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December 31, 2019

Estimated useful life

Acquired and in-licensed rights

Less: accumulated amortization

Total intangible assets, net

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2019	Mar. 11, 2020	Jun. 28, 2019
Cover [Abstract]
Entity Registrant Name	Verastem, Inc.
Entity Central Index Key	0001526119
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 110,799,682
Entity Common Stock, Shares Outstanding		148,410,387
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 43,514	$ 129,867
Short-term investments	31,992	119,786
Accounts receivable, net	2,524	306
Inventory	3,096	327
Prepaid expenses and other current assets	3,835	2,973
Total current assets	84,961	253,259
Property and equipment, net	947	1,369
Right-of-use asset, net	3,077
Intangible assets, net	20,008	21,577
Restricted Cash	35,241	241
Other assets	812	790
Total assets	145,046	277,236
Current liabilities:
Accounts payable	9,655	10,253
Accrued expenses	19,365	21,108
Lease liability, short-term	420
Derivative liability, short-term	450
Current portion of long-term debt		5,716
Total current liabilities	29,890	37,077
Non-current liabilities:
Long-term debt	35,067	19,506
Convertible senior notes	68,556	95,231
Lease liability, long-term	3,489
Other non-current liabilities	870	1,123
Total liabilities	137,872	152,937
Stockholders’ equity:
Preferred stock, $0.0001 par value; 5,000 shares authorized, no shares issued and outstanding at December 31, 2019 and December 31, 2018, respectively
Common stock, $0.0001 par value; 200,000 shares authorized, 80,118 and 73,806 shares issued and outstanding at December 31, 2019 and December 31, 2018, respectively	8	7
Additional paid-in capital	531,937	499,741
Accumulated other comprehensive income	14	127
Accumulated deficit	(524,785)	(375,576)
Total stockholders’ equity	7,174	124,299
Total liabilities and stockholders’ equity	$ 145,046	$ 277,236

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares shares in Thousands	Dec. 31, 2019	Dec. 31, 2018
CONSOLIDATED BALANCE SHEETS
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000	5,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000	200,000
Common stock, shares issued	80,118	73,806
Common stock, shares outstanding	80,118	73,806

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	$ 17,456	$ 26,718
Operating expenses:
Cost of sales - product	1,238	165
Cost of sales - intangible amortization	1,569	423
Research and development	45,778	43,648	$ 46,423
Selling, general and administrative	101,212	77,265	21,381
Total operating expenses	149,797	121,501	67,804
Loss from operations	(132,341)	(94,783)	(67,804)
Other (expense)/ income	(641)	25,556
Interest income	4,381	2,603	561
Interest expense	(20,608)	(5,810)	(559)
Net loss	$ (149,209)	$ (72,434)	$ (67,802)
Net loss per share—basic	$ (2.00)	$ (1.12)	$ (1.76)
Net loss per share—diluted	$ (2.00)	$ (1.37)	$ (1.76)
Weighted average common shares outstanding used in computing:
Net loss per share—basic (in shares)	74,578	64,962	38,422
Net loss per share—diluted (in shares)	74,578	69,321	38,422
Net loss	$ (149,209)	$ (72,434)	$ (67,802)
Unrealized (loss) gain on available-for-sale securities	(113)	129	(31)
Comprehensive loss	(149,322)	(72,305)	$ (67,833)
Product revenue, net
Revenue:
Total revenue	12,339	1,718
License and collaboration revenue
Revenue:
Total revenue	$ 5,117	$ 25,000

CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Common stock	Additional paid-in capital	Accumulated other comprehensive (loss) income	Accumulated deficit	Total
Balance at Dec. 31, 2016	$ 4	$ 307,587	$ 29	$ (235,323)	$ 72,297
Balance (in shares) at Dec. 31, 2016	36,992,418
Increase (Decrease) in Stockholders' Equity
Net loss				(67,802)	(67,802)
Unrealized (loss) gain on available-for-sale securities			(31)		(31)
Issuance of common stock resulting from follow-on offering, net of issuance costs	$ 1	24,691			24,692
Issuance of common stock resulting from follow-on offering, net of issuance costs (in shares)	8,422,877
Issuance of common stock resulting from at-the-market transactions, net of issuance costs		23,053			23,053
Issuance of common stock resulting from at-the-market transactions, net of issuance costs (in shares)	5,036,879
Issuance of common stock resulting from exercise of stock options		442			442
Issuance of common stock resulting from exercise of stock options (in shares)	348,734
Stock-based compensation expense		5,050		(17)	5,033
Balance at Dec. 31, 2017	$ 5	360,823	(2)	(303,142)	57,684
Balance (in shares) at Dec. 31, 2017	50,800,908
Increase (Decrease) in Stockholders' Equity
Net loss				(72,434)	(72,434)
Unrealized (loss) gain on available-for-sale securities			129		$ 129
Conversion of Notes into common stock (in shares)					20,936,548
Issuance of common stock resulting from follow-on offering, net of issuance costs	$ 1	81,188			$ 81,189
Issuance of common stock resulting from follow-on offering, net of issuance costs (in shares)	16,111,110
Issuance of common stock resulting from at-the-market transactions, net of issuance costs	$ 1	24,275			24,276
Issuance of common stock resulting from at-the-market transactions, net of issuance costs (in shares)	6,481,475
Issuance of common stock resulting from exercise of stock options		809			809
Issuance of common stock resulting from exercise of stock options (in shares)	412,851
Stock-based compensation expense		6,671			6,671
Reclassification of derivative liability to equity		25,975			25,975
Balance at Dec. 31, 2018	$ 7	499,741	127	(375,576)	$ 124,299
Balance (in shares) at Dec. 31, 2018	73,806,344				73,806,000
Increase (Decrease) in Stockholders' Equity
Net loss				(149,209)	$ (149,209)
Unrealized (loss) gain on available-for-sale securities			(113)		(113)
Conversion of Notes into common stock	$ 1	9,516			9,517
Conversion of Notes into common stock (in shares)	5,767,872
Change in fair value of conversion option of Notes on exchange		13,640			13,640
Issuance of common stock under Employee Stock Purchase Plan		439			439
Issuance of common stock under Employee Stock Purchase Plan (in shares)	341,701
Issuance of common stock resulting from vesting of restricted stock units		(68)			(68)
Issuance of common stock resulting from vesting of restricted stock units (in shares)	109,707
Issuance of common stock resulting from exercise of stock options		130			130
Issuance of common stock resulting from exercise of stock options (in shares)	91,907
Stock-based compensation expense		8,539			8,539
Balance at Dec. 31, 2019	$ 8	$ 531,937	$ 14	$ (524,785)	$ 7,174
Balance (in shares) at Dec. 31, 2019	80,117,531				80,118,000

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Follow-on offerings
Issuance of common stock, issuance costs	$ 361	$ 324
At-the-market equity offering program
Issuance of common stock, issuance costs	$ 0	$ 112

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net loss	$ (149,209)	$ (72,434)	$ (67,802)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	429	996	556
Amortization of acquired intangible asset	1,569	423
Amortization of right-of-use asset and lease liability	181
Stock-based compensation expense	8,539	6,671	5,033
Amortization of deferred financing costs, debt discounts and premiums and discounts on available-for-sale marketable securities	7,131	1,814	223
Change in fair value of interest make whole provision and conversion option for Notes	641	(25,556)
Gain on sale of fixed assets		(79)
Changes in operating assets and liabilities:
Accounts receivable, net	(2,218)	(306)
Inventory	(2,769)	(327)
Prepaid expenses, other current assets and other assets	(877)	(1,167)	(943)
Accounts payable	(598)	1,048	5,046
Accrued expenses and other liabilities	(1,707)	13,902	577
Other long-term liabilities	370	500
Net cash used in operating activities	(138,518)	(74,515)	(57,310)
Investing activities
Purchases of property and equipment	(7)	(1,507)
Sales of property and equipment		82
Acquisition of intangible asset		(22,000)
Purchases of investments	(94,123)	(125,452)	(7,957)
Maturities of investments	183,743	10,500	51,910
Net cash provided by (used in) investing activities	89,613	(138,377)	43,953
Financing activities
Proceeds from long-term debt, net of issuance costs	9,670	9,900	14,811
Deferred debt financing costs			(138)
Proceeds from issuance of convertible senior notes, net of issuance costs		145,297
Proceeds from the exercise of stock options and employee stock purchase program	569	809	442
Principal payments on the convertible senior notes	(12,174)
Interest make-whole payments on the 2019 Notes	(438)
Settlement of restricted stock for tax withholdings	(68)
Proceeds from the issuance of common stock, net		105,156	48,069
Net cash (used in) provided by financing activities	(2,441)	261,162	63,184
(Decrease) increase in cash, cash equivalents and restricted cash	(51,346)	48,270	49,827
Cash, cash equivalents and restricted cash at beginning of period	130,608	82,338	32,511
Cash, cash equivalents and restricted cash at end of period	79,262	130,608	82,338
Supplemental disclosure
Cash paid for interest	12,424	2,107	295
Supplemental disclosure of non-cash investing and financing activities
Common stock issuance costs included in accounts payable and accrued expenses	15	$ 15	$ 324
Conversion of Notes into common stock	9,517
Change in fair value of conversion option of Notes on exchange	$ 13,640

Nature of business	12 Months Ended
Nature of business	Dec. 31, 2019
Nature of business
Nature of business	1. Nature of business Verastem, Inc. (the Company) is a biopharmaceutical company focused on developing and commercializing medicines to improve the survival and quality of life of cancer patients. On September 24, 2018, the Company’s first commercial product, COPIKTRA® (duvelisib), was approved by the U.S. Food and Drug Administration (the FDA) for the treatment of adult patients with certain hematologic cancers including relapsed or refractory chronic lymphocytic leukemia/ small lymphocytic lymphoma (CLL/SLL) after at least two prior therapies and relapsed or refractory follicular lymphoma (FL) after at least two prior systemic therapies. Its marketed product, COPIKTRA, and most advanced product candidates, defactinib and CH5126766, utilize a multi-faceted approach designed to treat cancers originating either in the blood or major organ systems. The Company is currently developing its product candidates in both preclinical and clinical studies as potential therapies for certain cancers, including leukemia, lymphoma, lung cancer, head and neck cancer, ovarian cancer, colorectal cancer, lung cancer, pancreatic cancer, and mesothelioma. The Company believes that these compounds may be beneficial as therapeutics either as single agents or when used in combination with immuno-oncology agents, other pathway inhibitors or other current and emerging standard of care treatments in aggressive cancers that do not adequately respond to currently available therapies. The consolidated financial statements include the accounts of Verastem Securities Company and Verastem Europe GmbH, wholly-owned subsidiaries of the Company. All financial information presented has been consolidated and includes the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The Company is subject to the risks associated with other life science companies, including, but not limited to, possible failure of preclinical testing or clinical trials, competitors developing new technological innovations, market acceptance and the commercial success of COPIKTRA, or any of the Company’s investigational product candidates following receipt of regulatory approval, protection of proprietary technology and the continued ability to obtain adequate financing to fund the Company’s future operations. If the Company does not successfully commercialize COPIKTRA or any of its other product candidates, it will be unable to generate product revenue or achieve profitability and may need to raise additional capital. The Company has historical losses from operations and anticipates that it will continue to incur losses as it continues the research and development of its product candidates and commercialization of COPIKTRA. As of December 31, 2019, the Company had cash, cash equivalents, restricted cash and short-term investments of $111.3 million, inclusive of $35.7 million of restricted cash, and accumulated deficit of $524.8 million. On March 3, 2020, the Company received gross proceeds of approximately $100.0 million from the sale of 46,511,628 shares of Common Stock (see Note 19). The Company expects its existing cash resources, including the proceeds from the sale of Common Stock in March 2020, along with revenue the Company expects to generate from sales of COPIKTRA, will be sufficient to fund its planned operations through 12 months from the date of issuance of these consolidated financial statements. The Company expects to finance the future development costs of its clinical product portfolio with its existing cash, cash equivalents and short-term investments, or through strategic financing opportunities that could include, but are not limited to collaboration agreements, future offerings of its equity, or the incurrence of debt. However, there is no guarantee that any of these strategic or financing opportunities will be executed or executed on favorable terms, and some could be dilutive to existing stockholders. If the Company fails to obtain additional future capital, it may be unable to complete its planned preclinical studies and clinical trials and obtain approval of certain investigational product candidates from the FDA or foreign regulatory authorities.

Significant accounting policies

12 Months Ended

Dec. 31, 2019

Significant accounting policies

Significant accounting policies

2. Significant accounting policies

Basis of presentation

The accompanying financial statements of the Company have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) under the assumption that the Company will continue as a going concern for the next twelve months. Accordingly, they do not include any adjustments that might result from the uncertainty related to the Company’s ability to continue as a going concern.

Use of estimates

The preparation of the Company’s financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including estimates related to revenue recognition, including returns, rebates, and other pricing adjustments, accruals and stock‑based compensation expense. The Company bases its estimates on historical experience and other market‑specific or other relevant assumptions that it believes to be reasonable. Actual results could differ from such estimates.

Segment and geographic information

Operating segments are defined as components of an enterprise about which separate discrete information is available and regularly reviewed by the chief operating decision maker, or decision‑making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one operating segment, which is the business of developing and commercializing drugs for the treatment of cancer. All material long-lived assets of the Company reside in the United States.

Cash, cash equivalents and restricted cash

The Company considers all highly liquid investments with an original or remaining maturity of three months or less at the date of purchase to be cash equivalents. Cash equivalents consist of a U.S. Government money market funds and corporate bonds and commercial paper of publicly traded companies. Cash equivalents are reported at fair value.

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


	December 31, 2019		December 31, 2018
Cash and cash equivalents	$	43,514	$	129,867
Restricted cash		35,748		741
Total cash, cash equivalents and restricted cash	$	79,262	$	130,608

Amounts included in restricted cash as of December 31, 2019 represent cash that the Company is contractually obligated to maintain in accordance with the terms of the 2019 Term Loan Agreement, cash received pursuant to a funded research and development agreement with the Leukemia and Lymphoma Society (LLS) (the “LLS Research Funding Agreement”) restricted for future expenditures for specific R&D studies and cash held to collateralize outstanding letters of credit provided as a security deposit for the Company’s office space located in Needham, Massachusetts in the amount of approximately $35.0 million, $0.5 million, and $0.2 million respectively. Restricted cash related to 2019 Term Loan Agreement and letters of credit are included in non-current restricted cash on the consolidated balance sheet, while cash related to LLS Research Funding Agreement is included in prepaid and other current assets on the consolidated balance sheet. Amounts included in restricted cash as of December 31, 2018 represent cash received pursuant to the LLS Research Funding Agreement of $0.5 million, which is included in prepaid and other currents on the consolidated balance sheet and cash held to collateralize outstanding letters of credit provided as a security deposit for the Company’s office space located in Needham of $0.2 million, which is included in non-current restricted cash on the consolidated balance sheet.

Fair value of financial instruments

The Company determines the fair value of its financial instruments based upon the fair value hierarchy, which prioritizes valuation inputs based on the observable nature of those inputs. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The hierarchy defines three levels of valuation inputs:


Level 1 inputs		Quoted prices in active markets for identical assets or liabilities that the Company can access at the measurement date.
Level 2 inputs		Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly.
Level 3 inputs		Unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability.

Items Measured at Fair Value on a Recurring Basis

The following table presents information about the Company’s financial instruments that are measured at fair value on a recurring basis (in thousands):




	December 31, 2019
Description	Total		Level 1		Level 2		Level 3
Financial assets
Cash equivalents	$	77,176	$	75,678	$	1,498	$	—
Short-term investments		31,992		—		31,992		—
Total financial assets	$	109,168	$	75,678	$	33,490	$	—
Derivative liability	$	450		—		—	$	450




	December 31, 2018
Description	Total		Level 1		Level 2		Level 3
Financial assets
Cash equivalents	$	127,689	$	60,092	$	67,597	$	—
Short-term investments		119,786		—		119,786		—
Total financial assets	$	247,475	$	60,092	$	187,383	$	—

The investments and cash equivalents have been initially valued at the transaction price and subsequently valued, at the end of each reporting period, utilizing third party pricing services or other market observable data. The pricing services utilize industry standard valuation models, including both income and market-based approaches and observable market inputs to determine value. These observable market inputs include reportable trades, benchmark yields, credit spreads, broker/dealer quotes, bids, offers, current spot rates and other industry and economic events. The Company validates the prices provided by third party pricing services by reviewing their pricing methods and matrices, obtaining market values from other pricing sources, analyzing pricing data in certain instances and confirming that the relevant markets are active. After completing its validation procedures, the Company did not adjust or override any fair value measurements provided by the pricing services as of December 31, 2019 and 2018.

During 2019, a derivative liability was recorded as a result of the issuance of the 2019 Notes. (see note 12). The Company initially determined fair value of the liability upon issuance, and then again at the balance sheet date. The fair value measurement of the derivative liability is classified as Level 3 under the fair value hierarchy and it has been valued using unobservable inputs. These inputs include: (1) a simulated share price at the time of conversion of the 2019 Notes, (2) assumed timing of conversion of the 2019 Notes, (3) risk-adjusted discount rate to present value the probability-weighted cash flows, and (4) entity specific cost of equity. Significant increases or decreases in any of those inputs in isolation could result in a significantly lower or higher fair value measurement.

The fair value of the derivative liability was determined using a Monte-Carlo simulation by calculating fair value of the 2019 Interest Make-Whole Payment to 2019 Note holders based on assumed timing of conversion of the 2019 Notes. At November 14, 2019 the risk-adjusted discount rate was determined to be 12.06% and entity specific cost of equity was determined to be 17.05%. At December 31, 2019, the risk-adjusted discount rate was determined to be 13.08% and entity specific cost of equity was determined to be 16.54%.

The following table represents a reconciliation of the derivative liability recorded in connection with the issuance of the 2019 Notes (in thousands):




January 1, 2019	$	—
Fair value recognized upon issuance of 2019 Notes		247
Fair value adjustment		641
Derivative liability extinguished upon conversion		(438)
December 31, 2019	$	450

During 2018, a derivative liability was initially recorded as a result of the issuance of the 2018 Notes. (see note 12). The Company initially determined fair value of the liability upon issuance, and then again upon the determination that the derivative instrument met the criteria to be reclassified into equity. The fair value measurement of the derivative liability is classified as Level 3 under the fair value hierarchy as it has been valued using unobservable inputs. These inputs include: (1) a simulated share price at the time of conversion of the Notes, (2) assumed timing of conversion of the Notes, and (3) the risk-adjusted discount rate used to present value the probability-weighted cash flows. Significant increases or decreases in any of those inputs in isolation could result in a significantly lower or higher fair value measurement.

The fair value of the derivative liability was determined using a binomial lattice model by calculating the fair value of the Notes with the conversion feature as compared to the fair value of the Notes without the conversion feature, with the difference representing the value of the conversion feature, or the derivative liability. The fair value of the Notes with the conversion feature at issuance was assumed to equal the issuance par value of $150.0 million with an implied discount rate of 12.1% which was determined by discounting the cash flows generated by the binomial lattice model back to the issuance par value. The fair value of the Notes without the conversion feature was calculated based on cash payment for the full par value of the Notes and was discounted by the implied discount rate of 12.1%. The fair value of the Notes with and without the conversion feature upon the Company’s shareholders increasing the number of authorized shares of common stock was determined using a similar approach with an implied discount rate of 16.2%, which was determined be evaluating the increase in credit spreads of publicly traded debt over a similar time period.

The following table represents a reconciliation of the derivative liability recorded in connection with the issuance of the 2018 Notes (in thousands):


January 1, 2018	$	—
Fair value recognized upon issuance of 2018 Notes		51,531
Fair value adjustment		(25,556)
Reclassification to equity		(25,975)
December 31, 2018	$	—

Fair Value of Financial Instruments

The fair value of the Company’s long-term debt is determined using a discounted cash flow analysis with current applicable rates for similar instruments as of the consolidated balance sheet dates. The carrying value of the Company’s long-term debt, including the current portion, at December 31, 2019 and 2018, was approximately $35.1 million and $25.2 million, respectively. At December 31, 2019 and 2018, the Company estimates that the fair value of its long-term debt, including the current portion, was approximately $37.0 and $26.9 million, respectively. The fair value of the Company’s long-term debt was determined using Level 3 inputs.

The fair value of the 2018 Notes and 2019 Notes was approximately $12.5 million and $50.5 million, respectively, as of December 31, 2019, which differs from the carrying value of the Notes. The fair value of the Notes is influenced by our stock price and stock price volatility. The fair value of the 2018 Notes and 2019 Notes was determined using Level 2 inputs.

Investments

Investments and cash equivalents consist of investments in a U.S. Government money market funds, overnight repurchase agreements collateralized by government agency securities or U.S. Treasury securities, corporate bonds and commercial paper of publicly traded companies that are classified as available‑for‑sale pursuant to Accounting Standards Codification (ASC) Topic 320, Investments—Debt and Equity Securities. The Company classifies investments available to fund current operations as current assets on its consolidated balance sheets. Investments are carried at fair value with unrealized gains and losses included as a component of accumulated other comprehensive income (loss), which is a separate component of stockholders’ equity, until such gains and losses are realized. The fair value of these securities is based on quoted prices for identical or similar assets. If a decline in the fair value is considered other‑than‑temporary, based on available evidence, the unrealized loss is transferred from other comprehensive loss to the consolidated statements of operations and comprehensive loss.

The Company reviews investments for other‑than‑temporary impairment whenever the fair value of an investment is less than the amortized cost and evidence indicates that an investment’s carrying amount is not recoverable within a reasonable period of time. To determine whether an impairment is other‑than‑temporary, the Company considers the intent to sell, or whether it is more likely than not that the Company will be required to sell, the investment before recovery of the investment’s amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with the Company’s investment policy, the severity and the duration of the impairment and changes in value subsequent to year end. Realized gains and losses are determined using the specific identification method and are included in interest income in the consolidated statements of operations and comprehensive loss.

There were no realized gains or losses on investments for the years ended December 31, 2019, 2018 or 2017. There were two debt securities and fourteen debt securities in an unrealized loss position as of December 31, 2019 and December 31, 2018, respectively. None of these investments had been in an unrealized loss position for more than 12 months as of December 31, 2019 or December 31, 2018, respectively. The fair value of these securities as of December 31, 2019 and December 31, 2018 was $5.8 million and $46.9 million, respectively, and the aggregate unrealized loss was immaterial. The Company considered the decline in the market value for these securities to be primarily attributable to current economic conditions. As it was not more likely than not that the Company would be required to sell these securities before the recovery of their amortized cost basis, which may be at maturity, the Company did not consider these investments to be other-than-temporarily impaired as of December 31, 2019 and December 31, 2018, respectively.

