Curis (CRIS) 10-K 16 Mar 21 2020 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Mar. 12, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	000-30347
Entity Registrant Name	CURIS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3505116
Entity Address, Address Line One	128 Spring Street, Building C - Suite 500
Entity Address, City or Town	Lexington
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02421
City Area Code	617
Local Phone Number	503-6500
Title of 12(b) Security	Common Stock, $0.01 par value per share
Trading Symbol	CRIS
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 54.4
Entity Common Stock, Shares Outstanding		91,507,498
Documents Incorporated by Reference	Specified portions of the registrant’s proxy statement for the annual meeting of stockholders scheduled to be held on May 27, 2021, which are to be filed with the Commission not later than 120 days after the close of the Registrant’s fiscal year ended December 31, 2020 pursuant to Regulation 14A, have been incorporated by reference in Items 10-14 of Part III of this Annual Report on Form 10-K.
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0001108205

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 129,610	$ 15,430
Restricted cash, short-term	0	153
Short-term investments	38,884	5,113
Accounts receivable	3,043	3,244
Prepaid expenses and other current assets	1,215	1,063
Total current assets	172,752	25,003
Long-term investments	14,564	0
Property and equipment, net	663	154
Restricted cash, long-term	816	816
Operating lease right-of-use asset	6,578	149
Goodwill	8,982	8,982
Other assets	3	3
Total assets	204,358	35,107
Current liabilities:
Accounts payable	4,166	4,465
Accrued liabilities	3,625	1,910
Current portion of operating lease liability	1,731	166
Current portion of long-term debt	557	0
Total current liabilities	10,079	6,541
Long-term operating lease liability	5,040	0
Liability related to the sale of future royalties, net	58,235	62,477
Long-term debt, net	334	0
Total liabilities	73,688	69,018
Stockholders’ equity (deficit):
Common stock, $0.01 par value—151,875,000 shares authorized, 91,502,461 shares issued and outstanding at December 31, 2020; 101,250,000 shares authorized, 33,241,793 shares issued and outstanding at December 31, 2019	915	332
Additional paid-in capital	1,176,647	982,738
Accumulated deficit	(1,046,889)	(1,016,981)
Accumulated other comprehensive loss	(3)	0
Total stockholders’ equity (deficit)	130,670	(33,911)
Total liabilities and stockholders’ equity (deficit)	$ 204,358	$ 35,107

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	151,875,000	101,250,000
Common stock, shares issued (in shares)	91,502,461	33,241,793
Common stock, shares outstanding (in shares)	91,502,461	33,241,793

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Revenues, net:
Total revenues, net	$ 10,835	$ 10,004
Costs and expenses:
Cost of royalties	534	503
Research and development	23,068	22,302
General and administrative	12,131	11,555
Total costs and expenses	35,733	34,360
Loss from operations	(24,898)	(24,356)
Other expense:
Loss on debt extinguishment	0	(3,495)
Interest income	63	614
Imputed interest expense related to the sale of future royalties	(5,095)	(4,055)
Interest expense, debt	0	(791)
Other income (expense), net	22	(58)
Total other expense	(5,010)	(7,785)
Net loss	$ (29,908)	$ (32,141)
Net loss per common share (basic and diluted) (in dollars per share)	$ (0.61)	$ (0.97)
Weighted average common shares (basic and diluted) (in shares)	48,670,381	33,180,516
Unrealized net loss on marketable securities	$ (3)	$ 0
Total comprehensive loss	(29,911)	(32,141)
Royalties
Revenues, net:
Total revenues, net	10,724	10,418
Other revenue
Revenues, net:
Total revenues, net	214	0
Contra revenue, net
Revenues, net:
Total revenues, net	$ (103)	$ (414)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Total	Aspire Capital Fund, LLC	Demand Sales Agreement	Common Stock	Common StockPrivate Placement	Common StockAspire Capital Fund, LLC	Common StockDemand Sales Agreement	Additional Paid-in Capital	Additional Paid-in CapitalPrivate Placement	Additional Paid-in CapitalAspire Capital Fund, LLC	Additional Paid-in CapitalDemand Sales Agreement	Accumulated Deficit	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2018				33,159,253
Beginning balance at Dec. 31, 2018	$ (4,496)			$ 332				$ 980,012				$ (984,840)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances of common stock upon the exercise of stock options and for purchases under the ESPP (in shares)				91,013
Issuances of common stock upon the exercise of stock options and for purchases under the ESPP	68							68
Recognition of stock-based compensation	2,658							2,658
Cancellation of restricted stock awards (in shares)				(8,473)
Cancellation of restricted stock awards	0
Net loss	$ (32,141)											(32,141)
Ending balance (in shares) at Dec. 31, 2019	33,241,793			33,241,793
Ending balance at Dec. 31, 2019	$ (33,911)			$ 332				982,738				(1,016,981)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances of common stock upon the exercise of stock options and for purchases under the ESPP (in shares)				80,544
Issuances of common stock upon the exercise of stock options and for purchases under the ESPP	58							58
Recognition of stock-based compensation	2,698							2,698
Issuance of stock (in shares)					14,000,000	7,990,516	6,298,648
Issuance of stock	15,965	$ 8,099	$ 7,914		$ 140	$ 81	$ 63		$ 15,825	$ 8,018	$ 7,851
Issuance of common stock under registration statement, net of issuance costs (in shares)				29,500,000
Issuance of common stock under registration statement, net of issuance costs	$ 159,031			$ 295				158,736
Exercise of stock options (in shares)	391,122			390,960
Exercise of stock options	$ 727			$ 4				723
Unrealized loss on marketable securities	(3)												(3)
Net loss	$ (29,908)											(29,908)
Ending balance (in shares) at Dec. 31, 2020	91,502,461			91,502,461
Ending balance at Dec. 31, 2020	$ 130,670			$ 915				$ 1,176,647				$ (1,046,889)	$ (3)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (29,908)	$ (32,141)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	144	125
Non-cash lease expense	177	(45)
Stock-based compensation expense	2,698	2,658
Amortization of debt issuance costs	0	8
Non-cash imputed interest expense related to the sale of future royalties	45	287
Non-cash interest expense (income) on investments	33	(64)
Loss on extinguishment of debt	0	3,495
Loss on disposal of fixed assets	24	29
Changes in operating assets and liabilities:
Accounts receivable	201	(380)
Prepaid expenses and other assets	(153)	(237)
Accounts payable and accrued and other liabilities	1,000	60
Total adjustments	4,169	5,936
Net cash used in operating activities	(25,739)	(26,205)
Cash flows from investing activities:
Purchases of investments	(53,449)	(11,465)
Sales and maturities of investments	5,078	7,050
Purchases of property and equipment	(677)	(41)
Net cash used in investing activities	(49,048)	(4,456)
Cash flows from financing activities:
Proceeds from PPP Loan	891	0
Proceeds from issuance of common stock	159,447	0
Proceeds of registered direct offering	17,500	0
Payments of stock issuance costs	(1,535)	0
Proceeds from royalty interest purchase agreement with Oberland Capital Management	0	65,000
Payment of transaction costs on royalty interest purchase agreement	0	(584)
Proceeds from issuance of common stock under the Company’s stock-based compensation plans	785	68
Payment of liability of future royalties, net of imputed interest	(4,287)	(2,226)
Payment on termination of credit agreement with HealthCare Royalty Partners, III, L.P.	0	(37,162)
Payments made on Curis Royalty’s debt	0	(1,825)
Net cash provided by financing activities	188,814	23,271
Net (decrease) increase in cash and cash equivalents and restricted cash	114,027	(7,390)
Cash and cash equivalents and restricted cash, beginning of period	16,399	23,789
Cash and cash equivalents and restricted cash, end of period	130,426	16,399
Supplemental cash flow data:
Issuance costs in accounts payable	416	0
Non-cash commitment shares issued to Aspire Capital	900	0
Cash paid for interest	5,050	4,716
Right-of-use assets obtained in exchange for lease liabilities	7,169	0
Aspire Capital Fund, LLC
Cash flows from financing activities:
Proceeds from issuance of common stock	8,099	0
Demand Sales Agreement
Cash flows from financing activities:
Proceeds from issuance of common stock	8,176	0
Payments of stock issuance costs	$ (262)	$ 0

