Ended

Mar. 31, 2022

Share-based Payment Arrangement [Abstract]

Schedule of Share-Based Compensation Expense


	Three Months Ended March 31,
	2022		2021
Research and development	$	502	$	178
General and administrative	1,392		780
Total Share Based Compensation	$	1,894	$	958

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, 2021	15,703	$1.93	8.03	$	82
Granted	1,080	$0.71
Exercised	—	—
Canceled or forfeited	—	—
Outstanding at March 31, 2022	16,783	$1.85	7.92	$	1
Exercisable at March 31, 2022	8,513	$1.68	7.26	$	1

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


	Three Months Ended March 31,
	2022	2021
Fair market value	$0.71	$3.15
Grant exercise price	$0.71	$3.15
Expected term (in years)	6.0	6.0
Risk-free interest rate	1.7%	0.8%
Expected volatility	71.9%	75.0%
Dividend yield	—%	—%

Schedule of the Status of Restricted Stock Units

The following table sets forth a summary of the Company's RSU and PSU activity for the three months ended March 31, 2022:


	Restricted Stock Units (in thousands)	Weighted Average Grant Date Fair Value
Unvested at December 31, 2021	3,041	$0.80
Granted RSU	3,960	$0.67
Granted PSU	1,004	$0.67
Unvested at March 31, 2022	8,005	$0.72

RESTRUCTURING AND RELATED ACTIVITIES (Tables)

3 Months Ended

Mar. 31, 2022

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, (in thousands):


Balance as of December 31, 2021	$	1,497
Cash payments	(507)
Balance at March 31, 2022	$	990

DESCRIPTION OF BUSINESS (Details) shares in Millions, $ in Millions	1 Months Ended
	Sep. 30, 2016 USD ($) shares	Apr. 30, 2018 patient
Variable Interest Entity [Line Items]
Number of patients \| patient		133
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	$ 12.5
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	7.0
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	$ 3.0

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Liabilities:
Contingent consideration	$ 39,100	$ 52,000
Recurring \| Quoted Prices in Active Markets (Level 1)
Assets:
Money market funds (cash equivalents)	16,378	16,382
Liabilities:
Contingent consideration	0	0
Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Money market funds (cash equivalents)	0	0
Liabilities:
Contingent consideration	0	0
Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Money market funds (cash equivalents)	0	0
Liabilities:
Contingent consideration	39,100	52,000
Carrying Amount \| Recurring
Assets:
Money market funds (cash equivalents)	16,378	16,382
Liabilities:
Contingent consideration	39,100	52,000
Fair Value \| Recurring
Assets:
Money market funds (cash equivalents)	16,378	16,382
Liabilities:
Contingent consideration	$ 39,100	$ 52,000

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS - Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2021
Fair Value, Option, Quantitative Disclosures [Line Items]
Contingent consideration liability, measurement input	0.097		0.080
License agreement, royalty rate	2.00%
Decrease in the fair value of contingent consideration	$ (12,900)	$ 48,160
Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Probability of achieving clinical and regulatory milestones	45.00%
Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Probability of achieving clinical and regulatory milestones	55.00%
Discount Rate
Fair Value, Option, Quantitative Disclosures [Line Items]
Weighted-average cost of capital	9.00%		9.30%
Discount Rate \| Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Contingent consideration liability, measurement input	0.090		0.080
Discount Rate \| Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Contingent consideration liability, measurement input	0.097		0.093

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS - Summary of Changes in Fair Value of Company's Total Contingent Consideration (Details) - Significant Unobservable Inputs (Level 3) $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 52,000
Change in fair value of contingent consideration	(12,900)
Ending balance	$ 39,100

RECEIVABLES (Details) - USD ($) $ in Thousands	3 Months Ended
RECEIVABLES (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivables	$ 1,011		$ 21,011
Other receivables	1,041		3,482
Decrease in other receivables	2,441	$ 0
German VAT recovery
Accounts, Notes, Loans and Financing Receivable [Line Items]
Decrease in other receivables	1,800
Roche
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivables	$ 1,000
Milestone achieved			$ 20,000

INTANGIBLES AND GOODWILL - Composition of Intangible Assets (Details) - IPR&D intangible assets: - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Total Intangibles	$ 14,700	$ 14,700
European Union \| Vicinium
Finite-Lived Intangible Assets [Line Items]
Total Intangibles	$ 14,700	$ 14,700

INTANGIBLES AND GOODWILL - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Mar. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Intangibles impairment charge	$ 31,700
Goodwill	$ 13,100	$ 13,064	$ 13,064
Percentage of fair value in excess of carrying amount		29.00%
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	Mar. 31, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Research and development	$ 981	$ 1,841
Payroll-related expenses	2,675	2,967
Restructuring charge related	990	1,497
Professional fees	2,582	1,941
Other	50	9
Total Accrued Expenses	$ 7,278	$ 8,255

COMMITMENTS AND CONTINGENCIES (Details)	Mar. 31, 2022 lawsuit
Commitments and Contingencies Disclosure [Abstract]
Number of lawsuits	3

