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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2019	Aug. 06, 2019
Document And Entity Information [Abstract]
Entity Registrant Name	Sesen Bio, Inc.
Entity Central Index Key	0001485003
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Emerging Growth Company	true
Entity Small Business	true
Entity Transition Period Flag	true
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		101,265,896

CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 64,931	$ 50,422
Prepaid expenses and other current assets	2,598	1,334
Total current assets	67,529	51,756
Property and equipment, net	376	321
Restricted cash	20	20
Intangible assets	46,400	46,400
Goodwill	13,064	13,064
Other assets	223	0
Total assets	127,612	111,561
Current liabilities:
Accounts payable	2,176	1,367
Accrued expenses	5,630	4,746
Other current liabilities	142	0
Total current liabilities	7,948	6,113
Other liabilities	367	313
Deferred tax liability	12,528	12,528
Contingent consideration	91,400	48,400
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value per share; 5,000,000 shares authorized at June 30, 2019 and December 31, 2018 and no shares issued and outstanding at June 30, 2019 and December 31, 2018	0	0
Common stock, $0.001 par value per share; 200,000,000 shares authorized at June 30, 2019 and December 31, 2018 and 101,265,896 and 77,456,180 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively	101	77
Additional paid-in capital	262,107	230,154
Accumulated deficit	(246,839)	(186,024)
Total stockholders’ equity	15,369	44,207
Total liabilities and stockholders’ equity	$ 127,612	$ 111,561

CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock, par value (in USD 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 USD per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	101,265,896	77,456,180
Common stock, shares outstanding (in shares)	101,265,896	77,456,180

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating expenses:
Research and development	$ 7,944	$ 2,779	$ 12,630	$ 6,034
General and administrative	2,617	2,351	5,672	4,303
Loss from change in fair value of contingent consideration	44,000	3,900	43,000	2,700
Total operating expenses	54,561	9,030	61,302	13,037
Loss from operations	(54,561)	(9,030)	(61,302)	(13,037)
Other income:
Other income, net	226	72	487	116
Total other income, net	226	72	487	116
Net loss and comprehensive loss	$ (54,335)	$ (8,958)	$ (60,815)	$ (12,921)
Net loss per share — basic and diluted (in dollars per share)	$ (0.67)	$ (0.16)	$ (0.77)	$ (0.28)
Weighted-average number of common shares used in net loss per share- basic and diluted (in shares)	80,739	56,421	79,107	46,105

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)		34,702,565
Beginning balance (in shares)		43,105,466
Beginning balance at Dec. 31, 2017	$ 18,034	$ 35	$ 170,330	$ (152,331)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options and vesting of restricted stock awards (in shares)		4,430
Exercise of stock options and vesting of restricted stock awards	0
Issuance of common stock pursuant to the 2014 ESPP (in shares)		9,565
Issuance of common stock pursuant to the 2014 ESPP	10		10
Exercise of common stock warrants (in shares)		420,778
Exercise of common stock warrants	336		336
Issuance of common stock and common stock warrants, net of issuance costs (in shares)		7,968,128
Issuance of common stock and common stock warrants, net of issuance costs	9,040	$ 8	9,032
Stock-based compensation expense	401		401
Net loss	(3,963)			(3,963)
Ending balance (in shares) at Mar. 31, 2018		43,105,466
Ending balance at Mar. 31, 2018	23,858	$ 43	180,109	(156,294)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)		77,010,999
Beginning balance at Dec. 31, 2017	18,034	$ 35	170,330	(152,331)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(12,921)
Ending balance (in shares) at Jun. 30, 2018		77,010,999
Ending balance at Jun. 30, 2018	64,064	$ 77	229,239	(165,252)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)		43,105,466
Beginning balance (in shares)		77,010,999
Beginning balance at Mar. 31, 2018	23,858	$ 43	180,109	(156,294)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options and vesting of restricted stock awards (in shares)		55,259
Exercise of stock options and vesting of restricted stock awards	29		29
Exercise of common stock warrants (in shares)		8,294,718
Exercise of common stock warrants	6,918	$ 8	6,910
Issuance of common stock and common stock warrants, net of issuance costs (in shares)		25,555,556
Issuance of common stock and common stock warrants, net of issuance costs	41,932	$ 26	41,906
Stock-based compensation expense	285		285
Net loss	(8,958)			(8,958)
Ending balance (in shares) at Jun. 30, 2018		77,010,999
Ending balance at Jun. 30, 2018	64,064	$ 77	229,239	(165,252)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)		77,010,999
Beginning balance (in shares)		77,456,180
Beginning balance (in shares)		77,464,781
Beginning balance at Dec. 31, 2018	44,207	$ 77	230,154	(186,024)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock pursuant to the 2014 ESPP (in shares)		8,601
Issuance of common stock pursuant to the 2014 ESPP	7		7
Stock-based compensation expense	326		326
Net loss	(6,480)			(6,480)
Ending balance (in shares) at Mar. 31, 2019		77,464,781
Ending balance at Mar. 31, 2019	38,060	$ 77	230,487	(192,504)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)		101,265,896
Beginning balance at Dec. 31, 2018	$ 44,207	$ 77	230,154	(186,024)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options and vesting of restricted stock awards (in shares)	30,000
Exercise of common stock warrants (in shares)	3,361,115
Net loss	$ (60,815)
Ending balance (in shares) at Jun. 30, 2019		101,265,896
Ending balance at Jun. 30, 2019	15,369	$ 101	262,107	(246,839)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)		77,464,781
Beginning balance (in shares)		101,265,896
Beginning balance at Mar. 31, 2019	38,060	$ 77	230,487	(192,504)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options and vesting of restricted stock awards (in shares)		30,000
Exercise of stock options and vesting of restricted stock awards	$ 45		45
Exercise of common stock warrants (in shares)	3,400,000	3,361,115
Exercise of common stock warrants	$ 3,434	$ 4	3,430
Issuance of common stock and common stock warrants, net of issuance costs (in shares)		20,410,000
Issuance of common stock and common stock warrants, net of issuance costs	27,809	$ 20	27,789
Stock-based compensation expense	356		356
Net loss	(54,335)			(54,335)
Ending balance (in shares) at Jun. 30, 2019		101,265,896
Ending balance at Jun. 30, 2019	$ 15,369	$ 101	$ 262,107	$ (246,839)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)		101,265,896

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities
Net loss	$ (60,815,000)	$ (12,921,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	107,000	101,000
Stock-based compensation expense	682,000	686,000
Loss from change in fair value of contingent consideration	43,000,000	2,700,000
Gain on sale of equipment	0	(5,000)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(1,487,000)	(426,000)
Accounts payable	809,000	403,000
Accrued expenses and other liabilities	961,000	(517,000)
Net cash used in operating activities	(16,743,000)	(9,979,000)
Investing activities
Purchases (sales) of equipment	(43,000)
Purchases (sales) of equipment		5,000
Net cash (used in) provided by investing activities	(43,000)	5,000
Financing activities
Proceeds from exercise of common stock options	45,000	29,000
Proceeds from issuance of common stock and the issuance and exercise of common stock warrants, net of issuance costs	31,243,000	58,226,000
Proceeds from sale of common stock pursuant to 2014 ESPP	7,000	10,000
Net cash provided by financing activities	31,295,000	58,265,000
Net increase in cash, cash equivalents and restricted cash	14,509,000	48,291,000
Cash, cash equivalents and restricted cash at beginning of period	50,442,000	14,690,000
Cash, cash equivalents and restricted cash at end of period	64,951,000	62,981,000
Supplemental non-cash operating activities
Right-of-use assets obtained in exchange for operating lease liability	236,480,000	0
Cash paid for amounts included in the measurement of lease liabilities	76,071,000	0
Capital Expenditures Incurred but Not yet Paid	$ 119,000	$ 0