Cash, cash equivalents and investments consist of the following (in thousands):


	December 31, 2019
			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Cash, cash equivalents & restricted cash:
Cash and money market accounts	$	77,764	$	—	$	—	$	77,764
Corporate bonds and commercial paper (due within 90 days)		1,498		—		—		1,498
Total cash and cash equivalents	$	79,262	$	—	$	—	$	79,262
Investments:
Corporate bonds and commercial paper (due within 1 year)	$	31,979	$	14	$	—	$	31,993
Total investments	$	31,979	$	14	$	—	$	31,993
Total cash, cash equivalents and investments	$	111,241	$	14	$	—	$	111,255


	December 31, 2018
			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Cash and cash equivalents:
Cash and money market accounts	$	62,270	$	—	$	—	$	62,270
Corporate bonds and commercial paper (due within 90 days)		67,590	$	8	$	(1)	$	67,597
Total cash and cash equivalents	$	129,860	$	8	$	(1)	$	129,867
Investments:
Corporate bonds and commercial paper (due within 1 year)	$	119,666	$	132	$	(12)	$	119,786
Total investments	$	119,666	$	132	$	(12)	$	119,786
Total cash, cash equivalents and investments	$	249,526	$	140	$	(13)	$	249,653

Concentrations of credit risk and off‑balance sheet risk

Cash and cash equivalents, investments, and trade accounts receivable are financial instruments that potentially subject the Company to concentrations of credit risk. The Company mitigates this risk by maintaining its cash and cash equivalents and investments with high quality, accredited financial institutions. The management of the Company’s investments is not discretionary on the part of these financial institutions. As of December 31, 2019, the Company’s cash, cash equivalents and investments were deposited at three financial institutions and it has no significant off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements.

As of December 31, 2019 and 2018, there were two customers that cumulatively made up more than 50% of the Company’s trade accounts receivable balance. The Company assesses the creditworthiness of all its customers and sets and reassesses customer credit limits to ensure collectability of any trade accounts receivable balances are assured.

For the year ended December 31, 2019 and 2018, four customers and two customers, respectively, individually accounted for greater than 10% of the Company’s total revenues.

Property and equipment

Property and equipment consist of laboratory equipment, office furniture, computer equipment and leasehold improvements. Expenditures for repairs and maintenance are recorded to expense as incurred, whereas major betterments are capitalized as additions to property and equipment. Depreciation and amortization are calculated using the straight‑line method over the following estimated useful lives of the assets:


Laboratory equipment		5 years
Furniture		5 years
Computer equipment		3 years
Leasehold improvements		Lesser of useful life or life of lease

Upon retirement or sale, the cost of the disposed asset and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is recognized.

The Company reviews its long‑lived assets for impairment whenever events or changes in business circumstances indicate that the carrying value of assets may not be recoverable. Recoverability is measured by comparison of the asset’s book value to future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book value of the assets exceed their fair value, which is measured based on the projected discounted future net cash flows arising from the assets. No impairment losses have been recorded through December 31, 2019.

Other assets

Other assets primarily consist of prepayments made to contract research organizations (CROs). As of December 31, 2019 and 2018, other assets were primarily comprised of approximately $755,000 of prepaid CRO expenses that the Company assumed and paid to Infinity pursuant to the license agreement between the Company and Infinity.

Research and development costs

The Company expenses research and development costs to operations as incurred. Research and development expenses consist of:

employee‑related expenses, including salaries, benefits, travel and stock‑based compensation expense;

external research and development expenses incurred under arrangements with third parties, such as CROs, clinical trial sites, manufacturing organizations and consultants, including the scientific advisory board;

license fees;

facilities, depreciation and other expenses, which include direct and allocated expenses for rent and maintenance of facilities, depreciation of equipment, and laboratory supplies; and

costs associated with COPIKTRA prior to the Company concluding that regulatory approval is probable and that its net realizable value is recoverable.

The Company accounts for nonrefundable advance payments for goods and services that will be used in future research and development activities as expenses when the services have been performed or when the goods have been received rather than when the payment is made.

Stock‑based compensation

The Company recognizes stock‑based compensation expense for stock options, and restricted stock units (RSUs) issued to employees and directors based on the grant date fair value of the awards on a straight‑line basis over the requisite service period, which typically is the vest period. The Company recognized stock-based compensation for shares issued to employees under our employee stock purchase plan (ESPP) plan Historically, the Company recorded stock‑based compensation expense for stock options and RSUs issued to non‑employees based on the estimated fair value of the services received or of the equity instruments issued, whichever is more reliably measured, based on the vesting date fair value of the awards on a straight‑line basis over the vesting period. Effective January 1, 2019, the Company recognizes stock-based compensation expense for stock options and RSUs issued to non-employees based on the grant date fair value of the awards on the straight-line basis over the requisite service period. Awards subject to performance-based vesting requirements are expensed utilizing an accelerated attribution model if achievement of the performance criteria is determined to be probable.

The grant date fair value of stock options is estimated using the Black‑Scholes option pricing model that takes into account the fair value of its common stock, the exercise price, the expected life of the option, the expected volatility of its common stock, expected dividends on its common stock, and the risk-free interest rate over the expected life of the option. The Company applies the simplified method described in the Securities and Exchange Commission (SEC) Staff Accounting Bulletin (SAB) Topic 14.D.2 to calculate the expected term as it does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term for options granted to employees. The expected term is applied to the stock option grant group as a whole, as the Company does not expect substantially different exercise or post‑vesting termination behavior among its population. The Company has not paid and do not anticipate paying cash dividends on our shares of common stock; therefore, the expected dividend yield is assumed to be zero.

The Company issues shares under the Company’s employee stock purchase plan (ESPP) to employees. Stock-based compensation expense for discounted purchases under the ESPP is measured using the Black-Scholes model to compute the fair value of the lookback provision plus the purchase discount and is recognized as compensation expense over the offering period.

For annual periods ending on or before December 31, 2017, the computation of expected volatility is based on the historical volatility of five companies, including the Company and a representative group of four public biotechnology and life sciences companies with similar characteristics to the Company, including similar stage of product development and therapeutic focus. As of the first quarter of 2018, the Company had sufficient company-specific historical and implied volatility information. As such, for the annual period ending December 31, 2018, the computation of expected volatility is based only on the historical volatility of the Company’s common stock. The risk‑free interest rate is based on a treasury instrument whose term is consistent with the expected term of the stock options.

The Company accounts for forfeitures as they occur. Stock‑based awards issued to non-employees, including directors for non‑board related services, are accounted for based on the fair value of such services received or of the equity instruments issued, whichever is more reliably measured. Stock option awards to non-employees are revalued at each reporting date and upon vesting using the Black‑Scholes option pricing model and are expensed on a straight‑line basis over the vesting period.

Leases

Effective January 1, 2019, the Company adopted FASB ASC Topic 842, Leases (ASC 842). This standard requires lessees to recognize in the statement of financial position a liability to make lease payments and a right-of-use asset representing its right to use the underlying asset for the lease term for both finance and operating leases.

At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances within the arrangement. A lease is identified where an arrangement conveys the right to control the use of identified property, plant, and equipment for a period of time in exchange for consideration. Leases which are identified within the scope of ASC 842 and which have a term greater than one year are recognized on the Company’s consolidated balance sheets as right-of-use assets, lease liabilities and, if applicable, long-term lease liabilities. The Company has elected not to recognize leases with terms of one year or less on its consolidated balance sheets. Operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected remaining lease term. However, certain adjustments to the right-of-use asset may be required for items such as initial direct costs paid or incentives received. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rates to calculate the present value of lease payments. Incremental borrowing rates are the rates the Company incurs to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment.

In accordance with ASC 842, components of a lease are split into three categories: lease components (e.g., land, building, etc.), non-lease components (e.g., common area maintenance, maintenance, consumables, etc.), and non-components (e.g., property taxes, insurance, etc.). The fixed and in-substance fixed contract consideration (including any related to non-components) must be allocated based on fair values to the lease components and non-lease components. Although separation of lease and non-lease components is required, certain practical expedients are available. Entities may elect the practical expedient to not separate lease and non-lease components. Rather, they would account for each lease component and the related non-lease component together as a single component. The Company has elected to account for the lease and non-lease components of each of its operating leases as a single lease component and allocate all of the contract consideration to the lease component only. The lease component results in an operating right-of-use asset being recorded on the consolidated balance sheets and amortized on a straight-line basis as lease expense.

Revenue Recognition

The Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services, in accordance with ASC 606 Revenue from Contracts with Customers. To determine revenue recognition contracts with its customers, the Company performs the following five step assessment: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception and once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract, determines which goods and services are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied.

Product Revenue, Net – The Company sells COPIKTRA to a limited number of specialty pharmacies and specialty distributors in the United States. These customers subsequently resell COPIKTRA either directly to patients, or to community hospitals or oncology clinics with in-office dispensaries who in turn distribute COPIKTRA to patients. In addition to distribution agreements with customers, the Company also enters into arrangements with (1) certain government agencies and various private organizations (Third-Party Payers), which may provide for chargebacks or discounts with respect to the purchase of COPIKTRA, and (2) Medicare and Medicaid, which may provide for certain rebates with respect to the purchase of COPIKTRA.

The Company recognizes revenue on sales of COPIKTRA when a customer obtains control of the product, which occurs at a point in time (typically upon delivery). Product revenues are recorded at the wholesale acquisition costs, net of applicable reserves for variable consideration. Components of variable consideration include trade discounts and allowances, Third-Party Payer chargebacks and discounts, government rebates, other incentives, such as voluntary co-pay assistance, product returns, and other allowances that are offered within contracts between the Company and customers, payors, and other indirect customers relating to the Company’s sale of COPIKTRA. These reserves, as detailed below, are based on the amounts earned, or to be claimed on the related sales, and are classified as reductions of accounts receivable or a current liability. These estimates take into consideration a range of possible outcomes based upon relevant factors such as, customer contract terms, information received from third parties regarding the anticipated payor mix for COPIKTRA, known market events and trends, industry data, and forecasted customer buying and payment patterns. Overall, these reserves reflect the Company’s best estimates of the amount of consideration to which it is entitled with respect to sales made.

The amount of variable consideration which is included in the transaction price may be constrained and is included in the net sales price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized under contracts will not occur in a future period. The Company’s analyses contemplate the application of the constraint in accordance with ASC 606. For the year ended December 31, 2019, the Company determined a material reversal of revenue would not occur in a future period for the estimates detailed below and, therefore, the transaction price was not reduced further. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s estimates, the Company will adjust these estimates, which would affect net product revenue and earnings in the period such variances become known.

Trade Discounts and Allowances: The Company generally provides customers with invoice discounts on sales of COPIKTRA for prompt payment, which are explicitly stated in the Company’s contracts and are recorded as a reduction of revenue in the period the related product revenue is recognized. In addition, the Company compensates its specialty distributor customers for sales order management, data, and distribution services. The Company has determined such services are not distinct from the Company’s sale of COPIKTRA to the specialty distributor customers and, therefore, these payments have also been recorded as a reduction of revenue within the consolidated statements of operations and comprehensive loss through December 31, 2019.

Third-Party Payer Chargebacks, Discounts and Fees: The Company executes contracts with Third-Party Payers which allow for eligible purchases of COPIKTRA at prices lower than the wholesale acquisition cost charged to customers who directly purchase the product from the Company. In some cases, customers charge the Company for the difference between what they pay for COPIKTRA and the ultimate selling price to the Third-Party Payers. These reserves are established in the same period that the related revenue is recognized, resulting in a reduction of product revenue and accounts receivable, net. Chargeback amounts are generally determined at the time of resale to the qualified Third-Party Payer by customers, and the Company generally issues credits for such amounts within a few weeks of the customer’s notification to the Company of the resale. Reserves for chargebacks consist of credits that the Company expects to issue for units that remain in the distribution channel inventories at the end of each reporting period that the Company expects will be sold to Third-Party Payers, and chargebacks that customers have claimed, but for which the Company has not yet issued a credit. In addition, the Company compensates certain Third-Party Payers for administrative services, such as account management and data reporting. These administrative service fees have also been recorded as a reduction of product revenue within the consolidated statements of operations and comprehensive loss through December 31, 2019.

Government Rebates: The Company is subject to discount obligations under state Medicaid programs and Medicare. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included in accrued expenses on the consolidated balance sheets. For Medicare, the Company also estimates the number of patients in the prescription drug coverage gap for whom the Company will owe an additional liability under the Medicare Part D program. The Company’s liability for these rebates consists of invoices received for claims from prior quarters that have not been paid or for which an invoice has not yet been received, estimates of claims for the current quarter, and estimated future claims that will be made for product that has been recognized as revenue, but which remains in the distribution channel inventories at the end of each reporting period.

Other Incentives: Other incentives which the Company offers include voluntary co-pay assistance programs, which are intended to provide financial assistance to qualified commercially-insured patients with prescription drug co-payments required by payors. The calculation of the accrual for co-pay assistance is based on an estimate of claims and the cost per claim that the Company expects to receive for product that has been recognized as revenue, but remains in the distribution channel inventories at the end of each reporting period. The adjustments are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included as a component of accrued expenses on the consolidated balance sheets.

Product Returns: Consistent with industry practice, the Company generally offers customers a limited right of return for product that has been purchased from the Company. The Company estimates the amount of its product sales that may be returned by its customers and records this estimate as a reduction of revenue in the period the related product revenue is recognized. The Company estimates product return liabilities using available industry data and its own sales information, including its visibility into the inventory remaining in the distribution channel.

Subject to certain limitations, the Company’s return policy allows for eligible returns of COPIKTRA for credit under the following circumstances:

Receipt of damaged product;

Shipment errors that were a result of an error by the Company;

Expired product that is returned during the period beginning three months prior to the product’s expiration and ending six months after the expiration date;

Product subject to a recall; and

Product that the Company, at its sole discretion, has specified can be returned for credit.

As of December 31, 2019, the Company has not received any returns.

If taxes should be collected from customers relating to product sales and remitted to governmental authorities, they will be excluded from product revenue. The Company expenses incremental costs of obtaining a contract when incurred, if the expected amortization period of the asset that the Company would have recognized is one year or less. However, no such costs were incurred during the year ended December 31, 2019.

Exclusive Licenses of Intellectual Property - The Company may enter into collaboration and licensing arrangements for research and development, manufacturing, and commercialization activities with collaboration partners for the development and commercialization of its product candidates, which have components within the scope of ASC 606. The arrangements generally contain multiple elements or deliverables, which may include (i) licenses, or options to obtain licenses, to the Company's intellectual property, (ii) research and development activities performed for the collaboration partner, (iii) participation on joint steering committees, and (iv) the manufacturing of commercial, clinical or preclinical material. Payments pursuant to these arrangements typically include non-refundable, upfront payments, milestone payments upon the achievement of significant development events, research and development reimbursements, sales milestones, and royalties on product sales. The amount of variable consideration is constrained until it is probable that the revenue is not at a significant risk of reversal in a future period. The contracts into which the Company enters generally do not include significant financing components.

In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under each of its collaboration and license agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract within the scope of ASC 606; (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 (or as) the Company satisfies each performance obligation. As part of the accounting for these arrangements, the Company must use significant judgment to determine: a) the number of performance obligations based on the determination under step (ii) above; b) the transaction price under step (iii) above; c) the stand-alone selling price for each performance obligation identified in the contract for the allocation of transaction price in step (iv) above; and d) the measure of progress in step (v) above. The Company uses judgment to determine whether milestones or other variable consideration, except for royalties, should be included in the transaction price as described further below.

If a license to the Company’s intellectual property is determined to be distinct from the other promises or performance obligations identified in the arrangement, the Company recognizes revenue from non-refundable, upfront fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. In assessing whether a promise or performance obligation is distinct from the other elements, the Company considers factors such as the research, development, manufacturing and commercialization capabilities of the collaboration partner and the availability of its associated expertise in the general marketplace. In addition, the Company considers whether the collaboration partner can benefit from a promise for its intended purpose without the receipt of the remaining elements, whether the value of the promise is dependent on the unsatisfied promise, whether there are other vendors that could provide the remaining promise, and whether it is separately identifiable from the remaining promise. For licenses that are combined with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress of each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The measure of progress, and thereby periods over which revenue should be recognized, is subject to estimates by management and may change over the course of the arrangement. Such a change could have a material impact on the amount of revenue the Company records in future periods.

Customer Options: If an arrangement is determined to contain customer options that allow the customer to acquire additional goods or services such as research and development services or manufacturing services, the goods and services underlying the customer options are not considered to be performance obligations at the inception of the arrangement; rather, such goods and services are contingent on exercise of the option, and the associated option fees are not included in the transaction price. The Company evaluates customer options for material rights or options to acquire additional goods or services for free or at a discount. If a customer option is determined to represent a material right, the material right is recognized as a separate performance obligation at the outset of the arrangement. The Company allocates the transaction price to material rights based on the relative standalone selling price, which is determined based on the identified discount and the estimated probability that the customer will exercise the option. Amounts allocated to a material right are not recognized as revenue until, at the earliest, the option is exercised.

Milestone Payments: At the inception of each arrangement that includes milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The Company evaluates factors such as the scientific, clinical, regulatory, commercial, and other risks that must be overcome to achieve the respective milestone in making this assessment. There is considerable judgment involved in determining whether it is probable that a significant revenue reversal would not occur. At the end of each subsequent reporting period, the Company reevaluates the probability of achievement of all milestones subject to constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment.

Royalties: For arrangements that include sales-based royalties, including milestone payments based on a level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its licensing arrangements.

Collaborative Arrangements: Contracts are considered to be collaborative arrangements when they satisfy the following criteria defined in ASC 808, Collaborative Arrangements: (i) the parties to the contract must actively participate in the joint operating activity and (ii) the joint operating activity must expose the parties to the possibility of significant risk and rewards, based on whether or not the activity is successful. Payments received from or made to a partner that are the result of a collaborative relationship with a partner, instead of a customer relationship, such as co-development activities, are recorded as a reduction or increase to research and development expense, respectively.

For a complete discussion of the Company’s accounting for its license and collaboration agreements, see Note 16, License and collaboration agreements.

Accounts Receivable, Net

Accounts receivable, net consists of amounts due from customers, net of applicable revenue reserves. Accounts receivable have standard payments that generally require payment within 30 to 90 days. The Company analyzes accounts that are past due for collectability and provides an allowance for receivables when collection becomes doubtful. Given the nature and limited history of collectability of the Company’s accounts receivable, an allowance for doubtful accounts is not deemed necessary at December 31, 2019.

Inventory

The Company capitalizes inventories manufactured in preparation for initiating sales of a product candidate when the related product candidate is considered to have a high likelihood of regulatory approval and the related costs are expected to be recoverable through sales of the inventories. In determining whether or not to capitalize such inventories, the Company evaluates, among other factors, information regarding the product candidate’s safety and efficacy, the status of regulatory submissions and communications with regulatory authorities and the outlook for commercial sales, including the existence of current or anticipated competitive drugs and the availability of reimbursement. In addition, the Company evaluates risks associated with manufacturing the product candidate, including the ability of the Company’s third-party suppliers to complete the validation batches and the remaining shelf life of the inventories. Costs associated with manufacturing product candidates prior to satisfying the inventory capitalization criteria are charged to research and development expense as incurred.

The Company values its inventories at the lower of cost or estimated net realizable value. The Company determines the cost of its inventories, which includes amounts related to materials and manufacturing overhead, on a first-in, first-out basis. The Company performs an assessment of the recoverability of capitalized inventory during each reporting period, and it writes down any excess and obsolete inventories to their estimated realizable value in the period in which the impairment is first identified. Such impairment charges, should they occur, are recorded within cost of sales - product. The determination of whether inventory costs will be realizable requires estimates by management. If actual market conditions are less favorable than projected by management, additional write-downs of inventory may be required which would be recorded as a cost of sales - product in the consolidated statements of operations and comprehensive loss.

Shipping and handling costs for product shipments are recorded as incurred in cost of sales - product along with costs associated with manufacturing the product, and any inventory write-downs.

Intangible Assets

The Company records finite-lived intangible assets related to certain capitalized milestone payments related to commercial products at their fair value. These assets are amortized on a straight-line basis over their remaining useful lives, which are estimated based on the shorter of the remaining underlying patent life or the estimated useful life of the underlying product.

The Company assesses its finite-lived intangible assets for impairment if indicators are present or changes in circumstance suggest that impairment may exist. Events that could result in an impairment include the receipt of additional clinical or nonclinical data regarding one of the Company’s drug candidates or a potentially competitive drug candidate, changes in the clinical development program for a drug candidate, or new information regarding potential sales for the drug. If impairment indicators are present or changes in circumstance suggest that impairment may exist, the Company performs a recoverability test by comparing the sum of the estimated undiscounted cash flows of each finite-lived intangible asset to its carrying value on the consolidated balance sheets. If the undiscounted cash flows used in the recoverability test are less than the carrying value, the Company would determine the fair value of the finite-lived intangible asset and recognize an impairment loss if the carrying value of the finite-lived intangible asset exceeds its fair value.

Income taxes

The Company accounts for income taxes 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 using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Tax benefits are recognized when it is more likely than not that a tax position will be sustained during an audit. Deferred tax assets are reduced by a valuation allowance if current evidence indicates that it is considered more likely than not that these benefits will not be realized.

Net loss per share

Basic net loss per common share is calculated by dividing net loss applicable to common stockholders by the weighted-average number of common shares outstanding during the period. Diluted net loss per common share is calculated by increasing the denominator by the weighted-average number of additional shares that could have been outstanding from securities convertible into common stock, such as stock options, restricted stock units and warrants (using the “treasury stock” method) and Notes (using the “if-converted” method), unless their effect on net loss per share is antidilutive. The effect of computing diluted net loss per common share was antidilutive for any potentially issuable shares of common stock from the conversion of stock options, restricted stock units and warrants and, as such, have been excluded from the calculation. However, under the “if-converted” method, convertible instruments that are-in-the-money, are assumed to have been converted as of the beginning of the period or when issued, if later. Additionally, the effects of any interest expense and changes in fair value of bifurcated derivatives shall be added back to the numerator of the diluted net loss per share calculation. Refer to Note 13 for further details related to the calculation of net loss per share.

Recently Issued Accounting Standards Updates

In November 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606, which makes targeted improvements for collaborative arrangements to clarify that certain transactions between collaborative arrangement participants should be accounted for as revenue under Topic 606 when the collaborative arrangement participant is a customer in the context of a unit of account, adds unit of account guidance in Topic 808 to align with guidance in Topic 606, and clarifies presentation of certain revenues with a collaborative arrangement participant which are not directly related to a third party. ASU 2018-18 is effective for annual and interim periods beginning after December 15, 2019, with early adoption permitted. The Company has not elected to early adopt this standard and is currently evaluating the impact the adoption of the standard will have on its consolidated financial statements and related disclosures.

In August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) 2018-15, Intangibles-Goodwill and Other-Internal Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract, which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. ASU 2018-15 is effective for annual and interim periods beginning after December 15, 2019, with early adoption permitted. The Company has not elected to early adopt this standard and is currently evaluating the impact the adoption of the standard will have on its consolidated financial statements and related disclosures.

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates certain disclosure requirements for fair value measurements for all entities, requires public entities to disclose certain new information and modifies some disclosure requirements. ASU 2018-13 is effective for all entities for annual and interim periods beginning after December 15, 2019. An entity is permitted to early adopt either the entire standard or only the provisions that eliminate or modify requirements. The Company has not elected to early adopt this standard and is currently evaluating the impact the adoption of the standard will have on its consolidated financial statements and related disclosures.

In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 will replace the incurred loss impairment methodology under current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. In November 2019, the FASB issued ASU 2019-10, Financial Instruments – Credit Losses (Topic 326), Derivatives (Topic 815), and Leases (Topic 842). This ASU delayed the required adoption for SEC filers that are smaller reporting companies as of their determination on November 15, 2019, until annual and interim periods beginning after December 15, 2022, with early adoption permitted. The Company has determined that as of November 15, 2019, it is a smaller reporting company and has not elected to early adopt this standard. The Company is currently evaluating the impact the adoption of the standard will have on its consolidated financial statements and related disclosures.