Nature of Business

Nature of Business	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	Nature of Business Curis, Inc. is a biotechnology company focused on the development of first-in-class and innovative therapeutics for the treatment of cancer. Throughout these consolidated financial statements, Curis, Inc. and our wholly owned subsidiaries are collectively referred to as “the Company,” “Curis,” “we,” “us,” or “our.” The Company conducts its research and development programs both internally and through strategic collaborations. The Company’s clinical stage drug candidates: • CA-4948, a small molecule inhibitor of Interleukin-1 receptor-associated kinase 4, or IRAK4, which is currently undergoing testing in a Phase 1 open-label dose escalating clinical trial in patients with non-Hodgkin lymphomas and a separate Phase 1 open-label, single arm dose escalating trial in patients with acute myeloid leukemia and myelodysplastic syndromes. Both trials were ongoing as of December 31, 2020. • CI-8993, a monoclonal antibody designed to antagonize the V-domain Ig suppressor of T cell activation (“VISTA”) signaling pathway. In June 2020, the Company announced that the U.S. Food and Drug Administration, or FDA, had cleared its Investigational New Drug (“IND”) application for CI-8993. In September 2020, enrollment for a Phase 1a/1b trial in patients with solid tumors commenced. The Company has an option to license CI-8993 from ImmuNext, Inc. ("ImmuNext"). The Company’s pipeline also includes the following: • Fimepinostat, a small molecule that potently inhibits the activity of histone deacetylase and phosphotidyl-inositol 3 kinase enzymes, which has been granted Orphan Drug Designation and Fast Track Designation for the treatment of MYC-altered diffuse large B-cell lymphoma, by the FDA in April 2015 and May 2018, respectively. The Company is currently evaluating future studies for fimepinostat. • CA-170, a small molecule antagonist of VISTA and PDL1, for which the Company announced initial data from a clinical study in patients with mesothelioma, in conjunction with the Society of lmmunotherapy of Cancer conference in November 2019. Based on this data, no further patients will be enrolled in the study. The Company is currently evaluating future studies for CA-170. • CA-327, a small molecule antagonist of TIM3 and PDL1, is a pre- IND stage oncology drug candidate. The Company is party to a collaboration with Genentech Inc. (“Genentech”), a member of the Roche Group, under which Genentech and F. Hoffmann-La Roche Ltd (“Roche”) are commercializing Erivedge® (vismodegib), a first-in-class orally administered small molecule Hedgehog signaling pathway antagonist. Erivedge is approved for the treatment of advanced basal cell carcinoma (“BCC”). In January 2015, the Company entered into an exclusive collaboration, with Aurigene Discovery Technologies Limited (“Aurigene”) for the discovery, development and commercialization of small molecule compounds in the areas of immuno-oncology and precision oncology, which was amended in September 2016 and February 2020. As of December 31, 2020, the Company had licensed four programs under the Aurigene collaboration. • IRAK4 Program - a precision oncology program of small molecule inhibitors of IRAK4. The development candidate is CA-4948, an orally available small molecule inhibitor of IRAK4. • PD1/VISTA Program - an immuno-oncology program of small molecule antagonists of PD1 and VISTA immune checkpoint pathways. The development candidate is CA-170, an orally available small molecule antagonist of VISTA and PDL1. • PD1/TIM3 Program - an immuno-oncology program of small molecule antagonists of PD1 and TIM3 immune checkpoint pathways. The development candidate is CA-327, an orally available small molecule antagonist of PDL1 and TIM3. • In March 2018, the Company exercised its option to license a fourth program, which is an immuno-oncology program. The COVID-19 pandemic, which began in December 2019, has had and may continue to have an adverse effect on the Company’s business, financial condition, results of operations, and prospects. With respect to ongoing clinical trials, the anticipated timing of enrollment and the overall timelines of the trials have experienced delays and could be further delayed to the extent the Company experiences further delays in enrollment due to the COVID-19 pandemic and the Company’s ability to collect patient data in a timely fashion may also be impacted. The Company is also experiencing delays in closing down its clinical trial sites related to its fimepinostat and CA-170 trials due to restrictions on non-essential workers imposed at those sites in response to COVID-19, which has delayed the winding down of these trials and may result in additional costs and expenses. In addition, the Company and its collaborators, third-party contract manufacturers, contract research organizations and clinical sites could experience delays or disruptions in supply and release of product candidates and/or procuring items that are essential for its research and development activities, including, for example, raw materials used in the manufacturing of its product candidates, basic medical and laboratory supplies used in its clinical trials or preclinical studies, or animals that are used for preclinical testing, in each case, for which there may be shortages because of ongoing efforts to address the outbreak. The Company cannot be certain what the overall impact of the COVID-19 pandemic will be on its business. The Company is subject to risks common to companies in the biotechnology industry as well as risks that are specific to the Company’s business, including, but not limited to: the Company’s ability to obtain adequate financing to fund its operations; the Company’s ability to advance and expand its research and development programs; the impacts of the COVID-19 pandemic and responsive actions related thereto; the Company’s relationship with Aurigene to support development of drug candidates under the parties’ collaboration agreement; the Company’s reliance on Roche and Genentech to successfully commercialize Erivedge in the approved indication of advanced BCC and to progress its clinical development in indications other than BCC; the ability of the Company and its wholly owned subsidiary, Curis Royalty, LLC (“Curis Royalty”) to satisfy the terms of the royalty interest purchase agreement (the “Oberland Purchase Agreement”) with TPC Investments I LP and TPC Investments II LP, referred to as the Purchasers, each of which is a Delaware limited partnership managed by Oberland Capital Management, LLC, and Lind SA LLC, referred to as the Agent, a Delaware limited liability company managed by Oberland Capital Management, LLC, as collateral agent for the Purchasers; the Company’s ability to obtain and maintain necessary intellectual property protection; development by the Company’s competitors of new or better technological innovations; the Company's dependence on key personnel; the Company’s ability to comply with regulatory requirements; the Company's ability to obtain and maintain applicable regulatory approvals and commercialize any approved product candidates; the Company’s ability to execute on its overall business strategies and the Company’s ability to maintain its listing on the Nasdaq Global Stock Market. The Company’s future operating results will largely depend on the progress of drug candidates currently in its development pipeline and the magnitude of payments that it may receive and make under its current and potential future collaborations. The results of the Company’s operations have varied and will likely continue to vary significantly from year to year and quarter to quarter and depend on a number of factors, including, but not limited to: the timing, outcome and cost of the Company’s preclinical studies and clinical trials for its drug candidates; Aurigene’s ability to support advancement of development candidates under the Company’s collaboration with Aurigene, as well as the Company’s ability to further develop programs under this collaboration; and Roche and Genentech’s ability to successfully commercialize Erivedge. The Company will require substantial funds to maintain research and development programs and support operations. The Company has incurred losses and negative cash flows from operations since its inception. As of December 31, 2020, the Company had an accumulated deficit of approximately $1.0 billion, incurred a loss of $29.9 million and used $25.7 million of cash in operations. The Company expects to continue to generate operating losses in the foreseeable future. The Company anticipates that its $183.1 million of existing cash, cash equivalents and investments at December 31, 2020 will be sufficient to fund operations for at least 12 months from the date of issuance of these financial statements. The Company’s ability to raise additional funds will depend, among other factors, on financial, economic and market conditions, many of which are outside of its control and it may be unable to raise financing when needed, or on terms favorable to the Company. If necessary funds are not available, the Company will have to delay, reduce the scope of, or eliminate some of its development programs, potentially delaying the time to market for or preventing the marketing of any of its product candidates.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies (a) Basis of Presentation and Principles of Consolidation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the U.S. (“GAAP”) and include the accounts of our wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. In accordance with Accounting Standards Update (“ASU”) 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40) , the Company has evaluated and determined that there are no conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the Consolidated Financial Statements are issued. (b) Use of Estimates and Assumptions The preparation of the Company’s consolidated financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts and disclosure of revenue, expenses and certain assets and liabilities at the balance sheet date. Such estimates include revenue recognition, including estimates related to the performance obligations under the Company’s collaboration agreements; the estimated repayment term of the Company’s debt and related short and long-term classification; the collectability of receivables; the carrying value of property and equipment and goodwill; the assumptions used in the Company’s valuation of stock-based compensation and the value of certain investments and liabilities. Actual results may differ from such estimates. The extent to which COVID-19 has had and may continue to have impacts on the Company’s business and financial results will depend on numerous evolving factors including, but not limited to: the magnitude and duration of the COVID-19 pandemic, the extent to which it will impact worldwide macroeconomic conditions including interest rates, employment rates and health insurance coverage, the speed of the anticipated recovery, and governmental and business responses to the pandemic. The Company assessed certain accounting matters that generally require consideration of forecasted financial information in context with the information reasonably available to the Company and the unknown future impacts of COVID-19 as of December 31, 2020 and through the date of this report. The Company’s future assessment of the magnitude and duration of the COVID-19 pandemic, as well as other factors, could result in material impacts to the Company’s consolidated financial statements in future reporting periods. (c) Cash Equivalents, Restricted Cash, and Investments Cash equivalents consist of highly liquid investments purchased with original maturities of three months or less. All other liquid investments are classified as marketable securities. The Company classified $0.8 million and $1.0 million of its cash as restricted cash, as of December 31, 2020 and December 31, 2019. This amount represents the security deposit delivered to the respective landlords of the Company's current and former Lexington, Massachusetts headquarters. The Company's combined cash and restricted cash balances were $130.4 million and $16.4 million as of December 31, 2020 and December 31, 2019, as presented on the Company's Consolidated Statements of Cash Flows. The Company’s short-term investments are marketable debt securities with original maturities of greater than three months from the date of purchase, but less than twelve months from the balance sheet date, and long-term investments are marketable debt securities with original maturities of greater than twelve months from the balance sheet. Marketable securities consist of commercial paper, corporate bonds and notes, and/or government obligations. All of the Company’s investments have been designated available-for-sale and are stated at fair value. Unrealized gains and temporary losses on investments are included in accumulated other comprehensive income (loss) as a separate component of stockholders’ deficit. Realized gains and losses, dividends and interest income are included in other income (expense) in the period during which the securities are sold. Any premium or discount arising at purchase is amortized and/or accreted to interest income. (d) Concentrations and Significant Customer Information Financial instruments which potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents, marketable securities, and accounts receivable. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. The Company’s credit risk related to investments is reduced as a result of the Company’s policy to limit the amount invested in any one issue. As of December 31, 2020, the Company did not have a material concentration in any single investment. The Company's operations are located entirely within the U.S. The Company focus is primarily on the development of first-in-class and innovative therapeutics for the treatment of cancer. The Company's customer, Genentech, accounted for 98% and 100% of the total gross revenues for December 31, 2020 and December 31, 2019, respectively. The Company’s accounts receivable at December 31, 2020 and December 31, 2019 represents amounts due from collaborators, primarily for royalties earned on sales of Erivedge by Genentech and Roche. The Company relies on third-parties to supply certain raw materials necessary to produce its drug candidates, including CA-4948, CI-8993, and fimepinostat, for preclinical studies and clinical trials. There are a small number of suppliers for certain raw materials that the Company uses to manufacture its drug candidates. (e) Long-Lived Assets Other than Goodwill Long-lived assets other than goodwill consist of property and equipment. The Company applies the guidance in FASB Codification Topic 360-10-05, Impairment or Disposal of Long-Lived Assets . If it were determined that the carrying value of the Company’s other long-lived assets might not be recoverable based upon the existence of one or more indicators of impairment, the Company would measure an impairment based on the difference between the carrying value and fair value of the asset. The Company did not recognize any material impairment charges for the years ended December 31, 2020 or December 31, 2019. Purchased equipment is recorded at cost. The Company does not currently hold any leased equipment. Depreciation and amortization are provided on the straight-line method over the estimated useful lives of the related assets or the remaining terms of the leases, whichever is shorter, as follows: Useful Life Laboratory equipment, computers and software 3-5 years Leasehold improvements Lesser of lease or asset life Office furniture and equipment 5 years (f) Leases In February 2016 the FASB issued ASU No. 2016-02, Leases (Topic 842) , a standard issued to increase transparency and comparability among organizations related to their leasing activities. This standard established a right-of-use model that requires the recognition of right-of-use assets and lease liabilities for most leases as well as provides disclosure with respect to certain qualitative and quantitative information related to a company's leasing arrangements to meet the objective of allowing users of financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. The FASB subsequently issued the following amendments to ASU 2016-02 that have the same effective date and transition date: ASU No. 2018-10, Codification Improvements to Topic 842, Leases , ASU No. 2018-11, Leases (Topic 842): Targeted Improvements , and ASU No. 2019-01, Leases (Topic 842): Codification Improvements . The Company adopted these amendments with ASU 2016-02 (collectively, the new leasing standards) effective January 1, 2019. The Company adopted the leasing standards using the modified retrospective transition approach, as of January 1, 2019, with no restatement of prior periods or cumulative adjustment to retained earnings. Upon adoption, the Company elected the package of transition practical expedients, which allowed Curis to carry forward prior conclusions related to whether any expired or existing contracts are or contain leases, the lease classification for any expired or existing leases and initial direct costs for existing leases. The Company also made an accounting policy election to not recognize leases with an initial term of 12 months or less within its consolidated balance sheets and to recognize those lease payments on a straight-line basis in its consolidated statements of income over the lease term. Upon adoption of the leasing standard Curis recognized an operating lease asset of approximately $1.0 million and a corresponding operating lease liability of approximately $1.1 million. The adoption of the leasing standard did not have an impact on the consolidated statement of income. The Company determines if an arrangement is a lease at contract inception. Operating lease assets represent the Company's right to use an underlying asset for the lease term and operating lease liabilities represent its obligation to make lease payments arising from the lease. Operating lease assets and liabilities are recognized at the commencement date of the lease based upon the present value of lease payments over the lease term. When determining the lease term, the Company includes options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. As most of the Company's leases do not provide an implicit interest rate, the Company uses its incremental borrowing rate, which is based on rates that would be incurred to borrow on a collateralized basis over a term equal to the lease payments in a similar economic environment, in determining the present value of lease payments. Right-of-use assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The lease payment used to determine the operating lease asset may include lease incentives, stated rent increases and was recognized as an operating lease right-of-use asset in the consolidated balance sheets. The Company's lease agreements may include both lease and non-lease components, which are accounted for as a single lease component when the payments are fixed. Variable payments included in the lease agreement are expensed as incurred. The Company's operating lease is reflected in operating lease right-of-use asset and operating lease liability in the consolidated balance sheets. Lease expense for lease payments is recognized on a straight-line basis over the lease term. For additional information on the adoption of the new leasing standards, please read Note 7, Leases and Commitments, to these consolidated financial statements. (g) Goodwill As of both December 31, 2020 and December 31, 2019, the Company had recorded goodwill of $9.0 million. The Company applies the guidance in the FASB Codification Topic 350, Intangibles—Goodwill and Other . During each of December 31, 2020 and December 31, 2019, the Company completed its annual goodwill impairment tests and determined that the Company represented a single reporting unit and as of those dates the fair value of the Company exceeded the carrying value of its net assets. Accordingly, no goodwill impairment was recognized for the years ended December 31, 2020 and December 31, 2019. (h) Revenue Recognition The Company’s business strategy includes entering into collaborative license and development agreements with biotechnology and pharmaceutical companies for the development and commercialization of the Company’s drug candidates. The terms of the agreements typically include non-refundable license fees, funding of research and development, payments based upon achievement of clinical development and regulatory objectives, and royalties on product sales. License Fees and Multiple Element Arrangements If a license to its intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company will recognize revenues from non-refundable, up-front fees allocated to the license at such time as the license is transferred to the licensee and the licensee is able to use, and benefit from, the license. For licenses that are bundled 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 from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, will adjust the measure of performance and related revenue recognition. If the Company is involved in a steering committee as part of a multiple element arrangement, the Company assesses whether its involvement constitutes a performance obligation or a right to participate. Steering committee services that are not determined to be distinct performance obligations are combined with other research services or performance obligations required under an arrangement, if any, in determining the level of effort required in an arrangement and the period over which the Company expects to complete its aggregate performance obligations. Appropriate methods of measuring progress include output methods and input methods. In determining the appropriate method for measuring progress, the Company considers the nature of service that it promises to transfer to the customer. When the Company decides on a method of measurement, the Company will apply that single method of measuring progress for each performance obligation satisfied over time and will apply that method consistently to similar performance obligations and in similar circumstances. If the Company cannot reasonably measure its progress toward complete satisfaction of a performance obligation because the Company lacks reliable information that would be required to apply an appropriate method of measuring progress, but it can reasonably estimate when the performance ceases or the remaining obligations become inconsequential and perfunctory, then revenue is not recognized until the Company can reasonably estimate when the performance obligation ceases or becomes inconsequential. Revenue is then recognized over the remaining estimated period of performance. Significant management judgment is required in determining the level of effort required under an arrangement and the period over which the Company is expected to complete its performance obligations under an arrangement. Contingent Research Milestone Payments ASC 606 constrains the amount of variable consideration included in the transaction price in that either all, or a portion, of an amount of variable consideration should be included in the transaction price. The variable consideration amount should be included only to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. The assessment of whether variable consideration should be constrained is largely a qualitative one that has two elements: the likelihood of a change in estimate, and the magnitude thereof. Variable consideration is not constrained if the potential reversal of cumulative revenue recognized is not significant, for example. If the consideration in a contract includes a variable amount, a company will estimate the amount of consideration in exchange for transfer of promised goods or services. The consideration also can vary if a company’s entitlement to the consideration is contingent on the occurrence or nonoccurrence of a future event. The Company considers contingent research milestone payments to fall under the scope of variable consideration, which should be estimated for revenue recognition purposes at the inception of the contract and reassessed ongoing at the end of each reporting period. The Company assesses whether contingent research milestones should be considered variable consideration that should be constrained and thus not part of the transaction price. This includes an assessment of the probability that all or some of the milestone revenues could be reversed when the uncertainty around whether or not the achievement of each milestone is resolved, and the amount of reversal could be significant. GAAP provides factors to consider when assessing whether variable consideration should be constrained. All of the factors should