Organization and Basis of Presentation	6 Months Ended
Organization and Basis of Presentation	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation Sesen Bio, Inc. (the “Company”), a Delaware corporation, is a late-stage clinical company developing targeted fusion protein therapeutics ("TFPTs") composed of an anti-cancer antibody fragment tethered to a protein toxin for the treatment of cancer. The Company genetically fuses the cancer-targeting antibody fragment and the cytotoxic protein payload into a single molecule which is produced through the Company's proprietary one-step manufacturing process. The Company targets tumor cell surface antigens with limited expression on normal cells. Binding of the target antigen by the TFPT allows for rapid internalization into the targeted cancer cell. The Company has designed its targeted fusion proteins to overcome the fundamental efficacy and safety challenges inherent in existing antibody-drug conjugates ("ADCs"), where a payload is chemically attached to a targeting antibody. Basis of presentation The condensed consolidated financial statements as of June 30, 2019 and December 31, 2018 and for the three and six months ended June 30, 2019 and 2018 and the related information contained within the notes to the condensed consolidated financial statements are unaudited. The unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting standards applicable to interim financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s consolidated financial position as of June 30, 2019, its results of operations for the three and six months ended June 30, 2019 and 2018, its statement of shareholders' equity for the six months ended June 30, 2019 and 2018, and its cash flows for the six months ended June 30, 2019 and 2018. The financial data and the other financial information disclosed in these notes to the condensed consolidated financial statements related to the three and six-month periods are also unaudited. The results of operations for the three and six months ended June 30, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019 or for any other future annual or interim period. The condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 that was filed with the Securities and Exchange Commission (“SEC”) on March 1, 2019 (the "2018 Form 10-K"). The condensed consolidated financial statements include the accounts of the Company, its wholly owned subsidiary, Viventia Bio Inc. ("Viventia"), and its indirect subsidiaries, Viventia Bio USA Inc. and Viventia Biotech (EU) Limited. All inter-company transactions and balances have been eliminated in consolidation. The condensed consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles. The functional currency of Viventia, Viventia Bio USA Inc. and Viventia Biotech (EU) Limited is the U.S. dollar. Liquidity The Company has financed its operations to date primarily through private placements of its common stock and preferred stock, and convertible bridge notes, venture debt borrowings, its initial public offering ("IPO"), follow-on public offerings, sales effected in an "at-the-market" offering, and the License Agreement (the "License Agreement") with F. Hoffmann La-Roche Inc. (collectively, "Roche"). As of June 30, 2019, the Company had cash and cash equivalents totaling $64.9 million, net working capital of $59.6 million and an accumulated deficit of $246.8 million. The future success of the Company is dependent on its ability to develop its product candidates and ultimately upon its ability to attain profitable operations. In order to commercialize its product candidates, the Company needs to complete clinical development and comply with comprehensive regulatory requirements. The Company is subject to a number of risks similar to other late-stage clinical companies, including, but not limited to, successful discovery and development of its product candidates, raising additional capital with favorable terms, development by its competitors of new technological innovations, protection of proprietary technology and market acceptance of the Company’s products. The successful discovery and development of product candidates requires substantial working capital which may not be available to the Company on favorable terms or not at all. On June 21, 2019, the Company raised approximately $28 million in net proceeds from the sale of 20,410,000 shares of its common stock and accompanying warrants to purchase up to 20,410,000 shares of its common stock in an underwritten public offering (the “June 2019 Financing”). The combined purchase price for each share of common stock and accompanying warrant was $1.47. Each warrant has an exercise price of $1.47 per share and is exercisable from date of issuance through June 21, 2020. In addition, between April 1, 2019 and June 30, 2019, the Company received proceeds of $3.4 million from the issuance of 3.4 million shares of its common stock due to the exercise of common stock purchase warrants issued in connection with (i) its underwritten public offering in November 2017 and (ii) its private placement of common stock warrants in March 2018. To date, the Company has no revenue from product sales and management expects continuing operating losses in the future. As of June 30, 2019, the Company had available cash and cash equivalents of $64.9 million, which it believes is sufficient to fund the Company’s current operating plan for at least the next twelve months after the date of this Form 10-Q filing. Management expects to seek additional funds through equity or debt financings or through additional collaboration, licensing transactions or other sources. The Company may be unable to obtain equity or debt financings or enter into additional collaboration or licensing transactions and, if necessary, the Company will be required to implement cost reduction strategies. The condensed consolidated financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty.

Significant Accounting Policies and Recent Accounting Pronouncements

6 Months Ended

Jun. 30, 2019

Accounting Policies [Abstract]

Significant Accounting Policies and Recent Accounting Pronouncements

Recently adopted accounting standards

In February 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2016-02, Leases (Topic 842) ("ASU 2016-02"). ASU 2016-02 addresses the financial reporting of leasing transactions. Under past guidance for lessees, leases are only included on the balance sheet if certain criteria, classifying the agreement as a capital lease, are met. This update requires the recognition of a right-of-use asset and a corresponding lease liability, discounted to the present value, for all leases that extend beyond 12 months. For operating leases, the asset and liability are expensed over the lease term on a straight-line basis, with all cash flows included in the operating section of the statement of cash flows. For finance leases, interest on the lease liability is recognized separately from the amortization of the right-of-use asset in the statement of operations and the repayment of the principal portion of the lease liability is classified as a financing activity while the interest component is included in the operating section of the statement of cash flows. This guidance is effective for annual and interim reporting periods beginning after December 15, 2018 including interim periods within those fiscal years. In July 2018, the FASB issued ASU No. 2018-10, Leases (Topic 842), Codification Improvements (“ASU 2018-10”), ASU No. 2018-11, Leases (Topic 842), Targeted Improvements (“ASU 2018-11”), and ASU No. 2019-01 Leases (Topic 842), Codification Improvements to provide additional guidance for the adoption Accounting Standards Codification (“ASC”) of Topic 842, Leases (“ASC 842”). ASU 2018-10 clarifies certain provisions and corrects unintended applications of the guidance, such as the rate implicit in a lease, impairment of the net investment in a lease, lessee reassessment of lease classifications, lessor reassessment of lease term and purchase options, variable payments that depend on an index or rate and certain transition adjustments. The amendments in ASU 2018-11 allow for an additional transition method, whereby at the adoption date the entity recognizes a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption, while the comparative period disclosures continue recognition under ASC 840, Leases (“ASC 840”). Additionally, ASU 2018-11 includes a practical expedient for separating contract components for lessors. The Company adopted ASC 842 using the optional transition method outlined in ASU 2018-11 as of January 1, 2019. The adoption of ASC 842 resulted in the recognition of operating lease right-of-use assets of approximately $236,000 and corresponding lease liabilities of approximately $236,000. The adoption of these ASUs did not have a material impact on the Company’s financial condition or results of operations, however, the adoption resulted in significant changes to the Company’s financial statement disclosures.

In January 2017, the FASB issued ASU No. 2017-04, Simplifying the Test for Goodwill Impairment ("ASU 2017-04"). ASU 2017-04 simplifies the accounting for goodwill impairment by removing Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. ASU 2017-04 is effective for annual or interim goodwill impairment tests in fiscal years beginning after December 15, 2019, and should be applied on a prospective basis. The Company adopted this guidance effective January 1, 2019. The adoption of ASU 2017-04 did not have a material impact on our condensed consolidated financial statements.

In June 2018, the FASB issued ASU No. 2018-07, Compensation-Stock Compensation (Topic 718) (“Topic 718”): Improvements to Nonemployee Share-Based Payment Accounting (“ASU 2018-07”). ASU 2018-07 expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from non-employees, and as a result, the accounting for share-based payments to non-employees will be substantially aligned. ASU 2018-07 is effective for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. The Company adopted this standard effective January 1, 2019. The adoption of ASU 2018-07 did not have a material impact on the Company’s financial position or results of operations.

In July 2018, the FASB issued ASU No. 2018-09, “Codification Improvements” (“ASU 2018-09”). ASU 2018-09 provides amendments to a wide variety of topics in the FASB’s Accounting Standards Codification, which applies to all reporting entities within the scope of the affected accounting guidance. The transition and effective date guidance are based on the facts and circumstances of each amendment. Some of the amendments in ASU 2018-09 do not require transition guidance and were effective upon issuance of ASU 2018-09. However, many of the amendments do have transition guidance with effective dates for annual periods beginning after December 15, 2018. ASU 2018-09 did not have a material impact on the Company’s financial statements and related disclosures.

Recently issued accounting pronouncements

In August 2018, the FASB issued ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract ("ASU 2018-15"). ASU 2018-15 requires a customer in a cloud computing arrangement that is a service contract to follow the internal-use software guidance to determine which implementation costs to defer and recognize as an asset. The effective date for ASU 2018-15 is for annual and interim periods beginning after December 15, 2019. Early adoption is permitted.

