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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2019	Feb. 29, 2020	Jun. 28, 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-K
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		109,988,768
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Shell Company	false
Entity Public Float			$ 137.2

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents	$ 48,121	$ 50,422
Prepaid expenses and other current assets	6,326	1,334
Total current assets	54,447	51,756
Restricted cash	20	20
Property and equipment, net	238	321
Intangibles	46,400	46,400
Goodwill	13,064	13,064
Other assets	196	0
Total Assets	114,365	111,561
Current liabilities:
Accounts payable	1,902	1,367
Accrued expenses	6,169	4,746
Other current liabilities	446	0
Total current liabilities	8,517	6,113
Contingent consideration	120,020	48,400
Deferred tax liability	12,528	12,528
Other liabilities	0	313
Total Liabilities	141,065	67,354
Commitments and contingencies
Stockholders’ (Deficit) Equity:
Preferred stock, $0.001 par value per share; 5,000,000 shares authorized at December 31, 2019 and 2018; no shares issued and outstanding at December 31, 2019 and 2018	0	0
Common stock, $0.001 par value per share; 200,000,000 shares authorized at December 31, 2019 and 2018; 106,801,409 and 77,456,180 shares issued and outstanding at December 31, 2019 and 2018, respectively	107	77
Additional paid-in capital	266,717	230,154
Accumulated deficit	(293,524)	(186,024)
Total Stockholders’ (Deficit) Equity	(26,700)	44,207
Total Liabilities and Stockholders’ (Deficit) Equity	$ 114,365	$ 111,561

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000.0	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)	200,000,000	200,000,000
Common stock, shares issued (in shares)	106,801,409	77,456,180
Common stock, shares outstanding (in shares)	106,801,409	77,456,180

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue:
Total revenue	$ 0	$ 0	$ 425
Operating expenses:
Research and development	24,663	14,077	12,510
General and administrative	12,208	11,623	8,070
Change in fair value of contingent consideration	71,620	8,800	9,100
Total operating expenses	108,491	34,500	29,680
Loss from Operations	(108,491)	(34,500)	(29,255)
Other income (expense):
Other income, net	991	807	226
Net Loss and Comprehensive Loss	$ (107,500)	$ (33,693)	$ (29,029)
Net loss per common share - basic and diluted (in dollars per share)	$ (1.18)	$ (0.55)	$ (1.11)
Weighted-average common shares outstanding - basic and diluted (in shares)	90,929	61,774	26,105
License revenue
Revenue:
Total revenue	$ 0	$ 0	$ 425

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ (DEFICIT) 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, 2016			24,531,964
Beginning balance at Dec. 31, 2016	$ 38,677		$ 25		$ 161,963		$ (123,311)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(29,029)
Share-based compensation	$ 1,381				1,381
Exercise of stock awards and vesting of restricted stock awards (in shares)	140,000		161,453
Exercises of stock options and vesting of restricted stock awards	$ 40				40
Sales of common stock under 2014 ESPP (in shares)			9,148
Sales of common stock under 2014 ESPP	12				12
Issuance of common stock and common stock warrants, net of issuance costs (in shares)			5,525,000
Issuance of common stock and common stock warrants, net of issuance costs	6,908		$ 6		6,902
Exercise of common stock warrants (in shares)			4,475,000
Exercise of common stock warrants	45		$ 4		41
Ending balance (in shares) at Dec. 31, 2017			34,702,565
Ending balance at Dec. 31, 2017	18,034		$ 35		170,330		(152,331)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(33,693)
Share-based compensation	$ 1,283				1,283
Exercise of stock awards and vesting of restricted stock awards (in shares)	439,000		443,443
Exercises of stock options and vesting of restricted stock awards	$ 277				277
Sales of common stock under 2014 ESPP (in shares)			20,992
Sales of common stock under 2014 ESPP	20				20
Issuance of common stock and common stock warrants, net of issuance costs (in shares)			33,523,684
Issuance of common stock and common stock warrants, net of issuance costs	50,971		$ 33		50,938
Exercise of common stock warrants (in shares)			8,765,496
Exercise of common stock warrants	7,315		$ 9		7,306
Ending balance (in shares) at Dec. 31, 2018			77,456,180
Ending balance at Dec. 31, 2018	44,207		$ 77		230,154		(186,024)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(107,500)
Share-based compensation	$ 1,237				1,237
Exercise of stock awards and vesting of restricted stock awards (in shares)	90,000		89,812
Exercises of stock options and vesting of restricted stock awards	$ 98				98
Sales of common stock under 2014 ESPP (in shares)			10,283
Sales of common stock under 2014 ESPP	8				8
Issuance of common stock and common stock warrants, net of issuance costs (in shares)			20,410,000	2,062,206
Issuance of common stock and common stock warrants, net of issuance costs	$ 27,833	$ 1,936	$ 21	$ 2	27,812	$ 1,934
Exercise of common stock warrants (in shares)	6,773,000		6,772,928
Exercise of common stock warrants	$ 5,481		$ 7		5,474
Ending balance (in shares) at Dec. 31, 2019			106,801,409
Ending balance at Dec. 31, 2019	$ (26,700)		$ 107		$ 266,717		$ (293,524)

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ (DEFICIT) EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Issuance costs	$ 2,171	$ 5,029	$ 1,047
ATM Facility
Issuance costs	$ 212

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows from Operating Activities:
Net loss	$ (107,500)	$ (33,693)	$ (29,029)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	219	208	285
Share-based compensation	1,237	1,283	1,381
Change in fair value of contingent consideration	71,620	8,800	9,100
Gain on sale of equipment	0	(5)	(108)
Other	0	0	(5)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(5,188)	(913)	164
Accounts payable	535	460	(760)
Accrued expenses and other liabilities	1,556	1,031	1,746
Deferred revenue	0	0	(425)
Due to related party	0	0	(114)
Net Cash Used in Operating Activities	(37,521)	(22,829)	(17,765)
Cash Flows from Investing Activities:
(Purchases) sales of property and equipment	136	2
(Purchases) sales of property and equipment			98
Net Cash (Used in) Provided by Investing Activities	(136)	(2)	98
Cash Flows from Financing Activities:
Proceeds from issuance of common stock and common stock warrants, net of issuance costs	27,833	50,971	6,908
Proceeds from exercises of common stock warrants	5,481	7,315	45
Proceeds from issuance of common stock under ATM Offering, net of issuance costs	1,936	0	0
Proceeds from exercises of stock options	98	277	40
Proceeds from sales of common stock under 2014 ESPP	8	20	12
Net Cash Provided by Financing Activities	35,356	58,583	7,005
Net (Decrease) Increase in Cash, Cash Equivalents and Restricted Cash	(2,301)	35,752	(10,662)
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	50,442	14,690	25,352
Cash, Cash Equivalents and Restricted Cash - End of Period	48,141	50,442	14,690
Supplemental disclosure of non-cash operating activities:
Right-of-use assets related to the adoption of ASC 842	236
Cash paid for amounts included in the measurement of lease liabilities	153
Supplemental disclosure of non-cash investing activities:
Adjustment to fair value of assets acquired and liabilities assumed in acquisition during provisional period	0	0	14,600
Supplemental disclosure of non-cash financing activities:
Issuance of pre-funded warrants to purchase common stock	$ 0	$ 0	$ 2,679

DESCRIPTION OF BUSINESS	12 Months Ended
DESCRIPTION OF BUSINESS	Dec. 31, 2019
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 developing targeted fusion protein therapeutics ("TFPTs") for the treatment of patients with cancer. The Company’s most advanced product candidate, Vicinium^®, 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. The Company has an ongoing single-arm, multi-center, open-label Phase 3 clinical trial of Vicinium as a monotherapy in patients with high-risk, bacillus Calmette-Guérin ("BCG")-unresponsive non-muscle invasive bladder cancer ("NMIBC") (the "VISTA Trial"). The VISTA Trial completed enrollment in April 2018 with a total of 133 patients, and in December 2019, the Company initiated submission of the Biologics License Application ("BLA") for Vicinium to the United States Food and Drug Administration ("FDA") under Rolling Review, which enables individual modules to be submitted and reviewed on an ongoing basis, rather than waiting for all sections to be completed before submission. The Company operates in one segment under the direction of its Chief Executive Officer (chief operating decision maker). The Company was formerly known as Eleven Biotherapeutics, Inc. until its name changed in May 2018. Viventia Acquisition In September 2016, the Company entered into a Share Purchase Agreement with Viventia Bio, Inc., a corporation incorporated under the laws of the Province of Ontario, Canada ("Viventia"), the shareholders of Viventia named therein (the “Selling Shareholders”) and, solely in its capacity as seller representative, Clairmark Investments Ltd., a corporation incorporated under the laws of the Province of Ontario, Canada (“Clairmark”) (the “Share Purchase Agreement”), pursuant to which the Company agreed to and simultaneously completed the acquisition of all of the outstanding capital stock of Viventia from the Selling Shareholders (the “Viventia Acquisition”). In connection with the closing of the Viventia Acquisition, the Company issued 4.0 million shares of its common stock to the Selling Shareholders, which at that time represented approximately 19.9% of the voting power of the Company as of immediately prior to the issuance of such shares. Clairmark is an affiliate of Leslie L. Dan, a director of the Company until his retirement in July 2019. In addition, under the Share Purchase Agreement, the Company is obligated to pay to the Selling Shareholders certain post-closing contingent cash payments upon the achievement of specified milestones and based upon net sales, in each case subject to the terms and conditions set forth in the Share Purchase Agreement, including: (i) a one-time milestone payment of $12.5 million payable upon the first sale of Vicinium (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) and 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 (collectively, the "Contingent Consideration"). 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 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. Liquidity and Going Concern As of December 31, 2019, the Company had cash and cash equivalents of $48.1 million, net working capital of $45.9 million and an accumulated deficit of $293.5 million. The Company incurred negative cash flows from operating activities of $37.5 million, $22.8 million and $17.8 million for the years ended December 31, 2019, 2018 and 2017, respectively. Since its inception, the Company has received no revenue from sales of its products, and management anticipates that operating losses will continue for the foreseeable future as the Company continues its ongoing Phase 3 VISTA Trial of Vicinium for the treatment of high-risk NMIBC and seeks marketing approval from the FDA. The Company has financed its operations to date primarily through private placements of its common stock, preferred stock, common stock warrants and convertible bridge notes, venture debt borrowings, its initial public offering ("IPO"), follow-on public offerings, sales effected in an "at-the-market" ("ATM") offerings, a License Agreement with F. Hoffmann-La Roche Ltd and Hoffman-La Roche Inc. (collectively, "Roche") (the "License Agreement with Roche") and, to a lesser extent, from a collaboration. See “Note 10. Stockholders’ Equity” below for information regarding the Company’s recently completed equity financings. Under Accounting Standards Codification ("ASC") Topic 205-40, Presentation of Financial Statements - Going Concern, management is required at each reporting period to evaluate whether there are conditions and events, considered in the aggregate, that raise substantial doubt about an entity's ability to continue as a going concern within one year after the date that the financial statements are issued. This evaluation initially does not take into consideration the potential mitigating effect of management's plans that have not been fully implemented as of the date the financial statements are issued. When substantial doubt exists, management evaluates whether the mitigating effect of its plans sufficiently alleviates the substantial doubt about the Company's ability to continue as a going concern. The mitigating effect of management's plans, however, is only considered if both (i) it is probable that the plans will be effectively implemented within one year after the date that the financial statements are issued and (ii) it is probable that the plans, when implemented, will mitigate the relevant conditions or events that raise substantial doubt about the entity's ability to continue as a going concern within one year after the date that the financial statements are issued. Generally, to be considered probable of being effectively implemented, the plans must have been approved by the Company's board of directors before the date that the financial statements are issued. The Company's future success is dependent on its ability to develop its product candidates, including Vicinium for the treatment of high-risk NMIBC, and ultimately upon its ability to attain profitable operations. In order to commercialize its product candidates, including Vicinium for the treatment of high-risk NMIBC, the Company needs to complete clinical development and comply with comprehensive regulatory requirements. The Company is subject to a number of risks similar to other late-stage clinical companies, including, but not limited to, successful discovery and development of its product candidates, raising additional capital, development and commercialization by its competitors of new technological innovations, protection of proprietary technology and market acceptance of its products. The successful discovery and development of product candidates, including Vicinium for the treatment of high-risk NMIBC, requires substantial working capital, and 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 at favorable terms, or at all. To the extent that the Company raises additional capital through the sale of equity or convertible debt securities, the ownership interests of existing stockholders will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect the rights of existing stockholders. Debt financing, if available, may involve agreements that include liens or other restrictive covenants limiting the Company's ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends. If the Company raises additional funds through government or other third-party funding, strategic collaborations and alliances or licensing arrangements, it may have to relinquish valuable rights to its technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable. If the Company is unable to raise additional funds when needed, it may be required to implement cost reduction strategies and delay, limit, reduce or terminate its product development or future commercialization efforts or grant rights to develop and market products or product candidates that management would otherwise prefer to develop and market. The Company's management does not believe that its cash and cash equivalents of $48.1 million as of December 31, 2019 is sufficient to fund the Company's current operating plan for at least twelve months after the issuance of these consolidated financial statements. Given the history of significant losses, negative cash flows from operations, limited cash resources currently on hand and dependence by the Company on its ability - about which there can be no certainty - to obtain additional financing to fund its operations after the current cash resources are exhausted, substantial doubt exists about the Company's ability to continue as a going concern. These consolidated financial statements were prepared under the assumption that the Company will continue as a going concern and 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.