be considered, and no factor is determinative. The Company considers all relevant factors. Reimbursement of Costs Reimbursement of research and development costs by third-party collaborators is recognized as revenue over time provided the Company has determined that it transfers control (i.e. performs the services) of a service over time and, therefore, satisfies a performance obligation according to the provisions outlined in ASC 606-10-25-27, Revenue Recognition . Royalty Revenue Since the first quarter of 2012, the Company has recognized royalty revenues related to Genentech’s and Roche’s sales of Erivedge. For arrangements that include sales based royalties, including milestone payments based on the level of sales, and where 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). The Company expects to continue recognizing royalty revenue from Genentech’s sales of Erivedge in the U.S. and in other markets where Genentech and Roche successfully obtain marketing approval, if any (see Note 11). However, a portion of potential Erivedge royalties will be paid to the Purchasers pursuant to the Oberland Purchase Agreement (see Note 9). Contra Revenue, Net Contra revenue, net represents shared costs, primarily related to intellectual property, with the Company's collaboration partners, and reserves for potential royalty reductions. With respect to each of the foregoing areas of revenue recognition, the Company exercises significant judgment in determining whether an arrangement contains multiple elements, and, if so, how much revenue is allocable to each element. In addition, the Company exercises its judgment in determining when its significant obligations have been met under such agreements and the specific time periods over which the Company recognized revenue, such as non-refundable, up-front license fees. To the extent that actual facts and circumstances differ from the Company's initial judgments, its revenue recognition with respect to such transactions would change accordingly and any such change could affect the Company's reported financial results. (i) Cost of Royalties The Company recognizes cost of royalties on Erivedge royalty revenue earned from Genentech related to obligations to third-party university licensors. The Company is also incurring research and development expenses under this collaboration related to the maintenance of these third-party licenses to certain background technologies. In addition, the Company records research and development expense for obligations to certain third-party university licensors upon earning payments from Genentech related to the achievement of clinical development and regulatory objectives under this collaboration. (j) Research and Development Research and development expense consists of costs incurred to discover, research and develop drug candidates. These expenses primarily include: (1) salaries and related expenses for personnel including stock-based compensation expense; (2) outside service costs, including clinical research organizations and contract manufacturing costs, among others; (3) sublicense payments; and (4) the costs of supplies and reagents, consulting, and occupancy and depreciation charges. The Company expenses research and development costs as they are incurred. (k) Basic and Diluted Loss per Common Share Basic and diluted net losses per share were determined by dividing net loss by the weighted average number of common shares outstanding during the period. Diluted net loss per common share is the same as basic net loss per common share for all periods presented, as the effect of the potential common stock equivalents is antidilutive due to the Company’s net loss position for all periods presented. For the Year Ended December 31, 2020 2019 Stock options outstanding 8,668,005 6,158,026 Total antidilutive securities 8,668,005 6,158,026 (l) Stock-Based Compensation The Company accounts for stock-based compensation transactions using a grant-date fair-value based method under FASB Codification Topic 718, Compensation-Stock Compensation . The Company measures compensation cost for stock-based compensation at fair value, including an estimate of forfeitures and recognizes the expense as compensation expense over the period that the recipient is required to provide service in exchange for the award, which generally is the vesting period. The Company uses the Black-Scholes option pricing model to measure the fair value of stock options. This model requires significant estimates related to the award’s expected life and future stock price volatility of the underlying equity security. In determining the amount of expense to be recorded, the Company also estimates forfeiture rates for awards, based on the probability that employees will complete the required service period. The Company estimates the forfeiture rate based on historical experience. If actual forfeitures differ significantly from the Company’s estimates, additional adjustments to compensation expense may be required in future periods. Ultimately, the actual expense recognized over the vesting period will only be for those shares that vest. The expected volatility is based on the annualized daily historical volatility of the Company’s stock price for a time period consistent with the expected term of each grant. Management believes that the historical volatility of the Company’s stock price best represents the future volatility of the stock price. The risk-free rate is based on the U.S. Treasury yield in effect at the time of grant for the expected term of the respective grant. The Company has not historically paid cash dividends, and does not expect to pay cash dividends in the foreseeable future. The stock price volatility and expected terms utilized in the calculation involve management’s best estimates at that time, both of which impact the fair value of the option calculated under the Black-Scholes methodology and, ultimately, the expense that will be recognized over the life of the option. GAAP also requires that the Company recognize compensation expense for only the portion of options that are expected to vest. Therefore, management calculated an estimated annual pre-vesting forfeiture rate that is derived from historical employee termination behavior since the inception of the Company, as adjusted. If the actual number of forfeitures differs from those estimated by management, additional adjustments to compensation expense may be required in future periods. (m) Comprehensive Loss Comprehensive loss is comprised of net loss and other comprehensive income (loss). Other comprehensive income (loss) includes unrealized holding gains and losses arising during the period on available-for-sale securities that are not other-than-temporarily impaired. (n) Segment Reporting The Company has determined that it operates in a single reportable segment, which is the research and development of innovative drug candidates for the treatment of human cancer. The Company expects that any products that are successfully developed and commercialized would be used in the healthcare industry and would be regulated in the United States by the FDA and in overseas markets by similar regulatory authorities. (o) Interest Expense on Liability related to the Sale of Future Royalties In March 2019 the Company entered into the Oberland Purchase Agreement with Oberland Capital. Pursuant to the terms of the Oberland Purchase Agreement the Company sold to Oberland a portion of its rights to receive royalties from Genentech on potential net sales of Erivedge. As a result of the obligation to pay future royalties to Oberland, the Company recorded the proceeds from this transaction as a liability on its Consolidated Balance Sheet that is accounted for using the interest method over the estimated life of the Oberland Purchase Agreement. As a result, the Company imputes interest on the transaction and records imputed interest expense at the estimated interest rate. The Company's estimate of the interest rate under the agreement is based on the amount of royalty payments expected to be received by Oberland over the life of the arrangement. On a quarterly basis, the Company assesses the expected royalty payments to Curis Royalty from Genentech using a combination of historical results and forecasts from market data sources. To the extent such payments are greater or less than the initial estimates or the timing of such payments is materially different than the original estimates, the Company will prospectively adjust the amortization of the liability. (p) New Accounting Pronouncements Recently Adopted In August 2018, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2018-13, Fair Value Measurement, which modified the disclosure requirements for fair value measurement under ASC 820. The standard was effective for annual reporting periods and interim periods within those annual periods, beginning after December 15, 2019, with early adoption permitted. The Company adopted the standard effective January 1, 2020 with no material impact to its Consolidated Financial Statements. Issued, Not Yet Adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. This standard requires that for most financial assets, losses be based on an expected loss approach which includes estimates of losses over the life of exposure that considers historical, current and forecasted information. Expanded disclosures related to the methods used to estimate the losses as well as a specific disaggregation of balances for financial assets are also required. The targeted transition relief standard allows filers an option to irrevocably elect the fair value option of ASC 825-10, Financial Instruments-Overall, applied on an instrument-by-instrument basis for eligible instruments. In November 2019 the effective date for smaller reporting companies was extended to January 1, 2023 with the issuance of ASU 2019-10 Financial Instruments-Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842) Effective Dates. The Company is currently evaluating the effects of this standard and does not expect that adoption of this standard will have a material impact on its consolidated financial statements.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company applies the provisions of ASC Topic 820, Fair Value Measurements (“ASC 820”) for its financial assets and liabilities that are re-measured and reported at fair value each reporting period and the non-financial assets and liabilities that are re-measured and reported at fair value on a non-recurring basis. Fair value is the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value, the Company considers the principal or most advantageous market in which it would transact and consider assumptions that market participants would use when pricing the asset or liability. ASC 820 establishes a three-level valuation hierarchy for disclosure of fair value measurements. Financial assets and liabilities are categorized within the valuation hierarchy based upon the lowest level of input that is significant to the measurement of fair value. The three levels of the hierarchy are defined as follows: Level 1 Quoted prices in active markets for identical assets or liabilities. Level 2 Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. In accordance with the fair value hierarchy, the following table shows the fair value as of December 31, 2020 and December 31, 2019 of those financial assets and liabilities that are measured at fair value on a recurring basis, according to the valuation techniques the Company used to determine their fair value. No financial assets or liabilities are measured at fair value on a nonrecurring basis at December 31, 2020 and December 31, 2019. Quoted Prices in Other Unobservable Fair Value (in thousands) As of December 31, 2020 Cash equivalents: Money market funds $ 115,278 $ — $ — $ 115,278 Short-term investments: Corporate commercial paper, bonds and notes — 38,884 — 38,884 Long-term investments: Corporate commercial paper, bonds and notes — 14,564 — 14,564 Total assets at fair value $ 115,278 $ 53,448 $ — $ 168,726 Quoted Prices in Other Unobservable Fair Value (in thousands) As of December 31, 2019 Cash equivalents: Money market funds $ 10,684 $ — $ — $ 10,684 US government obligations — 550 — 550 Corporate commercial paper, stock, bonds and notes — 300 — 300 Municipal bonds — 90 — 90 Short-term investments: Corporate commercial paper, stock, bonds and notes — 5,113 — 5,113 Total assets at fair value $ 10,684 $ 6,053 $ — $ 16,737