LEASES - Narrative (Details)	3 Months Ended
LEASES - Narrative (Details)	Mar. 31, 2022 USD ($) ft² term	Mar. 31, 2022 CAD ($) ft² term	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease cost, including related operating cost	$ 100,000		$ 100,000
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other assets			Other assets
Right-of-use asset	$ 100,000			$ 100,000
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities			Other current liabilities
Short term lease liability	$ 100,000			$ 100,000
Minimum
Lessee, Lease, Description [Line Items]
Short-term lease, renewal frequency	6 months	6 months
Maximum
Lessee, Lease, Description [Line Items]
Short-term lease, renewal frequency	12 months	12 months
CANADA
Lessee, Lease, Description [Line Items]
Office space (in square feet) \| ft²	31,100	31,100
Lease term	2 years
Renewal option \| term	1	1
Renewal term	3 years
Monthly rent	$ 14,500	$ 18,100
Related operating expenses	14,500	$ 18,200
Massachusetts
Lessee, Lease, Description [Line Items]
Monthly rent	2,100
Pennsylvania
Lessee, Lease, Description [Line Items]
Monthly rent	$ 18,400

STOCKHOLDERS' EQUITY - Equity Financing (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		2 Months Ended	3 Months Ended
	Nov. 29, 2021	Jul. 31, 2021	Mar. 31, 2021	Mar. 31, 2022	Dec. 31, 2021	Nov. 29, 2019
Class of Stock [Line Items]
Common stock, par value (in dollars per share)				$ 0.001	$ 0.001
ATM Facility
Class of Stock [Line Items]
Common stock, par value (in dollars per share)						$ 0.001
Aggregate sales price		$ 200.0
Shares reserved for future issuance amount				$ 97.8
Commission fixed rate	3.00%
Proceeds from sale of stock			$ 72.6
Sale of stock, number of units issued (in shares)			30.6
Weighted-average stock price per share (in dollars per share)			$ 2.44
Issuance of common stock, issuance cost			$ 2.2

STOCKHOLDERS' EQUITY - Preferred Stock (Details) - $ / shares	Mar. 31, 2022	Dec. 31, 2021
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 - Common Stock (Details)	3 Months Ended
STOCKHOLDERS' EQUITY - Common Stock (Details)	Mar. 31, 2022 vote shares	Dec. 31, 2021 shares	May 03, 2021 shares	May 02, 2021 shares
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	400,000,000	400,000,000	400,000,000	200,000,000
Common stock, shares issued (in shares)	199,463,645	199,463,645
Common stock, shares outstanding (in shares)	199,463,645	199,463,645
Common Stock
Class of Stock [Line Items]
Number of votes \| vote	1

STOCKHOLDERS' EQUITY - Summary of Common Stock Issued and Reserved for Issuance (Details) - shares	Mar. 31, 2022	Dec. 31, 2021
Class of Warrant or Right [Line Items]
Shares of common stock issued (in shares)	199,463,645	199,463,645
Shares of common stock reserved for issuance for:
Total shares of common stock issued and reserved for issuance (in shares)	227,275,000	229,640,000
Warrants
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance (in shares)	199,000	199,000
Stock options
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance (in shares)	16,783,000	15,703,000
Restricted stock units
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance (in shares)	4,965,000	3,041,000
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)	3,564,000	8,933,000
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	2,300,000

STOCKHOLDERS' EQUITY - Warrants (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2022 $ / shares shares
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	199
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Cancelled (in shares)	0
Warrants outstanding, ending balance (in shares)	199
Warrants, Expiring March 2023
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share) \| $ / shares	$ 0.55
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	132
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
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) \| $ / shares	$ 0.55
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	12
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
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) \| $ / shares	$ 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) \| $ / shares	$ 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

EARNINGS (LOSS) PER SHARE (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
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)	23,537	15,774
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	1,394
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)	16,783	14,380
RSU
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)	6,555	0
PSUs
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)	6,555	0

SHARE-BASED COMPENSATION - Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share Based Compensation	$ 1,894	$ 958
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share Based Compensation	502	178
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share Based Compensation	$ 1,392	$ 780