BASIS OF PRESENTATION	12 Months Ended
BASIS OF PRESENTATION	Dec. 31, 2019
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 ASC and Accounting Standards Updates ("ASUs"), promulgated by the Financial Accounting Standards Board ("FASB"). Use of Estimates The preparation of financial statements in accordance with GAAP and the rules and regulations of the United States Securities and Exchange Commission ("SEC") requires the use of estimates and assumptions, based on judgments considered reasonable, which affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The Company bases its estimates and assumptions on historical experience, known trends and events and various other factors that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Although management believes its estimates and assumptions are reasonable when made, they are based upon information available at the time they are made. Management evaluates the estimates and assumptions on an ongoing basis and, if necessary, makes adjustments. Due to the risks and uncertainties involved in the Company’s business and evolving market conditions, and given the subjective element of the estimates and assumptions made, actual results may differ from estimated results. The most significant estimates and judgments impact the fair value of intangible assets, goodwill and contingent consideration; income taxes (including the valuation allowance for deferred tax assets); research and development expenses; and going concern considerations. Principles of Consolidation The Company’s consolidated financial statements include the accounts of the Company, its wholly owned subsidiary Viventia and its indirect subsidiaries, Viventia Bio USA Inc. and Viventia Biotech (EU) Limited. All intercompany transactions and balances have been eliminated in consolidation. Foreign Currency Translation The functional currency of the Company and each of its subsidiaries is the U.S. dollar.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Cash, Cash Equivalents and Concentration of Credit Risk

The Company's cash is held on deposit in demand accounts at a large financial institution in amounts in excess of the Federal Deposit Insurance Corporation ("FDIC") insurance coverage limit of $250,000 per depositor, per FDIC-insured bank, per ownership category. Restricted cash represents cash held by the Company's primary commercial bank to collateralize the credit limit on the Company's corporate credit card. The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Financial instruments that potentially subject the Company to credit risk principally consists of cash equivalents. As of December 31, 2019 and 2018, the Company limited its credit risk associated with cash equivalents by placing investments in highly-rated money market funds.

Property and Equipment

Property and equipment are recorded at cost. Maintenance and repairs are charged to expense as incurred, and costs of improvements and renewals are capitalized. Depreciation is recognized using the straight-line method over the estimated useful lives of the relative assets. The Company uses an estimated useful life of five years for lab equipment, four years for furniture and fixtures, three years for computer equipment and software and the lesser of five years or the remaining lease term for leasehold improvements.

Impairment of Long-Lived Assets

Long-lived assets, such as property and equipment, are tested for impairment when events or changes in circumstances indicate that the carrying value of the asset may not be recoverable. Impairment testing of long-lived assets requires management to estimate the future net undiscounted cash flows of an asset using assumptions believed to be reasonable. Actual cash flows may differ from the estimates used in the impairment testing. If such assets are considered to be impaired, the Company recognizes an impairment loss when and to the extent that the estimated fair value of an asset is less than its carrying value. The Company did not recognize any impairment charges during the years ended December 31, 2019 and 2018. The Company recognized a de minimis amount of impairment charges in the year ended December 31, 2017 related to the strategic restructuring of the Company in August 2017.

Indefinite-Lived Intangible Assets

The Company's intangible assets consist of indefinite-lived, acquired in-process research and development ("IPR&D") worldwide product rights to Vicinium as a result of the Viventia Acquisition in 2016. IPR&D assets acquired in a business combination are considered indefinite-lived until the completion or abandonment of the associated research and development efforts. Amortization over the estimated useful life will commence at the time of Vicinium's launch in the respective markets, if approved. If regulatory approval to market Vicinium for the treatment of high-risk NMIBC is not obtained, the Company will immediately expense the related capitalized cost.

Indefinite-lived intangible assets are quantitatively tested for impairment at least annually during the fourth quarter of the fiscal year, or more often if indicators of impairment are present. Impairment testing of indefinite-lived intangible assets requires management to estimate the future discounted cash flows of an asset using assumptions believed to be reasonable, but which are unpredictable and inherently uncertain. Actual future cash flows may differ from the estimates used in impairment testing. The Company recognizes an impairment loss when and to the extent that the estimated fair value of an intangible asset is less than its carrying value. In addition, on a quarterly basis, the Company performs a qualitative review of its business operations to determine whether events or changes in circumstances have occurred which could indicate that the carrying value of its intangible assets was not recoverable. Based on the annual testing and quarterly reviews performed, the Company concluded that the carrying value of its intangible assets was not impaired as of December 31, 2019 and 2018.

Goodwill

Goodwill on the Company's consolidated balance sheet is the result of the Viventia Acquisition in September 2016 and represents the difference between the purchase price and the fair value of the identifiable tangible and intangible net assets acquired under the acquisition method of accounting. Goodwill is not amortized; rather than recording periodic amortization, goodwill is quantitatively tested for impairment at least annually during the fourth quarter of the fiscal year, or more often if indicators of impairment are present. Impairment testing of goodwill requires management to estimate the future discounted cash flows of a reporting unit using assumptions believed to be reasonable, but which are unpredictable and inherently uncertain. Actual future cash flows may differ from the estimates used in impairment testing. If the fair value of the equity of a reporting unit exceeds the reporting unit’s carrying value, including goodwill, then goodwill is considered not to be impaired. The Company recognizes a goodwill impairment when and to the extent that the fair value of the equity of a reporting unit is less than the reporting unit's carrying value, including goodwill. The Company has only one reporting unit. In addition, on a quarterly basis, the Company performs a qualitative review of its business operations to determine whether events or changes in circumstances have occurred which could have a material adverse effect on the estimated fair value of each reporting unit and thus indicate a potential impairment of the goodwill carrying value. Based on the annual testing and quarterly reviews performed, the Company concluded that there was no goodwill impairment during the years ended December 31, 2019, 2018 and 2017.

Contingent Consideration

Contingent consideration on the Company's consolidated balance sheet is the result of the Viventia Acquisition in September 2016 and represents the discounted present value of future launch milestones and net sales royalties due to the Selling Shareholders pursuant to the Share Purchase Agreement. See "Note 1. Description of Business" for additional information. Contingent consideration is measured at its estimated fair value on a recurring basis at each reporting period, with fluctuations in value resulting in a non-cash charge to earnings (or loss) during the period. The estimated fair value measurement is based on significant unobservable inputs (Level 3 within the fair value hierarchy), including internally developed financial forecasts, probabilities of success and timing of certain milestone events and achievements, which are unpredictable and inherently uncertain. Actual future cash flows may differ from the assumptions used to estimate the fair value of contingent consideration. The valuation of contingent consideration requires the use of significant assumptions and judgments, which management believes are consistent with those that would be made by a market participant. Management reviews its assumptions and judgments on an ongoing basis as additional market and other data is obtained, and any future changes in the assumptions and judgments utilized by management may cause the estimated fair value of contingent consideration to fluctuate materially, resulting in earnings volatility.

Leases

Effective January 1, 2019, the Company adopted ASC Topic 842, Leases (“ASC 842”) using the optional transition method outlined in ASU No. 2018-11, Leases (Topic 842), Targeted Improvements. The adoption of ASC 842 represents a change in accounting principle that aims to increase transparency and comparability among organizations by requiring the recognition of right-of-use assets and lease liabilities on the balance sheet for both operating and finance leases. In addition, the standard requires enhanced disclosures that meet the objective of enabling financial statement users to assess the amount, timing and uncertainty of cash flows arising from leases. The reported results for the year ended December 31, 2019 reflect the application of ASC 842 guidance, while the reported results for priors were prepared in accordance with the previous ASC Topic 840, Leases ("ASC 840") guidance. The adoption of ASC 842 resulted in the recognition of operating lease right-of-use assets and corresponding lease liabilities of $0.2 million on the Company’s consolidated balance sheet as of January 1, 2019. The adoption of this guidance did not have a material impact on the Company’s financial condition, results of operations or cash flows; however, the adoption did result in significant changes to the Company’s financial statement disclosures.

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


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


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


-	An entity need not reassess whether any expired or existing contracts are or contain leases;


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


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

The Company’s lease portfolio as of the adoption date 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 determines if an arrangement is a lease at the inception of the contract and has made a policy election to not separate out non-lease components from lease components, for all classes of underlying assets. The asset components of the Company’s operating leases are recorded as operating lease right-of-use assets and reported within other assets on the Company's consolidated balance sheet. The short-term and long-term liability components are recorded in other current liabilities and other liabilities, respectively, on the Company’s consolidated balance sheet. As of December 31, 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 include variable operating costs incurred during the period. Lease costs also include amounts related to short-term leases.

Research and Development Costs

Research and development activities are expensed in the period incurred. Research and development expenses consist of both internal and external costs associated with all basic research activities, clinical development activities and technical efforts required to develop a product candidate. Internal research and development consist primarily of personnel costs, including salaries, benefits and share-based compensation, facilities leases, research-related overhead, pre-approval regulatory and clinical trial costs, manufacturing and other contracted services, license fees and other external costs.

In certain circumstances, the Company is required to make advance payments to vendors for goods or services that will be received in the future for use in research and development activities. In such circumstances, the advance payments are recorded as prepaid assets and expensed when the activity has been performed or when the goods have been received.

Share-Based Compensation

The Company recognizes the grant-date fair value of share-based awards granted as compensation as expense on a straight-line basis over the requisite service period, which is generally the vesting period of the award. To date, the Company has not issued awards where vesting is subject to market conditions. From time to time, the Company has granted to its executives stock option awards which contain both performance-based and service-based vesting criteria. Performance milestone events were specific to the Company’s corporate goals, including certain clinical development objectives related to the VISTA Trial, as well as a past financing objective. Share-based compensation expense associated with performance-based vesting criteria is recognized using the accelerated attribution method if the performance condition is considered probable of achievement in management’s judgment. The fair value of stock options is estimated at the time of grant using the Black-Scholes option pricing model, which requires the use of inputs and assumptions such as the fair value of the underlying stock, exercise price of the option, expected term, risk-free interest rate, expected volatility and dividend yield.

The fair value of each grant of options during the years ended December 31, 2019, 2018 and 2017 was determined using the following methods and assumptions:

•

Expected Term. Due to the lack of historical exercise data and given the plain vanilla nature of the options granted by the Company, the expected term is determined using the “simplified" method, as prescribed in SEC Staff Accounting Bulletin ("SAB") No. 107 ("SAB 107"), whereby the expected life equals the arithmetic average of the vesting term (generally four years) and the original contractual term (ten years) of the option, taking into consideration multiple vesting tranches.


•	Risk-Free Interest Rate. The risk-free rate is based on the interest rate payable on United States Treasury securities in effect at the time of grant for a period that is commensurate with the assumed expected term.


•	Expected Volatility. The expected volatility is based on historical volatilities of a representative group of publicly traded biopharmaceutical companies which were commensurate with the assumed expected term, as prescribed in SAB 107.


•	Dividend Yield. The dividend yield is 0% because the Company has never declared or paid, and for the foreseeable future does not expect to declare or pay, a dividend on its common stock.

Income Taxes

Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and net operating loss ("NOL") and research and development credit ("R&D credit") carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in operations in the period that includes the enactment date. A valuation allowance is recorded to the extent it is more likely than not that some portion or all of the deferred tax assets will not be realized.

Unrecognized income tax benefits represent income tax positions taken on income tax returns that have not been recognized in the financial statements. The Company recognizes the benefit of an income tax position only if it is more likely than not (greater than 50%) that the tax position will be sustained upon tax examination, based solely on the technical merits of the tax position. Otherwise, no benefit is recognized. The tax benefits recognized are measured based on the largest benefit that has a greater than 50% likelihood of being realized upon ultimate settlement. The Company recognizes accrued interest and penalties related to uncertain tax positions as income tax expense in its consolidated statements of operations. As of December 31, 2019 and 2018, the Company did not have any uncertain tax positions.

Revenue Recognition

The Company has never received revenue from sales of its products. The Company has entered into the License Agreement with Roche, as discussed in "Note 15. License Agreements," pursuant to which the Company received upfront and development milestone payments in the third quarter of 2016 and may receive in the future additional development milestone payments and sales-based royalties. The Company recognizes revenue resulting from license agreements in accordance with ASC Topic 606, Revenue ("ASC 606"), which was effective for public companies on January 1, 2018. The Company adopted ASC 606 using the modified retrospective approach, and there was no resulting cumulative effect adjustment to opening accumulated deficit.

Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized for arrangements determined to be within the scope of ASC 606, the Company performs the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when each performance obligation is satisfied. The Company only recognizes revenue under the five-step model when collectability of payment is reasonably assured.

The Company neither received nor earned any additional development milestones or sales-based royalty payments from Roche during the years ended December 31, 2019, 2018 and 2017. During the first quarter of 2017, the Company transferred its remaining pre-clinical inventory to Roche and, upon completion of its final performance obligation, recognized $0.4 million of deferred revenue remaining from the upfront milestone payment received in August 2016.