Investments

Investments	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Investments	Investments The amortized cost, unrealized gains and losses and fair value of investments available-for-sale as of December 31, 2020 are as follows: (in thousands) Amortized Unrealized Unrealized Fair Value Corporate bonds and notes—short-term $ 38,888 $ — $ (4) $ 38,884 Corporate bonds and notes—long-term 14,563 1 — 14,564 Total investments $ 53,451 $ 1 $ (4) $ 53,448 The Company held no investments that have been in a continuous unrealized loss position for 12 months or longer. The Company evaluated its securities for other-than-temporary impairments based on quantitative and qualitative factors, and it considered the decline in market value for the applicable securities to be primarily attributable to current economic and market conditions. The Company will likely not be required to sell and does not intend to sell such securities before the recovery of its amortized cost bases. Based on the Company's analysis, it does not consider these investments to be other-than-temporarily impaired as of December 31, 2020. Short-term investments have maturities ranging from one The amortized cost, unrealized gains and losses and fair value of investments available-for-sale as of December 31, 2019 are as follows: (in thousands) Amortized Unrealized Unrealized Fair Value Corporate bonds and notes—short-term $ 5,113 $ — $ — $ 5,113 Total investments $ 5,113 $ — $ — $ 5,113 one

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment consist of the following: December 31, (in thousands) 2020 2019 Laboratory equipment, computers and software $ 1,736 $ 1,725 Leasehold improvements 214 185 Office furniture and equipment 779 331 2,729 2,241 Less—Accumulated depreciation and amortization (2,066) (2,087) Total $ 663 $ 154