The Company is currently evaluating the impact ASU 2018-15 will have on its consolidated financial statements.

In August 2018, the FASB issued ASU 2018-13— Fair Value Measurement (Topic 820): Disclosure Framework— Changes to the Disclosure Requirements for Fair Value Measurements ("ASU 2018-13"). ASU 2018-13 modifies fair value measurement disclosure requirements. The effective date for ASU 2018-13 is for annual and interim periods beginning after December 15, 2019. Early adoption is permitted. The Company is currently evaluating the impact ASU 2018-13 will have on its consolidated financial statements.

In June 2016, the FASB issued ASU 2016-13—Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"). ASU 2016-13 requires measurement and recognition of expected credit losses for financial assets held. The amendments in ASU 2016-13 eliminate the probable threshold for initial recognition of a credit loss in current GAAP and reflect an entity’s current estimate of all expected credit losses. ASU 2016-13 is effective for interim and annual reporting periods beginning January 1, 2020, and is to be applied using a modified retrospective transition method. Earlier adoption is permitted. The Company is currently evaluating the impact ASU 2016-13 will have on its consolidated financial statements.

Critical accounting policies

The Company’s significant accounting policies are described in Note 2, Significant Accounting Policies, in the 2018 Form 10-K. During the six months ended June 30, 2019, the Company adopted the following additional significant accounting policies:

Leases

Effective January 1, 2019, the Company adopted ASC 842 using the optional transition method. The adoption of ASC 842 represents a change in accounting principle that aims to increase transparency and comparability among organizations by requiring the recognition of right-of-use assets and lease liabilities on the balance sheet for both operating and finance leases. In addition, the standard requires enhanced disclosures that meet the objective of enabling financial statement users to assess the amount, timing, and uncertainty of cash flows arising from leases. The reported results for the three and six months ended June 30, 2019 reflect the application of ASC 842 guidance, while the reported results for prior periods were prepared in conjunction with ASC 840.

As part of the adoption of ASC 842, the Company utilized certain practical expedients outlined in the guidance. These practical expedients include:


•	Accounting policy election to use the short-term lease exception by asset class;


•	Election of the practical expedient package during transition, which includes:


◦	An entity need not reassess whether any expired or existing contracts are or contain leases.


◦	An entity need not reassess the classification for any expired or existing leases. As a result, all leases that were classified as operating leases in accordance with ASC 840 are classified as operating leases under ASC 842, and all leases that were classified as capital leases in accordance with ASC 840 are classified as finance leases under ASC 842.


◦	An entity need not reassess initial direct costs for any existing leases.

The Company’s lease portfolio as of the adoption date includes: a property lease for its manufacturing facility, a property lease for its headquarters in Cambridge, MA, and a property lease for office space in Philadelphia, PA. The Company also elected the short–term lease recognition exemption for all leases that qualify, where a right–of–use asset or lease liability will not be recognized for short–term leases. The Company determines if an arrangement is a lease at the inception of the contract and need not separate out non-lease components from lease components, for all classes of underlying assets. The asset components of the Company’s operating leases are recorded as operating lease right-of-use assets and reported within Other assets in the Company's condensed consolidated balance sheets. The short term and long term liability components are recorded in Other current liabilities and Other liabilities, respectively, in the Company’s condensed consolidated balance sheets. As of June 30, 2019, the Company did not have any finance leases.

Right-of-use assets and operating lease liabilities are recognized based on the present value of lease payments over the lease term at the commencement date. Existing leases in the Company’s lease portfolio as of the adoption date were valued as of January 1, 2019. The Company uses an incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments, if an implicit rate of return is not provided with the lease contract. Operating lease right-of-use assets are adjusted for incentives received.

Operating lease costs are recognized on a straight-line basis over the lease term, in accordance with ASC 842, and also includes variable operating costs incurred during the period. Lease costs also include amounts related to short term leases.

Fair Value of Financial Instruments

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

The fair value hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three broad levels as follows: Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly; and Level 3 inputs are unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement.

The following table presents information about the Company’s financial assets and liabilities that have been measured at fair value, and indicates the fair value hierarchy of the valuation inputs utilized to determine such fair value. The Company determines the fair value of contingent consideration using Level 3 inputs.

The following table summarizes the assets and liabilities measured at fair value on a recurring basis at June 30, 2019 (in thousands):



Description	June 30, 2019		Active Markets (Level 1)		Observable Inputs (Level 2)		Unobservable Inputs (Level 3)

Assets:
Cash and cash equivalents	$	64,931	$	64,931	$	—	$	—
Restricted cash	20		20		—		—
Total assets	$	64,951	$	64,951	$	—	$	—
Liabilities:
Contingent consideration	91,400		—		—		91,400
Total liabilities	$	91,400	$	—	$	—	$	91,400

The following table summarizes the assets and liabilities measured at fair value on a recurring basis at December 31, 2018 (in thousands):



Description	December 31, 2018		Active Markets (Level 1)		Observable Inputs (Level 2)		Unobservable Inputs (Level 3)

Assets:
Cash and cash equivalents	$	50,422	$	50,422	$	—	$	—
Restricted cash	20		20		—		—
Total assets	$	50,442	$	50,442	$	—	$	—
Liabilities:
Contingent consideration	48,400		—		—		48,400
Total liabilities	$	48,400	$	—	$	—	$	48,400

Contingent consideration

In 2016, the Company acquired Viventia through the issuance of common stock and contingent consideration (the "Acquisition"), pursuant to the terms of a share purchase agreement (the "Share Purchase Agreement"). The Company has valued the acquired assets and liabilities based on their estimated fair values as of September 20, 2016 and finalized its purchase accounting for the Acquisition during the third quarter of 2017. The contingent consideration relates to amounts potentially payable to Viventia's shareholders pursuant to the terms of the Share Purchase Agreement. Contingent consideration is measured at fair value and is based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. The valuation of contingent consideration uses assumptions the Company believes would be made by a market participant. The Company assesses these estimates on an on-going basis as additional data impacting the assumptions is obtained. Future changes in the fair value of contingent consideration related to updated assumptions and estimates are recognized within the condensed consolidated statements of operations and comprehensive loss.

Contingent consideration may change significantly as development progresses and additional data are obtained, impacting the Company’s assumptions regarding probabilities of successful achievement of related milestones used to estimate the fair value of the liability and the timing in which they are expected to be achieved. In evaluating the fair value information, considerable judgment is required to interpret the market data used to develop the estimates. The estimates of fair value may not be indicative of the amounts that could be realized in a current market exchange. Accordingly, the use of different market assumptions and/or different valuation techniques could result in materially different fair value estimates. The following table sets forth a summary of changes in the fair value of the Company's contingent consideration liability (in thousands):



Beginning balance, December 31, 2018	$	48,400
Loss from change in fair value of contingent consideration	43,000
Ending balance, June 30, 2019	$	91,400

The fair value of the Company’s contingent consideration was determined using probabilities of successful achievement of regulatory milestones and commercial sales, the period in which these milestones and sales are expected to be achieved ranging from 2021 to 2033, the level of commercial sales of Vicinium^®within the United States, Europe, Japan and other potential markets, discount rates ranging from 6.6% to 13.7% as of December 31, 2018 and 6.1% to 11.8% as of June 30, 2019. Significant changes in any of these assumptions would result in a significantly higher or lower fair value measurement. During the quarter ended June 30, 2019, the Company reassessed the total addressable global market for NMIBC and determined that both the global market size and estimated potential Vicinium commercial net sales within the global NMIBC market were likely higher than the Company’s previous estimates. Specific drivers of the increased revenue estimates include the expectation that Vicinium could achieve peak market penetration earlier than previously estimated, and the expectation that Vicinium sales outside the United States could be two to three times the expected sales volumes in the United States. As contingent consideration incorporates a royalty rate of 2% on all commercial net sales reported through December 2033, an increase in expected future net sales correlates to an increase in the fair value of the Company’s potential contingent consideration. Accordingly, the Company’s contingent consideration at June 30, 2019 was adjusted to reflect the Company’s updated view of the NMIBC market and Vicinium’s potential sales volumes in that market.