RECENT ACCOUNTING PRONOUNCEMENTS	12 Months Ended
RECENT ACCOUNTING PRONOUNCEMENTS	Dec. 31, 2019
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
RECENT ACCOUNTING PRONOUNCEMENTS	RECENT ACCOUNTING PRONOUNCEMENTS Adopted in 2019 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. Early adoption is permitted, the Company adopted this guidance effective January 1, 2019, and it did not have a material impact on the Company’s financial position, results of operations or cash flows. In June 2018, the FASB issued ASU No. 2018-07, Compensation - Stock Compensation (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 guidance effective January 1, 2019, and it did not have a material impact on the Company’s financial position, results of operations or cash flows. 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 ASC, 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 the 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. The Company adopted this guidance effective January 1, 2019, and it did not have a material impact on the Company’s financial position, results of operations or cash flows. Pending Adoption In June 2016, the FASB issued ASU No. 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 annual and interim periods beginning January 1, 2020 and is to be applied using a modified retrospective transition method. Earlier adoption is permitted. Because the Company holds only highly-rated money market funds, it does not expect the adoption of ASU 2016-13 to have a material impact on the Company's financial position, results of operations or cash flows. In August 2018, the FASB issued ASU No. 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. ASU 2018-13 is effective for annual and interim periods beginning after December 15, 2019. Early adoption is permitted. Because this ASU changes only the disclosure requirements and not the underlying accounting, the Company does not expect the adoption of ASU 2018-13 to have a material impact on the Company's financial position, results of operations or cash flows. In August 2018, the FASB issued ASU No. 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 amendments in this ASU should be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company will adopt the ASU prospectively to all implementation costs incurred after January 1, 2020 and does not expect the adoption of ASU 2016-13 to have a material impact on the Company's financial position, results of operations or cash flows. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes ("ASU 2019-12"). ASU 2019-12 simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The amendments in ASU 2019-12 also improve consistent application of and simplify GAAP for other areas of Topic 740 by clarifying and amending existing guidance. ASU 2109-12 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. Early adoption is permitted. The method with which the amendments in this ASU are to be applied varies depending on the nature of the tax item impacted by amendment. Because the Company generates losses and pays no income taxes, it does not expect the adoption of ASU 2019-12 to have a material impact on the Company's financial position, results of operations or cash flows.

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS

The carrying values of cash and cash equivalents, restricted cash, prepaid expenses and other current assets, and accounts payable on the Company’s consolidated balance sheets approximated their fair values as of December 31, 2019 and 2018 due to their short-term nature.

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


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


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


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

The following tables set forth the carrying amounts and fair values of the Company's financial instruments measured at fair value on a recurring basis as of December 31, 2019 and 2018 (in thousands):



	December 31, 2019
					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)	$	31,146	$	31,146	$	31,146	$	—	$	—
Liabilities:
Contingent consideration	$	120,020	$	120,020	$	—	$	—	$	120,020



	December 31, 2018
					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)	$	40,365	$	40,365	$	40,365	$	—	$	—
Liabilities:
Contingent consideration	$	48,400	$	48,400	$	—	$	—	$	48,400

The Company evaluates transfers between fair value levels at the end of each reporting period. There were no transfers of assets or liabilities between fair value levels during the year ended December 31, 2019.

Contingent Consideration

The estimated fair value of the Company’s contingent consideration was determined using probabilities of successful achievement of regulatory milestones and commercial sales, the period in which these milestones and sales are expected to be achieved ranging from 2021 to 2033, the level of commercial sales of Vicinium forecasted for the United States, Europe, Japan and other potential markets and discount rates ranging from 5.6% to 11.8% as of December 31, 2019 and 6.6% to 13.7% as of December 31, 2018. There have been no changes to the valuation methods utilized during the year ended December 31, 2019.

The following table sets forth a summary by quarter of the change in the fair value of the Company's contingent consideration liability, measured on a recurring basis at each reporting period, for the year ended December 31, 2019 (in thousands):



Balance at December 31, 2018	$	48,400
Change in fair value included in loss	(1,000		)
Balance at March 31, 2019	47,400
Change in fair value included in loss⁽¹⁾	44,000
Balance at June 30, 2019	91,400
Change in fair value included in loss⁽²⁾	3,600
Balance at September 30, 2019	95,000
Change in fair value included in loss⁽³⁾	25,020
Balance at December 31, 2019	$	120,020

⁽¹⁾During the quarter ended June 30, 2019, management reassessed the total addressable global market for high-risk NMIBC and determined that both the global market size and the estimated potential Vicinium commercial sales within the global 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 of Vicinium through December 2033, an increase in expected future net sales correlated to a $44.0 million increase in the estimated fair value of the Company’s contingent consideration as of June 30, 2019.

⁽²⁾The $3.6 million increase in the estimated fair value of contingent consideration was primarily attributable to a slightly lower discount rate, based on prevailing market conditions as of September 30, 2019, applicable to the earnout royalty payments potentially payable to Viventia's shareholders under the Share Purchase Agreement.

⁽³⁾The $25.0 million increase in the estimated fair value of contingent consideration was primarily attributable to increases in management's assumptions for both the estimated United States market share for Vicinium for the treatment of high-risk NMIBC, if approved, and the probability of success for achieving marketing approval by the FDA, based on expert commentary from a December 2019 public hearing of the FDA's Oncologic Drugs Advisory Committee during a review a competitor's product.

- 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

PROPERTY AND EQUIPMENT

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT

The following table sets forth the composition of property and equipment, net as of December 31, 2019 and 2018 (in thousands):



	December 31,
	2019			2018
Lab equipment	$	572		$	443
Furniture and fixtures	16			16
Computer equipment	87			80
Software	28			28
Leasehold improvements	293			293
Property and equipment, gross	996			860
Less: accumulated depreciation	(758		)	(539		)
Total Property and Equipment, Net	$	238		$	321

Depreciation expense was $0.2 million, $0.2 million and $0.3 million for the years ended December 31, 2019, 2018 and 2017, respectively. During the year ended December 31, 2017, the Company sold equipment with no remaining net book value for proceeds of $0.1 million.

INTANGIBLES AND GOODWILL INTANGIBLES AND GOODWILL

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

INTANGIBLES AND GOODWILL

Intangibles

Intangible assets on the Company's consolidated balance sheet are the result of the Viventia Acquisition in September 2016. The following table sets forth the composition of intangible assets as of December 31, 2019 and 2018 (in thousands):



	December 31,
	2019		2018
IPR&D intangible assets:
Vicinium United States rights	$	31,700	$	31,700
Vicinium European Union rights	14,700		14,700
Total Intangibles	$	46,400	$	46,400

Goodwill

Goodwill on the Company's consolidated balance sheet is the result of the Viventia Acquisition in September 2016. Goodwill had a carrying value of $13.1 million as of December 31, 2019 and 2018.

ACCRUED EXPENSES

12 Months Ended

Dec. 31, 2019

Payables and Accruals [Abstract]

ACCRUED EXPENSES

The following table sets forth the composition of accrued expenses as of December 31, 2019 and 2018 (in thousands):



	December 31,
	2019		2018
Research and development	$	3,688	$	2,928
Payroll-related expenses	1,638		1,045
Severance to former Executives and other employees	378		278
Professional fees	378		464
Other	87		31
Total Accrued Expenses	$	6,169	$	4,746

Management Changes

On August 26, 2019, the Company announced that Richard Fitzgerald departed as its Chief Financial Officer, effective immediately. In connection with his separation from the Company, Mr. Fitzgerald and the Company entered into a Separation Agreement and General Release dated as of September 9, 2019 (the “Fitzgerald Separation Agreement”), pursuant to which the Company provided Mr. Fitzgerald with twelve months of separation payments and benefits. The Company recorded $0.3 million of expense, which will be paid through the normal payroll cycle through August 2020.

On August 2, 2019, Dennis Kim, M.D., MPH departed as the Company's Chief Medical Officer, effective immediately. In connection with his separation from the Company, Dr. Kim and the Company entered into a Separation Agreement and General Release dated as of August 2, 2019 (the “Kim Separation Agreement”), pursuant to which the Company provided Dr. Kim with six months of separation payments in the amount of $0.2 million. In addition, Dr. Kim and the Company entered into a Consulting Agreement dated as of August 3, 2019 (the "Kim Consulting Agreement"), pursuant to which the Company agreed to pay Dr. Kim $0.1 million in consulting fees and transition expenses over the following three months ending November 2, 2019. The Company recorded $0.3 million of expenses related to these agreements. The Kim Consulting Agreement payments were made in a lump sum when the agreement concluded in November 2019. The separation payments will be paid through the normal payroll cycle through January 2020.

On August 7, 2018, the Company announced that Stephen A. Hurly departed as its President and Chief Executive Officer, effective immediately. In connection with his separation from the Company, Mr. Hurly and the Company entered into a Separation Agreement and General Release dated as of September 28, 2018 (the “Hurly Separation Agreement”), pursuant to which the Company provided Mr. Hurly with twelve months of separation payments and benefits. The Company recorded $0.6 million of expense, consisting of Mr. Hurly’s base salary at the time of his departure of $0.4 million plus his target annual bonus for 2018 of $0.2 million, which was paid through the normal payroll cycle through August 2019, when the Company completed its obligations related to the Hurly Separation Agreement.

The remaining amounts of accrued severance as of December 31, 2019 relate to terminations of other employees during 2019.

Reduction-in-Force

In August 2017, the Company's board of directors approved a strategic restructuring to eliminate a portion of the Company’s workforce in order to preserve resources and refocus the Company's efforts. In September 2017, the Company completed the manufacturing of all Vicinium necessary for its ongoing Phase 3 VISTA Trial and for its Cooperative Research and Development Agreement with the National Cancer Institute. In conjunction with this achievement, the Company ended its manufacturing activities in Winnipeg and redirected its resources toward completing the technology transfer process necessary to outsource commercial scale drug supply manufacturing in the event it obtains approval from the FDA to market Vicinium for the treatment of high-risk NMIBC. The Company recorded total restructuring costs of $0.1 million, which included separation payments and benefits, in the third quarter of 2017.

COMMITMENTS AND CONTINGENCIES

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

Executive Employment Agreements

The Company has entered into employment agreements and offer letters with certain of its key executives, providing for separation payments and benefits in certain circumstances, as defined in the agreements.

Legal Contingencies

The Company is not currently subject to any material legal proceedings and has recorded no legal contingencies.

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 31,100 square foot facility in Winnipeg, Manitoba which consists of manufacturing, laboratory, warehouse and office space, 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 $12,600 per month. In addition to rent expense, the Company expects to incur $12,300 per month in related operating expenses. Operating lease cost under this lease, including the related operating costs, was $0.3 million for the year ended December 31, 2019. Rent expense (under ASC 840), including the related operating costs, was $0.3 million for each of the years ended December 31, 2018 and 2017, respectively;

A short-term property lease for modular office space for its current corporate headquarters in Cambridge, MA under a lease that renews every four months and currently extends through August 2020. The minimum monthly rent for this office space is currently $7,900 per month, which is subject to change if and as the Company adds or deducts space to or from the lease. The Company recorded $0.1 million and $0.1 million in rent expense for the years ended December 31, 2019 and 2018, respectively, for this lease; and

A short-term property lease for modular office space in Philadelphia, PA under a lease that renews every six months and currently extends through October 2020. The minimum monthly rent for this office space is currently $13,500 per month, which is subject to change if and as the Company adds or deducts space to or from the lease. The Company recorded $0.1 million and $0.2 million in rent expense for the years ended December 31, 2019 and 2018, respectively, for this lease.

The components of lease cost for the year ended December 31, 2019 is as follows (in thousands):



	Year ended
Lease Cost:	December 31, 2019
Operating lease (including related operating costs)	$	298
Short-term property leases	263
Total Lease Costs	$	561



Supplemental Information:
Weighted-average remaining lease term - operating leases (in years)	0.75
Weighted-average discount rate - operating leases	12%

The following table sets forth the Company's future minimum lease payments under non-cancelable leases as of December 31, 2019 (in thousands):



Year ending December 31,	Minimum Lease Payments
2020	113
Total future minimum lease payments	113
Less: Amounts representing present value adjustment	(1		)
Operating lease current liabilities as of December 31, 2019	$	112

STOCKHOLDERS' (DEFICIT) EQUITY

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

STOCKHOLDERS' (DEFICIT) EQUITY

Equity Financings

November 2019 ATM Offering

In November 2019, the Company entered into an Open Market Sale Agreement ^SM (the "Sales Agreement") with Jefferies LLC ("Jefferies"), under which the Company may issue and sell shares of its common stock from time to time for an aggregate sales price of up to $35.0 million through Jefferies (the "ATM Offering"). Sales of common stock under the Sales 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 common stock. The Company has no obligation to sell any of its common stock and may at any time suspend offers under the Sales Agreement or terminate the Sales Agreement. Subject to the terms and conditions of the Sales 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 floor of $1.00 per share. 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. The Company incurred $0.2 million in legal, accounting and printing costs related to the Prospectus Supplement filed with the SEC in connection with the ATM Offering. Through December 31, 2019, the Company raised $1.9 million of net proceeds from the sale of 2.1 million shares of common stock under the ATM Offering.

June 2019 Financing

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

June 2018 Financing

In June 2018, the Company raised $41.9 million of net proceeds from the sale of 25.6 million shares of common stock at a price of $1.80 per share in an underwritten public offering.

March 2018 Financing

In March 2018, the Company raised $9.0 million of net proceeds from the sale of (i) 8.0 million shares of common stock at a price of $1.13 per share in a registered direct public offering and (ii) 8.0 million warrants to purchase shares of common stock (the "2018 Warrants") at a price of $0.125 per 2018 Warrant in a concurrent private placement (collectively, the “March 2018 Financing”). Subject to certain ownership limitations, the 2018 Warrants issued in the March 2018 Financing were exercisable immediately upon issuance at an original exercise price of $1.20 per share, subject to adjustments as provided under the terms of such warrants, and have a five-year term expiring on March 23, 2023. See "Warrant Modifications" below for additional information.