Accrued Liabilities

Accrued Liabilities	12 Months Ended
	Dec. 31, 2020
Other Liabilities Disclosure [Abstract]
Accrued Liabilities	Accrued Liabilities Accrued liabilities consist of the following: December 31, (in thousands) 2020 2019 Accrued compensation $ 2,638 $ 1,413 Accrued license fees 375 — Professional fees 307 289 Other 305 208 Total $ 3,625 $ 1,910

Leases and Commitments

Leases and Commitments	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases and Commitments	Leases and Commitments (a) Operating Leases The Company has a single lease for real estate, including laboratory and office space, and certain equipment. The lease for the current real estate property used for office, research and laboratory space located at 128 Spring Street in Lexington, Massachusetts commenced on May 1, 2020 which is the date when the property became available for use to the Company. In accordance with the accounting requirements under ASC 842, the lease obligation was not recorded until its commencement. In July 2020 the Company prospectively remeasured the lease as a result of the change to the timing of lease payments, the change was not material. The discount rate associated with the Company's right-of-use asset was 9.95%. The total cash obligation for the base rent over the seven year term of this lease is approximately $8.2 million, of which $0.7 million was paid during 2020 . All of the Company's leases qualify as operating leases. The following table summarizes the presentation in the Company's consolidated balance sheet for the operating leases: Balance sheet location ( in thousands) As of December 31, 2020 As of December 31, 2019 Assets: Operating lease right-of-use asset $ 6,578 $ 149 Liabilities: Operating lease liability - short-term $ 1,731 $ 166 Operating lease liability - long-term $ 5,040 $ — Total operating liability $ 6,771 $ 166 The following table summarized the effect of lease costs in our consolidated statements of income. Income statement location ( in thousands) Year ended Year ended Operating lease cost Research and development $ 1,061 $ 651 General and administrative 275 351 1,336 $ 1,002 The Company’s lease payments for the next five years and thereafter is expected to be as follows: Year Ending December 31, (in thousands) 2021 $ 2,256 2022 1,144 2023 1,178 2024 1,213 2025 1,250 Thereafter 1,721 Total lease payments $ 8,762 Less: interest 1,991 Present value of operating lease liabilities $ 6,771 (b) License Agreements In exchange for the right to use licensed technology in its research and development efforts, the Company has entered into various license agreements. These agreements generally stipulate that the Company pay an annual license fee and is obligated to pay royalties on future revenues, if any, resulting from use of the underlying licensed technology. Such revenues may include, for example, up-front license fees, contingent payments upon collaborators’ achievement of development and regulatory objectives, and royalties. In addition, some of the agreements commit the Company to make contractually defined payments upon the attainment of scientific or clinical milestones. The Company expenses these payments as they are incurred and expenses royalty payments as related future product sales or as royalty revenues are recorded. The Company accrues expenses for scientific and clinical objectives over the period that the work required to meet the respective objective is completed, provided that the Company believes that the achievement of such objective is probable. The Company did not incur license fee expenses within the “Research and development” line item of its “Costs and expenses” section of its consolidated statement of operations for the years ended December 31, 2020 or 2019. For the years ended December 31, 2020 and December 31, 2019, the Company also recognized $0.5 million and $0.5 million as cost of royalty revenues in its Consolidated Statements of Operations and Comprehensive Loss related to such obligations (see Note 11 (a)).

Debt

Debt	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Debt	Debt On April 21, 2020, the Company entered into a promissory note evidencing an unsecured $0.9 million loan (the “PPP Loan”) under the Paycheck Protection Program (“PPP”), of the Coronavirus Aid, Relief, and Economic Security Act, (“CARES Act”). The PPP Loan was made by Silicon Valley Bank (“SVB”). The term of the PPP Loan is 24-months. The interest rate on the PPP Loan is 1%. Interest and principal payments have been deferred to the third quarter of fiscal year 2021. The promissory note evidencing the PPP Loan contains customary events of default relating to, among other things, payment defaults, breach of representations and warranties, or provisions of the promissory note, and cross-default provisions. The occurrence of an event of default may result in the repayment of all amounts outstanding, collection of all amounts the Company owes, and/or filing suit and obtaining judgment against the Company.

Liability Related to the Sale o

Liability Related to the Sale of Future Royalties	12 Months Ended
	Dec. 31, 2020
Nonmonetary Transactions [Abstract]
Liability Related to the Sale of Future Royalties	Liability Related to the Sale of Future Royalties On March 22, 2019, the Company and Curis Royalty entered into the royalty interest purchase agreement (“Oberland Purchase Agreement”) with entities managed by Oberland Capital Management, LLC (the “Purchasers”). The Company sold to the Purchasers a portion of its rights to receive royalties from Genentech on potential net sales of Erivedge. Concurrently with the closing of the Oberland Purchase Agreement Curis Royalty used a portion of the proceeds to terminate and repay the then existing loan with Healthcare Royalty. As upfront consideration for the purchase of the royalty rights, at closing the Purchasers paid to Curis Royalty $65.0 million less certain transaction expenses. Curis Royalty will also be entitled to receive up to approximately $70.7 million in milestone payments based on sales of Erivedge as follows: (i) $17.2 million if the Purchasers and Curis Royalty receive aggregate royalty payments pursuant to the Oberland Purchase Agreement in excess of $18.0 million during the calendar year 2021, subject to certain exceptions and (ii) $53.5 million if the Purchasers receive payments pursuant to the Oberland Purchase Agreement in excess of $117.0 million on or prior to December 31, 2026. The Oberland Purchase Agreement provides that after the occurrence of an event of default as defined under the security agreement by Curis Royalty, the Purchasers shall have the option, for a period of 180 days, to require Curis Royalty to repurchase a portion of certain royalty and royalty related payments, excluding a portion of non-U.S. royalties retained by Curis Royalty, referred to as the Purchased Receivables, at a price, referred to as the Put/Call Price, equal to a percentage, beginning at a low triple digit percentage and increasing over time up to a low mid triple digit percentage of the sum of the upfront purchase price and any portion of the milestone payments paid in a lump sum by the Purchasers, if any, minus certain payments previously received by the Purchasers with respect to the Purchased Receivables. Additionally, Curis Royalty shall have the option at any time to repurchase the Purchased Receivables at the Put/Call Price as of the date of such repurchase. No events of default existed as of December 31, 2020. As a result of the obligation to pay future royalties to Oberland, the Company recorded the proceeds from this transaction as a liability on its Consolidated Balance Sheet that will be accounted for using the interest method over the estimated life of the Oberland Purchase Agreement. As a result, the Company imputes interest on the transaction and records imputed interest expense at the estimated interest rate. The Company's estimate of the interest rate under the agreement is based on the amount of royalty payments expected to be received by Oberland over the life of the arrangement. The projected amount of royalty payments expected to be paid to Oberland involves the use of significant estimates and assumptions with respect to the revenue growth rate in the Company's projections of sales of Erivedge. The Company periodically assesses the expected royalty payments to Curis Royalty from Genentech using a combination of historical results and forecasts from market data sources. To the extent such payments are greater or less than its initial estimates or the timing of such payments is materially different than its original estimates, the Company will adjust the amortization of the liability. The Company determined the fair value of the liability related to the sale of future royalties at the time of the Oberland Purchase Agreement to be $65.0 million, with a current effective annual imputed interest rate of 8.2%. The Company incurred $0.6 million of transaction costs in connection with the agreement. These transaction costs will be amortized to imputed interest expense over the estimated term of the Oberland Purchase Agreement. The Company determined that the fair value assessment of the liability related to the sale of future royalties is a Level 3 assessment within the valuation hierarchy. The following table shows the activity with respect to the liability related to the sale of future royalties during the year ended December 31, 2020: (in thousands) Carrying value of liability related to the sale of future royalties at January 1, 2020 $ 62,477 Amortization of capitalized issuance costs 61 Imputed interest expense recognized for the year ended December 31, 2020 5,034 Less: payments to Oberland Capital, LLC (9,337) Carrying value of liability related to the sale of future royalties at December 31, 2020 $ 58,235 The following table shows the activity with respect to the liability related to the sale of future royalties during the year ended December 31, 2019: (in thousands) Liability related to the sale of future royalties at March 22, 2019 $ 65,000 Capitalized issuance costs, net (584) Imputed interest expense recognized for the year ended December 31, 2019 4,055 Less: payments to Oberland Capital, LLC (5,994) Carrying value of liability related to the sale of future royalties at December 31, 2019 $ 62,477