There have been no changes to the valuation methods utilized during the three and six months ended June 30, 2019. The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of assets or liabilities between levels during the three and six months ended June 30, 2019.

- 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

License Agreement with Roche	6 Months Ended
License Agreement with Roche	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License Agreement with Roche	License Agreement with Roche On June 10, 2016, the Company entered into the License Agreement with Roche, which became effective on August 16, 2016. Under the License Agreement, 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 or all other IL-6 antagonistic anti-IL-6 monoclonal antibodies , to make, have made, use, have used, register, have registered, sell, have sold, offer for sale, import and export any product containing such an antibody or any companion diagnostic used to predict or monitor response to treatment with such a product (collectively, the “Licensed Intellectual Property”). During 2016, the Company received an upfront license fee of $7.5 million and a milestone payment of $22.5 million. The Company is entitled to receive up to $240.0 million in additional consideration upon the achievement of specified regulatory, development and commercial milestones. Specifically, an aggregate amount of up to $175.0 million is payable to the Company for the achievement of specified milestones with respect to the first indication: $50.0 million in development milestones, $50.0 million in regulatory milestones and $75.0 million in commercialization milestones. Additional amounts of up to $65.0 million are payable upon the achievement of specified development and regulatory milestones in a second indication. 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% for 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 buy-out options. The License Agreement is subject to the provisions of Accounting Standards Codification 606, Revenue from Contracts with Customers ("ASC 606"), which was adopted effective January 1, 2018 utilizing a modified retrospective method. The Company concluded that all performance obligations had been achieved as of the adoption date and therefore the full transaction price was considered earned. The transaction price was determined to be the $30.0 million received in 2016. Additional consideration to be paid to the Company upon the achievement of certain milestones will be included if it is expected that the amounts will be received and the amounts would not be subject to a constraint. As of the date of the adoption, no amounts were expected to be received from the achievement of any milestones due to the nature of the milestones and the development status of the product candidates at the time of the adoption. As a result, there were no amounts required to be recorded as a cumulative adoption adjustment as the consideration recognized under ASC 606 was consistent with the amounts recognized under the previous accounting literature. During the three and six months ended June 30, 2019 and June 30, 2018, the Company concluded that there would be no adjustments to the transaction price as the Company continued to not expect any amounts to be received from any milestones within the License Agreement. This is due to the nature of the milestones and the development status of the product candidates as of the end of each reporting period. As a result, no revenue was recognized during the three-month and six-month periods ended June 30, 2019 and June 30, 2018 as all performance obligations had been previously achieved and there was no change in the transaction price during the period.

Accrued Expenses

6 Months Ended

Jun. 30, 2019

Payables and Accruals [Abstract]

Accrued Expenses

Accrued expenses consisted of the following (in thousands):



	June 30, 2019		December 31, 2018
Development costs	$	3,758	$	2,928
Employee compensation	906		1,045
Severance to former CEO and other employees	344		278
Professional fees	615		464
Other	7		31
	$	5,630	$	4,746

Stephen A. Hurly departed as the President and Chief Executive of the Company, effective as of August 7, 2018. In connection with his departure, Mr. Hurly and the Company entered into a separation agreement and general release, dated September 28, 2018 (the “Separation Agreement”), which sets forth the terms of Mr. Hurly’s separation from the Company. Pursuant to the Separation Agreement, which includes Mr. Hurly's agreement to a release of claims and complying with certain other continuing obligations contained therein, the Company is obligated to pay Mr. Hurly a total amount of $637,500, less applicable withholdings and deductions, which consists of the equivalent of twelve months of Mr. Hurly’s base salary ($425,000) immediately prior to his departure and Mr. Hurly’s annual target bonus for 2018 ($212,500). In addition, the Company, to the extent allowed by applicable law and the applicable plan documents, will continue to provide Mr. Hurly and certain of his dependents with group health and dental insurance for a period of up to twelve months after the effective date of the Separation Agreement. Accrued severance related to this agreement was $56,000 as of June 30, 2019. The remaining amounts of accrued severance as of June 30, 2019 relate to terminations of other employees during 2019.

Shareholder Equity

6 Months Ended

Jun. 30, 2019

Equity [Abstract]

Shareholder Equity

Equity Financings

On March 23, 2018, the Company raised approximately $9.0 million of net proceeds from the sale of 7,968,128 shares of common stock at a price of $1.13 per share in a registered direct public offering and the sale of common stock purchase warrants to purchase 7,968,128 shares of common stock at a price of $0.125 per warrant in a concurrent private placement (collectively, the “March 2018 Financing”). Subject to certain ownership limitations, the common stock purchase warrants issued in the March 2018 Financing were exercisable immediately upon issuance at an exercise price equal to $1.20 per share of common stock, subject to adjustments as provided under the terms of such common stock purchase warrants. The common stock purchase warrants are exercisable for five years from March 23, 2018.

On June 4, 2018, we raised approximately $41.9 million of net proceeds from the sale of 25,555,556 shares of our common stock in an underwritten public offering.

During the six months ended June 30, 2018, the Company received proceeds of $7.3 million from the exercise of outstanding warrants to purchase common stock issued in connection with (i) its underwritten public offering in November 2017 and (ii) its private placement of common stock warrants in March 2018.

On June 21, 2019, the Company completed the June 2019 Financing, which raised approximately $28 million of net proceeds, pursuant to which it issued 20,410,000 shares of common stock and accompanying warrants to acquire 20,410,000 shares of common stock. The combined purchase price for each share of common stock and accompanying warrant was $1.47. Subject to certain ownership limitations, such warrants were exercisable immediately at an exercise price equal to $1.47 per share of common stock, subject to adjustments as provided under the terms of such warrants and have a one-year term expiring on June 21, 2020.

Between April 1, 2019 and June 30, 2019, the Company received proceeds of $3.4 million from the exercise of outstanding warrants to purchase common stock issued in connection with (i) its underwritten public offering in November 2017 and (ii) its private placement of common stock warrants in March 2018.

Common stock warrants are accounted for in accordance with applicable accounting guidance provided in ASC Topic 815, Derivatives and Hedging - Contracts in Entity’s Own Equity, as either derivative liabilities or as equity instruments depending upon the specific terms of the warrant agreement. All of the Company’s warrants are classified as equity because they do not contain terms requiring derivative liability classification.

Warrants outstanding and warrant activity for the six-month period ended June 30, 2019 is as follows:



Description	Classification	Issuance Date	Exercise Price	Expiration Date	Balance December 31, 2018	Warrants Issued	Warrants Exercised	Warrants Expired	Balance June 30, 2019
Non-tradeable warrants	Equity	06/21/19	$1.47	June 2020	—	20,410,000	—	—	20,410,000
Non-tradeable warrants	Equity	03/23/18	$1.20	Mar. 2023	7,210,945	—	1,861,115	—	5,349,830
Non-tradeable warrants	Equity	11/01/17	$0.80	Nov. 2022	1,991,687	—	1,500,000	—	491,687
Non-tradeable warrants	Equity	05/11/15	$11.83	May 2025	27,500	—	—	—	27,500
Non-tradeable warrants	Equity	11/25/14	$11.04	Nov. 2024	27,500	—	—	—	27,500
					9,257,632	20,410,000	3,361,115	—	26,306,517

Share-Based Payments

At the Company's 2019 Annual Meeting of Stockholders (the “Annual Meeting”) held on June 19, 2019, the Company's stockholders approved an amendment to the 2014 Plan, that (i) increased the number of shares reserved for issuance under the 2014 Plan by 7,908,972 shares and (ii) eliminated the “evergreen” or automatic replenishment provision of the 2014 Plan pursuant to which the number of shares authorized for issuance under the 2014 Plan is automatically increased on an annual basis (collectively, the "2014 Plan Amendment").

As of June 30, 2019, the total number of shares of common stock available for issuance under the 2014 Plan was 9,045,174.