November 2017 Financing

In November 2017, the Company raised $7.0 million of net proceeds from the sale of (i) 5.5 million units (each unit consisting of one share of common stock and one warrant to purchase one share of common stock ("2017 Warrant")) at a price of $0.80 per unit and (ii) 4.5 million pre-funded units (each pre-funded unit consisting of one pre-funded warrant to purchase one share of common stock ("Pre-funded Warrant") and one 2017 Warrant) at a price of $0.79 per pre-funded unit (collectively, the "November 2017 Financing"). Each 2017 Warrant to purchase common stock contained in a unit or pre-funded unit had an original exercise price of $0.80 per share, was exercisable immediately and will expire five years from the date of issuance. See "Warrant Modifications" below for additional information. Each Pre-funded Warrant contained in a pre-funded unit was exercisable for one share of common stock at an exercise price of $0.01 per share. As of December 31, 2017, all of the Pre-funded Warrants sold in the November 2017 Financing were exercised by the holders.

Preferred Stock

Pursuant to its Amended and Restated Certificate of Incorporation (the "Certificate of Incorporation"), the Company is authorized to issue 5.0 million shares of "blank check" preferred stock, $0.001 par value per share, which enables its board of directors, from time to time, to create one or more series of preferred stock. Each series of preferred stock issued shall have the rights, preferences, privileges and restrictions as designated by the board of directors. The issuance of any series of preferred stock could affect, among other things, the dividend, voting and liquidation rights of the Company's common stock. The Company had no preferred stock issued and outstanding as of December 31, 2019 and 2018.

Common Stock

Pursuant to its Certificate of Incorporation, the Company is authorized to issue 200.0 million shares of common stock, $0.001 par value per share, of which 106.8 million and 77.5 million shares were issued and outstanding as of December 31, 2019 and 2018, respectively. In addition, the Company had reserved for issuance the following amounts of shares of its common stock for the purposes described below as of December 31, 2019 and 2018 (in thousands):



	December 31,
	2019	2018
Shares of common stock issued	106,801	77,456
Shares of common stock reserved for issuance for:
Warrants	22,895	9,258
Stock options	6,236	3,942
Shares available for grant under 2014 Stock Incentive Plan	8,753	2,001
Shares available for sale under 2014 Employee Stock Purchase Plan	28	38
Total shares of common stock issued and reserved for issuance	144,713	92,695

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

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

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

Warrants

All of the Company’s outstanding warrants are non-tradeable and equity-classified because they meet the derivative scope exception under ASC Topic 815-40, Derivatives and Hedging - Contracts in Entity’s Own Equity ("ASC 815-40"). The following table sets forth the Company's warrant activity for the year ended December 31, 2019 (in thousands):



Issued	Exercise Price	Expiration	December 31, 2018	Issued	(Exercised)		December 31, 2019
Jun-2019	$1.47	Jun-2020	—	20,410	—		20,410
Mar-2018	$0.95*	Mar-2023	7,211	—	(5,268	)	1,943
Nov-2017	$0.55*	Nov-2022	1,992	—	(1,505	)	487
May-2015	$11.83	Nov-2024	28	—	—		28
Nov-2014	$11.04	Nov-2024	27	—	—		27
			9,258	20,410	(6,773	)	22,895

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

During the year ended December 31, 2019, the Company received proceeds of $5.5 million from the exercises of 5.3 million 2018 Warrants and 1.5 million 2017 Warrants.

Warrant Modifications

In October 2019, the Company entered into transactions with holders of its outstanding 2018 Warrants and 2017 Warrants to purchase the Company's common stock.

2018 Warrants

On October 28, 2019, the Company entered into transactions with the holders of its outstanding 2018 Warrants pursuant to which such holders either (i) exercised their warrants pursuant to a Warrant Exercise Agreement (the "2018 Warrant Exercise Agreements") or (ii) amended their warrants pursuant to a Warrant Amendment Agreement (the "2018 Warrant Amendment Agreements"). As consideration for those holders executing the 2018 Warrant Exercise Agreements, the Company reduced the exercise price of the warrants from $1.20 to $0.60 per share of the Company's common stock, resulting in proceeds of $2.0 million from the exercise of 3.4 million warrants. Pursuant to the 2018 Warrant Amendment Agreements, the prohibition on certain variable rate transactions included in the 2018 Warrants was amended to exclude ATM offerings and the exercise price of the warrants was reduced from $1.20 to the lesser of (a) $0.95 per share of common stock and (b) the exercise price as determined from time to time pursuant to the anti-dilution provisions in the 2018 Warrant Amendment Agreements.

In connection with the 2018 Warrant Exercise Agreements and 2018 Warrant Amendment Agreements, the Company entered into an amendment to the Securities Purchase Agreement dated March 21, 2018 related to the March 2018 Financing, by and among the Company and each purchaser identified on the signature pages thereto, with certain holders representing greater than 50.1% of the securities issued based on initial subscription amounts, pursuant to which the prohibition on variable rate transactions, including ATM offerings, contained in section 4.12(b) was deleted in its entirety.

2017 Warrants

On October 28, 2019, the Company entered into transactions with the holders of its outstanding 2017 Warrants pursuant to which such holders either (i) exercised their warrants pursuant to a Warrant Exercise Agreement (the "2017 Warrant Exercise Agreements") or (ii) amended their warrants pursuant to a Warrant Amendment Agreement (the "2017 Warrant Amendment Agreements"). As consideration for those holders executing the 2017 Warrant Exercise Agreements, the Company reduced the exercise price of the warrants from $0.80 to $0.55 per share of the Company's common stock. Pursuant to the 2017 Warrant Amendment Agreements, the prohibition on certain variable rate transactions included in the 2017 Warrants was amended to exclude ATM offerings and the exercise price of the warrants was reduced from $0.80 to the lesser of (a) $0.55 per share of common stock and (b) the exercise price as determined from time to time pursuant to the anti-dilution provisions in the 2017 Warrant Amendment Agreements.

Accounting Implications

The 2018 Warrants and 2017 Warrants utilize the same Form of Warrant, which contained in Section 5d) a prohibition on variable rate transactions (as defined therein). The warrant holders agreed to waive such prohibition in exchange for the concessions from the Company described above. Management evaluated the warrants after modifications and determined that they continued to be equity-classified under the derivative scope exception of ASC 815-40. The warrants were revalued immediately before and immediately after the modifications to calculate the $1.1 million incremental value of the modified warrants. The Company considers this incremental value to be akin to an offering cost since the modifications were directly related to enabling the ATM Offering and would not have otherwise been incurred. Management initially capitalized the $1.1 million to deferred financing cost asset, with an offsetting credit to additional paid-in capital, and then reclassified the deferred financing cost asset to reduce the ATM Offering proceeds within equity as proceeds were received from sales of common stock under the ATM Offering.

LOSS PER SHARE

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

LOSS PER SHARE

The Company’s basic loss per common share is computed by dividing net loss by the weighted-average number of shares of common stock outstanding during the period. A net loss cannot be diluted, so when the Company is in a net loss position, basic and diluted loss per common share are the same. If in the future the Company achieves profitability, the denominator of a diluted earnings per common share calculation will include both the weighted-average number of shares outstanding and the number of common stock equivalents, if the inclusion of such common stock equivalents would be dilutive. Dilutive common stock equivalents potentially include warrants, stock options and non-vested restricted stock awards and units using the treasury stock method, along with the effect, if any, from outstanding convertible securities. The 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 December 31, 2019, 2018 and 2017 have been excluded from the denominator of the diluted loss per share of common stock outstanding calculation (in thousands):



	December 31,
	2019	2018	2017
Warrants	22,895	9,258	10,055
Stock options	6,236	3,942	2,696
Non-vested restricted stock awards	—	—	4
	29,131	13,200	12,755

SHARE-BASED COMPENSATION

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

SHARE-BASED COMPENSATION

The following table sets forth the amount of share-based compensation expense recognized by the Company by line item on its consolidated statements of operations for the years ended December 31, 2019, 2018 and 2017 (in thousands):



	Year ended December 31,
	2019		2018		2017
Research and development	$	188	$	505	$	404
General and administrative	1,049		778		977
Total Share-based Compensation	$	1,237	$	1,283	$	1,381

2014 Stock Incentive Plan

The Company's 2014 Stock Incentive Plan, as amended ("2014 Plan"), was adopted by its board of directors in December 2013 and subsequently approved by its stockholders in January 2014. The 2014 Plan became effective immediately prior to the closing of the Company's IPO in February 2014 and provides for the grant of incentive and non-qualified stock options, restricted stock awards and units, stock appreciation rights and other stock-based awards, with amounts and terms of grants determined by the Company's board of directors at the time of grant, to the Company's employees, officers, directors, consultants and advisors. Currently there are only stock options outstanding under the 2014 Plan, which 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 4.0 million stock options outstanding under the 2014 Plan as of December 31, 2019.

At the Annual Meeting of 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. There were 8.8 million shares of common stock available for issuance under the 2014 Plan as of December 31, 2019.

2009 Stock Incentive Plan

The Company maintains a 2009 Stock Incentive Plan, as amended and restated ("2009 Plan"), which provided for the grant of incentive and non-qualified stock options and restricted stock awards and 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 remaining 0.1 million fully vested stock options outstanding under the 2009 Plan as of December 31, 2019.

Out-of-Plan Inducement Grants

From time to time, the Company has granted equity awards to its newly hired employees 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. As of December 31, 2019, there were 2.1 million stock options outstanding which were granted as employment inducement awards outside of the 2014 Plan.

Stock Options

The following table sets forth a summary of the Company’s total stock option activity, including awards granted under the 2014 Plan and 2009 Plan and inducement grants made outside of stockholder approved plans, for the years ended December 31, 2019, 2018 and 2017:



	Number of Shares under Option (in thousands)		Weighted-Average Exercise Price per Option	Weighted-Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2016	2,024		$4.41	8.73	$	841
Granted	1,303		$1.64
Exercised	(140	)	$0.28
Canceled or forfeited	(491	)	$5.10
Outstanding at December 31, 2017	2,696		$3.16	8.55	$	146
Granted	3,546		$1.71
Exercised	(439	)	$0.62
Canceled or forfeited	(1,861	)	$3.21
Outstanding at December 31, 2018	3,942		$2.12	9.14	$	57
Granted	3,986		$1.02
Exercised	(90	)	$1.10
Canceled or forfeited	(1,602	)	$1.78
Outstanding at December 31, 2019	6,236		$1.52	8.83	$	358
Exercisable at December 31, 2019	1,866		$2.31	8.06	$	62

The Company recognized share-based compensation expense related to stock options of $1.2 million, $1.1 million and $0.9 million for the years ended December 31, 2019, 2018 and 2017, respectively. As of December 31, 2019, there was $3.2 million of total unrecognized compensation cost related to non-vested stock options which the Company expects to recognize over a weighted-average period of 2.90 years. The weighted-average grant-date fair value of stock options granted during the years ended December 31, 2019, 2018 and 2017 were $0.69, $1.14 and $1.18, respectively. The total intrinsic value of options exercised for the years ended December 31, 2019, 2018 and 2017 was de minimis, $0.5 million and $0.3 million, respectively.

For the years ended December 31, 2019, 2018 and 2017, the grant-date fair value of stock options was determined using the following weighted-average inputs and assumptions in the Black-Scholes option pricing model:



	Year ended December 31,
	2019	2018	2017
Fair value of common stock	$1.02	$1.71	$1.74
Exercise price of the option	$1.02	$1.71	$1.74
Expected term (years)	5.98	5.97	5.59
Risk-free interest rate	2.1%	2.8%	1.9%
Expected volatility	78.1%	74.2%	81.6%
Dividend yield	—%	—%	—%

Performance-Based Grants

In October 2017, the Company granted to certain executives a total of 0.9 million performance-based stock options with an exercise price of $1.59 and a grant-date fair value of $1.12 per option. The four performance milestone events were specific to the Company’s corporate goals, including certain clinical development objectives related to the VISTA Trial, as well as a past financing objective. In the fourth quarter of 2017, management deemed it probable that two of the performance objectives were achieved. During 2018, management determined that one performance objective was achieved and deemed it probable that a second performance-based milestone would be achieved. The Company recognized share-based compensation expense related to performance-based stock options of de minimis, $0.2 million and $0.3 million for the years ended December 31, 2019, 2018 and 2017, respectively. As of December 31, 2019, there was no unrecognized compensation cost related the performance-based stock options granted in October 2017.

Restricted Stock

From time to time, prior to December 31, 2016 and upon approval by the board of directors, certain employees and advisors were granted restricted stock awards ("RSAs") and restricted stock units ("RSUs"), all of which were vested prior to December 31, 2018. The Company did not grant RSAs or RSUs during the years ended December 31, 2019, 2018 and 2017.

The following table sets forth a summary of the Company's restricted stock activity for the years ended December 31, 2018 and 2017:



	Non-vested Restricted Stock Awards (in thousands)		Weighted-Average Grant Date Fair Value	Non-vested Restricted Stock Units (in thousands)		Weighted-Average Grant Date Fair Value
Non-vested at December 31, 2016	22		$11.43	3		$4.09
Vested	(18	)	$11.43	(3	)	$4.09
Non-vested at December 31, 2017	4		$11.43	—
Vested	(4	)	$11.43
Non-vested at December 31, 2018	—

The Company recognized share-based compensation expense related to restricted stock of de minimis and $0.2 million for the years ended December 31, 2018 and 2017, respectively.

EMPLOYEE BENEFIT PLANS	12 Months Ended
EMPLOYEE BENEFIT PLANS	Dec. 31, 2019
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. 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 the Company’s 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 Company's common stock issued and sold pursuant to the 2014 ESPP are shown on the consolidated statements of changes in stockholders' (deficit) equity. As of December 31, 2019, there were approximately 28,000 shares of the Company's common stock available for sale under the 2014 ESPP. Defined Contribution Plans United States - 401(k) Plan The Company maintains a 401(k) defined contribution retirement plan which covers all of its U.S. 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. 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.