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Common Stock	Common Stock (a) 2020 Public Offering In December 2020, the Company completed an underwritten public offering of 29,500,000 shares of the Company's common stock, including 3,847,826 shares issued and sold to the underwriters upon the exercise in full of their option to purchase additional shares, at a price of $5.75 per share, for aggregate gross proceeds of $169.6 million, before deducting placement agent fees and other offering expenses of $10.2 million. The securities in this transaction were offered pursuant to a shelf registration statement on Form S-3 (File No. 333-224627) that was filed with the United States Securities and Exchange Commission ("SEC") on May 3, 2018, and declared effective by the SEC on May 17, 2018 and an additional registration statement on Form S-3 (File No. 333-251211) filed pursuant to Rule 462(b) which became automatically effective on December 9, 2020. (b) 2020 Registered Direct Offering In June 2020, the Company entered into a securities purchase agreement with certain institutional investors, pursuant to which the Company issued and sold, in a registered direct offering, an aggregate of 14,000,000 shares of the Company's common stock at a purchase price per share of $1.25, for aggregate gross proceeds of $17.5 million, before deducting fees of $1.0 million paid to the placement agent and other offering expenses of $0.5 million paid by the Company. JonesTrading acted as the exclusive placement agent for the transaction, and the shares were offered by the Company pursuant to a universal shelf registration statement on Form S-3, which was filed with the SEC on May 3, 2018 and declared effective by the SEC on May 17, 2018 (File No. 333-224627), and a prospectus supplement thereunder. (c) Charter Amendments On June 4, 2020, the Company's stockholders approved an increase to the number of authorized shares of its common stock from 101,250,000 shares to 151,875,000 shares. The Company filed an amendment to its certificate of incorporation on June 4, 2020 to effect such an increase. On May 23, 2019, the Company's stockholders approved an increase to the number of authorized shares of its common stock from 67,500,000 shares to 101,250,000 shares. The Company filed an amendment to its certificate of incorporation on May 23, 2019 to effect such increase. (d) 2020 Sales Agreement with JonesTrading Institutional Services LLC On March 4, 2020, the Company entered into a Capital on Demand™ Sales Agreement (the “Sales Agreement”) with JonesTrading to sell from time to time up to $30.0 million of the Company’s common stock through an “at-the-market” equity offering program under which JonesTrading acted as sales agent. Subject to the terms and conditions of the Sales Agreement, JonesTrading could sell the common stock by any method deemed to be an “at-the-market” offering as defined in Rule 415 promulgated under the Securities Act of 1933, as amended (the “Securities Act”), including sales made directly on the Nasdaq Global Market, on any other existing trading market for the common stock or to or through a market maker other than on an exchange. In addition, with the Company’s prior written approval, JonesTrading could also sell the common stock by any other method permitted by law, including in privately negotiated transactions. Pursuant to the terms of the Sales Agreement, the aggregate compensation payable to JonesTrading is 3% of the gross proceeds from sales of the common stock sold by JonesTrading pursuant to the Sales Agreement. Each party agreed in the Sales Agreement to provide indemnification and contribution against certain liabilities, including liabilities under the Securities Act, subject to the terms of the Sales Agreement. The Company terminated this sales agreement effective as of December 9, 2020. The Company did not incur any termination penalties as a result of the termination. As of the effective date of the termination of the Sales Agreement, the Company had sold an aggregate of 6,298,648 shares of common stock under the sales agreement for aggregate gross proceeds of $8.3 million and net proceeds of $7.9 million after deducting commissions and offering expenses. The $21.7 million of common stock that remained unsold at the time of termination is no longer available. (e) 2021 Sales Agreement with Cantor Fitzgerald & Co. and JonesTrading Institutional Services LLC On March 16, 2021, the Company entered into a sales agreement (the “2021 Sales Agreement”) with Cantor Fitzgerald & Co., or Cantor, and JonesTrading Institutional Services LLC , or JonesTrading, to sell from time to time up to $100.0 million of the Company’s common stock through an “at the market offering” program under which Cantor and JonesTrading act as sales agents. Subject to the terms and conditions of the 2021 Sales Agreement, Cantor and JonesTrading can sell the common stock by any method deemed to be an “at-the-market” offering as defined in Rule 415 promulgated under the Securities Act of 1933, as amended (the “Securities Act”). Pursuant to the terms of the 2021 Sales Agreement, the aggregate compensation payable to each of Cantor and JonesTrading is 3% of the gross proceeds from sales of the common stock sold by Cantor or JonesTrading, as applicable, pursuant to the 2021 Sales Agreement. Each party agreed in the 2021 Sales Agreement to provide indemnification and contribution against certain liabilities, including liabilities under the Securities Act, subject to the terms of the 2021 Sales Agreement. To date, the Company has not made any sales of common stock pursuant to the 2021 Sales Agreement. (a) Aspire Capital Fund LLC On February 26, 2020, the Company entered into a common stock purchase agreement (the “Agreement”) for the sale of up to $30.0 million of the Company's common stock with Aspire Capital. Under the terms of the Agreement, Aspire Capital has committed to purchase such shares of the Company's common stock at the Company’s request, from time to time during a 30-month period at prices based on the market price at the time of each sale, subject to specified terms and limitations. Aspire Capital made an initial investment of $3.0 million through the purchase of 2,693,965 shares of the Company's common stock. In 2020, Aspire Capital subsequently purchased an additional 4,650,000 shares of common stock for $5.4 million. In addition, in connection with entering into the agreement, the Company issued 646,551 shares of common stock to Aspire Capital as a commitment fee. As of December 31, 2020, a total of $21.6 million remained available under the agreement. The Company has the right to sell up to 150,000 shares of common stock per day to Aspire Capital, which total may be increased by mutual agreement up to an additional 2,000,000 shares per day. The extent to which the Company may rely on Aspire Capital as a source of funding will depend on a number of factors, including the prevailing market price of its common stock and the extent to which it is able to secure working capital from other sources. There are no warrants, derivatives, or other share classes associated with this Agreement. The Company will control the timing and amount of the further sale of its common stock to Aspire Capital. There are no restrictions on future financings and there are no financial covenants, participation rights, rights of first refusal, or penalties in the Agreement. The Company has the right to terminate the Agreement at any time without any additional cost or penalty. The Company also entered into a Registration Rights Agreement with Aspire Capital in connection with its entry into the Agreement. (b) 2015 Sales Agreement with Cowen On July 2, 2015, the Company entered into a sales agreement with Cowen, pursuant to which the Company could sell from time to time up to $30.0 million of the Company’s common stock through an “at-the-market” equity offering program under which Cowen was to act as sales agent. The Company did not sell shares of common stock under this sales agreement during the years ended December 31, 2019 or December 31, 2020.