SHARE-BASED COMPENSATION - Narrative (Details) - USD ($)	1 Months Ended		3 Months Ended
	May 31, 2021	Jun. 30, 2019	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Oct. 01, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares)			16,783,000		15,703,000
Share-based compensation expense			$ 1,894,000	$ 958,000
Unrecognized compensation cost, non-vested stock options			$ 9,600,000
Weighted average period unvested stock to be recognized			2 years 6 months 21 days
Weighted-average grant-date fair value of stock options granted (in dollars per share)			$ 0.45	$ 2.05
Exercise of stock options (in shares)			0
Share-based Payment Arrangement, Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares)			3,500,000
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)			16,783,000		15,703,000
Share-based compensation expense			$ 1,300,000	$ 1,000,000
Stock options \| 2014 Stock Incentive Plan
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)			3,600,000
Award vesting period			4 years
Expected term			10 years
Options outstanding (in shares)			13,200,000
Stock options \| 2014 Stock Incentive Plan \| Vesting on the First Anniversary of Date of Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of original number of shares subject to the option vesting			25.00%
Stock options \| 2014 Stock Incentive Plan \| Vesting at End of Each Successive Three-Month Period Thereafter
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of original number of shares subject to the option vesting			6.25%
Stock options \| Stock Incentive Plan 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term			10 years
Vested stock options outstanding (in shares)			100,000
RSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)			4,965,000		3,041,000
Share-based compensation expense			$ 600,000	$ 0
Weighted average period unvested stock to be recognized			2 years 11 months 8 days
Unvested grant restricted stock units (in shares)			3,960,000	0
Unrecognized compensation expense			$ 5,000,000
RSU \| Retention Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares received per award (in shares)						1
PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense			$ 600,000	$ 0
Weighted average period unvested stock to be recognized			2 years 11 months 8 days
Unvested grant restricted stock units (in shares)			1,004,000	0
Unrecognized compensation expense			$ 5,000,000
PSUs \| Retention Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares received per award (in shares)						1
Percent of base salary						50.00%
Achievement deemed probable, percent			20.00%

SHARE-BASED COMPENSATION - Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Number of Shares under Option (in thousands)
Outstanding at beginning of period (in shares)	15,703,000
Granted (in shares)	1,080,000
Exercised (in shares)	0
Canceled or forfeited (in shares)	0
Outstanding at end of period (in shares)	16,783,000	15,703,000
Exercisable at end of period (in shares)	8,513,000
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 1.93
Granted (in dollars per share)	0.71
Exercised (in dollars per share)	0
Cancelled or forfeited (in dollars per share)	0
Outstanding at end of period (in dollars per share)	1.85	$ 1.93
Exercisable at end of period (in dollars per share)	$ 1.68
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-average Remaining Contractual Life (in years), Outstanding	7 years 11 months 1 day	8 years 10 days
Weighted-average Remaining Contractual Life (in years), Exercisable	7 years 3 months 3 days
Aggregate Intrinsic Value, Outstanding	$ 1	$ 82
Aggregate Intrinsic Value, Exercisable	$ 1

SHARE-BASED COMPENSATION - Weighted-Average Inputs and Assumptions (Details) - Stock options - $ / shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair market value (in dollars per share)	$ 0.71	$ 3.15
Grant exercise price (in dollars per share)	$ 0.71	$ 3.15
Expected term (in years)	6 years	6 years
Risk-free interest rate	1.70%	0.80%
Expected volatility	71.90%	75.00%
Dividend yield	0.00%	0.00%

SHARE-BASED COMPENSATION - Summary of Status and Changes of Unvested Restricted Stock (Details) - $ / shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Number of Shares
Unvested, beginning balance (in shares)	3,041,000
Unvested, ending balance (in shares)	8,005,000
Weighted-Average Grant Date Fair Value
Unvested beginning balance (in dollars per share)	$ 0.80
Unvested ending balance (in dollars per share)	$ 0.72
RSU
Number of Shares
Granted (in shares)	3,960,000	0
Weighted-Average Grant Date Fair Value
Granted (in dollars per share)	$ 0.67
PSUs
Number of Shares
Granted (in shares)	1,004,000	0
Weighted-Average Grant Date Fair Value
Granted (in dollars per share)	$ 0.67

EMPLOYEE BENEFIT PLANS (Details) - USD ($) shares in Millions	1 Months Ended	3 Months Ended
	May 31, 2021	Mar. 31, 2022	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

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 ($)	Jan. 31, 2022 USD ($)	Sep. 30, 2016 USD ($)	Aug. 31, 2016 USD ($)	Jun. 30, 2016 USD ($) period	Mar. 31, 2022 USD ($)	Mar. 31, 2022 EUR (€)	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	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, 2020 USD ($)
Organization And Basis Of Presentation [Line Items]
License and related revenue								$ 0					$ 4,310,000
License agreement, royalty rate								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								$ 55,559	€ 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
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 \| EBI-031
Organization And Basis Of Presentation [Line Items]
Milestone achieved								$ 20,000,000		20,000,000
Payment terms								30 days	30 days
License and related revenue										$ 20,000,000
Proceeds from milestone achieved				$ 20,000,000
Roche \| EBI-031 \| Minimum
Organization And Basis Of Presentation [Line Items]
License agreement, royalty rate								7.50%
Roche \| EBI-031 \| Maximum
Organization And Basis Of Presentation [Line Items]
License agreement, royalty rate								15.00%
Roche \| IL-6
Organization And Basis Of Presentation [Line Items]
License agreement, royalty rate								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
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
Qilu Pharmaceutical Co., Ltd.
Organization And Basis Of Presentation [Line Items]
Royalty period			12 years

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) $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($)
Restructuring Reserve [Roll Forward]
Beginning Balance	$ 1,497
Cash payments	(507)
Ending Balance	$ 990