INCOME TAXES

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

INCOME TAXES

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



	Year ended December 31,
	2019			2018			2017
Country:
United States	$	(27,468	)	$	(15,977	)	$	(9,246	)
Canada	(80,032		)	(17,716		)	(19,783		)
Total Loss before Income Taxes	$	(107,500	)	$	(33,693	)	$	(29,029	)

The Company did not record current or deferred income tax or benefit for the years ended December 31, 2019, 2018 and 2017.

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



	Year ended December 31,
	2019		2018		2017
United States federal statutory income tax rate	21.0	%	21.0	%	34.0	%
Impact of foreign rate differential	4.4		1.6		(2.6	)
State taxes, net of federal benefit	0.6		1.3		1.4
Stock option cancellations	—		(1.2	)	(0.8	)
Contingent consideration	(18.0	)	(5.5	)	(10.7	)
General business credits and other credits	0.4		0.7		0.8
Permanent differences	—		(0.3	)	0.3
Other	(0.5	)	0.5		—
United States federal statutory tax rate change	—		—		(50.6	)
Change in valuation allowance	(7.9	)	(18.1	)	28.2
Effective Income Tax Rate	—	%	—	%	—	%

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



	December 31,
	2019			2018
Deferred tax assets:
NOL carryforwards	$	50,727		$	43,212
R&D credit carryforwards	4,385			3,876
Accruals and other	2,464			2,011
Capitalized start-up costs	91			122
Other	57			32
Gross deferred tax assets	57,724			49,253
Deferred tax liabilities:
IPR&D	(12,528		)	(12,528		)
Property and equipment	—			(60		)
Gross deferred tax liabilities	(12,528		)	(12,588		)
Valuation allowance	(57,724		)	(49,193		)
Net Deferred Tax Liability	$	(12,528	)	$	(12,528	)

In assessing the realizability of the Company's deferred tax assets, management considers all relevant positive and negative evidence in determining whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The realization of deferred tax assets is dependent on several factors, including the generation of sufficient taxable income prior to the expiration of the NOL and R&D credit carryforwards. The Company has generated NOLs since its inception, and management believes that it is more likely than not that the Company's deferred tax assets will not be realized. As a result, valuation allowances of $57.7 million and $49.2 million have been established as of December 31, 2019 and 2018, respectively. The $8.5 million increase in the valuation allowance was attributable to the NOL for the year ended December 31, 2019.

The net deferred tax liability of $12.5 million primarily relates to the potential future impairments or amortization associated with IPR&D intangible assets, which is not deductible for tax purposes and cannot be considered as a source of income to realize deferred tax assets. As a result, the Company recorded the deferred tax liability with an offset to goodwill.

The following table summarizes the Company's NOL and R&D and other credit carryforwards in the United States and Canada as of December 31, 2019 (in millions):



	Amount		Expiration Beginning in	Through
United States:
Federal NOL carryforwards - indefinite	$	41.2	None	None
Federal NOL carryforwards	$	118.9	2030	2039
State NOL carryforwards	$	131.2	2030	2039
Federal R&D credit carryforwards	$	2.2	2027	2039
State R&D credit carryforwards	$	0.9	2027	2039
Canada:
Federal non-capital loss carryforwards	$	32.6	2035	2039
Federal scientific research and experimental development expense carryforwards	$	6.2	2032	2039
Federal and provincial investment tax credit carryforwards	$	1.5	2032	2039

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

As of December 31, 2019, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company's consolidated statements of operations. Due to NOL and R&D credit carryforwards that remain unutilized, income tax returns filed in the United States, certain states within the United States and Canadian tax jurisdictions from the Company's inception through 2018 remain subject to examination by the taxing jurisdictions. There are currently no audits in process in any of the Company's tax filing jurisdictions.

LICENSE AGREEMENTS	12 Months Ended
LICENSE AGREEMENTS	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
LICENSE AGREEMENTS	LICENSE AGREEMENTS Vicinium 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. These patents cover some key aspects of Vicinium. The Company may be obligated to pay $0.75 million in milestone payments for the first product candidate that achieves applicable clinical development milestones. Based on current status, the Company anticipates that these milestones may be triggered by Vicinium's clinical development pathway. As part of the consideration, the Company is also obligated to pay up to a 4% royalty on the net product sales for products covered by or manufactured using a method covered by a valid claim in the Zurich patent rights. Royalties owed to Zurich will be reduced if the total royalty rate owed by the Company to Zurich and any other third party is 10% or greater, provided that the royalty rate to Zurich may not be less than 2% of net sales. The obligation to pay royalties in a particular country expires upon the expiration or termination of the last of the Zurich patent rights that covers the manufacture, use or sale of a product. There is no obligation to pay royalties in a country if there is no valid claim that covers the product or a method of manufacturing the product. 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. These patents cover some key aspects of Vicinium. Under the terms of the License Agreement with Micromet, the Company may be obligated to pay up to €3.6 million in milestone payments for the first product candidate that achieves applicable clinical development milestones. Based on current clinical status, the Company anticipates that certain of these milestones may be triggered by Vicinium’s clinical development pathway. 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 Vicinium. 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, which can be credited towards any royalty payment the Company owes to Micromet. 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. These patents and related know-how cover some key aspects of Vicinium. Under the terms of the License Agreement with XOMA, 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 Vicinium’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 Vicinium. 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. Other License Agreements License Agreement with Roche In June 2016, the Company entered into the License Agreement with Roche, 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 “Licensed Intellectual Property”). Under the License Agreement, Roche is required to continue developing, at its cost, EBI-031 and any other product made from the Licensed Intellectual Property that contains an IL-6 antagonist anti-IL monoclonal antibody (“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 License Agreement with Roche 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 commercial 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 $72.5 million in development milestones, $50.0 million in regulatory milestones and $75.0 million in commercialization milestones. 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. 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% 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 License Agreement with Roche 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 License Agreement. Specifically, (i) Roche may exercise a buy-out option following the first dosing (“Initiation”) in the first Phase 2 study for a Licensed Product until the day before Initiation of the first Phase 3 study for a Licensed Product, in which case Roche is required to pay the Company $135.0 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 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 Licensed Product in either the United States or in the E.U., 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, $265.0 million, which amount would be reduced to $220.0 million if none of the Company’s patent rights containing a composition of matter claim covering any compound or Licensed Product has issued in the E.U. Termination Either the Company or Roche may each terminate the License Agreement with Roche if the other party breaches any of its material obligations under the License Agreement and does not cure such breach within a specified cure period. Roche may terminate the 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 License Agreement if, prior to the first filing of a BLA for a Licensed Product, there is a period of 12 months where Roche is not conducting sufficient development activities with respect to the products made from the Licensed Intellectual Property.

RELATED-PARTY TRANSACTIONS	12 Months Ended
RELATED-PARTY TRANSACTIONS	Dec. 31, 2019
Related Party Transactions [Abstract]
RELATED-PARTY TRANSACTIONS	RELATED-PARTY TRANSACTIONS The Company leases its facility in Winnipeg, Manitoba from an affiliate of Leslie L. Dan, a director of the Company until his retirement in July 2019. For each of the years ended December 31, 2019, 2018 and 2017, the Company paid $0.3 million of rent, which includes the related operating expenses. The Company pays fees under an intellectual property license agreement to Protoden Technologies Inc. ("Protoden"), a company owned by Clairmark, an affiliate of Mr. Dan, under an intellectual property licensing agreement. Pursuant to the agreement, the Company has an exclusive, perpetual, irrevocable and non-royalty bearing license, with the right to sublicense, to certain patents and technology to make, use and sell products that utilize such patents and technology. The annual fee is $0.1 million. Upon expiration of the term on December 31, 2024, the licenses granted to the Company will require no further payments to Protoden. For each of the years ended December 31, 2019, 2018 and 2017, the Company paid $0.1 million to this related party. The Company previously leased office space in Toronto, Ontario from Mr. Dan. The lease was terminated by the Company in December 2018. For each of the years ended December 31, 2018 and 2017, the Company paid $18,000 of rent.

SUPPLEMENTARY FINANCIAL INFORMATION (Unaudited)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

SUPPLEMENTARY FINANCIAL INFORMATION (Unaudited)

The following tables set forth selected financial information for the quarterly periods noted (in thousands, except per share data):



	2019
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Total revenue	$	—		$	—		$	—		$	—
Total operating expenses	$	6,741		$	54,561		$	13,451		$	33,738
Loss from operations	$	(6,741	)	$	(54,561	)	$	(13,451	)	$	(33,738	)
Net loss and comprehensive loss	$	(6,480	)	$	(54,335	)	$	(13,132	)	$	(33,553	)
Net loss per common share - basic and diluted	$	(0.08	)	$	(0.67	)	$	(0.13	)	$	(0.32	)



	2018
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Total revenue	$	—		$	—		$	—		$	—
Total operating expenses	$	4,007		$	9,030		$	14,397		$	7,066
Loss from operations	$	(4,007	)	$	(9,030	)	$	(14,397	)	$	(7,066	)
Net loss and comprehensive loss	$	(3,963	)	$	(8,958	)	$	(14,015	)	$	(6,757	)
Net loss per common share - basic and diluted	$	(0.11	)	$	(0.16	)	$	(0.18	)	$	(0.09	)

Quarterly computations of net loss per common share amounts are made independently for each quarterly reporting period, and the sum of the per share amounts for the quarterly reporting periods may not equal the per share amounts for the year-to-date reporting period.

SUBSEQUENT EVENTS	12 Months Ended
SUBSEQUENT EVENTS	Dec. 31, 2019
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS Listing Non-Compliance Notice On March 2, 2020, the Company received written notice (the “Notice”) from Nasdaq Stock Market LLC ("Nasdaq") indicating that the Company is not in compliance with the $1.00 minimum bid price requirement for continued listing on the Nasdaq Global Market, as set forth in Nasdaq Listing Rule 5450(a)(1). The Notice has no effect at this time on the listing of the Company’s common stock, which will continue to trade on the Nasdaq Global Market under the symbol “SESN.” In accordance with Nasdaq Listing Rule 5810(c)(3)(A), the Company has a period of 180 calendar days, or until August 31, 2020, to regain compliance with the minimum bid price requirement. To regain compliance, the closing bid price of the Company’s common stock must meet or exceed $1.00 per share for a minimum of ten consecutive business days during this 180-day period. If the Company is not in compliance by August 31, 2020, the Company may be afforded a second 180 calendar day period to regain compliance. To qualify, the Company would be required to apply to have its common stock listed on the Nasdaq Capital Market and meet the continued listing requirement for market value of publicly held shares and all other initial listing standards for the Nasdaq Capital Market, except for the minimum bid price requirement, and will need to provide written notice to Nasdaq of its intention to cure the deficiency during the second compliance period by effecting a reverse stock split, if necessary. The Company intends to monitor the closing bid price of its common stock and may, if appropriate, consider implementing available options to regain compliance with the minimum bid price requirement, including, but not limited to, a proposal for a reverse stock split of the Company's common stock to be submitted for stockholder approval at the Company's 2020 Annual Meeting of Stockholders. Stock Options Granted In January 2020, the Company granted 0.1 million stock options with an exercise price of $0.84 to new employees as inducement equity awards outside of the Company's 2014 Plan in accordance with Nasdaq Listing Rule 5635(c)(4). These stock options had a grant-date fair value of $0.59 and vest at the rate of 25% of the grant on the first anniversary of the date of grant and thereafter 6.25% of the grant at the end of each successive three-month period following the first anniversary of the date of grant, subject to the recipient's continued service with the Company through the applicable vesting dates. In February 2020, the Company's board of directors granted 3.1 million stock options with an exercise price of $0.89 to employees and officers under the Company's 2014 Plan. These stock options had a grant-date fair value of $0.62 and vest at the rate of 6.25% of the grant every three months over a period of four years, subject to the recipient's continued service with the Company through the applicable vesting dates.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Use of Estimates

The preparation of financial statements in accordance with GAAP and the rules and regulations of the United States Securities and Exchange Commission ("SEC") requires the use of estimates and assumptions, based on judgments considered reasonable, which affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The Company bases its estimates and assumptions on historical experience, known trends and events and various other factors that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Although management believes its estimates and assumptions are reasonable when made, they are based upon information available at the time they are made. Management evaluates the estimates and assumptions on an ongoing basis and, if necessary, makes adjustments. Due to the risks and uncertainties involved in the Company’s business and evolving market conditions, and given the subjective element of the estimates and assumptions made, actual results may differ from estimated results. The most significant estimates and judgments impact the fair value of intangible assets, goodwill and contingent consideration; income taxes (including the valuation allowance for deferred tax assets); research and development expenses; and going concern considerations.

Principles of Consolidation

The Company’s consolidated financial statements include the accounts of the Company, its wholly owned subsidiary Viventia and its indirect subsidiaries, Viventia Bio USA Inc. and Viventia Biotech (EU) Limited. All intercompany transactions and balances have been eliminated in consolidation.

Foreign Currency Translation

The functional currency of the Company and each of its subsidiaries is the U.S. dollar.

Cash, Cash Equivalents and Concentration of Credit Risk

Property and Equipment

Impairment of Long-Lived Assets

Indefinite-Lived Intangible Assets

Goodwill

Contingent Consideration

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; and


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

Research and Development Costs

Stock-Based Compensation

Share-Based Compensation

The fair value of each grant of options during the years ended December 31, 2019, 2018 and 2017 was determined using the following methods and assumptions:

•


•	Risk-Free Interest Rate. The risk-free rate is based on the interest rate payable on United States Treasury securities in effect at the time of grant for a period that is commensurate with the assumed expected term.


•	Expected Volatility. The expected volatility is based on historical volatilities of a representative group of publicly traded biopharmaceutical companies which were commensurate with the assumed expected term, as prescribed in SAB 107.