In December 2019, the FASB issued ASU No 2019-12, Simplifying Accounting for Income Taxes (ASU 2019-12). ASU 2019-12 removes certain exceptions for recognizing deferred taxes for investments, performing intraperiod allocation, calculating income taxes in interim periods and adds certain guidance to remove complexity in certain areas. ASU 2019-12 is effective for all entities for annual and interim periods beginning after December 15, 2020. An entity is permitted to early adopt either the entire standard or only the provisions that eliminate or modify requirements. The Company has not elected to early adopt this standard and is currently evaluating the impact the adoption of the standard will have on its consolidated financial statements and related disclosures.

Recently Adopted Accounting Standards Updates

In June 2018, the FASB issued ASU 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, which expands the scope of Topic 718 to include all share-based payment transactions for acquiring goods and services to be used or consumed in its own operations by issuing share-based payment awards. ASU 2018-07 also clarifies that Topic 718 does not apply to share-based payments used to effectively provide (1) financing to the issuer or (2) awards granted in conjunction with selling goods or services to customers as part of a contract and services from nonemployees. ASU 2018-07 specifies that Topic 718 applies to all share-based payment transactions accounted for under ASC 606. ASU 2018-07 was effective for annual and interim periods beginning after December 15, 2018, with early adoption permitted, but no earlier than the date on which ASC 606 is adopted. The Company adopted this standard prospectively effective January 1, 2019. The adoption of this ASU did not have an effect on the Company’s consolidated financial statements or related disclosures.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which supersedes the guidance under FASB Accounting Standards Codification (ASC) Topic 840, Leases, resulting in the creation of FASB ASC Topic 842, Leases (ASC 842). ASU 2016-02 requires lessees to recognize in the statement of financial position a liability to make lease payments and a right-of-use asset representing its right to use the underlying asset for the lease term for both finance and operating leases. The guidance also eliminates the current real estate-specific provisions for all entities. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements, which provides entities with relief from the costs of implementing certain aspects of the new leasing standard, ASU 2016-02. Under the amendments in ASU 2018-11, entities may elect not to restate the comparative periods presented when transitioning to ASC 842 (optional transition method) and lessors may elect not to separate lease and non-lease components when certain conditions are met (lessor relief practical expedient). The optional transition method applies to entities that have not yet adopted ASU 2016-02, which is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, with early adoption permitted.

The Company adopted this standard using the optional transition method effective January 1, 2019. Upon adoption of this standard, the Company recognized a lease liability and a corresponding right-of use asset of $4.0 million and $3.4 million, respectively, and derecognized a deferred rent liability and a corresponding lease incentive obligation of $0.4 million and $0.2 million, respectively. The Company did not record any cumulative effect adjustment to accumulated deficit as a result of adopting this standard. The Company also elected to adopt the practical expedients upon transition, which permit companies to not reassess lease identification, classification, and initial direct costs under ASU 2016-02 for leases that commenced prior to the effective date.

Inventory

12 Months Ended

Dec. 31, 2019

Inventory

Inventory

3. Inventory

During the third quarter of 2018, the Company began capitalizing inventory costs for COPIKTRA manufactured in preparation for its launch in the United States based on its evaluation of, among other factors, the status of the COPIKTRA NDA in the United States and the ability of its third-party suppliers to successfully manufacture commercial quantities of COPIKTRA, which provided the Company with reasonable assurance that the net realizable value of the inventory would be recoverable.

Inventory consists of the following (in thousands):



	December 31, 2019		December 31, 2018
Raw materials	$	955	$	—
Work in process		2,040		63
Finished goods		101		264
Total inventories	$	3,096	$	327

Costs incurred prior to the quarter-ended September 30, 2018 to manufacture COPIKTRA were expensed as operating expenses as incurred.

Property and equipment, net

12 Months Ended

Dec. 31, 2019

Property and equipment, net

Property and equipment, net

4. Property and equipment, net

Property and equipment and related accumulated depreciation are as follows (in thousands):


	December 31,		December 31,
	2019		2018
Leasehold improvements	$	146	$	146
Furniture and fixtures		1,074		1,074
Computer equipment		665		658
		1,885		1,878
Less: accumulated depreciation		(938)		(509)
Total property and equipment, net	$	947	$	1,369

During the year ended December 31, 2018, an amendment to the Company’s existing office space lease was executed whereby the Company relocated from its previous 15,197 rentable square foot location to an adjacent 27,810 rentable square foot location within the same building. As a result of this amendment, the Company shortened the useful life of the leasehold improvements related to the original location and depreciated this balance through the date which it vacated the original space. Upon vacating the original 15,197 rentable office space, the Company disposed of the leasehold improvements related to this location. No gain or loss from the disposal of leasehold improvements was recognized during the year ended December 31, 2018.

The Company recorded approximately $0.4 million, $1.0 million, and $0.6 million in depreciation expense for the years ended December 31, 2019, 2018 and 2017, respectively.

Intangible assets

12 Months Ended

Dec. 31, 2019

Intangible assets

Intangible assets

5. Intangible assets

The Company’s intangible assets consist of the following (in thousands):

Acquired and in-licensed rights as of December 31, 2019, consist of a $22.0 million milestone payment which became payable upon the FDA marketing approval on September 24, 2018 pursuant to the amended and restated license agreement with Infinity. The Company made a milestone payment of $22.0 million to Infinity in November 2018.

The Company recorded approximately $1.6 million and $0.4 million in amortization expense related to finite-lived intangible assets during the year ended December 31, 2019 and December 31, 2018, respectively, using straight-line methodology. Estimated future amortization expense for finite-lived intangible assets as of December 31, 2019 is approximately $1.6 million per year thereafter.

Accrued expenses

12 Months Ended

Dec. 31, 2019

Accrued expenses

Accrued expenses

6. Accrued expenses

Accrued expenses consist of the following (in thousands):



	December 31, 2019		December 31, 2018
Compensation and related benefits		7,399		8,749
Contract research organization costs		5,467		6,682
Commercialization costs		3,028		1,979
Interest		897		1,786
Consulting fees		1,610		494
Professional fees		573		482
Other		391		936
Total accrued expenses	$	19,365	$	21,108

Long-term debt

12 Months Ended

Dec. 31, 2019

Long-term debt

Long-term debt

7. Long-term debt

On March 21, 2017 (Closing Date), the Company entered into a term loan facility of up to $25.0 million with Hercules Capital, Inc. (Hercules). The term loan facility is governed by a loan and security agreement, dated March 21, 2017 (the Original Loan Agreement), which originally provided for up to four separate advances, of which an aggregate of $15.0 million were drawn down during the year ended December 31, 2017. The Original Loan Agreement was amended on January 4, 2018, March 6, 2018, and October 11, 2018, (the Amended Loan Agreement) to increase the total borrowing limit under the Original Loan Agreement from $25.0 million up to $50.0 million (the Amended Term Loan), pursuant to certain conditions of funding.

On April 23, 2019 (the Fourth Amendment Date) and November 14, 2019 (the Fifth Amendment Date), the Company entered into the Fourth Amendment and Fifth Amendment (together the Amendments) to the Original Loan Agreement with Hercules. The Amendments amend the Amended Loan Agreement (together, with the Amendments, the 2019 Term Loan Agreement).

Per the terms of the 2019 Term Loan Agreement, the Company may borrow up to an aggregate of $75.0 million, of which $35.0 million was outstanding immediately as of the Fourth Amendment Date (2019 Term A Loan) as a result of the existing outstanding principal of term loans of $25.0 million under the Amended Loan Agreement being converted into the 2019 Term A Loan, and an additional $10.0 million being drawn on the Fourth Amendment Date. The remaining $40.0 million of borrowing capacity may be drawn in multiple tranches comprised of (i) a term loan in an amount of up to $15.0 million upon us generating cumulative net product revenues (as defined in the 2019 Term Loan Agreement) of either (a) $37.5 million on or before April 30, 2020 or (b) $50.0 million on or before June 30, 2020 (2019 Term B Loan), and (ii) a term loan in an amount of up to $25.0 million available through December 31, 2021, subject to Hercules’ approval and certain other conditions specified in the 2019 Term Loan Agreement (the 2019 Term C Loan, and together with the 2019 Term A Loan and 2019 Term B Loan, the 2019 Term Loan). As of December 31, 2019, The Company has borrowed a total of $35.0 million in term loans.

The Fifth Amendment modified the financial covenants and collateral requirements. As of the Fifth Amendment Date, the Company must maintain cash in an aggregate amount greater than or equal to 100% of the outstanding term loans as collateral, until the Company’s receipt of Net Product Revenues (as defined in the 2019 Term Loan Agreement) of at least $20 million on or before December 31, 2020, measured on a trailing six month basis (Initial Net Product Revenue Threshold). As of December 31, 2019 the Company has not met the Initial Net Product Revenue Threshold and has recorded $35.0 million as non-current restricted cash on the consolidated balance sheet.

The 2019 Term Loan will mature on December 1, 2022 (2019 Term Loan Maturity Date). Each advance accrues interest at a floating per annum rate equal to the greater of (a) 9.75% or (b) the lesser of (i) 12.00% and (ii) the sum of (x) 9.75% plus (y) (A) the prime rate minus (B) 5.50%. The 2019 Term Loan provides for interest-only payments until April 1, 2021, which may be extended to December 1, 2021 pursuant to us generating $40.0 million in net product revenue on a trailing six-month basis on or prior to December 31, 2020 provided that no event of default has occurred. Thereafter, amortization payments will be payable monthly in equal installments of principal and interest (subject to recalculation upon a change in prime rates).

The 2019 Term Loan is secured by a lien on substantially all of our assets, other than intellectual property and contains customary covenants and representations, including a liquidity covenant, minimum net revenue covenant, financial reporting covenant and limitations on dividends, indebtedness, collateral, investments, distributions, transfers, mergers or acquisitions, taxes, corporate changes, deposit accounts, and subsidiaries.

On the Fourth Amendment Date, the Company was required to pay any outstanding accrued interest as well as the final payment fee equal to 4.5% on the outstanding principal balance of the Amended Term Loan, or $1.1 million. No prepayment charges were due as a result of executing the Amendment or conversion of the existing term loans into 2019 Term A Loans.

The events of default under the 2019 Term Loan Agreement include, without limitation, and subject to customary grace periods, (i) any failure by us to make any payments of principal or interest under 2019 Term Loan Agreement, promissory notes or other loan documents, (ii) any breach or default in the performance of any covenant under the 2019 Term Loan Agreement, (iii) any making of false or misleading representations or warranties in any material respect, (iv) our insolvency or bankruptcy, (v) certain attachments or judgments on the assets of Verastem, Inc., or (vi) the occurrence of any material default under certain agreements or obligations of ours involving indebtedness, or (vii) the occurrence of a material adverse effect. If an event of default occurs, Hercules is entitled to take enforcement action, including acceleration of amounts due under the 2019 Term Loan Agreement.

The 2019 Term Loan Agreement also contains other customary provisions, such as expense reimbursement and confidentiality. Hercules has indemnification rights and the right to assign the 2019 Term Loan.

The Company assessed all terms and features of the 2019 Term Loan Agreement in order to identify any potential embedded features that would require bifurcation or any beneficial conversion features. As part of this analysis, the Company assessed the economic characteristics and risks of the 2019 Term Loan Agreement, including put and call features. The Company determined that all features of the 2019 Term Loan Agreement were clearly and closely associated with a debt host and did not require bifurcation as a derivative liability, or the fair value of the feature was immaterial to the Company's consolidated financial statements. The Company reassesses the features on a quarterly basis to determine if they require separate accounting. There have been no changes to the Company’s original assessment through December 31, 2019.

The future principal payments under the 2019 Term Loan Agreement are as follows as of December 31, 2019 (in thousands):


2021	$	14,234
2022		20,766
Total principal payments	$	35,000

Product revenue reserves and allowances

12 Months Ended

Dec. 31, 2019

Product revenue reserves and allowances

Product revenue reserves and allowances

8. Product revenue reserves and allowances

As of December 31, 2019, the Company’s sole source of product revenue has been from sales of COPIKTRA in the United States, which it began shipping to customers on September 25, 2018. The following table summarizes activity in each of the product revenue allowance and reserve categories for the year ended December 31, 2019 (in thousands):


			Third-Party
	Trade		Payer		Government
	discounts		chargebacks,		rebates and
	and		discounts		other
	allowances		and fees		incentives		Returns		Total
Beginning Balance at December 31, 2017	$	—	$	—	$	—	$	—	$	—
Provision related to sales in the current year		69		120		157		2		348
Adjustments related to prior period sales		—		—		—		—		—
Credits and payments made		(40)		(32)		—		—		(72)
Balance at December 31, 2018	$	29	$	88	$	157	$	2	$	276
Provision related to sales in the current year		512		1,306		608		74		2,500
Adjustments related to prior period sales		—		—		(76)		—		(76)
Credits and payments made		(430)		(1,139)		(317)		—		(1,886)
Ending balance at December 31, 2019	$	111	$	255	$	372	$	76	$	814

Trade discounts and Third-Party Payer chargebacks and discounts are recorded as a reduction to accounts receivable, net on the consolidated balance sheets. Trade allowances and Third-Party Payer fees, government rebates, other incentives and returns are recorded as a component of accrued expenses on the consolidated balance sheets.

Leases

12 Months Ended

Dec. 31, 2019

Leases

Leases

9. Leases

On April 15, 2014, the Company entered into a lease agreement for approximately 15,197 square feet of office and laboratory space in Needham, Massachusetts. The lease term commenced on April 15, 2014 and was scheduled to expire on September 30, 2019. Effective February 15, 2018, the Company amended its lease agreement to relocate within the facility to another location consisting of 27,810 square feet of office space (the Amended Lease Agreement). The Amended Lease Agreement extends the expiration date of the lease from September 2019 through May 2025. Pursuant to the Amended Lease Agreement, the initial annual base rent amount is approximately $660,000, which increases during the lease term to $1.1 million for the last twelve-month period.

The Company has accounted for its Needham, Massachusetts office space as an operating lease. The Company’s lease contains an option to renew and extend the lease terms and an option to terminate the lease prior to the expiration date. The Company has not included the lease extension or the termination options within the right-of-use asset and lease liability on the consolidated balance sheets as neither option is reasonably certain to be exercised. The Company’s lease includes variable non-lease components (e.g., common area maintenance, maintenance, consumables, etc.) that are not included in the right-of-use asset and lease liability and are reflected as an expense in the period incurred. The Company does not have any other operating or finance leases.

In calculating the present value of future lease payments, the Company has elected to utilize its incremental borrowing rate based on the remaining lease term at the date of adoption of ASC 842. The Company has elected to account for lease components and associated non-lease components as a single lease component and has allocated all of the contract consideration to the lease components only. This will potentially result in the initial and subsequent measurement of the balances of the right-of-use asset and lease liability for leases being greater than if the policy election was not applied.

As of December 31, 2019 a right-of-use asset of $3.1 million and lease liability of $3.9 million are reflected on the consolidated balance sheets. The elements of lease expense were as follows (dollar amounts in thousands):


	Year ended
	December 31, 2019
Lease Expense
Operating lease expense	$	885
Total Lease Expense	$	885
Other Information - Operating Leases
Operating cash flows paid for amounts included in measurement of lease liabilities	$	703


		December 31, 2019
Other Balance Sheet Information - Operating Leases
Weighted average remaining lease term (in years)		5.5
Weighted average discount rate		14.60%
Maturity Analysis
2020	$	955
2021		1,019
2022		1,039
2023		1,060
2024		1,081
Thereafter		546
Total	$	5,700
Less: Present value discount		(1,791)
Lease Liability	$	3,909

The Company adopted ASU 2016-02 effective January 1, 2019 using the optional transition method permitted under ASU 2018-11. Accordingly, periods presented prior to January 1, 2019 were not restated to reflect the accounting principles adopted under ASU 2016-02. Prior to adoption, the Company recorded rent expense from its Needham office on a straight-line basis over the term of the lease with the deferred rent obligation included in accrued expenses (current portion) and other liabilities (noncurrent portion) in the consolidated balance sheet as of December 31, 2018. The Company amortized any leasehold improvements over the lesser of the useful life of those improvements or the life of the lease. For the year ended December 31, 2018, the Company recorded rent expense of $0.8 million.

At December 31, 2018, future minimum lease payments under non-cancelable leases under ASC 840 were as follows (in thousands):


2019	$	716
2020		971
2021		1,020
2022		1,041
2023		1,062
Thereafter		1,538
Total	$	6,348

Common stock

12 Months Ended

Dec. 31, 2019

Common stock.

Common stock

10. Common stock

As of December 31, 2019 and 2018, the Company had reserved the following shares of common stock for the issuance of common stock for vested restricted stock units, the exercise of stock options, and an outstanding warrant (in thousands):


	December 31,
	2019	2018
Shares reserved under equity compensation plans	15,389	15,572
Shares reserved for inducement grants	6,331	6,381
Shares reserved for 2018 Notes	3,950	20,937
Shares reserved for 2019 Notes	34,796	—
Total shares reserved	60,466	42,890

Each share of common stock is entitled to one vote. The holders of the common stock are also entitled to receive dividends whenever funds are legally available and when declared by the board of directors.

At-the-market equity offering programs

On March 30, 2017, the Company established an at-the-market equity offering program (ATM) pursuant to which it was able to offer and sell up to $35.0 million of its common stock at then-current market prices from time to time through Cantor, as sales agent. On August 28, 2017, the Company amended its sales agreement with Cantor to increase the maximum aggregate offering price of shares of common stock that can be sold under the ATM to $75.0 million. Through December 31, 2018, the Company sold 11,518,354 shares under the ATM for net proceeds of approximately $47.3 million (after deducting commissions and other offering expenses). During the year ended December 31, 2019, there were no sales under the ATM. As of December 31, 2019 we can issue an additional $26.6 million of gross proceeds under this program.

Equity offering

On May 16, 2018, the Company entered into an underwriting agreement with Cantor relating to the underwritten offering of 7,777,778 shares (the Shares) of the Company’s common stock (the Underwriting Agreement). Cantor agreed to purchase the Shares pursuant to the Underwriting Agreement at a price of $4.31 per share. In addition, the Company granted Cantor an option to purchase, at the public offering price less any underwriting discounts and commissions, an additional 1,166,666 shares of the Company’s common stock, exercisable for 30 days from the date of the prospectus supplement. The option was exercised by Cantor in full on May 23, 2018. The aggregate proceeds from Cantor, net of underwriting discounts and offering costs, were approximately $38.3 million.

On June 14, 2018, the Company entered into a purchase agreement with Consonance Capital Master Account L.P. and P Consonance Opportunities Ltd. (collectively, Consonance) relating to the registered offering of 7,166,666 shares of its common stock at a price of $6.00 per share. The aggregate proceeds from Consonance, net of offering costs, were approximately $42.9 million.

On December 14, 2017, the Company entered into an underwriting agreement with BTIG, LLC relating to the underwritten offering of 8,422,877 shares of its common stock at a price of $2.97 per share, for aggregate proceeds, net of underwriting discounts and offering costs, of approximately $24.7 million.

Stock-based compensation

12 Months Ended

Dec. 31, 2019

Stock-based compensation

Stock-based compensation

11. Stock‑based compensation

Stock‑based compensation expense as reflected in the Company’s consolidated statements of operations and comprehensive loss was as follows (in thousands):


	Year ended December 31,
	2019		2018		2017
Research and development	$	1,501	$	2,043	$	1,381
Selling, general and administrative		7,038		4,628		3,652
Total stock-based compensation expense	$	8,539	$	6,671	$	5,033

All of the $8.5 million, $6.7 million, and $5.0 million of stock-based compensation expense recorded during the years ended December 31, 2019, 2018 and 2017, respectively, was recorded to additional paid-in capital.

The Company has awards outstanding under two equity compensation plans, the Amended and Restated 2012 Incentive Plan (the 2012 Plan) and the 2010 Equity Incentive Plan (the 2010 Plan), as well as the inducement award program. Terms of stock award agreements, including vesting requirements, are determined by the board of directors, subject to the provisions of the individual plans. To date, most options granted by the Company vest twenty-five percent (25%) one year from vesting start date and six and a quarter percent (6.25%) for each successive three-month period, thereafter (subject to acceleration of vesting in the event of certain change of control transactions) and are exercisable for a period of ten years from the date of grant.

2012 Incentive Plan

The 2012 Plan became effective immediately upon the closing of the Company’s IPO in February 2012. Upon effectiveness of the 2012 Plan, the Company ceased making awards under the 2010 Plan. The 2012 Plan initially allowed the Company to grant awards for up to 3,428,571 shares of common stock, plus the number of shares of common stock available for grant under the 2010 Plan as of the effectiveness of the 2012 Plan (which was an additional 30,101 shares), plus that number of shares of common stock related to awards outstanding under the 2010 Plan which terminate by expiration, forfeiture, cancellation or otherwise. The 2012 Plan included an “evergreen provision” that allowed for an annual increase in the number of shares of common stock available for issuance under the 2012 Plan. The annual increase was added on the first day of each year from 2013 through 2018 and was equal to the lesser of 1,285,714 shares of common stock and 4.0% of the number of shares of common stock outstanding, or a lesser amount as determined by the board of directors. On each of January 1, 2018, January 1, 2017 and January 1, 2016, the number of shares available for issuance under the 2012 Plan increased by 1,285,714 under this provision. On December 18, 2018, the shareholders of the Company approved the Amended and Restated 2012 Incentive Plan which increased the maximum number of shares available for issuance under the 2012 Plan to 16,628,425 and eliminated the evergreen provision.

Awards under the 2012 Plan may include the following award types: incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock awards, restricted stock units (RSUs), other stock‑based or cash‑based awards and any combination of the foregoing. As of December 31, 2019, under the 2012 Plan, the Company has granted stock options for 19,733,446 shares of common stock, of which 5,644,811 have been forfeited and 456,865 have been exercised, and granted restricted stock units for 1,922,622 shares of common stock, of which 443,277 have been forfeited and 851,256 have vested. The exercise price of each option has been equal to the closing price of a share of our common stock on the grant date.

Inducement Award Program

In December 2014, the Company established an inducement award program (in accordance with Nasdaq Listing Rule 5635(c)(4)) under which it may grant non-statutory stock options to purchase, and RSUs in respect of up to an aggregate of 750,000 shares of common stock to new or prospective employees as inducement to enter into employment with the Company. In December 2016, the Board of Directors authorized and reserved 580,000 additional shares of common stock under this program. In December 2017, the Board of Directors authorized and reserved 2,500,000 additional shares of common stock under this program. In June and December 2018, the Board of Directors authorized and reserved 1,700,000 and 1,250,000 additional shares of common stock under this program, respectively. The program is governed by the terms of the 2012 Plan, but shares issued pursuant to the program are not issued under the 2012 Plan. As of December 31, 2019, the Company had granted options for 6,094,671 shares of common stock under the program, of which 2,212,738 have been forfeited and 323,750 have been exercised, and granted restricted stock units for 162,200 shares, of which 62,200 have been forfeited and 50,000 have vested. As of December 31, 2019, 3,608,183 remain available for future issuance.