In September 2016, the Company issued 650,000 inducement equity awards outside the 2014 Plan in accordance with Nasdaq Listing Qualifications Department (“Nasdaq”) Listing Rule 5635(c)(4). The inducement equity awards were approved and recommended by the Company's Compensation Committee, approved by the Board of Directors and were made as an inducement material to certain individuals’ acceptance of employment with the Company in accordance with Nasdaq Listing Rule 5635(c)(4). In August 2018, the Company issued 1,350,000 inducement equity awards outside the 2014 Plan in accordance with Nasdaq Listing Rule 5635(c)(4). The inducement equity awards were approved and recommended by the Company's Compensation Committee, approved by the Board of Directors and were made as an inducement material to Dr. Thomas R. Cannell’s acceptance of employment with the Company in accordance with Nasdaq Listing Rule 5635(c)(4). In December 2018, the Company issued 425,000 inducement equity awards outside the 2014 Plan in accordance with Nasdaq Listing Rule 5635(c)(4). The inducement equity awards were approved and recommended by the Company's Compensation Committee, approved by the Board of Directors and were made as an inducement material to Dr. Dennis Kim’s acceptance of employment with the Company in accordance with Nasdaq Listing Rule 5635(c)(4). As of June 30, 2019, the total amount of shares outstanding classified as inducement awards was 1,875,000.

The Company also maintains the Company's 2009 Stock Incentive Plan, as amended and restated, and the Company's 2014 Employee Stock Purchase Plan (the "2014 ESPP").

Stock-Based Compensation Expense

Stock-based compensation expense by award type was as follows (in thousands):



	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Stock options	$	355	$	283	$	680	$	659
Restricted stock	—		—		$	—	22
Employee stock purchase plan	—		2		2		5
	$	355	$	285	$	682	$	686

The Company allocated stock-based compensation expense as follows in the condensed consolidated statements of operations and comprehensive loss (in thousands):



	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Research and development expense	$	86	$	123	$	139	$	288
General and administrative expense	269		162		$	543	$	398
	$	355	$	285	$	682	$	686

At June 30, 2019, there was $3.4 million of total unrecognized compensation expense related to unvested stock options for employee and non-employee consultants and shares issued pursuant to the 2014 ESPP. This unrecognized compensation expense is expected to be recognized over a weighted-average period of 2.98 years.

Stock Options

A summary of the stock option activity is presented below:



	Shares		Weighted-Average Exercise Price
Outstanding at December 31, 2018	3,941,947		$	2.12
Granted	2,425,115		0.93
Exercised	(30,000	)	1.50
Cancelled or forfeited	(558,018	)	2.30
Outstanding at June 30, 2019	5,779,044		$	1.60
Exercisable at June 30, 2019	1,189,418		$	2.86

In October 2017, the Company issued stock option awards to certain employees which contained performance vesting conditions. These options vested in installments based on the achievement of certain strategic and clinical milestones. In January 2018, March 2018, June 2018, and July 2019, the Compensation Committee of our Board determined that certain performance milestones were met. Stock-based compensation expense associated with these performance-based stock options is recognized over the service and performance period if any performance condition is considered probable of achievement using management’s best estimate. For these performance-based awards, the Company recorded $2,000 and ($16,000) of expense in the three and six months ended June 30, 2019, respectively. The expense in the six months ended June 30, 2019 reflects forfeitures recorded during the period. The Company recorded $63,000 and $274,000 of expense in the three and six months ended June 30, 2018, respectively. As of June 30, 2019, there was no unrecognized compensation expense remaining related to performance-based awards.

Restricted Stock

From time to time, upon approval by the Board, certain employees, directors and consultants have been granted restricted shares of common stock and restricted stock units. As of June 30, 2019, the Company does not have any outstanding restricted stock awards or restricted stock units.

Employee Stock Purchase Plan

On March 14, 2019, the Company issued and sold 8,601 shares of its common stock pursuant to the 2014 ESPP at a purchase price of $0.8356 per share and on March 14, 2018, the Company issued and sold 9,565 shares of its common stock pursuant to the 2014 ESPP at a purchase price of $0.9800 per share. No shares were issued under the 2014 ESPP for the three months ended June 30, 2019. 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.

Net (Loss) Income Per Share

6 Months Ended

Jun. 30, 2019

Earnings Per Share [Abstract]

Net (Loss) Income Per Share

Basic net (loss) income per share is calculated by dividing net (loss) income by the weighted-average shares outstanding during the period, without consideration for common stock equivalents. Diluted net (loss) income per share is calculated by adjusting weighted-average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock method. For purposes of the diluted net (loss) income per share calculation, stock options, unvested restricted stock, and common stock warrants are considered to be common stock equivalents. Warrants to purchase the Company’s common stock participate in any dividends declared by the Company 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 they have no contractual obligation to share in the losses of the Company.

The following common stock equivalents were excluded from the calculation of diluted net (loss) income per share for the periods indicated because including them would have had an anti-dilutive effect or the exercise prices were greater than the average market price of the common shares.



	Three Months Ended June 30,		Six Months Ended June 30,
	2019	2018	2019	2018
Stock options	5,779,044	4,027,826	5,779,044	4,027,826
Common stock warrants	26,306,517	9,307,632	26,306,517	9,307,632
	32,085,561	13,335,458	32,085,561	13,335,458

Cash, cash equivalents and restricted cash

6 Months Ended

Jun. 30, 2019

Cash and Cash Equivalents [Abstract]

Cash, cash equivalents and restricted cash

The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same such amounts shown in the condensed consolidated statements of cash flows (in thousands):



	June 30,	December 31,
	2019	2018
Cash and cash equivalents	64,931	$	50,422
Restricted cash	20	20
Total cash, cash equivalents and restricted cash	64,951	50,442

Amounts included in restricted cash represent cash held to collateralize a credit limit with Silicon Valley Bank of $20,000 as of June 30, 2019 and December 31, 2018, respectively.

Related Party Transactions	6 Months Ended
Related Party Transactions	Jun. 30, 2019
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions The Company leases an approximately 31,100 square foot manufacturing, laboratory, and office facility in Winnipeg, Manitoba, from an affiliate of Leslie L. Dan, a director of the Company until his retirement effective July 16, 2019, under a five-year renewable lease through September 2020 with a right to renew the lease for one subsequent five-year term. Operating lease cost under this lease, which includes related operating expenses, was $71,000 and $146,000 for the three and six months ended June 30, 2019, respectively. Under ASC 840, rent expense for this lease was $80,000 and $161,000 for the three and six months ended June 30, 2018, respectively. The Company pays fees, under an intellectual property license agreement, to Protoden Technologies, Inc. (“Protoden”), a company owned by Clairmark Investments Ltd. (“Clairmark”), an affiliate of Mr. Dan. Pursuant to the agreement, the Company has an exclusive, perpetual, irrevocable and non-royalty bearing license, with the right to sublicense, under certain patents and technology to make, use and sell products that utilize such patents and technology for an annual fee of $100,000. Upon expiration of the term, the licenses granted to the Company will require no further payments to Protoden. During each of the six-month periods ended June 30, 2019 and 2018, $100,000 was paid to Clairmark pursuant to the license agreement.

Operating Leases

6 Months Ended

Jun. 30, 2019

Leases [Abstract]

Operating Leases

On January 1, 2019, the Company adopted ASC 842 using the optional transition method. The Company’s lease portfolio includes: an operating lease for its manufacturing facility in Winnipeg, Manitoba, a short-term property lease for its headquarters in Cambridge, MA and a short-term property lease for office space in Philadelphia, PA. The asset component of the Company’s operating leases is recorded as operating lease right-of-use assets and reported within other assets in the Company's condensed consolidated balance sheets. The short term and long term liability components are recorded in other current liabilities and other liabilities, respectively, in the Company’s condensed consolidated balance sheets.