•	Dividend Yield. The dividend yield is 0% because the Company has never declared or paid, and for the foreseeable future does not expect to declare or pay, a dividend on its common stock.

Income Taxes

Revenue Recognition

Recent Accounting Pronouncements

Adopted in 2019

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. Early adoption is permitted, the Company adopted this guidance effective January 1, 2019, and it did not have a material impact on the Company’s financial position, results of operations or cash flows.

In June 2018, the FASB issued ASU No. 2018-07, Compensation - Stock Compensation (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 guidance effective January 1, 2019, and it did not have a material impact on the Company’s financial position, results of operations or cash flows.

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 ASC, 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 the 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. The Company adopted this guidance effective January 1, 2019, and it did not have a material impact on the Company’s financial position, results of operations or cash flows.

Pending Adoption

In June 2016, the FASB issued ASU No. 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 annual and interim periods beginning January 1, 2020 and is to be applied using a modified retrospective transition method. Earlier adoption is permitted. Because the Company holds only highly-rated money market funds, it does not expect the adoption of ASU 2016-13 to have a material impact on the Company's financial position, results of operations or cash flows.

In August 2018, the FASB issued ASU No. 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. ASU 2018-13 is effective for annual and interim periods beginning after December 15, 2019. Early adoption is permitted. Because this ASU changes only the disclosure requirements and not the underlying accounting, the Company does not expect the adoption of ASU 2018-13 to have a material impact on the Company's financial position, results of operations or cash flows.

In August 2018, the FASB issued ASU No. 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 amendments in this ASU should be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company will adopt the ASU prospectively to all implementation costs incurred after January 1, 2020 and does not expect the adoption of ASU 2016-13 to have a material impact on the Company's financial position, results of operations or cash flows.

In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes ("ASU 2019-12"). ASU 2019-12 simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The amendments in ASU 2019-12 also improve consistent application of and simplify GAAP for other areas of Topic 740 by clarifying and amending existing guidance. ASU 2109-12 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. Early adoption is permitted. The method with which the amendments in this ASU are to be applied varies depending on the nature of the tax item impacted by amendment. Because the Company generates losses and pays no income taxes, it does not expect the adoption of ASU 2019-12 to have a material impact on the Company's financial position, results of operations or cash flows.

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Summary of assets and liabilities measured at fair value on a recurring basis

The following tables set forth the carrying amounts and fair values of the Company's financial instruments measured at fair value on a recurring basis as of December 31, 2019 and 2018 (in thousands):



	December 31, 2019
					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)	$	31,146	$	31,146	$	31,146	$	—	$	—
Liabilities:
Contingent consideration	$	120,020	$	120,020	$	—	$	—	$	120,020



	December 31, 2018
					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)	$	40,365	$	40,365	$	40,365	$	—	$	—
Liabilities:
Contingent consideration	$	48,400	$	48,400	$	—	$	—	$	48,400

Summary of Contingent Consideration Liability



Balance at December 31, 2018	$	48,400
Change in fair value included in loss	(1,000		)
Balance at March 31, 2019	47,400
Change in fair value included in loss⁽¹⁾	44,000
Balance at June 30, 2019	91,400
Change in fair value included in loss⁽²⁾	3,600
Balance at September 30, 2019	95,000
Change in fair value included in loss⁽³⁾	25,020
Balance at December 31, 2019	$	120,020

PROPERTY AND EQUIPMENT (Tables)

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Schedule of Composition of Property and Equipment

The following table sets forth the composition of property and equipment, net as of December 31, 2019 and 2018 (in thousands):



	December 31,
	2019			2018
Lab equipment	$	572		$	443
Furniture and fixtures	16			16
Computer equipment	87			80
Software	28			28
Leasehold improvements	293			293
Property and equipment, gross	996			860
Less: accumulated depreciation	(758		)	(539		)
Total Property and Equipment, Net	$	238		$	321

INTANGIBLES AND GOODWILL (Tables)

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Composition of Intangible Assets

The following table sets forth the composition of intangible assets as of December 31, 2019 and 2018 (in thousands):



	December 31,
	2019		2018
IPR&D intangible assets:
Vicinium United States rights	$	31,700	$	31,700
Vicinium European Union rights	14,700		14,700
Total Intangibles	$	46,400	$	46,400

ACCRUED EXPENSES (Tables)

12 Months Ended

Dec. 31, 2019

Payables and Accruals [Abstract]

Components of accrued expenses

The following table sets forth the composition of accrued expenses as of December 31, 2019 and 2018 (in thousands):



	December 31,
	2019		2018
Research and development	$	3,688	$	2,928
Payroll-related expenses	1,638		1,045
Severance to former Executives and other employees	378		278
Professional fees	378		464
Other	87		31
Total Accrued Expenses	$	6,169	$	4,746

COMMITMENTS AND CONTINGENCIES (Tables)

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Schedule of Lease Cost

The components of lease cost for the year ended December 31, 2019 is as follows (in thousands):



	Year ended
Lease Cost:	December 31, 2019
Operating lease (including related operating costs)	$	298
Short-term property leases	263
Total Lease Costs	$	561



Supplemental Information:
Weighted-average remaining lease term - operating leases (in years)	0.75
Weighted-average discount rate - operating leases	12%

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

The following table sets forth the Company's future minimum lease payments under non-cancelable leases as of December 31, 2019 (in thousands):



Year ending December 31,	Minimum Lease Payments
2020	113
Total future minimum lease payments	113
Less: Amounts representing present value adjustment	(1		)
Operating lease current liabilities as of December 31, 2019	$	112

STOCKHOLDERS' (DEFICIT) EQUITY (Tables)

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Summary of Common Stock

In addition, the Company had reserved for issuance the following amounts of shares of its common stock for the purposes described below as of December 31, 2019 and 2018 (in thousands):



	December 31,
	2019	2018
Shares of common stock issued	106,801	77,456
Shares of common stock reserved for issuance for:
Warrants	22,895	9,258
Stock options	6,236	3,942
Shares available for grant under 2014 Stock Incentive Plan	8,753	2,001
Shares available for sale under 2014 Employee Stock Purchase Plan	28	38
Total shares of common stock issued and reserved for issuance	144,713	92,695

Summary of Warrants Outstanding and Warrant Activity

The following table sets forth the Company's warrant activity for the year ended December 31, 2019 (in thousands):



Issued	Exercise Price	Expiration	December 31, 2018	Issued	(Exercised)		December 31, 2019
Jun-2019	$1.47	Jun-2020	—	20,410	—		20,410
Mar-2018	$0.95*	Mar-2023	7,211	—	(5,268	)	1,943
Nov-2017	$0.55*	Nov-2022	1,992	—	(1,505	)	487
May-2015	$11.83	Nov-2024	28	—	—		28
Nov-2014	$11.04	Nov-2024	27	—	—		27
			9,258	20,410	(6,773	)	22,895

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

- Definition

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

+ References

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+ Details

LOSS PER SHARE (Tables)

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Schedule of Potentially Dilutive Securities



	December 31,
	2019	2018	2017
Warrants	22,895	9,258	10,055
Stock options	6,236	3,942	2,696
Non-vested restricted stock awards	—	—	4
	29,131	13,200	12,755

SHARE-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Schedule of Share-Based Compensation Expense



	Year ended December 31,
	2019		2018		2017
Research and development	$	188	$	505	$	404
General and administrative	1,049		778		977
Total Share-based Compensation	$	1,237	$	1,283	$	1,381

Schedule of Stock Option Activity



	Number of Shares under Option (in thousands)		Weighted-Average Exercise Price per Option	Weighted-Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2016	2,024		$4.41	8.73	$	841
Granted	1,303		$1.64
Exercised	(140	)	$0.28
Canceled or forfeited	(491	)	$5.10
Outstanding at December 31, 2017	2,696		$3.16	8.55	$	146
Granted	3,546		$1.71
Exercised	(439	)	$0.62
Canceled or forfeited	(1,861	)	$3.21
Outstanding at December 31, 2018	3,942		$2.12	9.14	$	57
Granted	3,986		$1.02
Exercised	(90	)	$1.10
Canceled or forfeited	(1,602	)	$1.78
Outstanding at December 31, 2019	6,236		$1.52	8.83	$	358
Exercisable at December 31, 2019	1,866		$2.31	8.06	$	62

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



	Year ended December 31,
	2019	2018	2017
Fair value of common stock	$1.02	$1.71	$1.74
Exercise price of the option	$1.02	$1.71	$1.74
Expected term (years)	5.98	5.97	5.59
Risk-free interest rate	2.1%	2.8%	1.9%
Expected volatility	78.1%	74.2%	81.6%
Dividend yield	—%	—%	—%

Summary of Status and Changes of Unvested Restricted Stock

The following table sets forth a summary of the Company's restricted stock activity for the years ended December 31, 2018 and 2017:



	Non-vested Restricted Stock Awards (in thousands)		Weighted-Average Grant Date Fair Value	Non-vested Restricted Stock Units (in thousands)		Weighted-Average Grant Date Fair Value
Non-vested at December 31, 2016	22		$11.43	3		$4.09
Vested	(18	)	$11.43	(3	)	$4.09
Non-vested at December 31, 2017	4		$11.43	—
Vested	(4	)	$11.43
Non-vested at December 31, 2018	—

INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Components of Pre-tax Income (Loss)

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



	Year ended December 31,
	2019			2018			2017
Country:
United States	$	(27,468	)	$	(15,977	)	$	(9,246	)
Canada	(80,032		)	(17,716		)	(19,783		)
Total Loss before Income Taxes	$	(107,500	)	$	(33,693	)	$	(29,029	)

Reconciliation of Expected Income Tax Expense

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



	Year ended December 31,
	2019		2018		2017
United States federal statutory income tax rate	21.0	%	21.0	%	34.0	%
Impact of foreign rate differential	4.4		1.6		(2.6	)
State taxes, net of federal benefit	0.6		1.3		1.4
Stock option cancellations	—		(1.2	)	(0.8	)
Contingent consideration	(18.0	)	(5.5	)	(10.7	)
General business credits and other credits	0.4		0.7		0.8
Permanent differences	—		(0.3	)	0.3
Other	(0.5	)	0.5		—
United States federal statutory tax rate change	—		—		(50.6	)
Change in valuation allowance	(7.9	)	(18.1	)	28.2
Effective Income Tax Rate	—	%	—	%	—	%

Components of Deferred Tax Assets and Liabilities

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



	December 31,
	2019			2018
Deferred tax assets:
NOL carryforwards	$	50,727		$	43,212
R&D credit carryforwards	4,385			3,876
Accruals and other	2,464			2,011
Capitalized start-up costs	91			122
Other	57			32
Gross deferred tax assets	57,724			49,253
Deferred tax liabilities:
IPR&D	(12,528		)	(12,528		)
Property and equipment	—			(60		)
Gross deferred tax liabilities	(12,528		)	(12,588		)
Valuation allowance	(57,724		)	(49,193		)
Net Deferred Tax Liability	$	(12,528	)	$	(12,528	)

Schedule of Credit Carryforwards

The following table summarizes the Company's NOL and R&D and other credit carryforwards in the United States and Canada as of December 31, 2019 (in millions):



	Amount		Expiration Beginning in	Through
United States:
Federal NOL carryforwards - indefinite	$	41.2	None	None
Federal NOL carryforwards	$	118.9	2030	2039
State NOL carryforwards	$	131.2	2030	2039
Federal R&D credit carryforwards	$	2.2	2027	2039
State R&D credit carryforwards	$	0.9	2027	2039
Canada:
Federal non-capital loss carryforwards	$	32.6	2035	2039
Federal scientific research and experimental development expense carryforwards	$	6.2	2032	2039
Federal and provincial investment tax credit carryforwards	$	1.5	2032	2039

SUPPLEMENTARY FINANCIAL INFORMATION (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Selected Financial Information

The following tables set forth selected financial information for the quarterly periods noted (in thousands, except per share data):



	2019
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Total revenue	$	—		$	—		$	—		$	—
Total operating expenses	$	6,741		$	54,561		$	13,451		$	33,738
Loss from operations	$	(6,741	)	$	(54,561	)	$	(13,451	)	$	(33,738	)
Net loss and comprehensive loss	$	(6,480	)	$	(54,335	)	$	(13,132	)	$	(33,553	)
Net loss per common share - basic and diluted	$	(0.08	)	$	(0.67	)	$	(0.13	)	$	(0.32	)



	2018
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Total revenue	$	—		$	—		$	—		$	—
Total operating expenses	$	4,007		$	9,030		$	14,397		$	7,066
Loss from operations	$	(4,007	)	$	(9,030	)	$	(14,397	)	$	(7,066	)
Net loss and comprehensive loss	$	(3,963	)	$	(8,958	)	$	(14,015	)	$	(6,757	)
Net loss per common share - basic and diluted	$	(0.11	)	$	(0.16	)	$	(0.18	)	$	(0.09	)

DESCRIPTION OF BUSINESS (Details) $ in Thousands, shares in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($) shares	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Variable Interest Entity [Line Items]
Number of operating segments \| segment		1
Cash and cash equivalents		$ 48,121	$ 50,422
Net working capital		45,900
Accumulated deficit		293,524	186,024
Negative cash flows from operating activities incurred		$ 37,521	$ 22,829	$ 17,765
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 (as a percent)	19.90%
Period during which quarterly earn-outs are payable after date of net sales	15 years
Period in which acquiree is to use commercially reasonable efforts to achieve marketing authorizations	7 years
Viventia Bio Inc. \| Vicinium \| Collaborative Arrangement, Revenue based on Specified Milestone
Variable Interest Entity [Line Items]
Percentage of net sales of quarterly earn-out payments during earn-out periods	2.00%
Viventia Bio Inc. \| Vicinium \| Collaborative Arrangement, Revenue based on Specified Milestone \| United States
Variable Interest Entity [Line Items]
One-time milestone payment upon first sale of product	$ 12,500
Viventia Bio Inc. \| Vicinium \| Collaborative Arrangement, Revenue based on Specified Milestone \| Europe
Variable Interest Entity [Line Items]
One-time milestone payment upon first sale of product	7,000
Viventia Bio Inc. \| Vicinium \| Collaborative Arrangement, Revenue based on Specified Milestone \| Japan
Variable Interest Entity [Line Items]
One-time milestone payment upon first sale of product	$ 3,000