Stock Options

A summary of the Company’s stock option activity and related information for the year ended December 31, 2019 is as follows:


				Weighted-average
		Weighted-average		remaining	Aggregate
		exercise price per		contractual term	intrinsic value
	Shares	share		(years)	(in thousands)
Outstanding at December 31, 2018	12,522,867	$	5.42	7.8	$	6,909
Granted	8,280,682	$	2.09
Exercised	(91,907)	$	1.41
Forfeited/cancelled	(3,453,118)	$	4.67
Outstanding at December 31, 2019	17,258,524	$	4.00	7.3	$	185
Vested at December 31, 2019	7,641,065	$	5.45	5.3	$	121
Vested and expected to vest at December 31, 2019(1)	16,728,024	$	4.00	7.3	$	185

(1)

This represents the number of vested options as of December 31, 2019, plus the number of unvested options expected to vest as of December 31, 2019.

The fair value of each stock option was estimated using a Black‑Scholes option‑pricing model with the following assumptions:


	Year ended December 31,
	2019		2018		2017
Risk-free interest rate	1.98	%	2.65	%	2.02	%
Volatility	87	%	81	%	78	%
Dividend yield	—		—		—
Expected term (years)	5.9		5.8		5.8

The Company recorded stock‑based compensation expense associated with employee stock options of $7.1 million, $5.6 million, and $4.5 million for the years ended December 31, 2019, 2018, and 2017, respectively. The weighted‑average grant date fair value of options granted in the years ended December 31, 2019, 2018, and 2017 was $1.44, $3.72, and $1.83 per share, respectively. The fair value of options that vested during the years ended December 31, 2019, 2018, and 2017 was $7.3 million, $4.7 million, and $4.8 million, respectively. The aggregate intrinsic value of options exercised (i.e., the difference between the market price at exercise and the price paid by employees to exercise the option) during the years ended December 31, 2019 and 2018 was $0.1 million and $1.8 million, respectively.

During the first quarter of 2018, the Company granted stock options to purchase a total of 582,500 shares of common stock to certain executives that vest only upon the achievement of specified performance conditions. The Company determined that two of the performance conditions had been achieved as of December 31, 2018. The Company has recognized approximately $0.1 million and $0.7 million of stock-based compensation expense during the year ended December 31, 2019 and 2018, respectively, related to awards that vest upon the achievement of performance conditions. As December 31, 2019, a total of 260,000 performance-based options remain unvested which are expected to vest, which have a weighted average exercise price of $1.52 per share, weighted average remaining contractual term of 9.6 years and $0 aggregate intrinsic value.

In June 2016, the Company granted stock options to purchase a total of 500,000 shares of common stock to certain employees that vest only upon the achievement of specified performance conditions. The Company determined that 50% of performance conditions had been achieved during the year ended December 31, 2016. As a result, 250,000 shares vested in October 2016 and the Company recognized stock-based compensation expense related to these awards of approximately $0.2 million for the year ended December 31, 2016. In September 2017, the Company determined that the remaining performance conditions had been achieved and as a result the remaining 250,000 shares vested and the Company recognized stock-based compensation expense of approximately $0.4 million during the year ended December 31, 2017. The increase in stock-based compensation expense recognized for the awards which vested during the year ended December 31, 2017, as compared to the awards which vested during the year ended December 31, 2016, is a result of the revaluation of an award held by a non-employee to fair value on the vesting date.

At December 31, 2019, there was $14.0 million of total unrecognized compensation cost related to unvested stock options and the Company expects to recognize this cost over a remaining weighted-average period of 2.8 years.

Restricted Stock Units (RSUs)

The Company awards RSUs to employees under its 2012 Incentive Plan and Inducement Award Program. Each RSU entitles the holder to receive one share of the Company’s common stock when the RSU vests. The RSUs generally vest in either (i) four substantially equal installments on each of the first four anniversaries of the vesting commencement date, or (ii) 100 percent on the first anniversary of the vesting commencement date, subject to the employee’s continued employment with, or service to, the Company on such vesting date. Compensation expense is recognized on a straight-line basis.

A summary of RSU activity during the year ended December 31, 2019 is as follows:


	Shares	Weighted-average grant date fair value per share
Outstanding at December 31, 2018	306,750	$	5.24
Granted	798,904	$	2.57
Vested	(141,439)	$	6.93
Forfeited/cancelled	(286,126)	$	3.86
Outstanding at December 31, 2019	678,089	$	2.36

The Company recorded stock‑based compensation expense associated with employee RSUs of $1.0 million, $0.4 million, and less than $0.1 million for the years ended December 31, 2019, 2018, and 2017, respectively. No RSUs were granted during the years ended December 31, 2017. The total fair value of restricted stock units vested during the years ended December 31, 2019, 2018, and 2017 was approximately $0.3 million, $0.0 million, and $0.0 million, respectively.

At December 31, 2019, there was $1.2 million of total unrecognized compensation cost related to unvested RSUs and the Company expects to recognize this cost over a remaining weighted-average period of 2.6 years.

Employee stock purchase plan

At the Special Meeting of Stockholders, held on December 18, 2018, the stockholders approved the 2018 Employee Stock Purchase Plan (2018 ESPP). On June 21, 2019, the board of directors of the Company amended and restated the 2018 ESPP, to account for certain non-material changes to the plan’s administration (the Amended and Restated 2018 ESPP). The Amended and Restated 2018 ESPP provides eligible employees with the opportunity, through regular payroll deductions, to purchase shares of the Company’s common stock at 85% of the lesser of the fair market value of the common stock (a) on the date the option is granted, which is the first day of the purchase period, and (b) on the exercise date, which is the last business day of the purchase period. The Amended and Restated 2018 ESPP generally allows for two six-month purchase periods per year beginning in January and July, or such other periods as determined by the compensation committee of our board of directors. The Company has reserved 2,000,000 shares of common stock for the administration of the Amended and Restated 2018 ESPP. The fair value of shares expected to be purchased under the Amended and Restated 2018 ESPP was calculated using the Black-Scholes model with the following assumptions:


	Six Months ended June 30,		Six Months ended December 31,
	2019		2019
Risk-free interest rate	2.46	%	2.10	%
Volatility	79	%	95	%
Dividend yield	—		—
Expected term (years)	0.4		0.5

For the year ended December 31, 2019, the Company has recognized $0.4 million of stock-based compensation expense under the Amended and Restated 2018 ESPP. During the year ended December 31, 2019, the Company issued 341,701 shares of common stock for proceeds of $0.4 million under the Amended and Restated 2018 ESPP.

Convertible Senior Notes	12 Months Ended
Convertible Senior Notes	Dec. 31, 2019
Convertible Senior Notes
Convertible Senior Notes	12. Convertible Senior Notes On October 17, 2018, the Company closed a registered direct public offering of $150.0 million aggregate principal amount of the Company’s 5.00% Convertible Senior Notes due 2048 (the 2018 Notes), for net proceeds of approximately $145.3 million. The 2018 Notes are governed by the terms of a base indenture for senior debt securities (the Base Indenture), as supplemented by the first supplemental indenture thereto (the Supplemental Indenture and together with the 2018 Base Indenture, the 2018 Indenture), each dated October 17, 2018, by and between the Company and Wilmington Trust, National Association, as trustee. The 2018 Notes are senior unsecured obligations of the Company and bear interest at a rate of 5.00% per annum, payable semi-annually in arrears on May 1 and November 1 of each year, beginning on May 1, 2019. The 2018 Notes will mature on November 1, 2048, unless earlier repurchased, redeemed or converted in accordance with their terms. The 2018 Notes are convertible into shares of the Company’s common stock, par value $0.0001 per share, together, if applicable, with cash in lieu of any fractional share, at an initial conversion rate of 139.5771 shares of common stock per $1,000 principal amount of the Notes, which corresponds to an initial conversion price of approximately $7.16 per share of common stock and represents a conversion premium of approximately 15.0% above the last reported sale price of the common stock of $6.23 per share on October 11, 2018. Upon conversion, converting noteholders will be entitled to receive accrued interest on their converted 2018 Notes. To the extent the Company has insufficient authorized but unissued shares to settle conversions in shares of common stock, the Company would be required to settle the deficiency in cash. The Company will have the right, exercisable at its option, to cause all Notes then outstanding to be converted automatically if the “Daily VWAP” (as defined in the 2018 Indenture) per share of the Company’s common stock equals or exceeds 130% of the conversion price on each of at least 20 VWAP Trading Days (as defined in the 2018 Indenture), whether or not consecutive, during any 30 consecutive VWAP Trading Day period commencing on or after the date the Company first issued the 2018 Notes. The conversion rate is subject to adjustment from time to time upon the occurrence of certain events, including, but not limited to, the issuance of stock dividends and payment of cash dividends, but will not be adjusted for any accrued and unpaid interest. Prior to November 1, 2022, the Company will not have the right to redeem the 2018 Notes. On or after November 1, 2022, the Company may elect to redeem the 2018 Notes, in whole or in part, at a cash redemption price equal to the principal amount of the 2018 Notes to be redeemed, plus accrued and unpaid interest, if any. Unless the Company has previously called all outstanding 2018 Notes for redemption, the 2018 Notes will be subject to repurchase by the Company at the holders’ option on each of November 1, 2023, November 1, 2028, November 1, 2033, November 1, 2038 and November 1, 2043 (or, if any such date is not a business day, on the next business day) at a cash repurchase price equal to the principal amount of the 2018 Notes to be repurchased, plus accrued and unpaid interest, if any. If a “Fundamental Change” (as defined in the 2018 Indenture) occurs at any time, subject to certain conditions, holders may require the Company to purchase all or any portion of their 2018 Notes at a purchase price equal to 100% of the principal amount of the 2018 Notes to be purchased, plus accrued and unpaid interest. If a “Fundamental Change” occurs on or before November 1, 2022 and a holder elects to convert its Notes in connection with such change, such holder may be entitled to an increase in the conversion rate in certain circumstances as set forth in the Indenture. The 2018 Notes are the Company’s senior, unsecured obligations and will be senior in right of payment to the Company’s future indebtedness that is expressly subordinated in right of payment to the 2018 Notes; equal in right of payment with the Company’s existing and future indebtedness that is not so subordinated, and effectively subordinated to the Company’s existing and future secured indebtedness, to the extent of the value of the collateral securing such indebtedness. The 2018 Notes are structurally subordinated to all existing and future indebtedness and other liabilities, including trade payables, and (to the extent the Company is not a holder thereof) preferred equity, if any, of the Company’s subsidiaries. The 2018 Indenture includes customary covenants and set forth certain events of default after which the 2018 Notes may be declared immediately due and payable and set forth certain types of bankruptcy or insolvency events of default involving the Company or certain of its subsidiaries after which the 2018 Notes become automatically due and payable The Company assessed all terms and features of the 2018 Notes in order to identify any potential embedded features that would require bifurcation. As part of this analysis, the Company assessed the economic characteristics and risks of the 2018 Notes, including the conversion, put and call features. Per the terms of the 2018 Indenture, upon conversion of the 2018 Notes, a portion of the principal may be settled in cash until the date upon which the Company’s stockholders approve an increase in the number of authorized shares of common stock, or the Authorized Share Effective Date, as defined. In consideration of this provision, the Company concluded the conversion feature required bifurcation as a derivative. The fair value of the conversion feature derivative was determined based on the difference between the fair value of the 2018 Notes with the conversion option and the fair value of the 2018 Notes without the conversion option. The Company determined that the fair value of the derivative upon issuance of the 2018 Notes was $51.5 million and recorded this amount as a derivative liability and the offsetting amount as a debt discount as a reduction to the carrying value of the 2018 Notes on the closing date, or October 17, 2018. On December 18, 2018, the Authorized Share Effective Date was achieved as the Company’s stockholders approved an increase in the number of authorized shares of Common Stock. Following this approval, no portion of the 2018 Notes are settleable in cash upon conversion. As such, the Company determined that the conversion feature no longer met the definition of a derivative following the increase in the number of authorized shares of common stock. As of December 18, 2018, the Company determined the fair value of the conversion feature was $25.9 million. The Company recorded the change in the fair value of the conversion feature for the period from October 17, 2018 to December 18, 2018 of $25.6 million as other income on the consolidated statements of operations and comprehensive loss. As of December 18, 2018, the fair value of the conversion option was reclassified to additional paid-in capital on the consolidated balance sheets as it qualified for a scope exception from derivative accounting. Accordingly, the conversion feature will no longer be measured at fair value on the Company’s financial statements. On November 14, 2019 and December 23, 2019, we entered into privately negotiated agreements to exchange approximately $114.3 million and $7.4 million, respectively, aggregate principal amount of the 2018 Notes for (i) approximately $62.9 million and $4.0 million, respectively, aggregate principal amount of 5.00% Convertible Senior Second Lien Notes due 2048 (the 2019 Notes) (ii) an aggregate of approximately $11.4 million and $0.7 million in 2018 Notes principal repayment and (iii) accrued interest on the 2018 Notes through November 14, 2019 and December 23, 2019, respectively. The 2019 Notes are governed by the terms of an indenture (the 2019 Indenture). The 2019 Notes are senior secured obligations of the Company and bear interest at 5.00% per annum, payable semi-annually in arrears on May 1 and November 1 of each year. The 2019 Notes will mature on November 1, 2048, unless earlier repurchased, redeemed or converted in accordance with the terms. The Company determined 2019 Notes exchange met the definition of a troubled debt restructuring under ASC 470-60, Troubled Debt Restructurings by Debtors, as the Company was experiencing financial difficulties and the lenders granted a concession. The future undiscounted cash flows of the 2019 Notes after the exchange exceeded the carrying value of the converted 2018 Notes prior to the exchange. As such no gain was recognized as a result of the exchange. The Company reduced the carrying value of the Notes by the cash given and the change in fair value of the conversion option driven by the reduction in conversion price. The change in fair value of the conversion option was determined to be $13.6 million. The 2019 Notes are convertible into shares of our common stock, par value $0.0001 per share, together, if applicable, with cash in lieu of any fractional share, at an initial conversion rate of 606.0606 shares of common stock per $1,000 principal amount of the 2019 Notes, which corresponds to an initial conversion price of approximately $1.65 per share of common stock and represents a conversion premium of approximately 52.8% above the last reported sale price of our common stock of $1.08 per share on November 11, 2019. We will have the right, exercisable at our option, to cause all 2019 Notes then outstanding to be converted automatically if the “Daily VWAP” (as defined in the 2019 Indenture) per share of our common stock equals or exceeds 121% of the conversion price on each of at least 20 VWAP Trading Days, whether or not consecutive, during any 30 consecutive VWAP Trading Day period commencing on or after the date we first issued the 2019 Notes. (Company’s Mandatory Conversion Option) Upon conversion, converting noteholders will be entitled to receive accrued interest on their converted 2019 Notes. In addition, if the 2019 Notes are converted with a conversion date that is on or prior to November 1, 2020, other than in connection with the Company’s exercise of the Company’s Mandatory Conversion Option then the consideration due upon any such conversion will also include a cash interest make-whole payment for all future scheduled interest payments on the converted 2019 Notes through November 1, 2020 (2019 Notes Interest Make-Whole Provision). The conversion rate is subject to adjustment from time to time upon the occurrence of certain events, including, but not limited to, the issuance of stock dividends and payment of cash dividends, but will not be adjusted for any accrued and unpaid interest. We assessed all terms and features of the 2019 Notes in order to identify any potential embedded features that would require bifurcation. As part of this analysis, we assessed the economic characteristics and risks of the 2019 Notes, including the conversion, put and call features. In consideration of the 2019 Notes Interest Make-Whole Provision, we concluded the provision required bifurcation as a derivative. The fair value of the 2019 Interest Make-Whole Provision was determined using a Monte Carlo model. It was determined that the fair value of the derivative upon the November 14, 2019 and December 23, 2019 issuance of the 2019 Notes was $0.2 million in aggregate; and recorded this amount as a derivative liability and the offsetting amount as a debt discount as a reduction to the carrying value of the 2019 Notes on the closing dates. During the period November 14, 2019 to December 31, 2019, the Company paid out approximately $0.4 million in 2019 Interest Make-Whole payments which was recorded as a reduction of the derivative liability. As of December 31, 2019, we determined the fair value of the 2019 Interest Make-Whole Provision was $0.5 million. The Company recorded the change in the fair value of the 2019 Interest Make-Whole Provision for the period from November 14, 2019 to December 31, 2019 of $0.6 million as other expense on the consolidated statements of operations and comprehensive loss. The Company determined that all other features of the 2018 Notes and 2019 Notes were clearly and closely associated with a debt host and did not require bifurcation as a derivative liability, or the fair value of the feature was immaterial to the Company's consolidated financial statements. The Company reassesses the features on a quarterly basis to determine if they require separate accounting. There have been no changes to the Company’s original assessment through December 31, 2019. The Company determined that the expected life of the 2018 Notes and 2019 Notes was equal to the period through November 1, 2023 as this represents the point at which the 2018 Notes and 2019 Notes are initially subject to repurchase by the Company at the option of the holders. Accordingly, the total debt discount, inclusive of the fair value of the embedded conversion feature derivative at issuance, is being amortized using the effective interest method through November 1, 2023. For the year ended December 31, 2019, the Company recognized an aggregate of $16.0 million of interest expense related to the 2018 and 2019 Notes. For the year ended December 31, 2019, 2019 Note holders converted $9.5 million aggregate principal of 2019 Notes in exchange for 5,767,872 shares of common stock and $0.4 million of cash for 2019 Interest Make-Whole Provision.

Net Loss per Share

12 Months Ended

Dec. 31, 2019

Net Loss per Share

Net Loss per Share

13. Net Loss per Share

ASC 260 “Earnings Per Share” requires the Company to calculate its net loss per share based on basic and diluted net loss per share, as defined. Basic EPS excludes dilution and is computed by dividing net loss by the weighted average number of shares outstanding for the period. For the years ended December 31, 2019 and 2017 net loss, basic and diluted EPS are the same as the assumed exercise of stock options, restricted stock units, and the Notes are anti-dilutive. For the year ended December 31, 2018, the dilutive effect of the outstanding Notes issued by the Company is reflected in diluted EPS using the if-converted method.

The computation of basic and diluted net income (loss) per share attributable to common stockholders consists of the following:


	Year Ended December 31,
	2019	2018	2017
Net loss	(149,209)	(72,434)	(67,802)
Less: Other income	—	(25,556)	—
Add: Interest expense	—	3,071	—
Adjusted diluted net loss	(149,209)	(94,919)	(67,802)

Weighted average shares outstanding	74,578	64,962	38,422
Add: Dilutive effect of the Notes	—	4,359	—
Weighted average diluted shares outstanding	74,578	69,321	38,422

Net loss per share - basic	(2.00)	(1.12)	(1.76)
Net loss per share - diluted	(2.00)	(1.37)	(1.76)

For the year ended December 31, 2018, in calculating the effect of the Notes on diluted net loss per share, the change in fair value of the bifurcated derivative of $25.6 million is subtracted while the interest expense of $3.1 million is added to the Company’s net loss. As of December 31, 2018, upon conversion of all outstanding Notes, the Company would be required to issue 20,936,548 shares. Under the “if-converted” method, convertible instruments are assumed to have been converted as of the beginning of the period or when issued, if later. Accordingly, the weighted average number of potentially issuable shares upon conversion of the Notes was determined by weighting the number of shares potentially issuable as of December 31, 2018, 20,936,548 shares, over the total number of days the Notes were outstanding for the period, 76 days, to calculate an additional 4,359,391 shares to be added to the denominator.

The following potentially dilutive securities were excluded from the calculation of diluted net loss per share due to their anti-dilutive effect:


	Year Ended December 31,
	2019	2018	2017
Outstanding stock options	17,258,524	12,522,867	8,719,978
Outstanding restricted stock units	678,089	306,750	—
2018 Notes	3,950,032	—	—
2019 Notes	34,796,363	—	—
Total potentially dilutive securities	56,683,008	12,829,617	8,719,978

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Taxes

Income Taxes

14. Income Taxes

As of December 31, 2019, the Company had federal and state net operating loss carryforwards of approximately $371.7 million and $392.3 million, respectively, which are available to reduce future taxable income. The Company also had federal and state tax credits of $20.6 million and $3.0 million, respectively, which may be used to offset future tax liabilities. The net operating loss (NOL) and tax credit carryforwards will expire at various dates through 2039, except for $136.3 million of federal net operating loss carryforwards which may be carried forward indefinitely. NOL and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities and may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three‑year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code, as well as similar state provisions. This could limit the amount of tax attributes that can be utilized annually 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.

A reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations follows:



	December 31,
	2019		2018
Income tax benefit using U.S. federal statutory rate	21.00	%	21.00	%
State tax benefit, net of federal benefit	4.26	%	6.38	%
Research and development tax credits	1.67	%	5.61	%
Cancellation of debt	(4.76)	%	—	%
Permanent items	(1.41)	%	(0.65)	%
Change in the valuation allowance	(20.33)	%	(31.82)	%
Other	(0.43)	%	(0.52)	%
	—	%	—	%

The principal components of the Company’s deferred tax assets and liabilities are as follows (in thousands):


	December 31,
	2019		2018
Deferred tax assets:
Net operating loss carryforwards	$	101,039	$	88,829
Capitalized research and development		2,230		2,545
Research and development credits		22,944		19,725
Stock-based compensation		4,445		3,756
Other		1,451		543
Total deferred tax assets		132,109		115,398
Deferred tax liabilities:
Debt discount		(3,702)		(13,617)
Total deferred tax liabilities		(3,702)		(13,617)
Net deferred tax asset prior to valuation allowance		128,407		101,781
Valuation allowance		(128,407)		(101,781)
Net deferred tax asset	$	—	$	—

The Company has recorded a valuation allowance against its deferred tax assets at December 31, 2019 and 2018 because the Company’s management believes that it is more likely than not that these assets will not be fully realized. The increase in the valuation allowance of approximately $26.6 million in the year ended December 31, 2019 primarily relates to the generation of net operating losses and research and development credits.

The Company’s reserves related to taxes are based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is more likely than not to be realized following resolution of any potential contingencies present related to the tax benefit. From inception and through December 31, 2019, the Company had no unrecognized tax benefits or related interest and penalties accrued. The Company has not conducted a study of research and development (R&D) credit carryforwards. This 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 amounts are being presented as an uncertain tax position. A full valuation allowance has been provided against the Company’s R&D credits and, if an adjustment is required, this adjustment would be offset by an adjustment to the valuation allowance. Thus, there would be no impact to the consolidated balance sheet or statement of operations if an adjustment were required. The Company would recognize both accrued interest and penalties related to unrecognized benefits in income tax expense. The Company’s uncertain tax positions are related to years that remain subject to examination by relevant tax authorities. Since the Company is in a loss carryforward position, the Company is generally subject to examination by the U.S. federal, state and local income tax authorities for all tax years in which a loss carryforward is available.