Operating lease cost is recognized on a straight-line basis over the lease term. The components of lease cost for the three and six months ended June 30, 2019 are as follows (in thousands):



	Three months ended June 30, 2019	Six months ended June 30, 2019
Lease Cost:
Operating lease cost (including related operating costs)	71	146
Short-term lease cost	53	129
Total lease cost	124	275



Supplemental Information:	Six months ended June 30, 2019
Weighted-average remaining lease term - operating leases (in years)	1.25
Weighted-average discount rate - operating leases	12	%

Future minimum lease payments under non-cancelable operating leases under ASC 842 as of June 30, 2019 are as follows (in thousands):



	Operating lease payments
2019 (1)	76
2020	113
Total future minimum lease payments	189
Less: amounts representing present value adjustment	9
Operating lease liabilities as of June 30, 2019	180
Less: current portion of operating lease liabilities	142
Operating lease liabilities, net of current portion	38

(1) Amounts are for the remaining six months ending December 31, 2019

The Company leases a manufacturing facility located in Winnipeg, Manitoba Canada, which consists of an approximately 31,100 square foot manufacturing, laboratory, warehouse and office facility, under a five-year renewable lease through September 2020 with a right to renew the lease for one subsequent five-year term. The minimum monthly rent under this lease is approximately $12,600 per month. The Company expects to incur approximately $12,300 in related operating expenses per month. Operating lease cost under this lease, including the related operating costs, was $71,000 and $146,000 for the three and six months ended June 30, 2019, respectively. Under ASC 840, rent expense for this lease, including related operating costs, was $80,000 and $161,000 for the three and six months ended June 30, 2018, respectively.

The Company leases its current corporate headquarters in Cambridge, Massachusetts under a short-term lease that extends through December 31, 2019. The minimum monthly rent for this office space is approximately $8,000 per month. The Company recorded $24,000 and $51,000 in short-term lease cost for the three and six months ended June 30, 2019, respectively. Under ASC 840, the Company recorded $36,000 and $62,000 in rent expense for the three and six months ended June 30, 2018, respectively, for this lease.

The Company leases office space in Philadelphia, PA, where it occupies office space under a short-term lease that extends through December 31, 2019. Currently, the minimum monthly rent under this lease is approximately $11,000 per month. The Company recorded $29,000 and $78,000 in short term lease cost for the three and six months ended June 30, 2019, respectively. Under ASC 840, the Company recorded $32,000 and $56,000 in rent expense for the three and six months ended June 30, 2018, respectively, for this lease.

Subsequent Events	6 Months Ended
Subsequent Events	Jun. 30, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Not applicable.

Significant Accounting Policies and Recent Accounting Pronouncements (Policies)

6 Months Ended

Jun. 30, 2019

Accounting Policies [Abstract]

Basis of presentation

The condensed consolidated financial statements as of June 30, 2019 and December 31, 2018 and for the three and six months ended June 30, 2019 and 2018 and the related information contained within the notes to the condensed consolidated financial statements are unaudited. The unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting standards applicable to interim financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s consolidated financial position as of June 30, 2019, its results of operations for the three and six months ended June 30, 2019 and 2018, its statement of shareholders' equity for the six months ended June 30, 2019 and 2018, and its cash flows for the six months ended June 30, 2019 and 2018. The financial data and the other financial information disclosed in these notes to the condensed consolidated financial statements related to the three and six-month periods are also unaudited. The results of operations for the three and six months ended June 30, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019 or for any other future annual or interim period. The condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 that was filed with the Securities and Exchange Commission (“SEC”) on March 1, 2019 (the "2018 Form 10-K").

The condensed consolidated financial statements include the accounts of the Company, its wholly owned subsidiary, Viventia Bio Inc. ("Viventia"), and its indirect subsidiaries, Viventia Bio USA Inc. and Viventia Biotech (EU) Limited. All inter-company transactions and balances have been eliminated in consolidation. The condensed consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles.

The functional currency of Viventia, Viventia Bio USA Inc. and Viventia Biotech (EU) Limited is the U.S. dollar.

Recently adopted accounting standards and Recently issued accounting standards

Recently adopted accounting standards

Recently issued accounting pronouncements

The Company is currently evaluating the impact ASU 2018-15 will have on its consolidated financial statements.

Critical accounting policies

Leases

As part of the adoption of ASC 842, the Company utilized certain practical expedients outlined in the guidance. These practical expedients include:


•	Accounting policy election to use the short-term lease exception by asset class;


•	Election of the practical expedient package during transition, which includes:


◦	An entity need not reassess whether any expired or existing contracts are or contain leases.


◦	An entity need not reassess the classification for any expired or existing leases. As a result, all leases that were classified as operating leases in accordance with ASC 840 are classified as operating leases under ASC 842, and all leases that were classified as capital leases in accordance with ASC 840 are classified as finance leases under ASC 842.


◦	An entity need not reassess initial direct costs for any existing leases.

Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table summarizes the assets and liabilities measured at fair value on a recurring basis at June 30, 2019 (in thousands):



Description	June 30, 2019		Active Markets (Level 1)		Observable Inputs (Level 2)		Unobservable Inputs (Level 3)

Assets:
Cash and cash equivalents	$	64,931	$	64,931	$	—	$	—
Restricted cash	20		20		—		—
Total assets	$	64,951	$	64,951	$	—	$	—
Liabilities:
Contingent consideration	91,400		—		—		91,400
Total liabilities	$	91,400	$	—	$	—	$	91,400

The following table summarizes the assets and liabilities measured at fair value on a recurring basis at December 31, 2018 (in thousands):



Description	December 31, 2018		Active Markets (Level 1)		Observable Inputs (Level 2)		Unobservable Inputs (Level 3)

Assets:
Cash and cash equivalents	$	50,422	$	50,422	$	—	$	—
Restricted cash	20		20		—		—
Total assets	$	50,442	$	50,442	$	—	$	—
Liabilities:
Contingent consideration	48,400		—		—		48,400
Total liabilities	$	48,400	$	—	$	—	$	48,400

Summary of Contingent Consideration Obligations

The following table sets forth a summary of changes in the fair value of the Company's contingent consideration liability (in thousands):



Beginning balance, December 31, 2018	$	48,400
Loss from change in fair value of contingent consideration	43,000
Ending balance, June 30, 2019	$	91,400

Accrued Expenses (Tables)

6 Months Ended

Jun. 30, 2019

Payables and Accruals [Abstract]

Components of Accrued Expenses

Accrued expenses consisted of the following (in thousands):



	June 30, 2019		December 31, 2018
Development costs	$	3,758	$	2,928
Employee compensation	906		1,045
Severance to former CEO and other employees	344		278
Professional fees	615		464
Other	7		31
	$	5,630	$	4,746

Shareholder Equity (Tables)

6 Months Ended

Jun. 30, 2019

Equity [Abstract]

Summary of Warrants Outstanding and Warrant Activity

Warrants outstanding and warrant activity for the six-month period ended June 30, 2019 is as follows:



Description	Classification	Issuance Date	Exercise Price	Expiration Date	Balance December 31, 2018	Warrants Issued	Warrants Exercised	Warrants Expired	Balance June 30, 2019
Non-tradeable warrants	Equity	06/21/19	$1.47	June 2020	—	20,410,000	—	—	20,410,000
Non-tradeable warrants	Equity	03/23/18	$1.20	Mar. 2023	7,210,945	—	1,861,115	—	5,349,830
Non-tradeable warrants	Equity	11/01/17	$0.80	Nov. 2022	1,991,687	—	1,500,000	—	491,687
Non-tradeable warrants	Equity	05/11/15	$11.83	May 2025	27,500	—	—	—	27,500
Non-tradeable warrants	Equity	11/25/14	$11.04	Nov. 2024	27,500	—	—	—	27,500
					9,257,632	20,410,000	3,361,115	—	26,306,517

Summary of Stock-Based Compensation Expense

Stock-based compensation expense by award type was as follows (in thousands):



	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Stock options	$	355	$	283	$	680	$	659
Restricted stock	—		—		$	—	22
Employee stock purchase plan	—		2		2		5
	$	355	$	285	$	682	$	686

The Company allocated stock-based compensation expense as follows in the condensed consolidated statements of operations and comprehensive loss (in thousands):



	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Research and development expense	$	86	$	123	$	139	$	288
General and administrative expense	269		162		$	543	$	398
	$	355	$	285	$	682	$	686

Summary of Stock Option Activity and Related Information

A summary of the stock option activity is presented below:



	Shares		Weighted-Average Exercise Price
Outstanding at December 31, 2018	3,941,947		$	2.12
Granted	2,425,115		0.93
Exercised	(30,000	)	1.50
Cancelled or forfeited	(558,018	)	2.30
Outstanding at June 30, 2019	5,779,044		$	1.60
Exercisable at June 30, 2019	1,189,418		$	2.86

Net (Loss) Income Per Share (Tables)

6 Months Ended

Jun. 30, 2019

Earnings Per Share [Abstract]