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)	3 Months Ended	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)	Mar. 31, 2017 USD ($)	Dec. 31, 2019 USD ($) reporting_unit	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)
Property, Plant and Equipment [Line Items]
Insurance coverage limit		$ 250,000
Impairment of long-lived assets		0	$ 0
Impairment of intangible assets		$ 0	0
Number of reporting units \| reporting_unit		1
Goodwill impairment		$ 0	$ 0	$ 0
Operating lease current liabilities as of December 31, 2019		$ 112,000
Expected term		5 years 11 months 23 days	5 years 11 months 21 days	5 years 6 months 32 days
Dividend yield		0.00%	0.00%	0.00%
Lab equipment
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)		5 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)		4 years
Computer equipment
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)		3 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)		5 years
ASU 2016-02
Property, Plant and Equipment [Line Items]
Right-of-use asset					$ 200,000
Operating lease current liabilities as of December 31, 2019					$ 200,000
License revenue \| Roche
Property, Plant and Equipment [Line Items]
Deferred revenue	$ 400,000
Performance-Based Awards
Property, Plant and Equipment [Line Items]
Award vesting period		4 years
Expected term		10 years

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Liabilities:
Contingent consideration	$ 120,020	$ 95,000	$ 91,400	$ 47,400	$ 48,400
Carrying Amount
Assets:
Money market funds (cash equivalents)	31,146				40,365
Fair Value \| Recurring
Assets:
Money market funds (cash equivalents)	31,146				40,365
Liabilities:
Contingent consideration	120,020				48,400
Fair Value \| Recurring \| Quoted Prices in Active Markets (Level 1)
Assets:
Money market funds (cash equivalents)	31,146				40,365
Liabilities:
Contingent consideration	0				0
Fair Value \| Recurring \| Significant other Observable Inputs (Level 2)
Assets:
Money market funds (cash equivalents)	0				0
Liabilities:
Contingent consideration	0				0
Fair Value \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Money market funds (cash equivalents)	0				0
Liabilities:
Contingent consideration	$ 120,020				$ 48,400

FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS - Summary of Changes in Fair Value of Contingent Consideration (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 95,000	$ 91,400	$ 47,400	$ 48,400
Change in fair value included in loss	25,020	3,600	44,000	(1,000)
Ending balance	120,020	95,000	91,400	$ 47,400
Change in fair value of contingent consideration	$ 25,000	$ 3,600	$ 44,000
Discount Rate \| Minimum
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Contingent consideration liability, measurement input	0.056				0.066
Discount Rate \| Maximum
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Contingent consideration liability, measurement input	0.118				0.137
Royalty Rate
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Contingent consideration liability, measurement input	0.02

PROPERTY AND EQUIPMENT - Property and Equipment and Related Accumulated Depreciation (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 996	$ 860
Less: accumulated depreciation	(758)	(539)
Total Property and Equipment, Net	238	321
Lab equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	572	443
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	16	16
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	87	80
Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	28	28
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 293	$ 293

PROPERTY AND EQUIPMENT - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 219,000	$ 208,000	$ 285,000
Property, plant and equipment, disposals			0
Proceeds from sale of property and equipment			$ 98,000

INTANGIBLES AND GOODWILL - Composition of Intangible Assets (Details) - IPR&D intangible assets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Total Intangibles	$ 46,400	$ 46,400
United States \| Vicinium
Finite-Lived Intangible Assets [Line Items]
Total Intangibles	31,700	31,700
Europe \| Vicinium
Finite-Lived Intangible Assets [Line Items]
Total Intangibles	$ 14,700	$ 14,700

INTANGIBLES AND GOODWILL - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 13,064	$ 13,064

ACCRUED EXPENSES - Components of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Research and development	$ 3,688	$ 2,928
Payroll-related expenses	1,638	1,045
Severance to former Executives and other employees	378	278
Professional fees	378	464
Other	87	31
Total accrued expenses	$ 6,169	$ 4,746

ACCRUED EXPENSES - Additional Information (Details) - USD ($) $ in Thousands	Sep. 09, 2019	Aug. 02, 2019	Sep. 28, 2018	Dec. 31, 2019	Aug. 03, 2019	Dec. 31, 2018	Sep. 30, 2017
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Expense recorded related to management changes				$ 378		$ 278
Restructuring costs							$ 100
Former Chief Financial Officer
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Separation Agreement, period of separation payments and benefits agreed to	12 months
Expense recorded related to management changes	$ 300
Former Chief Medical Officer
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Separation Agreement, period of separation payments and benefits agreed to		6 months
Expense recorded related to management changes					$ 300
Separation payments		$ 200
Consulting fees and transition expenses					$ 100
Former President And Chief Executive Officer
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Separation Agreement, period of separation payments and benefits agreed to			12 months
Expense recorded related to management changes			$ 600
Base salary			400
Bonuses			$ 200

COMMITMENTS AND CONTINGENCIES - Additional Information (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) ft² option	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Commitments And Contingencies [Line Items]
Operating lease (including related operating costs)	$ 298,000
Canada
Commitments And Contingencies [Line Items]
Office space, square foot \| ft²	31,100
Lease term	5 years
Renewal option \| option	1
Monthly rent	$ 12,600
Related operating expenses	12,300
Operating lease (including related operating costs)	$ 300,000
Rent expense Under ASC 840		$ 300,000	$ 300,000
Massachusetts
Commitments And Contingencies [Line Items]
Lease term	4 months
Monthly rent	$ 7,900
Operating lease (including related operating costs)	100,000
Rent expense Under ASC 840		100,000
Pennsylvania
Commitments And Contingencies [Line Items]
Monthly rent	13,500
Rent expense Under ASC 840	$ 100,000	$ 200,000

COMMITMENTS AND CONTINGENCIES - Lease Costs (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Lease Cost:
Operating lease (including related operating costs)	$ 298
Short-term property leases	263
Total Lease Costs	$ 561
Supplemental Information:
Weighted-average remaining lease term - operating leases (in years)	9 months
Weighted-average discount rate - operating leases	12.00%

COMMITMENTS AND CONTINGENCIES - Minimum Aggregate Future Lease Commitment (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Minimum Lease Payments
2020	$ 113
Total future minimum lease payments	113
Less: Amounts representing present value adjustment	(1)
Operating lease current liabilities as of December 31, 2019	$ 112

STOCKHOLDERS' (DEFICIT) EQUITY - Equity Financing (Details) - USD ($)		1 Months Ended				12 Months Ended
	Nov. 01, 2017	Nov. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019
Common Stock Capital Shares Reserved For Future Issuance [Line Items]
Sale of stock, floor price per share (in dollars per share)		$ 1.00
Stock price per share (in dollars per share)				$ 1.80	$ 1.13
Commission fixed rate		3.00%
Legal, accounting and printing costs						$ 200,000
Proceeds from sale of stock	$ 7,000,000		$ 27,800,000	$ 41,900,000	$ 9,000,000
Sale of stock, shares issued (in shares)	5,500,000		20,400,000	25,600,000	8,000,000
Number of warrants (in shares)			20,400,000		8,000,000
Stock and warrants price per share (in dollars per share)			$ 1.47
Exercise price per warrant (in dollars per share)	$ 0.80		$ 1.47		$ 1.20
Warrants exercise period			1 year		5 years
Warrant price per unit (in dollars per share)	0.01				$ 0.125
Common Stock
Common Stock Capital Shares Reserved For Future Issuance [Line Items]
Stock price per share (in dollars per share)	$ 0.80
Number of warrants (in shares)	1
Pre-Funded Warrant
Common Stock Capital Shares Reserved For Future Issuance [Line Items]
Number of warrants (in shares)	4,500,000
Warrant price per unit (in dollars per share)	$ 0.79
Common Warrants
Common Stock Capital Shares Reserved For Future Issuance [Line Items]
Number of warrants (in shares)	1
Expiration period	5 years
ATM Facility
Common Stock Capital Shares Reserved For Future Issuance [Line Items]
Aggregate sales price		$ 35,000,000.0
Proceeds from sale of stock						$ 1,900,000
Sale of stock, shares issued (in shares)						2,100,000

STOCKHOLDERS' (DEFICIT) EQUITY - Preferred Stock (Details) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Preferred stock, shares authorized (in shares)	5,000,000.0	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' (DEFICIT) EQUITY - Common Stock (Details)	12 Months Ended
STOCKHOLDERS' (DEFICIT) EQUITY - Common Stock (Details)	Dec. 31, 2019 vote $ / shares shares	Dec. 31, 2018 $ / shares shares	Dec. 31, 2017 shares	Dec. 31, 2016 shares
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, par value (in dollars per share) \| $ / shares	$ 0.001	$ 0.001
Common stock, shares issued (in shares)	106,801,409	77,456,180
Common Stock
Class of Stock [Line Items]
Common stock, shares outstanding (in shares)	106,801,409	77,456,180	34,702,565	24,531,964
Number of votes \| vote	1

STOCKHOLDERS' (DEFICIT) EQUITY - Summary of Common Stock Issued and Reserved for Issuance (Details) - shares	Dec. 31, 2019	Dec. 31, 2018
Class of Warrant or Right [Line Items]
Common stock, shares issued (in shares)	106,801,409	77,456,180
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance (in shares)	6,236,000	3,942,000
Total shares of common stock issued and reserved for issuance (in shares)	144,713,000	92,695,000
Warrants
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance (in shares)	22,895,000	9,258,000
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)	8,753,000	2,001,000
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)	28,000	38,000

STOCKHOLDERS' (DEFICIT) EQUITY - Warrants (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2018	Nov. 01, 2017
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)		$ 1.47	$ 1.20	$ 0.80
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	9,258
Warrants Issued (in shares)	20,410
Warrants Exercised (in shares)	(6,773)
Warrants outstanding, ending balance (in shares)	22,895
Warrants, Expiring June 2020
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)	$ 1.47
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	0
Warrants Issued (in shares)	20,410
Warrants Exercised (in shares)	0
Warrants outstanding, ending balance (in shares)	20,410
Warrants, Expiring March 2023
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)	$ 0.95
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	7,211
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	(5,268)
Warrants outstanding, ending balance (in shares)	1,943
Warrants, Expiring November 2022
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)	$ 0.55
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	1,992
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	(1,505)
Warrants outstanding, ending balance (in shares)	487
Warrants, Expiring November 2024, Issued May 2015
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)	$ 11.83
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	28
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants outstanding, ending balance (in shares)	28
Warrants, Expiring November 2024, Issued November 2014
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)	$ 11.04
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	27
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants outstanding, ending balance (in shares)	27

STOCKHOLDERS' (DEFICIT) EQUITY - Warrants Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Oct. 28, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Oct. 31, 2019	Oct. 27, 2019	Jun. 30, 2019	Mar. 31, 2018	Nov. 01, 2017
Class of Warrant or Right [Line Items]
Proceeds from exercises of common stock warrants		$ 5,481	$ 7,315	$ 45
Exercises of common stock warrants (in shares)		6,773,000
Exercise price per warrant (in dollars per share)							$ 1.47	$ 1.20	$ 0.80
Increase in warrant value		$ 1,100
Common Stock
Class of Warrant or Right [Line Items]
Exercises of common stock warrants (in shares)		6,772,928	8,765,496	4,475,000
2018 Warrants [Member] \| Common Stock
Class of Warrant or Right [Line Items]
Exercises of common stock warrants (in shares)			5,300,000
2017 Warrants [Member] \| Common Stock
Class of Warrant or Right [Line Items]
Exercises of common stock warrants (in shares)				1,500,000
Warrants, Expiring March 2023
Class of Warrant or Right [Line Items]
Exercises of common stock warrants (in shares)		5,268,000
Exercise price per warrant (in dollars per share)		$ 0.95
Warrants, Expiring March 2023 \| Common Stock
Class of Warrant or Right [Line Items]
Proceeds from exercises of common stock warrants	$ 2,000
Exercises of common stock warrants (in shares)	3,400,000
Exercise price per warrant (in dollars per share)	$ 0.60				$ 0.95	$ 1.20
2018 Warrant Amendment, Amendment to Securities Purchase Agreement
Class of Warrant or Right [Line Items]
Minimum percentage of securities issued	50.10%
Warrants, Expiring November 2022
Class of Warrant or Right [Line Items]
Exercises of common stock warrants (in shares)		1,505,000
Exercise price per warrant (in dollars per share)		$ 0.55
Warrants, Expiring November 2022 \| Common Stock
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)	$ 0.55				$ 0.55	$ 0.80

LOSS PER SHARE (Details) - shares shares in Thousands	12 Months Ended
LOSS PER SHARE (Details) - shares shares in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
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)	29,131	13,200	12,755
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)	22,895	9,258	10,055
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)	6,236	3,942	2,696
Non-vested restricted stock awards
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)	0	0	4

SHARE-BASED COMPENSATION - Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 1,237	$ 1,283	$ 1,381
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	188	505	404
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 1,049	$ 778	$ 977