Commitments and contingencies	12 Months Ended
Commitments and contingencies	Dec. 31, 2019
Commitments and contingencies
Commitments and contingencies	15. Commitments and contingencies The Company has entered into a lease agreement for approximately 27,810 square feet of office space in Needham, Massachusetts. Please refer to Note 9 for further details regarding the minimum aggregate future lease commitments as of December 31, 2019. In conjunction with the execution of the Amended Lease Agreement, the Company has provided a security deposit in the form of a letter of credit in the amount of $0.2 million as of December 31, 2019 and December 31, 2018. The amount is included in non-current restricted cash on the consolidated balance sheets as of December 31, 2019. Pursuant to the terms of various agreements, the Company may be required to pay various development, regulatory and commercial milestones. In addition, if any products related to these agreements are approved for sale, the Company may be required to pay significant royalties on future sales. The payment of these amounts, however, is contingent upon the occurrence of various future events, which have a high degree of uncertainty of occurring.

License and collaboration agreements	12 Months Ended
License and collaboration agreements	Dec. 31, 2019
License and collaboration agreements
License and collaboration agreements	16. License and collaboration agreements Infinity Pharmaceuticals, Inc. (Infinity) In November 2016, the Company entered into an amended and restated license agreement with Infinity under which it acquired an exclusive worldwide license for the research, development, commercialization, and manufacture of products in oncology indications containing duvelisib. In connection with the license agreement, the Company assumed operational and financial responsibility for certain activities that were part of Infinity’s duvelisib program, including the DUO study for patients with relapsed/refractory CLL, and Infinity maintained a portion of the financial responsibility for the shutdown of certain other clinical studies. The Company is obligated to use diligent efforts to develop and commercialize a product in an oncology indication containing duvelisib. During the term of the license agreement, Infinity has agreed not to research, develop, manufacture or commercialize duvelisib in any other indication in humans or animals. Pursuant to the terms of the license agreement, the Company was required to make the following payments to Infinity in cash or, at the Company’s election, in whole or in part, in shares of the Company’s common stock: (i) $6.0 million upon the completion of the DUO study if the results of the DUO study met certain pre-specified criteria, which was paid in cash by the Company to Infinity in October 2017 and recorded as research and development expense in the consolidated statements of operations and comprehensive loss, and (ii) $22.0 million upon the approval of a NDA in the United States or an application for marketing authorization with a regulatory authority outside of the United States for a product in an oncology indication containing duvelisib, which was paid in cash by the Company to Infinity in November 2018 and recorded as an intangible asset in the consolidated balance sheets. The Company is also obligated to pay Infinity royalties on worldwide net sales of any products in an oncology indication containing duvelisib ranging from the mid-single digits to the high single-digits. The royalties will expire on a product-by-product and country-by-country basis until the latest to occur of (i) the last-to-expire patent right covering the applicable product in the applicable country, (ii) the last-to-expire patent right covering the manufacture of the applicable product in the country of manufacture of such product, (iii) the expiration of non-patent regulatory exclusivity in such country and (iv) ten years following the first commercial sale of a product in a country, provided that if royalties on net sales for a product in the United States are payable solely on the basis of non-patent regulatory exclusivity, the applicable royalty on net sales for such product in the United States will be reduced by 50%. The royalties are also subject to reduction by 50% of certain third-party royalty payments or patent litigation damages or settlements which might be required to be paid by the Company if litigation were to arise, with any such reductions capped at 50% of the amounts otherwise payable during the applicable royalty payment period. In addition to the foregoing, the Company is obligated to pay Infinity an additional royalty of 4% on worldwide net sales of any products in an oncology indication containing duvelisib to cover the reimbursement of research and development costs owed by Infinity to Mundipharma International Corporation Limited (MICL) and Purdue Pharmaceutical Products L.P. (Purdue). Once Infinity has fully reimbursed MICL and Purdue, the royalty obligations will be reduced to 1% of net sales in the United States. These trailing MICL royalties are payable until the later to occur of the last-to-expire of specified patent rights and the expiration of non-patent regulatory exclusivities in a country. Each of the above royalty rates is reduced by 50% on a product-by-product and country-by-country basis if the applicable royalty is payable solely on the basis of non-patent regulatory exclusivity. In addition, the trailing MICL royalties are subject to reduction by 50% of certain third-party royalty payments or patent litigation damages or settlements which might be required to be paid by the Company if litigation were to arise, with any such reductions capped at 50% of the amounts otherwise payable during the applicable royalty payment period. On March 5, 2019, Infinity and Healthcare Royalty Partners III, L.P. (HCR) entered into a purchase and sale agreement, in which HCR paid Infinity a $30.0 million upfront payment and is entitled to receive up to $20.0 million in potential milestone payments from Infinity. In exchange HCR has received the right to receive the royalties due to Infinity from us under the license agreement. As a result, we now pay royalties previously due to Infinity to HCR. We will continue to pay Infinity for the royalties due to MICL and Purdue described above. The Company evaluated the license agreement with Infinity under ASC Topic 805, Business Combinations, and ASU 2017-01 and concluded that as substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar assets, the transaction did not meet the requirements to be accounted for as a business combination and therefore was accounted for as an asset acquisition. All consideration to be paid under the license agreement is contingent in nature and will be recognized when the respective contingency is resolved. During the year ended December 31, 2019 and 2018, the Company recorded royalty expense of $1.0 million, and $0.1 million, respectively related to the HCR, Infinity, MICL, and Purdue royalty payments, which are included in costs of sales - product within the consolidated statements of operation. There were no royalties paid to Infinity or HCR during the year ended December 31, 2017. Pfizer Inc. (Pfizer) On July 11, 2012, the Company entered into a license agreement with Pfizer Inc. (Pfizer), under which Pfizer granted the Company worldwide, exclusive rights to research, develop, manufacture and commercialize products containing certain of Pfizer’s inhibitors of focal adhesion kinase (the FAK Products) for all therapeutic, diagnostic and prophylactic uses in humans. The Company is solely responsible, at its expense, for the clinical development of the FAK Products, which is to be conducted in accordance with an agreed upon development plan. The Company is also responsible for all manufacturing and commercialization activities at its own expense. Pfizer is required to provide the Company with an initial quantity of clinical supply of one of the FAK Products for an agreed upon price. Under the agreement, the Company made a one-time cash payment to Pfizer in the amount of $1.5 million and issued 192,012 shares of its common stock. Pfizer is also eligible to receive up to $2.0 million in developmental milestones and up to an additional $125.0 million based on the successful attainment of regulatory and commercial sales milestones. Pfizer is also eligible to receive high single to mid-double-digit royalties on future net sales of the FAK Products. The Company’s royalty obligations with respect to each FAK Product in each country begin on the date of first commercial sale of the FAK Product in that country, and end on the later of 10 years after the date of first commercial sale of the FAK Product in that country or the date of expiration or abandonment of the last claim contained in any issued patent or patent application licensed by Pfizer to the Company that covers the FAK Product in that country. The Company accounted for the license agreement as the licensing of in process research and development with no alternative future use. Yakult Honsha Co., Ltd. (Yakult) On June 5, 2018, the Company entered into a license and collaboration agreement (the Yakult Agreement) with Yakult, under which the Company granted exclusive rights to Yakult to develop and commercialize products containing duvelisib in Japan for the treatment, prevention, palliation or diagnosis of all oncology indications in humans or animals. Under the terms of the Yakult Agreement, Yakult received an exclusive right to develop and commercialize products containing duvelisib in Japan under mutually agreed upon development and commercialization plans at its own cost and expense. Yakult also received certain limited manufacturing rights in the event that the Company is unable to manufacture or supply sufficient quantities of duvelisib or products containing duvelisib to Yakult during the term of the Yakult Agreement. The Company retained all rights to duvelisib outside of Japan. Yakult paid the Company an upfront, non-refundable payment of $10.0 million in June 2018. The Company is also entitled to receive aggregate payments of up to $90.0 million if certain development, regulatory and commercial milestones are successfully achieved. Yakult is obligated to pay the Company a double-digit royalty on net sales of products containing duvelisib in Japan, subject to reduction in certain circumstances, and to fund certain global development costs related to worldwide clinical trials conducted by the Company in which Yakult has opted to participate (Global Clinical Trials) on a pro-rata basis. Unless earlier terminated by either party, the Yakult Agreement will expire upon the fulfillment of Yakult’s royalty obligations to the Company for the sale of any products containing duvelisib in Japan, which royalty obligations expire, on a product-by-product basis, upon the last to occur of (a) expiration of valid claims covering such product, (b) expiration of regulatory exclusivity for such product or (c) 10 years from first commercial sale of such product. Yakult may terminate the Yakult Agreement in its entirety at any time with 180 days’ written notice. Either party may terminate the Yakult Agreement in its entirety with 60 days’ written notice for the other party’s material breach if such party fails to cure the breach. The Company may terminate the Yakult Agreement if (i) Yakult fails to use commercially reasonable efforts to develop and commercialize products containing duvelisib in Japan or (ii) Yakult challenges any patent licensed by the Company to Yakult under the Yakult Agreement. Either party may terminate the Yakult Agreement in its entirety upon certain insolvency events involving the other party. Subsequently, on February 28, 2019, the Company entered into a supply agreement with Yakult (the Yakult Supply Agreement), under which the Company agreed to provide Yakult with drug product for clinical and commercial use in accordance with the Yakult Agreement. Under the terms of the Yakult Supply Agreement, the Company also granted to Yakult a limited manufacturing license to fill, finish, package, and label the drug product solely for clinical and commercial purposes in Japan. The Company first assessed the Yakult Agreement under ASC 808 to determine whether the Yakult Agreement (or part of the Yakult Agreement) represents a collaborative arrangement based on the risks and rewards and activities of the parties pursuant to the Yakult Agreement. The Company accounts for collaborative arrangements (or elements within the contract that are deemed part of a collaborative arrangement), which represent a collaborative relationship and not a customer relationship, outside the scope of ASC 606. For a component of the Yakult Agreement, the Company concluded that both the Company and Yakult are exposed to significant risks while developing duvelisib and ultimately would share in the reward upon successful commercialization of duvelisib. The Company then considered each remaining component in the Yakult Agreement to determine if ASC 606 should be applied to those components. Generally, the components in the Yakult Agreement fall under one of two potential research and development activities: (i) the parties’ joint participation in Global Clinical Trials and (ii) the territory-specific development of duvelisib. For the parties’ participation in the Global Clinical Trials, the Company concluded that the research and development activities and payments related to such activities are not within the scope of ASC 606 as Yakult is not a customer of the Company with regards to these activities in the context of the Yakult Agreement. As such, costs incurred to execute the Global Clinical Trials will be recorded as research and development expense and payments received from Yakult related to such will be recorded as a reduction of research and development expense. For Territory-specific activities, the Company concluded that Yakult is a customer with regard to this component in the context of the Yakult Agreement. As such, the Territory-specific component and all related payments are within the scope of ASC 606. The Company determined that there were two material promises associated with the territory-specific activities: (i) an exclusive license to develop and commercialize duvelisib in the territory and (ii) the initial technology transfer. The Company determined that the exclusive license and initial technology transfer were not distinct from another, as the license has limited value without the initial technology. Therefore, the exclusive license and initial technology transfer are combined as a single performance obligation. The Company evaluated the option rights for manufacturing and supply services to determine whether they represent material rights to Yakult and concluded that the options were not issued at a significant and incremental discount and therefore do not represent material rights. As such, they are not performance obligations at the outset of the arrangement. Based on this assessment, the Company concluded one performance obligation exists at the outset of the Yakult Agreement: the exclusive license combined with the initial technology transfer. The Company determined that the upfront payment of $10.0 million constitutes the transaction price as of the outset of the Yakult Agreement. Future potential milestone payments were fully constrained as the risk of significant revenue reversal related to these amounts has not yet been resolved. The achievement of the future potential milestones is not within the Company’s control and is subject to certain research and development success or regulatory approvals and therefore carry significant uncertainty. The Company will reevaluate the likelihood of achieving future milestones at the end of each reporting period. As all performance obligations have been satisfied, if the risk of significant revenue reversal is resolved, any future milestone revenue from the arrangement will be added to the transaction price (and thereby recognized as revenue) in the period the risk is relieved. The Company has recognized $0.1 million of collaboration revenue under the Yakult Supply Agreement for the year ended December 31, 2019. The Company satisfied the performance obligation upon delivery of the license and initial technology transfer and recognized the upfront payment of $10.0 million as license revenue during year ended December 31, 2018. CSPC Pharmaceutical Group Limited (CSPC) On July 26, 2018, the Company and CSPC entered into an Exclusivity Agreement which granted CSPC the exclusive right to negotiate a licensing agreement with the Company for duvelisib in China. CSPC paid the Company a non-refundable exclusivity fee of $5.0 million in August 2018 (Exclusivity Fee) which was creditable against any payments agreed to under the terms of a potential definitive license agreement. Subsequently, on September 25, 2018, the Company entered into a license and collaboration agreement with CSPC (the CSPC Agreement), under which the Company granted exclusive rights to CSPC to develop and commercialize products containing duvelisib in the People’s Republic of China (China), Hong Kong, Macau and Taiwan (collectively, the CSPC Territory) for the treatment, prevention, palliation or diagnosis of all oncology indications in humans. Under the terms of the CSPC Agreement, CSPC received an exclusive right to develop and commercialize products containing duvelisib in the CSPC Territory under mutually agreed upon development and commercialization plans at its own cost and expense. CSPC also received certain limited manufacturing rights in the event that the Company is unable to manufacture or supply sufficient quantities of duvelisib or products containing duvelisib to CSPC during the term of the CSPC Agreement. The Company retained all rights to duvelisib outside of the CSPC Territory. CSPC paid the Company an aggregate upfront, non-refundable payment of $15.0 million, less the previously paid $5.0 million Exclusivity Fee. The Company is also entitled to receive aggregate payments of up to $160.0 million if certain development, regulatory and commercial milestones are successfully achieved. CSPC is obligated to pay the Company a double-digit royalty on net sales of products containing duvelisib in the CSPC Territory, subject to reduction in certain circumstances, and to fund certain global development costs related to worldwide clinical trials conducted by the Company in which CSPC has opted to participate (Global Clinical Trials) on a pro-rata basis. Unless earlier terminated by either party, the CSPC Agreement will expire upon the fulfillment of CSPC’s royalty obligations to the Company for the sale of any products containing duvelisib in the CSPC Territory, which royalty obligations expire, on a product-by-product basis, upon the last to occur of (a) expiration of valid claims covering such product, (b) expiration of regulatory exclusivity for such product or (c) 10 years from first commercial sale of such product. CSPC may terminate the CSPC Agreement in its entirety at any time with 180 days’ written notice. Either party may terminate the CSPC Agreement in its entirety with 60 days’ written notice for the other party’s material breach if such party fails to cure the breach. The Company may terminate the CSPC Agreement if (i) CSPC fails to use commercially reasonable efforts to develop and commercialize products containing duvelisib in the CSPC Territory or (ii) CSPC challenges any patent licensed by the Company to CSPC under the CSPC Agreement. Either party may terminate the CSPC Agreement in its entirety upon certain insolvency events involving the other party. The Company first assessed the CSPC Agreement under ASC 808 to determine whether the CSPC Agreement (or part of the CSPC Agreement) represents a collaborative arrangement based on the risks and rewards and activities of the parties pursuant to the CSPC Agreement. The Company accounts for collaborative arrangements (or elements within the contract that are deemed part of a collaborative arrangement), which represent a collaborative relationship and not a customer relationship, outside the scope of ASC 606. For a component of the CSPC Agreement, the Company concluded that both the Company and CSPC are exposed to significant risks while developing duvelisib and ultimately would share in the reward upon successful commercialization of duvelisib. The Company then considered each remaining component in the CSPC Agreement to determine if ASC 606 should be applied to those components. Generally, the components in the CSPC Agreement fall under one of two potential research and development activities: (i) the parties’ joint participation in Global Clinical Trials and (ii) the territory-specific development of duvelisib. For the parties’ participation in the Global Clinical Trials, the Company concluded that the research and development activities and payments related to such activities are not within the scope of ASC 606 as CSPC is not a customer of the Company with regards to these activities in the context of the CSPC Agreement. As such, costs incurred to execute the Global Clinical Trials will be recorded as research and development expense and payments received from CSPC related to such will be recorded as a reduction of research and development expense. For CSPC Territory-specific activities, the Company concluded that CSPC is a customer with regard to this component in the context of the CSPC Agreement. As such, the CSPC Territory-specific component and all related payments are within the scope of ASC 606. The Company determined that there were two material promises associated with the territory-specific activities: (i) an exclusive license to develop and commercialize duvelisib in the territory and (ii) the initial technology transfer. The Company determined that the exclusive license and initial technology transfer were not distinct from another, as the license has limited value without the initial technology. Therefore, the exclusive license and initial technology transfer are combined as a single performance obligation. The Company evaluated the option rights for manufacturing and supply services to determine whether they represent material rights to CSPC and concluded that the options were not issued at a significant and incremental discount and therefore do not represent material rights. As such, they are not performance obligations at the outset of the arrangement. Based on this assessment, the Company concluded one performance obligation exists at the outset of the CSPC Agreement: the exclusive license combined with the initial technology transfer. The Company determined that the upfront payment of $15.0 million constitutes the transaction price as of the outset of the CSPC Agreement. Future potential milestone payments were fully constrained as the risk of significant revenue reversal related to these amounts has not yet been resolved. The achievement of the future potential milestones is not within the Company’s control and is subject to certain research and development success or regulatory approvals and therefore carry significant uncertainty. The Company will reevaluate the likelihood of achieving future milestones at the end of each reporting period. As all performance obligations have been satisfied, if the risk of significant revenue reversal is resolved, any future milestone revenue from the arrangement will be added to the transaction price (and thereby recognized as revenue) in the period the risk is relieved. For the year ended December 31, 2019 there have been no additional milestones achieved under the CSPC Agreement. The Company satisfied the performance obligation upon delivery of the license and initial technology transfer and recognized the upfront payment of $15.0 million as license revenue during the year ended December 31, 2018. Sanofi On July 25, 2019, the Company entered into a license and collaboration agreement with Sanofi (the Sanofi Agreement), under which the Company granted exclusive rights to Sanofi to develop and commercialize products containing duvelisib in Russia, the Commonwealth of Independent States (CIS), Turkey, the Middle East and Africa (collectively the “Sanofi Territory”) for the treatment, prevention, palliation or diagnosis of any oncology indication in humans or animals. Under the terms of the Sanofi Agreement, Sanofi received the exclusive right to develop and commercialize products containing duvelisib in the Sanofi Territory under mutually agreed upon development and commercialization plans at Sanofi’s own cost and expense. In addition, Sanofi received certain limited manufacturing rights in the event the Company is unable to manufacture or supply sufficient quantities of duvelisib or products containing duvelisib to Sanofi during the term of the Sanofi Agreement. The Company retained all rights to duvelisib outside the Sanofi Territory, except for those territories previously and exclusively licensed to other partners. Sanofi paid the Company an upfront, non-refundable payment of $5.0 million in August 2019. The Company is also entitled to receive aggregate payments of up to $42.0 million if certain regulatory and commercial milestones are successfully achieved. Sanofi is obligated to pay the Company double-digit royalties on net sales of products containing duvelisib in the Sanofi Territory, subject to reduction in certain circumstances. Unless earlier terminated by either party, the Sanofi Agreement will expire upon the fulfillment of Sanofi’s royalty obligations to the Company for the sale of any products containing duvelisib in the Sanofi Territory, which royalty obligations expire, on a product-by-product and country-by-country basis, upon the last to occur, in each specific country, of (a) expiration of valid patent claims covering such product, (b) expiration of regulatory exclusivity for such product or (c) 10 years from the first commercial sale of such product in such country. Sanofi may terminate the Sanofi Agreement on a product-by-product basis or on a country-by country basis at any time with 180 days’ written notice. Either party may terminate the Sanofi Agreement in its entirety with 60 days’ written notice for the other party’s material breach if such party fails to cure the breach. Subject to certain limitations, the Company may terminate the Sanofi Agreement immediately if Sanofi challenges any patent covering a product or compound licensed by the Company to Sanofi under the Sanofi Agreement. The Company also has the right to terminate Sanofi’s rights to products containing duvelisib in any specific country if Sanofi fails to use certain efforts to develop and commercialize products containing duvelisib in such country. Either party may terminate the Sanofi Agreement in its entirety upon certain insolvency events involving the other party. The Company first assessed the Sanofi Agreement under ASC 808 to determine whether the Sanofi Agreement (or part of the Sanofi Agreement) represents a collaborative arrangement based on the respective risks, rewards and activities of the parties. The Company accounts for collaborative arrangements (or elements within the contract that are deemed part of a collaborative arrangement), which represent a collaborative relationship and not a customer relationship, outside the scope of ASC 606. The Company concluded that the Sanofi Agreement (or part of the Sanofi Agreement) does not represent a collaborative arrangement under ASC 808. The Company then considered each component in the Sanofi Agreement to determine if ASC 606 should be applied to those components. Generally, the component in the Sanofi Agreement that falls under potential research and development activities is the development of duvelisib specifically in the Sanofi Territory. For development of duvelisib specifically in the Sanofi Territory, the Company has concluded that Sanofi is a customer with regard to this component in the context of the Sanofi Agreement. As such, the Sanofi Territory component and all related payments are within the scope of ASC 606. The Company determined that there were two material promises associated with the Sanofi territory-specific activities: (i) an exclusive license to develop and commercialize duvelisib in the Sanofi Territory and (ii) the initial technology transfer. The Company determined that the exclusive license and initial technology transfer were not distinct from one another, as the license has limited value without the initial technology transfer. Therefore, the exclusive license and initial technology transfer are combined as a single performance obligation. The Company evaluated the option rights for manufacturing and supply services to determine whether they represent material rights to Sanofi and concluded that the options were not issued at a significant and incremental discount and therefore do not represent material rights. As such, they are not performance obligations at the outset of the arrangement. Based on this assessment, the Company concluded that one performance obligation exists at the outset of the Sanofi Agreement, which is the exclusive license combined with the initial technology transfer. The Company has determined that the upfront payment of $5.0 million constituted the transaction price at the outset of the Sanofi Agreement. Future potential milestone payments were fully constrained as the risk of significant revenue reversal related to these amounts has not yet been resolved. The achievement of the future potential milestones is not within the Company’s control and is subject to certain regulatory approvals and therefore carry significant uncertainty. The Company will reevaluate the likelihood of achieving future milestones at the end of each reporting period. As all performance obligations have been satisfied, if the risk of significant revenue reversal is resolved, any future milestone revenue from the arrangement will be added to the transaction price (and thereby recognized as revenue) in the period the risk is relieved. The Company satisfied the performance obligation upon delivery of the license and initial technology transfer and recognized the upfront payment of $5.0 million as license and collaboration revenue during the year ended December 31, 2019.

Employee benefit plan	12 Months Ended
Employee benefit plan	Dec. 31, 2019
Employee benefit plan
Employee benefit plan	17. Employee benefit plan In June 2011, the Company adopted a 401(k) retirement and savings plan (the 401(k) Plan) covering all employees. The 401(k) Plan allows employees to make pre‑tax or post‑tax contributions up to the maximum allowable amount set by the Internal Revenue Service. Under the 401(k) Plan, the Company may make discretionary contributions as approved by the board of directors. The Company made contributions to the 401(k) Plan of approximately $1.3, $0.8 million, and $0.3 million for the years ended December 31, 2019, 2018, and 2017, respectively.