Schedule of Antidilutive Securities



	Three Months Ended June 30,		Six Months Ended June 30,
	2019	2018	2019	2018
Stock options	5,779,044	4,027,826	5,779,044	4,027,826
Common stock warrants	26,306,517	9,307,632	26,306,517	9,307,632
	32,085,561	13,335,458	32,085,561	13,335,458

Cash, cash equivalents and restricted cash (Tables)

6 Months Ended

Jun. 30, 2019

Cash and Cash Equivalents [Abstract]

Reconciliation of Cash, Cash Equivalents and Restricted Cash



	June 30,	December 31,
	2019	2018
Cash and cash equivalents	64,931	$	50,422
Restricted cash	20	20
Total cash, cash equivalents and restricted cash	64,951	50,442

Operating Leases (Tables)

6 Months Ended

Jun. 30, 2019

Leases [Abstract]

Lease Cost

The components of lease cost for the three and six months ended June 30, 2019 are as follows (in thousands):



	Three months ended June 30, 2019	Six months ended June 30, 2019
Lease Cost:
Operating lease cost (including related operating costs)	71	146
Short-term lease cost	53	129
Total lease cost	124	275



Supplemental Information:	Six months ended June 30, 2019
Weighted-average remaining lease term - operating leases (in years)	1.25
Weighted-average discount rate - operating leases	12	%

Minimum Aggregate Future Lease Commitment

Future minimum lease payments under non-cancelable operating leases under ASC 842 as of June 30, 2019 are as follows (in thousands):



	Operating lease payments
2019 (1)	76
2020	113
Total future minimum lease payments	189
Less: amounts representing present value adjustment	9
Operating lease liabilities as of June 30, 2019	180
Less: current portion of operating lease liabilities	142
Operating lease liabilities, net of current portion	38

(1) Amounts are for the remaining six months ending December 31, 2019

Organization and Basis of Presentation (Details) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended	6 Months Ended
	Jun. 21, 2019	Jun. 04, 2018	Mar. 23, 2018	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents				$ 64,931	$ 64,931		$ 50,422
Net working capital				59,600	59,600
Accumulated deficit				246,839	246,839		$ 186,024
Proceeds from sale of stock	$ 28,000	$ 41,900	$ 9,000
Sale of stock, shares issued (in shares)	20,410,000	25,555,556	7,968,128
Number of warrants (in shares)	20,410,000		7,968,128
Stock and warrants price per share (in usd per share)	$ 1.47
Exercise price per warrant (in usd per share)	$ 1.47		$ 1.20
Proceeds from issuance of common stock and the issuance and exercise of common stock warrants				$ 3,400	$ 31,243	$ 58,226
Exercise of common stock warrants (in shares)				3,400,000	3,361,115

Significant Accounting Policies and Recent Accounting Pronouncements - Recently Adopted Accounting Standards (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liability	$ 180
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use asset		$ 236
Operating lease liability		$ 236

Fair Value of Financial Instruments - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Assets:
Restricted cash	$ 20	$ 20
Liabilities:
Contingent consideration	91,400	48,400
Unobservable Inputs (Level 3)
Liabilities:
Contingent consideration	91,400	48,400
Recurring
Assets:
Cash and cash equivalents	64,931	50,422
Restricted cash	20	20
Total assets	64,951	50,442
Liabilities:
Contingent consideration	91,400	48,400
Total liabilities	91,400	48,400
Recurring \| Active Markets (Level 1)
Assets:
Cash and cash equivalents	64,931	50,422
Restricted cash	20	20
Total assets	64,951	50,442
Liabilities:
Contingent consideration	0	0
Total liabilities	0	0
Recurring \| Observable Inputs (Level 2)
Assets:
Cash and cash equivalents	0	0
Restricted cash	0	0
Total assets	0	0
Liabilities:
Contingent consideration	0	0
Total liabilities	0	0
Recurring \| Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Restricted cash	0	0
Total assets	0	0
Liabilities:
Contingent consideration	91,400	48,400
Total liabilities	$ 91,400	$ 48,400

Fair Value of Financial Instruments - Summary of Changes in Fair Value of Contingent Consideration (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance, December 31, 2018	$ 91,400	$ 48,400
Ending balance, June 30, 2019	91,400
Unobservable Inputs (Level 3)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance, December 31, 2018	91,400	$ 48,400
Loss from change in fair value of contingent consideration	43,000
Ending balance, June 30, 2019	$ 91,400

Fair Value of Financial Instruments - Additional Information (Details)	Jun. 30, 2019	Dec. 31, 2018
Discount Rate \| Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration liability measurements used (in percentage)	0.061	0.066
Discount Rate \| Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration liability measurements used (in percentage)	0.118	0.137
Royalty Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration liability measurements used (in percentage)	0.020

License Agreement with Roche (Details) - USD ($)			3 Months Ended		6 Months Ended		7 Months Ended
License Agreement with Roche (Details) - USD ($)	Jan. 01, 2018	Jun. 10, 2016	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2016
Organization And Basis Of Presentation [Line Items]
Adjustments to transaction price			$ 0	$ 0	$ 0	$ 0
Revenue recognized			$ 0	$ 0	$ 0	$ 0
Roche
Organization And Basis Of Presentation [Line Items]
Up-front license fee							$ 7,500,000
Additional up-front fee		$ 240,000,000
Roche \| Collaborative Arrangement, Revenue Based on Development Milestone
Organization And Basis Of Presentation [Line Items]
Amount payable upon achievement of specified milestones		50,000,000
Roche \| First Indication
Organization And Basis Of Presentation [Line Items]
Amount payable upon achievement of specified milestones		175,000,000
Roche \| Collaborative Arrangement, Revenue Based on Regulatory Milestone
Organization And Basis Of Presentation [Line Items]
Amount payable upon achievement of specified milestones		50,000,000
Roche \| Collaborative Arrangement, Revenue Based on Commercialization Milestone
Organization And Basis Of Presentation [Line Items]
Amount payable upon achievement of specified milestones		75,000,000
Roche \| Second Indication
Organization And Basis Of Presentation [Line Items]
Amount payable upon achievement of specified milestones		$ 65,000,000
Roche \| EBI-031 \| Minimum
Organization And Basis Of Presentation [Line Items]
Royalty rate (in percentage)		7.50%
Roche \| EBI-031 \| Maximum
Organization And Basis Of Presentation [Line Items]
Royalty rate (in percentage)		15.00%
Roche \| EBI-031 \| Collaborative Arrangement, Revenue Based on Development Milestone
Organization And Basis Of Presentation [Line Items]
Amount payable upon achievement of specified milestones							$ 22,500,000
Roche \| IL-6
Organization And Basis Of Presentation [Line Items]
Royalty rate (in percentage)		50.00%
Roche
Organization And Basis Of Presentation [Line Items]
Revenue recognized, transaction price	$ 30,000,000

Accrued Expenses (Details) - USD ($)	Sep. 28, 2018	Jun. 30, 2019	Dec. 31, 2018
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Development costs		$ 3,758,000	$ 2,928,000
Employee compensation		906,000	1,045,000
Severance to former CEO and other employees		344,000	278,000
Professional fees		615,000	464,000
Other		7,000	31,000
Total accrued expenses		5,630,000	$ 4,746,000
Former President and Chief Executive Officer
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Severance to former CEO and other employees	$ 637,500	$ 56,000
Base salary	425,000
Bonuses	$ 212,500
Separation Agreement, health and dental insurance coverage period (up to)	12 months

Shareholder Equity - Equity Financing (Details) - USD ($) $ / shares in Units, $ in Millions				3 Months Ended	6 Months Ended
	Jun. 21, 2019	Jun. 04, 2018	Mar. 23, 2018	Jun. 30, 2019	Jun. 30, 2018
Equity [Abstract]
Proceeds from sale of stock	$ 28.0	$ 41.9	$ 9.0
Sale of stock, shares issued (in shares)	20,410,000	25,555,556	7,968,128
Stock price per share (in usd per share)			$ 1.13
Number of warrants (in shares)	20,410,000		7,968,128
Warrant price per unit (in usd per unit)			$ 0.125
Exercise price per warrant (in usd per share)	$ 1.47		$ 1.20
Warrants exercise period	1 year		5 years
Proceeds from warrant exercises				$ 3.4	$ 7.3
Stock and warrants price per share (in usd per share)	$ 1.47