SHARE-BASED COMPENSATION - Additional Information (Details) - USD ($)	1 Months Ended		12 Months Ended
	Jun. 30, 2019	Oct. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares)			6,236,000	3,942,000	2,696,000	2,024,000
Share-based compensation expense			$ 1,237,000	$ 1,283,000	$ 1,381,000
Unrecognized compensation expense			$ 3,200,000
Option granted, weighted average grant date fair value (in dollars per share)			$ 0.69	$ 1.14	$ 1.18
Total intrinsic value of options exercised				$ 500,000	$ 300,000
Stock options granted (in shares)			3,986,000	3,546,000	1,303,000
Inducement Equity Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares)			2,100,000
Performance-Based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
Share-based compensation expense				$ 200,000	$ 300,000
Unrecognized compensation expense			$ 0
Option granted, weighted average grant date fair value (in dollars per share)		$ 1.12
Stock options granted (in shares)		900,000.0
Stock options exercise price (in dollars per share)		$ 1.59
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense			$ 1,200,000	$ 1,100,000	900,000
Weighted average period unvested stock to be recognized			2 years 10 months 23 days
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense					$ 200,000
2014 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares)			4,000,000
Number of shares reserved for issuance (in shares)	7,900,000
Stock incentive plan, shares remained available for future issuance (in shares)			8,800,000
2014 Stock Incentive Plan \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
Expected term			10 years
2009 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested stock options outstanding (in shares)			100,000
Vesting on the First Anniversary of Date of Grant \| 2014 Stock Incentive Plan \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of original number of shares subject to the option vesting			25.00%
Vesting at End of Each Successive Three-Month Period Thereafter \| 2014 Stock Incentive Plan \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of original number of shares subject to the option vesting			6.25%

SHARE-BASED COMPENSATION - Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Outstanding at beginning of period (in shares)	3,942,000	2,696,000	2,024,000
Granted (in shares)	3,986,000	3,546,000	1,303,000
Exercised (in shares)	(90,000)	(439,000)	(140,000)
Cancelled or forfeited (in shares)	(1,602,000)	(1,861,000)	(491,000)
Outstanding at end of period (in shares)	6,236,000	3,942,000	2,696,000	2,024,000
Exercisable at end of period (in shares)	1,866,000
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 2.12	$ 3.16	$ 4.41
Granted (in dollars per share)	1.02	1.71	1.64
Exercised (in dollars per share)	1.10	0.62	0.28
Cancelled or forfeited (in dollars per share)	1.78	3.21	5.10
Outstanding at end of period (in dollars per share)	1.52	$ 2.12	$ 3.16	$ 4.41
Exercisable at end of period (in dollars per share)	$ 2.31
Weighted-Average Remaining Contractual Life (in years)
Remaining contractual life of stock options outstanding	8 years 9 months 28 days	9 years 1 month 20 days	8 years 6 months 17 days	8 years 8 months 22 days
Exercisable at end of period	8 years 23 days
Outstanding intrinsic value beginning of period	$ 358	$ 57	$ 146	$ 841
Aggregate intrinsic value exercisable	$ 62

SHARE-BASED COMPENSATION - Weighted-Average Inputs and Assumptions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Payment Arrangement [Abstract]
Fair value of common stock (in dollars per share)	$ 1.02	$ 1.71	$ 1.74
Exercise price of the option (in dollars per share)	$ 1.02	$ 1.71	$ 1.74
Expected term (years)	5 years 11 months 23 days	5 years 11 months 21 days	5 years 6 months 32 days
Risk-free interest rate	2.10%	2.80%	1.90%
Expected volatility	78.10%	74.20%	81.60%
Dividend yield	0.00%	0.00%	0.00%

SHARE-BASED COMPENSATION - Summary of Status and Changes of Unvested Restricted Stock (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Non-vested Restricted Stock Awards
Number of Shares
Unvested, beginning balance (in shares)	4,000	22,000
Vested (in shares)	(4,000)	(18,000)
Unvested, ending balance (in shares)	0	4,000
Weighted-Average Grant Date Fair Value
Unvested beginning balance (in dollars per share)	$ 11.43	$ 11.43
Vested (in dollars per share)	$ 11.43	11.43
Unvested ending balance (in dollars per share)		$ 11.43
Non-vested Restricted Stock Units
Number of Shares
Unvested, beginning balance (in shares)	0	3,000
Vested (in shares)		(3,000)
Unvested, ending balance (in shares)		0
Weighted-Average Grant Date Fair Value
Unvested beginning balance (in dollars per share)		$ 4.09
Vested (in dollars per share)		$ 4.09

EMPLOYEE BENEFIT PLANS (Details) - USD ($)	12 Months Ended
EMPLOYEE BENEFIT PLANS (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Feb. 28, 2014
Defined Benefit Plan Disclosure [Line Items]
Shares of common stock reserved for issuance (in shares)	6,236,000	3,942,000
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)			200,000
Common stock purchase price, discount rate	15.00%
Common stock available for sale (in shares)	28,000

INCOME TAXES - Components of Pre-tax Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Total pre-tax income (loss)	$ (107,500)	$ (33,693)	$ (29,029)
United States
Income Taxes [Line Items]
Pre-tax income (loss) U.S.	(27,468)	(15,977)	(9,246)
Canada
Income Taxes [Line Items]
Pre-tax income (loss) Canada	$ (80,032)	$ (17,716)	$ (19,783)

INCOME TAXES - Reconciliation of Expected Income Tax Expense (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation:
United States federal statutory income tax rate	21.00%	21.00%	34.00%
Impact of foreign rate differential	4.40%	1.60%	(2.60%)
State taxes, net of federal benefit	0.60%	1.30%	1.40%
Stock option cancellations	0.00%	(1.20%)	(0.80%)
Contingent consideration	(18.00%)	(5.50%)	(10.70%)
General business credits and other credits	0.40%	0.70%	0.80%
Permanent differences	0.00%	(0.30%)	0.30%
Other	(0.50%)	0.50%	0.00%
United States federal statutory tax rate change	0.00%	0.00%	(50.60%)
Change in valuation allowance	(7.90%)	(18.10%)	28.20%
Effective Income Tax Rate	0.00%	0.00%	0.00%

INCOME TAXES - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Valuation allowance	$ 57,724	$ 49,193
Valuation allowance change	8,500
Deferred income tax liabilities, net	12,528	$ 12,528
NOL carryforward reduced amount	$ 800

INCOME TAXES - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
NOL carryforwards	$ 50,727	$ 43,212
R&D credit carryforwards	4,385	3,876
Accruals and other	2,464	2,011
Capitalized start-up costs	91	122
Other	57	32
Gross deferred tax assets	57,724	49,253
Deferred tax liabilities:
IPR&D	(12,528)	(12,528)
Property and equipment	0	(60)
Gross deferred tax liabilities	(12,528)	(12,588)
Valuation allowance	(57,724)	(49,193)
Net Deferred Tax Liability	$ (12,528)	$ (12,528)

INCOME TAXES - Schedule of Credit Carryforwards (Details) $ in Millions	Dec. 31, 2019 USD ($)
United States \| Federal
Income Taxes [Line Items]
NOL carryforwards	$ 118.9
United States \| State
Income Taxes [Line Items]
NOL carryforwards	131.2
Indefinite \| United States \| Federal
Income Taxes [Line Items]
NOL carryforwards	41.2
R&D credit carryforwards \| United States \| Federal
Income Taxes [Line Items]
Tax credit carryforwards	2.2
R&D credit carryforwards \| United States \| State
Income Taxes [Line Items]
Tax credit carryforwards	0.9
R&D credit carryforwards \| Canada
Income Taxes [Line Items]
Tax credit carryforwards	6.2
Non-capital loss carryforwards \| Canada
Income Taxes [Line Items]
Tax credit carryforwards	32.6
Investment tax credit carryforwards \| Canada
Income Taxes [Line Items]
Tax credit carryforwards	$ 1.5

LICENSE AGREEMENTS (Details) $ in Thousands		3 Months Ended	12 Months Ended
LICENSE AGREEMENTS (Details) $ in Thousands	Jun. 10, 2016 USD ($) option indication	Sep. 15, 2016 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 EUR (€)
University of Zurich
Organization And Basis Of Presentation [Line Items]
License agreement, royalty on net product sales, percentage			4.00%	4.00%
License agreement, rate requiring reduction in the amount of royalties owed			10.00%	10.00%
License agreement, royalty on net product sales, minimum			2.00%	2.00%
Roche
Organization And Basis Of Presentation [Line Items]
License agreement, up-front fee	$ 7,500
License agreement, additional up-front fee	$ 262,500
License agreement, number of unrelated Indications \| indication	2
License agreement, option periods \| option	2
License agreement, buyout amount under first option period	$ 135,000
License agreement, period to pay buyout option once exercised	30 days
License agreement, buyout amount under second option period	$ 265,000
License agreement, buyout amount under second option period, upon non-issuance of patent rights or licensed product	$ 220,000
License agreement, period for termination where sufficient development activities are not performed	12 months
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%
Micromet AG
Organization And Basis Of Presentation [Line Items]
License agreement, royalty on net product sales, percentage			3.50%	3.50%
Potential milestone payments \| €				€ 3,600,000
License Agreement, royalty payment, reduction, conditions not met			1.50%	1.50%
License maintenance fees \| €				€ 50,000
XOMA Ireland Limited
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone			$ 250
License agreement, royalty on net product sales, percentage			2.50%	2.50%
License agreement, rate requiring reduction in the amount of royalties owed			50.00%	50.00%
License agreement, royalty on net product sales, minimum			1.75%	1.75%
Collaborative Arrangement, Revenue Based on Clinical Development Milestone \| University of Zurich
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone			$ 750
First Indication \| Roche
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone	$ 197,500
Collaborative arrangement, revenue based on development milestone \| Roche
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone	72,500
Collaborative arrangement, revenue based on development milestone \| Roche \| EBI-031
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone		$ 22,500
Collaborative arrangement, revenue based on regulatory milestone \| Roche
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone	50,000
Collaborative arrangement, revenue based on commercialization milestone \| Roche
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone	75,000
Second Indication \| Roche
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone	$ 65,000

RELATED-PARTY TRANSACTIONS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Majority Shareholder \| Facility in Winnipeg, Manitola
Related Party Transaction [Line Items]
Rent expense in related party transaction	$ 300	$ 300	$ 300
Majority Shareholder \| Facility in Toronto, Ontario
Related Party Transaction [Line Items]
Rent expense in related party transaction		18	18
Protoden \| Intellectual Property
Related Party Transaction [Line Items]
Rent expense in related party transaction	100	$ 100	$ 100
Annual fee for remaining term of lease	$ 100

SUPPLEMENTARY FINANCIAL INFORMATION (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 425
Total operating expenses	33,738	13,451	54,561	6,741	7,066	14,397	9,030	4,007	108,491	34,500	29,680
Loss from Operations	(33,738)	(13,451)	(54,561)	(6,741)	(7,066)	(14,397)	(9,030)	(4,007)	(108,491)	(34,500)	(29,255)
Net loss and comprehensive loss	$ (33,553)	$ (13,132)	$ (54,335)	$ (6,480)	$ (6,757)	$ (14,015)	$ (8,958)	$ (3,963)	$ (107,500)	$ (33,693)	$ (29,029)
Net loss per common share - basic and diluted (in dollars per share)	$ (0.32)	$ (0.13)	$ (0.67)	$ (0.08)	$ (0.09)	$ (0.18)	$ (0.16)	$ (0.11)	$ (1.18)	$ (0.55)	$ (1.11)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

SUBSEQUENT EVENTS (Details) - $ / shares	1 Months Ended		12 Months Ended
SUBSEQUENT EVENTS (Details) - $ / shares	Feb. 29, 2020	Jan. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Subsequent Event [Line Items]
Stock options granted (in shares)			3,986,000	3,546,000	1,303,000
Granted exercise price (in dollars per share)			$ 1.02	$ 1.71	$ 1.64
Subsequent Event \| 2014 Stock Incentive Plan
Subsequent Event [Line Items]
Stock options granted (in shares)		100,000
Granted exercise price (in dollars per share)		$ 0.84
Stock options grant-date fair value (in dollars per share)		$ 0.59
Vesting on the First Anniversary of Date of Grant \| Subsequent Event \| 2014 Stock Incentive Plan
Subsequent Event [Line Items]
Vesting rights rate		25.00%
Vesting at End of Each Successive Three-Month Period Thereafter \| Subsequent Event \| 2014 Stock Incentive Plan
Subsequent Event [Line Items]
Vesting rights rate		6.25%
Stock options \| 2014 Stock Incentive Plan
Subsequent Event [Line Items]
Award vesting period			4 years
Award expiration period			10 years
Stock options \| Vesting on the First Anniversary of Date of Grant \| 2014 Stock Incentive Plan
Subsequent Event [Line Items]
Vesting rights rate			25.00%
Stock options \| Vesting at End of Each Successive Three-Month Period Thereafter \| 2014 Stock Incentive Plan
Subsequent Event [Line Items]
Vesting rights rate			6.25%
Share-based Payment Arrangement, Nonemployee \| Stock options \| Subsequent Event \| 2014 Stock Incentive Plan
Subsequent Event [Line Items]
Stock options granted (in shares)	3,100,000
Granted exercise price (in dollars per share)	$ 0.89
Stock options grant-date fair value (in dollars per share)	$ 0.62
Vesting rights rate	6.25%
Award vesting period	3 months
Award expiration period	4 years

Label	Element	Value
Accounting Standards Update 2016-09, Forfeiture Rate Component [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 0
Accounting Standards Update 2016-09, Forfeiture Rate Component [Member] \| Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	9,000
Accounting Standards Update 2016-09, Forfeiture Rate Component [Member] \| Additional Paid-in Capital [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (9,000)