Subsequent events	12 Months Ended
Subsequent events	Dec. 31, 2019
Subsequent events.
Subsequent events	19. Subsequent events The Company reviews all activity subsequent to year end but prior to the issuance of the consolidated financial statements for events that could require disclosure or that could impact the carrying value of assets or liabilities as of the consolidated balance sheet date. The Company is not aware of any material subsequent events other than the following: Chugai Pharmaceutical Co., Ltd. (Chugai) Agreement On January 7, 2020, the Company entered into a license agreement (the Chugai Agreement) with Chugai Pharmaceutical Co., Ltd. (Chugai) whereby Chugai granted the Company an exclusive worldwide license for the development, commercialization and manufacture of products containing CH5126766, a dual RAF/MEK inhibitor. Under the terms of the Chugai Agreement, the Company received an exclusive right to develop and commercialize products containing CH5126766 at the Company’s cost and expense. Upon execution of the Chugai Agreement, the Company is required to pay Chugai a non-refundable payment of $3.0 million which was paid in February 2020. The Company is further obligated to pay Chugai double-digit royalties on net sales of products containing CH5126766, subject to reduction in certain circumstances. Chugai also obtained opt back rights to develop and commercialize CH5126766 (a) in the European Union, which option may be exercised through the date the Company submits a NDA to the FDA for a product which contains CH5126766 as the sole active pharmaceutical ingredient and (b) in Japan and Taiwan, which option may be exercised through the date the Company receives marketing authorization from the FDA for a product which contains CH5126766 as the sole active pharmaceutical ingredient. As consideration for executing either option, Chugai would have to make a payment to the Company calculated on the Company’s development costs to date. Restructuring On February 27, 2020, the Company committed to an operational plan to reduce overall operating expenses, including the elimination of approximately 31 positions across the Company and other cost-saving measures (the “Restructuring”). The Restructuring is designed to streamline operations, speed execution of the Company’s clinical development of defactinib and CH5126766, and reflect a focused, account-based approach in the field. The Company expects to substantially complete the workforce reduction by the end of the first quarter of 2020. The Company expects the Restructuring to reduce annualized operating expenses to a range of approximately $70 million to $85 million beginning in the first quarter of 2020. The Company expects to record a charge of approximately $1.9 million in the first quarter of 2020 as a result of the Restructuring, consisting of one-time termination benefits for employee severance, benefits, and related costs, all of which are expected to result in cash expenditures and substantially all of which will be paid out over the next three months. Issuance of Common Stock On March 3, 2020, the Company sold 46,511,628 shares of Common Stock at a purchase price of $2.15 per share for aggregate gross proceeds of approximately $100.0 million, before deducting fees to the placement agents and other offering expenses payable by the Company pursuant to a securities purchase agreement. 2019 Notes Conversion From January 1, 2020 through the date of issuance of these consolidated financial statements, the aggregate principal amount of $51.2 million of the Company’s 2019 Notes have been converted into 31,044,835 shares of common stock. As a result, as of the date the issuance of these consolidated financials the Company has $6.2 million aggregate principal amount outstanding of 2019 Notes. On March 9, 2020, the Company exercised the Company’s Mandatory Conversion Option for the remaining $6.2 million of 2019 Notes outstanding which will require the remaining 2019 Notes to be converted into approximately 3.8 million shares of common stock in March 2020.

Significant accounting policies (Policies)

12 Months Ended

Dec. 31, 2019

Significant accounting policies

Basis of presentation

Use of estimates

Segment and geographic information

Cash, cash equivalents and restricted cash


	December 31, 2019		December 31, 2018
Cash and cash equivalents	$	43,514	$	129,867
Restricted cash		35,748		741
Total cash, cash equivalents and restricted cash	$	79,262	$	130,608

Fair value of financial instruments


Level 1 inputs		Quoted prices in active markets for identical assets or liabilities that the Company can access at the measurement date.
Level 2 inputs		Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly.
Level 3 inputs		Unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability.

Items Measured at Fair Value on a Recurring Basis

The following table presents information about the Company’s financial instruments that are measured at fair value on a recurring basis (in thousands):




	December 31, 2019
Description	Total		Level 1		Level 2		Level 3
Financial assets
Cash equivalents	$	77,176	$	75,678	$	1,498	$	—
Short-term investments		31,992		—		31,992		—
Total financial assets	$	109,168	$	75,678	$	33,490	$	—
Derivative liability	$	450		—		—	$	450




	December 31, 2018
Description	Total		Level 1		Level 2		Level 3
Financial assets
Cash equivalents	$	127,689	$	60,092	$	67,597	$	—
Short-term investments		119,786		—		119,786		—
Total financial assets	$	247,475	$	60,092	$	187,383	$	—

The following table represents a reconciliation of the derivative liability recorded in connection with the issuance of the 2019 Notes (in thousands):




January 1, 2019	$	—
Fair value recognized upon issuance of 2019 Notes		247
Fair value adjustment		641
Derivative liability extinguished upon conversion		(438)
December 31, 2019	$	450

The following table represents a reconciliation of the derivative liability recorded in connection with the issuance of the 2018 Notes (in thousands):


January 1, 2018	$	—
Fair value recognized upon issuance of 2018 Notes		51,531
Fair value adjustment		(25,556)
Reclassification to equity		(25,975)
December 31, 2018	$	—

Fair Value of Financial Instruments

Investments

Cash, cash equivalents and investments consist of the following (in thousands):


	December 31, 2019
			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Cash, cash equivalents & restricted cash:
Cash and money market accounts	$	77,764	$	—	$	—	$	77,764
Corporate bonds and commercial paper (due within 90 days)		1,498		—		—		1,498
Total cash and cash equivalents	$	79,262	$	—	$	—	$	79,262
Investments:
Corporate bonds and commercial paper (due within 1 year)	$	31,979	$	14	$	—	$	31,993
Total investments	$	31,979	$	14	$	—	$	31,993
Total cash, cash equivalents and investments	$	111,241	$	14	$	—	$	111,255


	December 31, 2018
			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Cash and cash equivalents:
Cash and money market accounts	$	62,270	$	—	$	—	$	62,270
Corporate bonds and commercial paper (due within 90 days)		67,590	$	8	$	(1)	$	67,597
Total cash and cash equivalents	$	129,860	$	8	$	(1)	$	129,867
Investments:
Corporate bonds and commercial paper (due within 1 year)	$	119,666	$	132	$	(12)	$	119,786
Total investments	$	119,666	$	132	$	(12)	$	119,786
Total cash, cash equivalents and investments	$	249,526	$	140	$	(13)	$	249,653

Concentrations of credit risk and off-balance sheet risk

Concentrations of credit risk and off‑balance sheet risk

For the year ended December 31, 2019 and 2018, four customers and two customers, respectively, individually accounted for greater than 10% of the Company’s total revenues.

Property and equipment


Laboratory equipment		5 years
Furniture		5 years
Computer equipment		3 years
Leasehold improvements		Lesser of useful life or life of lease

Upon retirement or sale, the cost of the disposed asset and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is recognized.

Other assets

Research and development costs

The Company expenses research and development costs to operations as incurred. Research and development expenses consist of:

employee‑related expenses, including salaries, benefits, travel and stock‑based compensation expense;

license fees;

facilities, depreciation and other expenses, which include direct and allocated expenses for rent and maintenance of facilities, depreciation of equipment, and laboratory supplies; and

costs associated with COPIKTRA prior to the Company concluding that regulatory approval is probable and that its net realizable value is recoverable.

Stock-based compensation

Stock‑based compensation

Leases

Revenue Recognition

Subject to certain limitations, the Company’s return policy allows for eligible returns of COPIKTRA for credit under the following circumstances:

Receipt of damaged product;

Shipment errors that were a result of an error by the Company;

Expired product that is returned during the period beginning three months prior to the product’s expiration and ending six months after the expiration date;

Product subject to a recall; and

Product that the Company, at its sole discretion, has specified can be returned for credit.

As of December 31, 2019, the Company has not received any returns.

For a complete discussion of the Company’s accounting for its license and collaboration agreements, see Note 16, License and collaboration agreements.

Accounts Receivable, Net

Inventory

Shipping and handling costs for product shipments are recorded as incurred in cost of sales - product along with costs associated with manufacturing the product, and any inventory write-downs.

Intangible Assets

Income taxes

Net loss per share

Recently Issued and/or Adopted Accounting Standards Updates

Recently Issued Accounting Standards Updates

Recently Adopted Accounting Standards Updates

Significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2019

Significant accounting policies

Schedule of reconciliation of cash, cash equivalents and restricted cash


	December 31, 2019		December 31, 2018
Cash and cash equivalents	$	43,514	$	129,867
Restricted cash		35,748		741
Total cash, cash equivalents and restricted cash	$	79,262	$	130,608

Schedule of financial instruments measured at fair value on a recurring basis

The following table presents information about the Company’s financial instruments that are measured at fair value on a recurring basis (in thousands):




	December 31, 2019
Description	Total		Level 1		Level 2		Level 3
Financial assets
Cash equivalents	$	77,176	$	75,678	$	1,498	$	—
Short-term investments		31,992		—		31,992		—
Total financial assets	$	109,168	$	75,678	$	33,490	$	—
Derivative liability	$	450		—		—	$	450




	December 31, 2018
Description	Total		Level 1		Level 2		Level 3
Financial assets
Cash equivalents	$	127,689	$	60,092	$	67,597	$	—
Short-term investments		119,786		—		119,786		—
Total financial assets	$	247,475	$	60,092	$	187,383	$	—

Schedule of derivative liability




January 1, 2019	$	—
Fair value recognized upon issuance of 2019 Notes		247
Fair value adjustment		641
Derivative liability extinguished upon conversion		(438)
December 31, 2019	$	450


January 1, 2018	$	—
Fair value recognized upon issuance of 2018 Notes		51,531
Fair value adjustment		(25,556)
Reclassification to equity		(25,975)
December 31, 2018	$	—

Schedule of cash, cash equivalents and investments

Cash, cash equivalents and investments consist of the following (in thousands):


	December 31, 2019
			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Cash, cash equivalents & restricted cash:
Cash and money market accounts	$	77,764	$	—	$	—	$	77,764
Corporate bonds and commercial paper (due within 90 days)		1,498		—		—		1,498
Total cash and cash equivalents	$	79,262	$	—	$	—	$	79,262
Investments:
Corporate bonds and commercial paper (due within 1 year)	$	31,979	$	14	$	—	$	31,993
Total investments	$	31,979	$	14	$	—	$	31,993
Total cash, cash equivalents and investments	$	111,241	$	14	$	—	$	111,255


	December 31, 2018
			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Cash and cash equivalents:
Cash and money market accounts	$	62,270	$	—	$	—	$	62,270
Corporate bonds and commercial paper (due within 90 days)		67,590	$	8	$	(1)	$	67,597
Total cash and cash equivalents	$	129,860	$	8	$	(1)	$	129,867
Investments:
Corporate bonds and commercial paper (due within 1 year)	$	119,666	$	132	$	(12)	$	119,786
Total investments	$	119,666	$	132	$	(12)	$	119,786
Total cash, cash equivalents and investments	$	249,526	$	140	$	(13)	$	249,653

Schedule of estimated useful lives of the assets


Laboratory equipment		5 years
Furniture		5 years
Computer equipment		3 years
Leasehold improvements		Lesser of useful life or life of lease

Inventory (Tables)

12 Months Ended

Dec. 31, 2019

Inventory

Schedule of inventory

Inventory consists of the following (in thousands):



	December 31, 2019		December 31, 2018
Raw materials	$	955	$	—
Work in process		2,040		63
Finished goods		101		264
Total inventories	$	3,096	$	327

Property and equipment, net (Tables)

12 Months Ended

Dec. 31, 2019

Property and equipment, net

Schedule of property equipment and related accumulated depreciation

Property and equipment and related accumulated depreciation are as follows (in thousands):


	December 31,		December 31,
	2019		2018
Leasehold improvements	$	146	$	146
Furniture and fixtures		1,074		1,074
Computer equipment		665		658
		1,885		1,878
Less: accumulated depreciation		(938)		(509)
Total property and equipment, net	$	947	$	1,369

Intangible assets (Tables)

12 Months Ended

Dec. 31, 2019

Intangible assets

Schedule of intangible assets

The Company’s intangible assets consist of the following (in thousands):

Accrued expenses (Tables)

12 Months Ended

Dec. 31, 2019

Accrued expenses

Schedule of accrued expenses

Accrued expenses consist of the following (in thousands):



	December 31, 2019		December 31, 2018
Compensation and related benefits		7,399		8,749
Contract research organization costs		5,467		6,682
Commercialization costs		3,028		1,979
Interest		897		1,786
Consulting fees		1,610		494
Professional fees		573		482
Other		391		936
Total accrued expenses	$	19,365	$	21,108

Long-term debt (Tables)

12 Months Ended

Dec. 31, 2019

Long-term debt

Schedule of future principal payments under the Loan Agreement

The future principal payments under the 2019 Term Loan Agreement are as follows as of December 31, 2019 (in thousands):


2021	$	14,234
2022		20,766
Total principal payments	$	35,000

Product revenue reserves and allowances (Tables)

12 Months Ended

Dec. 31, 2019

Product revenue reserves and allowances

Schedule of product revenue allowance and reserve categories

The following table summarizes activity in each of the product revenue allowance and reserve categories for the year ended December 31, 2019 (in thousands):


			Third-Party
	Trade		Payer		Government
	discounts		chargebacks,		rebates and
	and		discounts		other
	allowances		and fees		incentives		Returns		Total
Beginning Balance at December 31, 2017	$	—	$	—	$	—	$	—	$	—
Provision related to sales in the current year		69		120		157		2		348
Adjustments related to prior period sales		—		—		—		—		—
Credits and payments made		(40)		(32)		—		—		(72)
Balance at December 31, 2018	$	29	$	88	$	157	$	2	$	276
Provision related to sales in the current year		512		1,306		608		74		2,500
Adjustments related to prior period sales		—		—		(76)		—		(76)
Credits and payments made		(430)		(1,139)		(317)		—		(1,886)
Ending balance at December 31, 2019	$	111	$	255	$	372	$	76	$	814

Lease (Tables)

12 Months Ended

Dec. 31, 2019

Leases

Summary of elements of lease expenses


	Year ended
	December 31, 2019
Lease Expense
Operating lease expense	$	885
Total Lease Expense	$	885
Other Information - Operating Leases
Operating cash flows paid for amounts included in measurement of lease liabilities	$	703


		December 31, 2019
Other Balance Sheet Information - Operating Leases
Weighted average remaining lease term (in years)		5.5
Weighted average discount rate		14.60%
Maturity Analysis
2020	$	955
2021		1,019
2022		1,039
2023		1,060
2024		1,081
Thereafter		546
Total	$	5,700
Less: Present value discount		(1,791)
Lease Liability	$	3,909

Schedule of Minimum Future Lease Commitments (ASC 840)

At December 31, 2018, future minimum lease payments under non-cancelable leases under ASC 840 were as follows (in thousands):


2019	$	716
2020		971
2021		1,020
2022		1,041
2023		1,062
Thereafter		1,538
Total	$	6,348

Common stock (Tables)

12 Months Ended

Dec. 31, 2019

Common stock.

Schedule of shares of common stock reserved for the issuance of common stock for vested restricted stock units and the exercise of stock options


	December 31,
	2019	2018
Shares reserved under equity compensation plans	15,389	15,572
Shares reserved for inducement grants	6,331	6,381
Shares reserved for 2018 Notes	3,950	20,937
Shares reserved for 2019 Notes	34,796	—
Total shares reserved	60,466	42,890

Stock-based compensation (Tables)

12 Months Ended

Dec. 31, 2019

Stock-based compensation

Schedule of stock-based compensation expense as reflected in the Company's consolidated statements of operations and comprehensive loss

Stock‑based compensation expense as reflected in the Company’s consolidated statements of operations and comprehensive loss was as follows (in thousands):


	Year ended December 31,
	2019		2018		2017
Research and development	$	1,501	$	2,043	$	1,381
Selling, general and administrative		7,038		4,628		3,652
Total stock-based compensation expense	$	8,539	$	6,671	$	5,033

Summary of stock option activity and related information


				Weighted-average
		Weighted-average		remaining	Aggregate
		exercise price per		contractual term	intrinsic value
	Shares	share		(years)	(in thousands)
Outstanding at December 31, 2018	12,522,867	$	5.42	7.8	$	6,909
Granted	8,280,682	$	2.09
Exercised	(91,907)	$	1.41
Forfeited/cancelled	(3,453,118)	$	4.67
Outstanding at December 31, 2019	17,258,524	$	4.00	7.3	$	185
Vested at December 31, 2019	7,641,065	$	5.45	5.3	$	121
Vested and expected to vest at December 31, 2019(1)	16,728,024	$	4.00	7.3	$	185

(1)

This represents the number of vested options as of December 31, 2019, plus the number of unvested options expected to vest as of December 31, 2019.

Schedule of assumptions used to estimate fair value of each stock option on grant date


	Year ended December 31,
	2019		2018		2017
Risk-free interest rate	1.98	%	2.65	%	2.02	%
Volatility	87	%	81	%	78	%
Dividend yield	—		—		—
Expected term (years)	5.9		5.8		5.8

Schedule of restricted stock units


	Shares	Weighted-average grant date fair value per share
Outstanding at December 31, 2018	306,750	$	5.24
Granted	798,904	$	2.57
Vested	(141,439)	$	6.93
Forfeited/cancelled	(286,126)	$	3.86
Outstanding at December 31, 2019	678,089	$	2.36

Schedule of assumptions used to estimate fair value of each employee stock purchase plan on grant date


	Six Months ended June 30,		Six Months ended December 31,
	2019		2019
Risk-free interest rate	2.46	%	2.10	%
Volatility	79	%	95	%
Dividend yield	—		—
Expected term (years)	0.4		0.5

Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2019

Net Loss per Share

Schedule of computation of basic and diluted net income (loss) per share


	Year Ended December 31,
	2019	2018	2017
Net loss	(149,209)	(72,434)	(67,802)
Less: Other income	—	(25,556)	—
Add: Interest expense	—	3,071	—
Adjusted diluted net loss	(149,209)	(94,919)	(67,802)

Weighted average shares outstanding	74,578	64,962	38,422
Add: Dilutive effect of the Notes	—	4,359	—
Weighted average diluted shares outstanding	74,578	69,321	38,422

Net loss per share - basic	(2.00)	(1.12)	(1.76)
Net loss per share - diluted	(2.00)	(1.37)	(1.76)

Schedule of potentially anti-dilutive securities excluded from calculation of diluted net loss per share


	Year Ended December 31,
	2019	2018	2017
Outstanding stock options	17,258,524	12,522,867	8,719,978
Outstanding restricted stock units	678,089	306,750	—
2018 Notes	3,950,032	—	—
2019 Notes	34,796,363	—	—
Total potentially dilutive securities	56,683,008	12,829,617	8,719,978

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Taxes

Schedule of reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations



	December 31,
	2019		2018
Income tax benefit using U.S. federal statutory rate	21.00	%	21.00	%
State tax benefit, net of federal benefit	4.26	%	6.38	%
Research and development tax credits	1.67	%	5.61	%
Cancellation of debt	(4.76)	%	—	%
Permanent items	(1.41)	%	(0.65)	%
Change in the valuation allowance	(20.33)	%	(31.82)	%
Other	(0.43)	%	(0.52)	%
	—	%	—	%

Schedule of principal components of deferred tax assets and liabilities

The principal components of the Company’s deferred tax assets and liabilities are as follows (in thousands):


	December 31,
	2019		2018
Deferred tax assets:
Net operating loss carryforwards	$	101,039	$	88,829
Capitalized research and development		2,230		2,545
Research and development credits		22,944		19,725
Stock-based compensation		4,445		3,756
Other		1,451		543
Total deferred tax assets		132,109		115,398
Deferred tax liabilities:
Debt discount		(3,702)		(13,617)
Total deferred tax liabilities		(3,702)		(13,617)
Net deferred tax asset prior to valuation allowance		128,407		101,781
Valuation allowance		(128,407)		(101,781)
Net deferred tax asset	$	—	$	—

Quarterly financial information (unaudited, in thousands, except per share data) (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly financial information (unaudited, in thousands, except per share data)

Schedule of Quarterly Financial Information

18. Quarterly financial information (unaudited, in thousands, except per share data)


	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
	Ended		Ended		Ended		Ended
	March 31,		June 30,		September 30,		December 31,
	2019		2019		2019		2019
Revenue:
Product revenue, net	$	1,671	$	3,019	$	4,032	$	3,617
License and collaboration revenue		—		117		5,000		—
Total revenue		1,671		3,136		9,032		3,617
Operating expenses:
Cost of sales - product	$	158	$	377	$	371	$	332
Cost of sales - intangible amortization		392		392		392		393
Research and development		9,758		11,346		12,219		12,455
Selling, general and administrative		26,033		29,298		22,153		23,728
Total operating expenses		36,341		41,413		35,135		36,908
Loss from operations		(34,670)		(38,277)		(26,103)		(33,291)
Other income/(expense)		—		—		—		(641)
Interest income		1,497		1,268		1,005		611
Interest expense		(4,929)		(5,185)		(5,041)		(5,453)
Net loss	$	(38,102)	$	(42,194)	$	(30,139)	$	(38,774)
Net loss per share —basic	$	(0.52)	$	(0.57)	$	(0.41)	$	(0.51)
Net loss per share —diluted	$	(0.52)	$	(0.57)	$	(0.41)	$	(0.51)
Weighted-average number of common shares used in net loss per share —basic and diluted
Net loss per share —basic		73,854		73,877		74,228		76,331
Net loss per share —diluted		73,854		73,877		74,228		76,331


	First Quarter			Second Quarter			Third Quarter		Fourth Quarter
	Ended			Ended			Ended		Ended
	March 31,			June 30,			September 30,		December 31,
	2018			2018			2018		2018
Revenue:
Product revenue, net	$	—		$	—		$	508	$	1,210
License and collaboration revenue		—			10,000			15,000		—
Total revenue		—			10,000			15,508		1,210
Operating expenses:
Cost of sales - product	$	—		$	—		$	49	$	116
Cost of sales - intangible amortization		—			—			31		392
Research and development		10,934			12,381			11,571		8,762
Selling, general and administrative		9,827			15,813			25,426		26,199
Total operating expenses		20,761			28,194			37,077		35,469
Loss from operations		(20,761)			(18,194)			(21,569)		(34,259)
Other income		—			—			—		25,556
Interest income		191			343			763		1,306
Interest expense		(480)			(516)			(862)		(3,952)
Net loss	$	(21,050)		$	(18,367)		$	(21,668)	$	(11,349)
Net loss per share —basic	$	(0.41)		$	(0.30)		$	(0.29)	$	(0.15)
Net loss per share —diluted	$	(0.41)		$	(0.30)		$	(0.29)	$	(0.37)
Weighted-average number of common shares used in net loss per share —basic and diluted
Net loss per share —basic		50,835	(a)		61,256	(a)(b)		73,644		73,766
Net loss per share —diluted		50,835	(a)		61,256	(a)(b)		73,644		91,061	(c)

(a)

In the first and second quarters of 2018, the Company sold 167,065 and 6,314,410 shares of its common stock under the Company’s at-the-market equity offering program, which resulted in net proceeds of $0.6 million and $23.7 million, respectively.