Shareholder Equity - Warrants (Details) - $ / shares	3 Months Ended	6 Months Ended
Shareholder Equity - Warrants (Details) - $ / shares	Jun. 30, 2019	Jun. 30, 2019	Jun. 21, 2019	Mar. 23, 2018
Class of Warrant or Right [Line Items]
Exercise price per warrant (in usd per share)			$ 1.47	$ 1.20
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)		9,257,632
Warrants Issued (in shares)		20,410,000
Warrants Exercised (in shares)	3,400,000	3,361,115
Warrants Expired (in shares)		0
Warrants outstanding, ending balance (in shares)	26,306,517	26,306,517
Warrants, Expiring June 2020
Class of Warrant or Right [Line Items]
Exercise price per warrant (in usd per share)	$ 1.47	$ 1.47
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)		0
Warrants Issued (in shares)		20,410,000
Warrants Exercised (in shares)		0
Warrants Expired (in shares)		0
Warrants outstanding, ending balance (in shares)	20,410,000	20,410,000
Warrants, Expiring March 2023
Class of Warrant or Right [Line Items]
Exercise price per warrant (in usd per share)	$ 1.20	$ 1.20
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)		7,210,945
Warrants Issued (in shares)		0
Warrants Exercised (in shares)		1,861,115
Warrants Expired (in shares)		0
Warrants outstanding, ending balance (in shares)	5,349,830	5,349,830
Warrants, Expiring November 2022
Class of Warrant or Right [Line Items]
Exercise price per warrant (in usd per share)	$ 0.80	$ 0.80
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)		1,991,687
Warrants Issued (in shares)		0
Warrants Exercised (in shares)		1,500,000
Warrants Expired (in shares)		0
Warrants outstanding, ending balance (in shares)	491,687	491,687
Warrants, Expiring May 2025
Class of Warrant or Right [Line Items]
Exercise price per warrant (in usd per share)	$ 11.83	$ 11.83
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)		27,500
Warrants Issued (in shares)		0
Warrants Exercised (in shares)		0
Warrants Expired (in shares)		0
Warrants outstanding, ending balance (in shares)	27,500	27,500
Warrants, Expiring November 2024
Class of Warrant or Right [Line Items]
Exercise price per warrant (in usd per share)	$ 11.04	$ 11.04
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)		27,500
Warrants Issued (in shares)		0
Warrants Exercised (in shares)		0
Warrants Expired (in shares)		0
Warrants outstanding, ending balance (in shares)	27,500	27,500

Shareholder Equity - Share-Based Payments (Details) - shares		1 Months Ended			6 Months Ended
	Jun. 19, 2019	Dec. 31, 2018	Aug. 31, 2018	Sep. 30, 2016	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option to purchase shares (in shares)		425,000		650,000	2,425,115
Outstanding classified as inducement awards (in shares)		3,941,947			5,779,044
Inducement awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding classified as inducement awards (in shares)					1,875,000
Chief Executive Officer \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option to purchase shares (in shares)			1,350,000
2014 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares reserved for future issuance (in shares)	7,908,972
Shares available for issuance (in shares)					9,045,174

Shareholder Equity - Stock-Based Compensation Expense (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 355,000	$ 285,000	$ 682,000	$ 686,000
Unrecognized compensation expense	0		0
2014 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense	3,400,000		$ 3,400,000
Period for recognition			2 years 11 months 23 days
Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	86,000	123,000	$ 139,000	288,000
General and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	269,000	162,000	543,000	398,000
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	355,000	283,000	680,000	659,000
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	0	0	0	22,000
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 0	$ 2,000	$ 2,000	$ 5,000

Shareholder Equity - Summary of Stock Option Activity (Details) - $ / shares	1 Months Ended		6 Months Ended
	Dec. 31, 2018	Sep. 30, 2016	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at beginning of period (in shares)			3,941,947
Granted (in shares)	425,000	650,000	2,425,115
Exercised (in shares)			(30,000)
Cancelled or forfeited (in shares)			(558,018)
Outstanding at end of period (in shares)	3,941,947		5,779,044
Exercisable at end of period (in shares)			1,189,418
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding at beginning of period (in USD per share)			$ 2.12
Granted (in USD per share)			0.93
Exercised (in USD per share)			1.50
Cancelled or forfeited (in USD per share)			2.30
Outstanding at end of period (in USD per share)	$ 2.12		1.60
Exercisable at end of period (in USD per share)			$ 2.86

Shareholder Equity - Stock Options and Employee Stock Purchase Plan (Details) - USD ($)			3 Months Ended		6 Months Ended
	Mar. 14, 2019	Mar. 14, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Equity [Abstract]
Compensation expense related to vested awards			$ 2,000	$ 63,000	$ (16,000)	$ 274,000
Unrecognized compensation expense			0		0
2014 ESPP
Equity [Abstract]
Unrecognized compensation expense			$ 3,400,000		$ 3,400,000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock pursuant to the 2014 ESPP (in shares)	8,601	9,565	0
Purchase price of shares authorized (in USD per share)	$ 0.8356	$ 0.9800

Net (Loss) Income Per Share - Antidilutive Securities (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
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)	32,085,561	13,335,458	32,085,561	13,335,458
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)	5,779,044	4,027,826	5,779,044	4,027,826
Common stock 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)	26,306,517	9,307,632	26,306,517	9,307,632

Cash, cash equivalents and restricted cash (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 64,931	$ 50,422
Restricted cash	20	20
Total cash, cash equivalents and restricted cash	$ 64,951	$ 50,442	$ 62,981	$ 14,690

Related Party Transactions (Details) - Director affiliate	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) ft² option	Jun. 30, 2018 USD ($)
Protoden Intellectual Property
Related Party Transaction [Line Items]
Operating lease costs and rent expense in related party transaction			$ 100,000	$ 100,000
Annual fee under license agreement			$ 100,000
Lease Facility In Winnipeg, Manitoba
Related Party Transaction [Line Items]
Office space, square foot \| ft²			31,100
Lease term	5 years		5 years
Renewal option \| option			1
Lease renewal term	5 years		5 years
Operating lease costs and rent expense in related party transaction	$ 71,000	$ 80,000	$ 146,000	$ 161,000

Operating Leases - Lease Costs (Details) $ in Thousands	3 Months Ended	6 Months Ended
Operating Leases - Lease Costs (Details) $ in Thousands	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
Lease Cost:
Operating lease cost (including related operating costs)	$ 71	$ 146
Short-term lease cost	53	129
Total lease cost	$ 124	$ 275
Supplemental Information:
Weighted-average remaining lease term - operating leases (in years)	1 year 3 months	1 year 3 months
Weighted-average discount rate - operating leases	12.00%	12.00%

Operating Leases - Minimum Aggregate Future Lease Commitments (Details) $ in Thousands	Jun. 30, 2019 USD ($)
Leases [Abstract]
2019	$ 76
2020	113
Total future minimum lease payments	189
Less: amounts representing present value adjustment	9
Operating lease liabilities as of June 30, 2019	180
Less: current portion of operating lease liabilities	142
Operating lease liabilities, net of current portion	$ 38

Operating Leases - Narrative (Details)	3 Months Ended		6 Months Ended
Operating Leases - Narrative (Details)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) ft² term	Jun. 30, 2018 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease cost (including related operating costs)	$ 71,000		$ 146,000
Short-term lease cost	$ 53,000		$ 129,000
Canada
Lessee, Lease, Description [Line Items]
Office space, square foot \| ft²			31,100
Lease term	5 years		5 years
Renewal option \| term			1
Renewal term	5 years		5 years
Monthly rent			$ 13,000
Related operating expenses			12,300
Operating lease cost (including related operating costs)	$ 71,000		146,000
Rent expense Under ASC 840				$ 161,000
Massachusetts
Lessee, Lease, Description [Line Items]
Monthly rent			8,000
Rent expense Under ASC 840		$ 36,000		62,000
Short-term lease cost	24,000		51,000
Pennsylvania
Lessee, Lease, Description [Line Items]
Monthly rent			11,000
Rent expense Under ASC 840		$ 32,000		$ 56,000
Short-term lease cost	$ 29,000		$ 78,000