(b)

In the second quarter of 2018, the Company closed underwritten offerings in which it sold 8,944,444 shares and 7,166,666 shares of its common stock at a price of $4.31 per share and $6.00 per share, respectively, for aggregate proceeds, net of underwriting discounts and offering costs, of $38.3 million and $42.9 million, respectively

(c)

In the fourth quarter of 2018, utilizing the “if-converted” method, the Company’s Notes are assumed to have been converted as of the issuance date. Accordingly, the weighted average number of potentially issuable shares upon conversion of the Notes was determined by weighting the number of shares issuable upon conversion at December 31, 2018, or 20,936,548, over the total days outstanding, 76 days, to calculate an additional 17,295,409 shares to be added to the weighted-average number of shares.

Nature of business (Details) - USD ($) $ in Thousands		12 Months Ended
Nature of business (Details) - USD ($) $ in Thousands	Mar. 03, 2020	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
Nature of business
Cash, cash equivalents, restricted cash and short-term investments				$ 111,300
Restricted Cash and Cash Equivalents		$ 741		35,748
Accumulated deficit		(375,576)		$ (524,785)
Proceeds from Issuance of Common Stock		$ 105,156	$ 48,069
Subsequent events
Nature of business
Sale of Stock, Number of Shares Issued in Transaction	46,511,628
Proceeds from Issuance of Common Stock	$ 100,000

Significant accounting policies - Segment and geographic information (Details)	12 Months Ended
	Dec. 31, 2019 item
Segment and geographic information
Number of operating segments	1

Significant accounting policies - Cash, cash equivalents and restricted cash (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Significant accounting policies
Cash and cash equivalents	$ 43,514	$ 129,867
Restricted cash	35,748	741
Total cash, cash equivalents and restricted cash	$ 79,262	$ 130,608	$ 82,338	$ 32,511

Significant accounting policies - Cash, cash equivalents and restricted cash - Security deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted Cash and Cash Equivalents, Noncurrent	$ 35,241	$ 241
Research and development agreement with the Leukemia and Lymphoma Society \| Prepaid Expenses and Other Current Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted Cash and Cash Equivalents, Current	500	500
Letter of credit \| Office and Laboratory Space in Needham, Massachusetts
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted Cash and Cash Equivalents, Noncurrent	200	$ 200
2019 Term Loan Agreement [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted Cash and Cash Equivalents, Noncurrent	$ 35,000

Significant accounting policies - Fair Value Financial Instruments, Measured at Fair Value (Details) - Recurring basis - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financial assets
Cash equivalents	$ 77,176	$ 127,689
Short-term investments	31,992	119,786
Total financial assets	109,168	247,475
Derivative liability	450
Level 1
Financial assets
Cash equivalents	75,678	60,092
Total financial assets	75,678	60,092
Level 2
Financial assets
Cash equivalents	1,498	67,597
Short-term investments	31,992	119,786
Total financial assets	33,490	$ 187,383
Level 3
Financial assets
Derivative liability	$ 450

Significant accounting policies - Fair Value Financial Instruments, Derivative Liability (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Nov. 14, 2019	Oct. 17, 2018
Reconciliation of derivative liability
Fair value recognized upon issuance of Convertible Senior Notes	$ 247	$ 51,531
Fair value adjustment	641	(25,556)
Derivative liability extinguished upon conversion	(438)
Reclassification to equity		$ (25,975)
Derivative liability at	450
5.00% Convertible Senior Notes due 2048
Derivative liability
Interest rate (as a percent)				5.00%
Par value of Notes at issuance	$ 150,000
5.00% Convertible Senior Notes due 2048 \| Discount rate, cash flows
Derivative liability
Discount rate (as a percent)	12.1
5.00% Convertible Senior Notes due 2048 \| Discount rate, credit spreads
Derivative liability
Discount rate (as a percent)	16.2
5.00% Convertible Senior Notes due 2048 \| Risk-adjusted discount rate
Derivative liability
Discount rate (as a percent)	13.08		12.06
5.00% Convertible Senior Notes due 2048 \| Cost Of Equity [Member]
Derivative liability
Discount rate (as a percent)	16.54		17.05

Significant accounting policies - Fair Value Financial Instruments, Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Term loan
Financial liabilities
Debt, carrying value	$ 35.1	$ 25.2
Level 2 \| 5.00% Convertible Senior Notes due 2048
Financial liabilities
Debt, fair value	12.5
Level 2 \| 5.00% Convertible Senior Second Lien Notes due 2048
Financial liabilities
Debt, fair value	50.5
Level 3 \| Term loan
Financial liabilities
Debt, fair value	$ 37.0	$ 26.9

Significant accounting policies - Investments (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($) item	Dec. 31, 2017 USD ($)
Investments
Realized gains or losses on investments	$ 0	$ 0	$ 0
Number of investments in unrealized loss position \| item	2	14
Number of investments in unrealized loss position for more than 12 months \| item	0	0
Unrealized loss on fair value	$ 5,800	$ 46,900
Cash and cash equivalents	43,514	129,867
Gross unrealized gains		8
Total cash, cash equivalents, and investments, gross unrealized gains	14	140
Gross unrealized losses		(1)
Total cash, cash equivalents, and investments, gross unrealized losses		(13)
Cash, cash equivalents, restricted cash and short-term investments	111,300
Amortized Cost
Investments
Cash and cash equivalents		129,860
Total cash, cash equivalents, and investments	111,241	249,526
Fair Value
Investments
Cash and cash equivalents, Fair value		129,867
Cash, cash equivalents, restricted cash and short-term investments	111,255	249,653
Cash and cash equivalents \| Amortized Cost
Investments
Cash and cash equivalents	79,262
Cash and cash equivalents \| Fair Value
Investments
Cash and cash equivalents, Fair value	79,262
Cash and money market accounts \| Amortized Cost
Investments
Cash and cash equivalents	77,764	62,270
Cash and money market accounts \| Fair Value
Investments
Cash and cash equivalents, Fair value	$ 77,764	$ 62,270
Corporate bonds and commercial paper
Investments
Original maturity period, cash and cash equivalents	90 days	90 days
Gross unrealized gains		$ 8
Gross unrealized losses		(1)
Corporate bonds and commercial paper \| Amortized Cost
Investments
Cash and cash equivalents	$ 1,498	67,590
Corporate bonds and commercial paper \| Fair Value
Investments
Cash and cash equivalents, Fair value	1,498	67,597
Investments
Investments
Gross unrealized gains	14	132
Gross unrealized losses		(12)
Investments \| Amortized Cost
Investments
Investments	31,979	119,666
Investments \| Fair Value
Investments
Short-term investments	$ 31,993	$ 119,786
Corporate bonds and commercial paper
Investments
Maturity period, investments	1 year	1 year
Gross unrealized gains	$ 14	$ 132
Gross unrealized losses		(12)
Corporate bonds and commercial paper \| Amortized Cost
Investments
Due within 1 year	31,979	119,666
Corporate bonds and commercial paper \| Fair Value
Investments
Due within 1 year	$ 31,993	$ 119,786

Significant accounting policies - Concentration of Credit Risk (Details)	12 Months Ended
	Dec. 31, 2019 customer item	Dec. 31, 2018 customer
Concentrations of credit risk and off-balance sheet risk
Off-balance sheet concentrations of credit risk description	As of December 31, 2019, the Company's cash, cash equivalents and investments were deposited at three financial institutions and it has no significant off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements.
Trade accounts receivable \| Credit Concentration Risk
Concentrations of credit risk and off-balance sheet risk
Number of financial institutions in which cash, cash equivalents and investments were deposited \| item	3
Number of customer	2	2
Trade accounts receivable \| Credit Concentration Risk \| Minimum
Concentrations of credit risk and off-balance sheet risk
Percentage	50.00%	50.00%
Revenue \| Customer Concentration Risk
Concentrations of credit risk and off-balance sheet risk
Number of customer	4	2
Revenue \| Customer Concentration Risk \| Minimum
Concentrations of credit risk and off-balance sheet risk
Percentage	10.00%	10.00%

Significant accounting policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)
Property and equipment, net
Impairment losses on long-lived assets \| $	$ 0
Share-based compensation
Number of companies expected volatility is based \| item	5
Number of companies with similar characteristics to the Company included in computation \| item	4
Exclusive license agreement \| Infinity
Other assets
Prepaid CRO Expenses \| $	$ 755,000	$ 755,000
Laboratory equipment
Property and equipment, net
Estimated useful lives	5 years
Furniture and fixtures
Property and equipment, net
Estimated useful lives	5 years
Computer equipment
Property and equipment, net
Estimated useful lives	3 years

Significant accounting policies - Revenue Recognition and Accounts Receivable, Net (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Revenue recognition
Practical expedient, incremental cost of obtaining contract	true
Incremental costs of obtaining a contract	$ 0
Minimum
Accounts Receivable
Threshold accounts receivable typically due	30 days
Maximum
Accounts Receivable
Threshold accounts receivable typically due	90 days
Prior to product's expiration
Revenue recognition
Period for eligible returns of expired product	3 months
After product's expiration date
Revenue recognition
Period for eligible returns of expired product	6 months

Significant accounting policies - Recently Issued or Adopted Accounting Standards Updates (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Recently Adopted Accounting Standards Updates
Lease liability	$ 3,909
Right-of use asset	3,077
Restricted Cash	$ 35,241		$ 241
ASU 2016-02
Recently Adopted Accounting Standards Updates
Derecognized deferred rent liability		$ 400
Derecognized lease incentive obligation		200
ASU 2016-02 \| Adjustment
Recently Adopted Accounting Standards Updates
Lease liability		4,000
Right-of use asset		$ 3,400

Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Inventory
Raw materials	$ 955
Work in process	2,040	$ 63
Finished goods	101	264
Total inventories	$ 3,096	$ 327

Property and equipment, net (Details) $ in Thousands	12 Months Ended
Property and equipment, net (Details) $ in Thousands	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Feb. 15, 2018 ft²	Apr. 15, 2014 ft²
Property and equipment
Property and equipment, gross	$ 1,885	$ 1,878
Less: accumulated depreciation	(938)	(509)
Property and equipment, net	947	1,369
Depreciation expenses	429	996	$ 556
Office and Laboratory Space in Needham, Massachusetts
Property and equipment
Area of space \| ft²				27,810	15,197
Leasehold improvements
Property and equipment
Property and equipment, gross	146	146
Leasehold improvements \| Office and Laboratory Space in Needham, Massachusetts
Property and equipment
Area of office space vacated \| ft²				15,197
Gain or loss from disposal of leasehold improvements		0
Furniture and fixtures
Property and equipment
Property and equipment, gross	1,074	1,074
Computer equipment
Property and equipment
Property and equipment, gross	$ 665	$ 658

Intangible assets (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
Intangible assets (Details) - USD ($) $ in Thousands	Nov. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Intangible assets
Less: accumulated amortization		$ (1,992)
Intangible assets, net		20,008	$ 21,577
Payments for milestone payment			22,000
Amortization of acquired intangible asset		1,569	$ 423
Future amortization per year thereafter		1,600
Acquired and in-license rights
Intangible assets
Intangible assets, gross		$ 22,000
Estimated useful life		14 years
Milestone payment payable		$ 22,000
Payments for milestone payment	$ 22,000

Accrued expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued expenses
Compensation and related benefits	$ 7,399	$ 8,749
Contract research organization costs	5,467	6,682
Commercialization costs	3,028	1,979
Interest	897	1,786
Consulting fees	1,610	494
Professional fees	573	482
Other	391	936
Total accrued expenses	$ 19,365	$ 21,108

Long-term debt - Hercules term loan facility (Details) $ in Thousands				9 Months Ended	12 Months Ended
	Nov. 14, 2019 USD ($)	Apr. 23, 2019 USD ($)	Mar. 21, 2017 USD ($) item	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Oct. 11, 2018 USD ($)	Mar. 27, 2017 USD ($)
Long-term debt
Amount drawn					$ 9,670	$ 9,900	$ 14,811
Restricted Cash					35,241	$ 241
2019 Term Loan Agreement [Member]
Long-term debt
Restricted Cash					35,000
Term loan
Long-term debt
Amount drawn				$ 15,000
Term loan \| Maximum
Long-term debt
Number of separate advances \| item			4
Medium-term Notes [Member] \| Original Loan Agreement
Long-term debt
Maximum borrowing capacity			$ 25,000						$ 25,000
Medium-term Notes [Member] \| Amended Term Loan
Long-term debt
Maximum borrowing capacity								$ 50,000
Outstanding amount		$ 25,000
Outstanding accrued interest and the final payment fee (as a percent)		4.50%
Outstanding accrued interest and the final payment fee		$ 1,100
Medium-term Notes [Member] \| 2019 Term Loan Agreement [Member]
Long-term debt
Maximum borrowing capacity		75,000
Outstanding amount		35,000			35,000
Amount drawn		10,000
Remaining borrowing capacity		$ 40,000
Restricted Cash					35,000
Percentage of restricted cash, collateral	100.00%
Future principal payments
2021					14,234
2022					20,766
Total principal payments					$ 35,000
Medium-term Notes [Member] \| 2019 Term Loan Agreement [Member] \| Prime rate
Long-term debt
Basis spread		5.50%
Medium-term Notes [Member] \| 2019 Term Loan Agreement [Member] \| Minimum
Long-term debt
Interest rate		9.75%
Medium-term Notes [Member] \| 2019 Term Loan Agreement [Member] \| Maximum
Long-term debt
Interest rate		12.00%
Medium-term Notes [Member] \| 2019 Term Loan Agreement [Member] \| On or before April 30, 2020
Long-term debt
Net product revenue		$ 37,500
Medium-term Notes [Member] \| 2019 Term Loan Agreement [Member] \| On or before June 30, 2020
Long-term debt
Net product revenue		50,000
Medium-term Notes [Member] \| 2019 Term Loan Agreement [Member] \| Trailing six months prior to December 31, 2020
Long-term debt
Net product revenue	$ 20,000	40,000
Medium-term Notes [Member] \| 2019 Term Loan Agreement [Member] \| Company’s option through December 31, 2021 \| Maximum
Long-term debt
Amount drawn		25,000
Medium-term Notes [Member] \| 2019 Term Loan Agreement [Member] \| Plan \| Maximum
Long-term debt
Amount drawn		$ 15,000

Product revenue reserves and allowances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Product revenue reserves and allowances
Product revenue reserves and allowances at beginning	$ 276
Provision related to sales in the current year	2,500	$ 348
Adjustments related to prior period sales	(76)
Credits and payments made	(1,886)	(72)
Product revenue reserves and allowances at ending	814	276
Trade discounts and allowances
Product revenue reserves and allowances
Product revenue reserves and allowances at beginning	29
Provision related to sales in the current year	512	69
Credits and payments made	(430)	(40)
Product revenue reserves and allowances at ending	111	29
Third-Party Payer chargebacks, discounts and fees
Product revenue reserves and allowances
Product revenue reserves and allowances at beginning	88
Provision related to sales in the current year	1,306	120
Credits and payments made	(1,139)	(32)
Product revenue reserves and allowances at ending	255	88
Government rebates and other incentives
Product revenue reserves and allowances
Product revenue reserves and allowances at beginning	157
Provision related to sales in the current year	608	157
Adjustments related to prior period sales	(76)
Credits and payments made	(317)
Product revenue reserves and allowances at ending	372	157
Returns
Product revenue reserves and allowances
Product revenue reserves and allowances at beginning	2
Provision related to sales in the current year	74	2
Product revenue reserves and allowances at ending	$ 76	$ 2

Leases - Leases (Details) - Office and Laboratory Space in Needham, Massachusetts $ in Thousands	Feb. 15, 2018 USD ($) ft²	Apr. 15, 2014 ft²
Leases
Area of space \| ft²	27,810	15,197
Minimum
Leases
Operating lease expense	$ 660
Maximum
Leases
Operating lease expense	$ 1,100

Leases - Balance sheet and other information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Leases
Right-of use asset	$ 3,077
Lease liability	3,909
Lease Expense
Operating lease expense	885
Total Lease Expense	885
Other Information - Operating Leases
Operating cash flows paid for amounts included in measurement of lease liabilities	$ 703
Weighted average remaining lease term (in years)	5 years 6 months
Weighted average discount rate	14.60%
Maturity Analysis
2020	$ 955
2021	1,019
2022	1,039
2023	1,060
2024	1,081
Thereafter	546
Total	5,700
Less: Present value discount	(1,791)
Lease Liability	$ 3,909

Leases - Schedule of Minimum Future Lease Commitments (ASC 840) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	$ 716
2020	971
2021	1,020
2022	1,041
2023	1,062
Thereafter	1,538
Total	6,348
Operating Leases, Rent Expense, Net [Abstract]
Rent expense	$ 800

Common stock (Details) $ in Millions			3 Months Ended		12 Months Ended	16 Months Ended
Common stock (Details) $ in Millions	Aug. 28, 2017 USD ($)	Mar. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) shares	Mar. 31, 2018 USD ($) shares	Dec. 31, 2019 USD ($) Vote shares	Dec. 31, 2018 USD ($) shares
Common stock
Shares reserved for issuance					60,466,000	42,890,000
Number of votes entitled for each share of common stock \| Vote					1
5.00% Convertible Senior Notes due 2048
Common stock
Shares reserved for issuance					3,950,000	20,937,000
5.00% Convertible Senior Second Lien Notes due 2048
Common stock
Shares reserved for issuance					34,796,000
At-the-market equity offering program \| Common stock
Common stock
Issuance of common stock, net of issuance costs (in shares)			6,314,410	167,065
Net proceeds from issuance of stock \| $			$ 23.7	$ 0.6
Inducement Award Program
Common stock
Shares reserved for issuance					6,331,000	6,381,000
2017 ATM Program \| At-the-market equity offering program \| Common stock
Common stock
Maximum value of common stock allowed to be sold \| $	$ 75.0	$ 35.0
Issuance of common stock, net of issuance costs (in shares)					0	11,518,354
Net proceeds from issuance of stock \| $						$ 47.3
Additional gross proceeds issuable \| $					$ 26.6
Equity compensation plans
Common stock
Shares reserved for issuance					15,389,000	15,572,000

Common stock - Equity offerings (Details) - Follow-on offerings - USD ($) $ / shares in Units, $ in Millions					3 Months Ended
	Jun. 14, 2018	May 23, 2018	May 16, 2018	Dec. 14, 2017	Jun. 30, 2018
Cantor \| Underwriting Agreement
Common stock
Options are exercisable from date of prospectus supplement			30 days
Common stock \| Underwriting Agreement
Common stock
Issuance of common stock, net of issuance costs (in shares)					8,944,444
Share price (in dollars per share)					$ 4.31
Net proceeds from issuance of stock					$ 38.3
Common stock \| Purchase Agreement
Common stock
Issuance of common stock, net of issuance costs (in shares)					7,166,666
Share price (in dollars per share)					$ 6.00
Net proceeds from issuance of stock					$ 42.9
Common stock \| Cantor \| Underwriting Agreement
Common stock
Issuance of common stock, net of issuance costs (in shares)		1,166,666
Net proceeds from issuance of stock		$ 38.3
Common stock \| Cantor \| Underwriting Agreement \| Plan
Common stock
Issuance of common stock, net of issuance costs (in shares)			7,777,778
Share price (in dollars per share)			$ 4.31
Common stock \| Consonance \| Purchase Agreement
Common stock
Issuance of common stock, net of issuance costs (in shares)	7,166,666
Share price (in dollars per share)	$ 6.00
Net proceeds from issuance of stock	$ 42.9
Common stock \| BTIG, LLC \| Underwriting Agreement
Common stock
Issuance of common stock, net of issuance costs (in shares)				8,422,877
Share price (in dollars per share)				$ 2.97
Net proceeds from issuance of stock				$ 24.7

Stock-based compensation - Stock-Based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock-based compensation
Total stock-based compensation expense	$ 8,539	$ 6,671	$ 5,033
Research and development
Stock-based compensation
Total stock-based compensation expense	1,501	2,043	1,381
Selling, general and administrative
Stock-based compensation
Total stock-based compensation expense	$ 7,038	$ 4,628	$ 3,652

Stock-based compensation - Equity Plans (Details)	12 Months Ended
Stock-based compensation - Equity Plans (Details)	Dec. 31, 2019 item
Stock-based compensation
Number of equity compensation plans	2
Stock options
Stock-based compensation
Expiration term	10 years
Stock options \| Four Annual Payments
Stock-based compensation
Vesting percentage	25.00%
Vesting period	1 year
Stock options \| First Anniversary Payment
Stock-based compensation
Vesting percentage	6.25%
Vesting period	3 months

Stock-based compensation - Stock Plans and Activity (Details) - shares				1 Months Ended					12 Months Ended
	Jan. 01, 2018	Jan. 01, 2017	Jan. 01, 2016	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017	Dec. 31, 2016	Feb. 29, 2012	Dec. 31, 2019	Dec. 31, 2017	Dec. 18, 2018	Dec. 31, 2014
Stock options
Stock-based compensation
Granted (in shares)									8,280,682
Exercised (in shares)									91,907
Restricted Stock Units
Stock-based compensation
Granted (in shares)									798,904	0
Forfeited (in shares)									286,126
Vested (in shares)									141,439
2012 Incentive Plan
Stock-based compensation
Number of shares reserved								3,428,571			16,628,425
Additional number of shares authorized for issuance	1,285,714	1,285,714	1,285,714					30,101
Percentage of outstanding shares of common stock used to compute annual increase in number of shares reserved									4.00%
2012 Incentive Plan \| Maximum
Stock-based compensation
Annual increase in number of shares reserved									1,285,714
2012 Incentive Plan \| Stock options
Stock-based compensation
Granted (in shares)									19,733,446
Forfeited (in shares)									5,644,811
Exercised (in shares)									456,865
2012 Incentive Plan \| Restricted Stock Units
Stock-based compensation
Granted (in shares)									1,922,622
Forfeited (in shares)									443,277
Vested (in shares)									851,256
Inducement Award Program
Stock-based compensation
Number of shares reserved												750,000
Additional number of shares authorized for issuance				1,250,000	1,700,000	2,500,000	580,000
Shares available for future grants									3,608,183
Inducement Award Program \| Stock options
Stock-based compensation
Granted (in shares)									6,094,671
Forfeited (in shares)									2,212,738
Exercised (in shares)									323,750
Inducement Award Program \| Restricted Stock Units
Stock-based compensation
Granted (in shares)									162,200
Forfeited (in shares)									62,200
Vested (in shares)									50,000

Stock-based compensation - Stock Options (Details) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended	12 Months Ended
	Sep. 30, 2017 shares	Oct. 31, 2016 shares	Jun. 30, 2016 shares	Mar. 31, 2018 shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) item $ / shares shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($)
Additional disclosures
Stock-based compensation expense					$ 8,539	$ 6,671	$ 5,033
Stock options
Shares
Outstanding at the beginning of the period (in shares) \| shares					12,522,867
Granted (in shares) \| shares					8,280,682
Exercised (in shares) \| shares					(91,907)
Forfeited/cancelled (in shares) \| shares					(3,453,118)
Outstanding at the end of the period (in shares) \| shares					17,258,524	12,522,867
Vested at the end of the period (in shares) \| shares					7,641,065
Vested and expected to vest at end of period (in shares) \| shares					16,728,024
Weighted-average exercise price per share
Outstanding at the beginning of the period (in dollars per share) \| $ / shares					$ 5.42
Granted (in dollars per share) \| $ / shares					2.09
Exercised (in dollars per share) \| $ / shares					1.41
Forfeited/cancelled (in dollars per share) \| $ / shares					4.67
Outstanding at the end of the period (in dollars per share) \| $ / shares					4.00	$ 5.42
Vested at the end of the period (in dollars per share) \| $ / shares					5.45
Vested and expected to vest at end of the period (in dollars per share) \| $ / shares					$ 4.00
Weighted-average remaining contractual term
Outstanding at the end of the period					7 years 3 months 18 days	7 years 9 months 18 days
Vested at the end of the period					5 years 3 months 18 days
Vested and expected to vest at the end of the period					7 years 3 months 18 days
Aggregate intrinsic value
Outstanding at the beginning of the period (in dollars)					$ 6,909
Outstanding at the end of the period (in dollars)					185	$ 6,909
Vested at the end of the period (in dollars)					121
Vested and expected to vest at end of the period (in dollars)					185
Aggregate intrinsic value of options exercised (in dollars)					$ 100	$ 1,800
Assumptions used to estimate fair value of each stock-based award on the grant date
Risk-free interest rate (as a percent)					1.98%	2.65%	2.02%
Volatility (as a percent)					87.00%	81.00%	78.00%
Dividend yield (as a percent)					0.00%	0.00%	0.00%
Expected term					5 years 10 months 24 days	5 years 9 months 18 days	5 years 9 months 18 days
Additional disclosures
Stock-based compensation expense					$ 7,100	$ 5,600	$ 4,500
Weighted-average grant date fair value (in dollars per share) \| $ / shares					$ 1.44	$ 3.72	$ 1.83
Fair value of vested stock options					$ 7,300	$ 4,700	$ 4,800
Total unrecognized stock-based compensation expense (in dollars)					$ 14,000
Weighted-average recognition period					2 years 9 months 18 days
Stock options vesting based on performance
Shares
Granted (in shares) \| shares			500,000	582,500
Vested at the end of the period (in shares) \| shares	250,000	250,000
Additional disclosures
Stock-based compensation expense					$ 100	$ 700	$ 400	$ 200
Number of performance conditions achieved \| item						2
Number of non-vested stock options \| shares					260,000
Weighted average exercise price \| $ / shares					$ 1.52
Weighted average remaining contractual term					9 years 7 months 6 days
Aggregate intrinsic value					$ 0
Percentage of performance conditions achieved								50.00%

Stock-based compensation - Restricted Stock (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) item $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) shares
Additional disclosures
Stock-based compensation expense \| $	$ 8,539	$ 6,671	$ 5,033
Restricted Stock Units
Stock-based compensation
Number of shares holder to receive when RSU vests	1
Shares
Unvested at the beginning of the period (in shares)	306,750
Granted (in shares)	798,904		0
Vested (in shares)	(141,439)
Forfeited (in shares)	(286,126)
Unvested at the end of the period (in shares)	678,089	306,750
Weighted-average grant date fair value
Unvested at the beginning of the period (in dollars per share) \| $ / shares	$ 5.24
Granted (in dollars per share) \| $ / shares	2.57
Vested (in dollars per share) \| $ / shares	6.93
Forfeited/cancelled (in dollars per share) \| $ / shares	3.86
Unvested at the end of the period (in dollars per share) \| $ / shares	$ 2.36	$ 5.24
Additional disclosures
Stock-based compensation expense \| $	$ 1,000	$ 400
Fair value of shares vested \| $	300	$ 0	$ 0
Unrecognized stock-based compensation expense \| $	$ 1,200
Weighted-average recognition period	2 years 7 months 6 days
Restricted Stock Units \| Maximum
Additional disclosures
Stock-based compensation expense \| $			$ 100
Restricted Stock Units \| Four Annual Payments
Stock-based compensation
Number of installments \| item	4
Number of anniversaries \| item	4
Restricted Stock Units \| First Anniversary Payment
Stock-based compensation
Vesting percentage	100.00%

Stock-based compensation - Employee Stock Purchase Plan (Details) $ in Thousands		6 Months Ended		12 Months Ended
	Dec. 18, 2018 item shares	Dec. 31, 2019 shares	Jun. 30, 2019	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)
Stock-based compensation
Shares reserved for issuance \| shares		60,466,000		60,466,000	42,890,000
Assumptions used to estimate fair value of each stock-based award on the grant date
Stock-based compensation expense				$ 8,539	$ 6,671	$ 5,033
Proceeds from the issuance of common stock, net					$ 105,156	$ 48,069
2018 ESPP
Stock-based compensation
Percent of common stock at market price to be purchased	85.00%
Shares reserved for issuance \| shares	2,000,000
Number of vesting periods \| item	2
Vesting period	6 months
Assumptions used to estimate fair value of each stock-based award on the grant date
Risk-free interest rate (as a percent)		2.10%	2.46%
Volatility (as a percent)		95.00%	79.00%
Expected term		6 months	4 months 24 days
Stock-based compensation expense				$ 400
Issuance of common stock under ESPP \| shares				341,701
Proceeds from the issuance of common stock, net				$ 400

Convertible Senior Notes (Details) $ / shares in Units, $ in Thousands					2 Months Ended	3 Months Ended		12 Months Ended
	Dec. 23, 2019 USD ($) D $ / shares	Nov. 14, 2019 USD ($) D $ / shares	Dec. 18, 2018 USD ($)	Oct. 17, 2018 USD ($) item D $ / shares	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares	Nov. 11, 2018 $ / shares	Oct. 11, 2018 $ / shares
Convertible Notes
Repayments of Convertible Debt								$ 12,174
Net proceeds									$ 145,297
Common stock, par value (in dollars per share) \| $ / shares					$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Initial conversion rate				139.5771
Change in fair value of conversion feature								$ (641)	$ 25,556
Change in fair value of conversion option of Notes on exchange								13,640
Other Nonoperating Income (Expenses)						$ (641)	$ 25,556	(641)	$ 25,556
Interest make-whole payments on the 2019 Notes								438
5.00% Convertible Senior Notes due 2048
Convertible Notes
Aggregate principal amount				$ 150,000
Debt Conversion, Original Debt, Amount	$ 7,400	$ 114,300
Repayments of Convertible Debt	700	11,400
Interest rate (as a percent)				5.00%
Net proceeds				$ 145,300
Common stock, par value (in dollars per share) \| $ / shares				$ 0.0001
Initial conversion price of Common Stock \| $ / shares				$ 7.16
Conversion premium above the last reported sales price of the Common Stock (as a percent)				15.00%
Sale price of the Common Stock \| $ / shares											$ 6.23
Percentage of stock price trigger for conversion				130.00%
Trading days \| item				20
Consecutive trading days \| D				30
Percentage price of principal amount to be purchased plus accrued and unpaid interest				100.00%
Debt discount				$ 51,500
Derivative liability				$ 51,500
Fair value of conversion feature			$ 25,900
Change in fair value of conversion feature			$ 25,600
5.00% Convertible Senior Second Lien Notes due 2048
Convertible Notes
Debt Conversion, Original Debt, Amount								9,500
Debt Conversion, Converted Instrument, Amount	$ 4,000	$ 62,900
Interest rate (as a percent)	5.00%	5.00%
Gains (Losses) on Restructuring of Debt								0
Common stock, par value (in dollars per share) \| $ / shares	$ 0.0001	$ 0.0001
Initial conversion rate	606.0606	606.0606
Initial conversion price of Common Stock \| $ / shares	$ 1.65	$ 1.65
Conversion premium above the last reported sales price of the Common Stock (as a percent)	52.80%	52.80%
Sale price of the Common Stock \| $ / shares	$ 1.08									$ 1.08
Percentage of stock price trigger for conversion	121.00%	121.00%
Trading days \| D	20	20
Consecutive trading days \| D	30	30
Debt discount	$ 200
Derivative liability	$ 200
Change in fair value of conversion option of Notes on exchange								13,600
Fair value of 2019 Interest Make-Whole Provision					$ 500	$ 500		500
Other Nonoperating Income (Expenses)					600
Interest expense								$ 16,000
Debt Conversion, Converted Instrument, Shares Issued \| shares								5,767,872
Interest make-whole payments on the 2019 Notes					$ 400			$ 400

Net Loss per Share - basic and diluted net income (loss) per share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
	Dec. 31, 2018	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
Computation of basic and diluted net income (loss) per share:
Net loss		$ (38,774)	$ (30,139)	$ (42,194)	$ (38,102)	$ (11,349)	$ (21,668)	$ (18,367)	$ (21,050)	$ (149,209)	$ (72,434)	$ (67,802)
Embedded Derivative, Gain (Loss) on Embedded Derivative, Net											(25,556)
Less: Other income		$ 641				$ (25,556)				641	(25,556)
Add: Interest expense											3,071
Adjusted diluted net loss										$ (149,209)	$ (94,919)	$ (67,802)
Weighted average shares outstanding										74,578,000	64,962,000	38,422,000
Add: Dilutive effect of the Notes	4,359,391					17,295,409					4,359,000
Weighted average diluted shares outstanding		76,331,000	74,228,000	73,877,000	73,854,000	91,061,000	73,644,000	61,256,000	50,835,000	74,578,000	69,321,000	38,422,000
Net loss per share - basic		$ (0.51)	$ (0.41)	$ (0.57)	$ (0.52)	$ (0.15)	$ (0.29)	$ (0.30)	$ (0.41)	$ (2.00)	$ (1.12)	$ (1.76)
Net loss per share - diluted		$ (0.51)	$ (0.41)	$ (0.57)	$ (0.52)	$ (0.37)	$ (0.29)	$ (0.30)	$ (0.41)	$ (2.00)	$ (1.37)	$ (1.76)

Net Loss per Share (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
Net Loss per Share (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net loss per share
Change in fair value of the bifurcated derivative				$ (25,556)
Interest expense				$ 3,071
Number of shares at issue				20,936,548
Number of shares at issuance	20,936,548	20,936,548
Number of days outstanding to calculate weighted average shares	76 days	76 days
Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)			56,683,008	12,829,617	8,719,978
Weighted-average number of shares of adjustments	4,359,391	17,295,409		4,359,000
Stock options
Net loss per share
Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)			17,258,524	12,522,867	8,719,978
Restricted Stock Units
Net loss per share
Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)			678,089	306,750
5.00% Convertible Senior Notes due 2048
Net loss per share
Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)			3,950,032
5.00% Convertible Senior Second Lien Notes due 2048
Net loss per share
Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)			34,796,363

Income Taxes - Operating Loss Carryforwards (Details) $ in Millions	Dec. 31, 2019 USD ($)
Federal
Operating loss carryforwards
Net operating loss carryforwards	$ 371.7
Operating loss carryforwards, indefinite period	136.3
State
Operating loss carryforwards
Net operating loss carryforwards	$ 392.3

Income Taxes - Tax Credits (Details) $ in Millions	12 Months Ended
Income Taxes - Tax Credits (Details) $ in Millions	Dec. 31, 2019 USD ($)
Tax credit carryforwards
Testing period for changes in ownership interest of significant shareholders	3 years
Federal
Tax credit carryforwards
Tax credits	$ 20.6
State
Tax credit carryforwards
Tax credits	$ 3.0

Income Taxes - Reconciliation of Income Taxes and Deferred Tax Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of income taxes computed using the U.S. federal statutory rate
Income tax benefit using U.S. federal statutory rate (as a percent)	21.00%	21.00%
State tax benefit, net of federal benefit (as a percent)	4.26%	6.38%
Research and development tax credits (as a percent)	1.67%	5.61%
Cancellation of debt	(4.76%)
Permanent items (as a percent)	(1.41%)	(0.65%)
Change in the valuation allowance (as a percent)	(20.33%)	(31.82%)
Other (as a percent)	(0.43%)	(0.52%)
Deferred tax assets:
Net operating loss carryforwards	$ 101,039,000	$ 88,829,000
Capitalized research and development	2,230,000	2,545,000
Research and development credits	22,944,000	19,725,000
Stock-based compensation	4,445,000	3,756,000
Other	1,451,000	543,000
Total deferred tax assets	132,109,000	115,398,000
Deferred tax liabilities:
Derivative liability	(3,702,000)	(13,617,000)
Total deferred tax liabilities	(3,702,000)	(13,617,000)
Net deferred tax asset	128,407,000	101,781,000
Valuation allowance	(128,407,000)	$ (101,781,000)
Additional disclosures
Increase (decrease) in valuation allowance	26,600,000
Unrecognized tax benefits	0
Interest and penalties accrued related to unrecognized tax benefits	0
Liability for uncertain tax positions	$ 0

Commitments and contingencies (Details) - Office and Laboratory Space in Needham, Massachusetts $ in Millions	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Feb. 15, 2018 ft²	Apr. 15, 2014 ft²
Property, Plant and Equipment [Line Items]
Area of space \| ft²			27,810	15,197
Letter of credit
Property, Plant and Equipment [Line Items]
Security deposit \| $	$ 0.2	$ 0.2

License and collaboration agreements - Infinity (Details) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
	Mar. 05, 2019	Nov. 30, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Exclusive license agreement \| Infinity
License and collaboration agreements
Payments upon study meeting certain pre-specified criteria		$ 6.0
Payments on approval of new drug application		$ 22.0
Royalty obligations term		10 years
Percentage of reduction in royalty on net sales		50.00%
Deduction in royalty payments as percentage of amount paid to third party		50.00%
Percentage royalty reductions capped		50.00%
Percentage of additional royalty on worldwide net sales		4.00%
Percentage of net sales for royalty obligations in the United States		1.00%
Percentage of reduction of royalty rate on basis of non-patent regulatory exclusivity		50.00%
Royalty payments			$ 1.0	$ 0.1	$ 0.0
Purchase And Sale Agreement Between Infinity and Healthcare Royalty Partners III, L.P. [Member]
License and collaboration agreements
Upfront payment	$ 30.0
Purchase And Sale Agreement Between Infinity and Healthcare Royalty Partners III, L.P. [Member] \| Maximum
License and collaboration agreements
Potential milestone payment receivable	$ 20.0

License and collaboration agreements - Pfizer (Details) - Exclusive license agreement - PFIZER $ in Millions	Jul. 11, 2012 USD ($) item shares
License and collaboration agreements
Number of products required from licensor for an agreed upon price \| item	1
One-time cash payment	$ 1.5
Issuance of common stock, net of issuance costs (in shares) \| shares	192,012
Royalty obligations term	10 years
Maximum
License and collaboration agreements
Eligible amount payable on developmental milestones to Pfizer	$ 2.0
Additional payable on successful attainment of regulatory and commercial sales milestones	$ 125.0

License and collaboration agreements - Yakult (Details) $ in Thousands		1 Months Ended	3 Months Ended							12 Months Ended
	Jun. 05, 2018 USD ($) item	Jun. 30, 2018 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
License and collaboration agreements
Revenue recognized			$ 3,617	$ 9,032	$ 3,136	$ 1,671	$ 1,210	$ 15,508	$ 10,000	$ 17,456	$ 26,718
License And Collaboration Agreement \| Yakult
License and collaboration agreements
Proceeds received		$ 10,000								$ 100
Maximum aggregate payments entitled to receive if all milestones successfully achieved	$ 90,000
Agreement obligations expire from first commercial sale of product (in years)	10 years
Number of days written prior notice required for other party to terminate agreement	180 days
Number of days written notice required to terminate agreement if fails to cure breach	60 days
Number of potential research and development activities \| item	2
Number of material promises \| item	2
Number of performance obligations at outset of the Agreement \| item	1
Revenue recognized											$ 10,000

License and collaboration agreements - CSPC (Details) $ in Thousands		1 Months Ended	3 Months Ended							12 Months Ended
	Sep. 25, 2018 USD ($) item	Aug. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
License and collaboration agreements
Revenue recognized			$ 3,617	$ 9,032	$ 3,136	$ 1,671	$ 1,210	$ 15,508	$ 10,000	$ 17,456	$ 26,718
Exclusivity Agreement \| CSPC
License and collaboration agreements
Proceeds received		$ 5,000
License And Collaboration Agreement \| CSPC
License and collaboration agreements
Upfront, non-refundable payment obligation to be received prior to initial Exclusivity Fee	$ 15,000
Maximum aggregate payments entitled to receive if all milestones successfully achieved	$ 160,000
Agreement obligations expire from first commercial sale of product (in years)	10 years
Number of days written prior notice required for other party to terminate agreement	180 days
Number of days written notice required to terminate agreement if fails to cure breach	60 days
Number of potential research and development activities \| item	2
Number of material promises \| item	2
Number of performance obligations at outset of the Agreement \| item	1
Revenue recognized											$ 15,000

License and collaboration agreements - Sanofi (Details) $ in Thousands		1 Months Ended	3 Months Ended							12 Months Ended
	Jul. 25, 2019 USD ($) item	Aug. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
License and collaboration agreements
Revenue recognized			$ 3,617	$ 9,032	$ 3,136	$ 1,671	$ 1,210	$ 15,508	$ 10,000	$ 17,456	$ 26,718
Sanofi
License and collaboration agreements
Number of additional milestones achieved										0
License And Collaboration Agreement \| Sanofi
License and collaboration agreements
Proceeds received		$ 5,000
Maximum aggregate payments entitled to receive if all milestones successfully achieved	$ 42,000
Agreement obligations expire from first commercial sale of product (in years)	10 years
Number of days written prior notice required for other party to terminate agreement	180 days
Number of days written notice required to terminate agreement if fails to cure breach	60 days
Number of material promises \| item	2
Number of performance obligations at outset of the Agreement \| item	1
Revenue recognized										$ 5,000

Employee benefit plan (Details) - USD ($) $ in Millions	12 Months Ended
Employee benefit plan (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee benefit plan
Contributions made under 401(k) plan	$ 1.3	$ 0.8	$ 0.3

Quarterly financial information (unaudited, in thousands, except per share data) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Revenue:
Total revenue	$ 3,617	$ 9,032	$ 3,136	$ 1,671	$ 1,210	$ 15,508	$ 10,000		$ 17,456	$ 26,718
Operating expenses:
Cost of sales - product	332	371	377	158	116	49			1,238	165
Cost of sales - intangible amortization	393	392	392	392	392	31			1,569	423
Research and development	12,455	12,219	11,346	9,758	8,762	11,571	12,381	$ 10,934	45,778	43,648	$ 46,423
Selling, general and administrative	23,728	22,153	29,298	26,033	26,199	25,426	15,813	9,827	101,212	77,265	21,381
Total operating expenses	36,908	35,135	41,413	36,341	35,469	37,077	28,194	20,761	149,797	121,501	67,804
Loss from operations	(33,291)	(26,103)	(38,277)	(34,670)	(34,259)	(21,569)	(18,194)	(20,761)	(132,341)	(94,783)	(67,804)
Other (expense)/ income	(641)				25,556				(641)	25,556
Interest income	611	1,005	1,268	1,497	1,306	763	343	191	4,381	2,603	561
Interest expense	(5,453)	(5,041)	(5,185)	(4,929)	(3,952)	(862)	(516)	(480)	(20,608)	(5,810)	(559)
Net loss	$ (38,774)	$ (30,139)	$ (42,194)	$ (38,102)	$ (11,349)	$ (21,668)	$ (18,367)	$ (21,050)	$ (149,209)	$ (72,434)	$ (67,802)
Net loss per share—basic	$ (0.51)	$ (0.41)	$ (0.57)	$ (0.52)	$ (0.15)	$ (0.29)	$ (0.30)	$ (0.41)	$ (2.00)	$ (1.12)	$ (1.76)
Net loss per share—diluted	$ (0.51)	$ (0.41)	$ (0.57)	$ (0.52)	$ (0.37)	$ (0.29)	$ (0.30)	$ (0.41)	$ (2.00)	$ (1.37)	$ (1.76)
Weighted average common shares outstanding used in computing:
Net loss per share—basic (in shares)	76,331	74,228	73,877	73,854	73,766	73,644	61,256	50,835	74,578	64,962	38,422
Net loss per share—diluted (in shares)	76,331	74,228	73,877	73,854	91,061	73,644	61,256	50,835	74,578	69,321	38,422
License and collaboration revenue
Revenue:
Total revenue		$ 5,000	$ 117			$ 15,000	$ 10,000		$ 5,117	$ 25,000
Product revenue, net
Revenue:
Total revenue	$ 3,617	$ 4,032	$ 3,019	$ 1,671	$ 1,210	$ 508			$ 12,339	$ 1,718

Quarterly financial information (unaudited, in thousands, except per share data) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended			12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2018
Number of shares at issuance	20,936,548	20,936,548
Number of days outstanding to calculate weighted average shares	76 days	76 days
Weighted-average number of shares of adjustments	4,359,391	17,295,409			4,359,000
At-the-market equity offering program \| Common stock
Issuance of common stock, net of issuance costs (in shares)			6,314,410	167,065
Net proceeds from issuance of stock			$ 23.7	$ 0.6
Follow-on offerings \| Common stock \| Underwriting Agreement
Issuance of common stock, net of issuance costs (in shares)			8,944,444
Net proceeds from issuance of stock			$ 38.3
Share price (in dollars per share)			$ 4.31
Follow-on offerings \| Common stock \| Purchase Agreement
Issuance of common stock, net of issuance costs (in shares)			7,166,666
Net proceeds from issuance of stock			$ 42.9
Share price (in dollars per share)			$ 6.00

Subsequent events (Details) $ / shares in Units, $ in Thousands			1 Months Ended		2 Months Ended	3 Months Ended	12 Months Ended
	Mar. 03, 2020 USD ($) $ / shares shares	Feb. 27, 2020 item	Mar. 31, 2020 USD ($) shares	Feb. 29, 2020 USD ($)	Mar. 11, 2020 USD ($) shares	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Subsequent events
Proceeds from the issuance of common stock, net								$ 105,156	$ 48,069
Subsequent events
Subsequent events
Issuance of common stock, net of issuance costs (in shares) \| shares	46,511,628
Share price (in dollars per share) \| $ / shares	$ 2.15
Proceeds from the issuance of common stock, net	$ 100,000
Chugai Pharmaceutical Co., Ltd. [Member] \| Subsequent events \| License and collaboration revenue
Subsequent events
Collaborative Arrangements One Time Cash Payment				$ 3,000
One-time Termination Benefits \| Subsequent events
Subsequent events
Charge of restructuring						$ 1,900
One-time Termination Benefits \| Scenario, Forecast \| Subsequent events
Subsequent events
Elimination of positions \| item		31
One-time Termination Benefits \| Scenario, Forecast \| Subsequent events \| Maximum
Subsequent events
Reduction in operating expenses						85,000
One-time Termination Benefits \| Scenario, Forecast \| Subsequent events \| Minimum
Subsequent events
Reduction in operating expenses						$ 70,000
5.00% Convertible Senior Second Lien Notes due 2048
Subsequent events
Debt Conversion, Original Debt, Amount							$ 9,500
Debt Conversion, Converted Instrument, Shares Issued \| shares							5,767,872
5.00% Convertible Senior Second Lien Notes due 2048 \| Subsequent events
Subsequent events
Debt Conversion, Original Debt, Amount					$ 51,200
Debt Conversion, Converted Instrument, Shares Issued \| shares					31,044,835
Convertible Debt					$ 6,200
5.00% Convertible Senior Second Lien Notes due 2048 \| Scenario, Forecast
Subsequent events
Debt Conversion, Original Debt, Amount			$ 6,200
Debt Conversion, Converted Instrument, Shares Issued \| shares			3,800,000