Research and Development Collab

Research and Development Collaborations	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Research and Development Collaborations	Research and Development Collaborations (a) Genentech In June 2003, the Company licensed its proprietary Hedgehog pathway antagonist technologies to Genentech for human therapeutic use. The primary focus of the collaborative research plan has been to develop molecules that inhibit the Hedgehog pathway for the treatment of various cancers. The collaboration is currently focused on the development of Erivedge, which is being commercialized by Genentech in the U.S. and by Genentech's parent company, Roche, in several other countries for the treatment of advanced BCC. Pursuant to the agreement, the Company is eligible to receive up to an aggregate of $115.0 million in contingent cash milestone payments, exclusive of royalty payments, in connection with the development of Erivedge or another small molecule Hedgehog pathway inhibitor, assuming the successful achievement by Genentech and Roche of specified clinical development and regulatory objectives. Of this amount, the Company has received $59.0 million in cash milestone payments as of December 31, 2020. In addition to these payments and pursuant to the collaboration agreement, the Company, is entitled to a royalty on net sales of Erivedge that ranges from 5% to 7.5%. The royalty rate applicable to Erivedge may be decreased by 2% on a country-by-country basis in certain specified circumstances, including when a competing product that binds to the same molecular target as Erivedge is approved by the applicable regulatory authority in another country and is being sold in such country, by a third-party for use in the same indication as Erivedge, or, when there is no issued intellectual property covering Erivedge in a territory in which sales are recorded. In 2015, the FDA and the European Medicine Agency’s Committee for Medicinal Products for Human Use, approved another Hedgehog signaling pathway inhibitor, Odomzo ® (sonidegib), which is marketed by Sun Pharmaceutical Industries Ltd., for use in locally advanced BCC. Beginning in the fourth quarter of 2015, Genentech applied the 2% royalty reduction on U.S. sales of Erivedge as a result of the first commercial sale of Odomzo in the U.S. and the Company anticipates that Genentech will reduce by 2% royalties on net sales of Erivedge outside of the United States on a country-by-country basis to the extent that sonidegib is approved by the applicable country's regulatory authority and is being sold in such country. However, pursuant to the Oberland Purchase Agreement, the Company has retained its rights with respect to the 2% of royalties that are subject to such reduction in countries where such reduction has not occurred, subject to the terms and conditions of the Oberland Purchase Agreement (the “Retained Royalty Amounts”). In March 2017, the Company and Curis Royalty entered into a credit agreement with HealthCare Royalty Partners III, L.P. (“HealthCare Royalty”) for the purpose of refinancing and terminating the loan from BioPharma-II. Accordingly, HealthCare Royalty made a $45.0 million loan at an annual interest rate of 9.95% to Curis Royalty, which was used in part to pay off $18.4 million in remaining loan obligations to BioPharma-II under the prior loan with the residual proceeds of $26.6 million distributed to the Company as sole equity member of Curis Royalty. The final maturity date of the loan was the earlier of such date that the principal is paid in full, or Curis Royalty's right to receive royalties under the collaboration agreement with Genentech is terminated. On March 22, 2019, the Company and Curis Royalty terminated, and repaid in full all amounts outstanding under, the loan with HealthCare Royalty. The Company has identified the following performance obligations related to the Genentech collaboration: 1. To grant the license for its Hedgehog antagonist programs and to provide service on both a steering committee and co-development steering committee. This performance obligation has been satisfied and only contingent royalty revenue remains to be recognized in the future. 2. To provide reimbursable research and development services. This performance obligation has been satisfied and no revenue remains to be recognized in the future. The Company recognized $10.7 million and $10.4 million in royalty revenues under the Genentech collaboration during the years ended December 31, 2020 and December 31, 2019, respectively. The Company also recorded $0.5 million as cost of royalty revenues within the costs and expenses section of its consolidated statements of operations and comprehensive loss during these same periods. Cost of royalty revenues is comprised of the 5% of the royalties earned by Curis Royalty with respect to Erivedge outside Australia, and 5% direct net sales in Australia (subject to decrease on expiration of the patent in April 2019 to 5% of the royalty payments that Curis Royalty receives from Genentech, through February 2022), that the Company is obligated to pay to university licensors. As further discussed in Note 9, a portion of royalty revenues received from Genentech on net sales of Erivedge will be paid to the Purchasers pursuant to the Oberland Purchase Agreement. The Company recorded other revenue of $0.1 million during the years ended December 31, 2020 and December 31, 2019, related to expenses incurred by the Company on behalf of Genentech that were paid by the Company and for which Genentech is obligated to reimburse the Company. Genentech incurred expenses of $0.2 million and $0.2 million in 2020 and 2019, respectively, under this collaboration for which the Company is obligated to reimburse to Genentech, and which the Company has recorded as contra-revenues in its consolidated statements of operations and comprehensive loss. The Company will continue to recognize revenue for expense reimbursement as such reimbursable expenses are incurred, provided that the provisions of the ASC 606 are met. The Company has recorded as amounts receivable from Genentech under this collaboration, comprised primarily of Erivedge royalties earned in the fourth quarters of 2020 and 2019 of $3.0 million and $3.2 million as of December 31, 2020 and 2019, respectively, in “accounts receivable” in the Company's current assets section of its consolidated balance sheets. (b) Aurigene In January 2015, the Company entered into an exclusive collaboration agreement with Aurigene for the discovery, development and commercialization of small molecule compounds in the areas of immuno-oncology and selected precision oncology targets. Under the collaboration agreement, Aurigene granted the Company an option to obtain exclusive, royalty-bearing licenses to relevant Aurigene technology to develop, manufacture and commercialize products containing certain of such compounds anywhere in the world, except for India and Russia, which are territories retained by Aurigene. In connection with the collaboration agreement, the Company issued to Aurigene 3,424,026 shares of its common stock valued at $24.3 million in partial consideration for the rights granted to the Company under the collaboration agreement, which the Company recognized as expense during the year ended December 31, 2015. The shares were issued pursuant to a stock purchase agreement with Aurigene dated January 18, 2015. In September 2016, the Company and Aurigene entered into an amendment to the collaboration agreement. Under the terms of the amendment, in exchange for the issuance by the Company to Aurigene of 2,041,666 shares of its common stock, Aurigene waived payment of up to a total of $24.5 million in potential milestones and other payments associated with the first four programs in the collaboration that may have become due from the Company under the collaboration agreement. To the extent any of these waived milestones or other payments are not payable by the Company, for example in the event one or more of the milestone events do not occur, the Company will have the right to deduct the unused waived amount from any one or more of the milestone payment obligations tied to achievement of commercial milestone events. The amendment also provides that, in the event supplemental program activities are performed by Aurigene, the Company will provide up to $2.0 million of additional funding for each of the third and fourth licensed program. The shares were issued pursuant to a stock purchase agreement with Aurigene dated September 7, 2016. In February 2020, the Company and Aurigene further amended their collaboration agreement. Under the terms of the amended agreement, Aurigene will fund and conduct a Phase 2b/3 randomized study evaluating CA-170, in combination with chemoradiation, in approximately 240 patients with non-squamous non-small cell lung cancer (nsNSCLC). In turn, Aurigene receives rights to develop and commercialize CA-170 in Asia, in addition to its existing rights in India and Russia, based on the terms of the original agreement. The Company retains U.S., European Union, and rest of world rights to CA-170, and is entitled to receive royalty payments on potential future sales of CA-170 in Asia at percentage rates ranging from the high single digits up to 10% subject to specified reductions. As of December 31, 2020, the Company has exercised its option to license the following four programs under the collaboration: 1. IRAK4 Program - a precision oncology program of small molecule inhibitors of IRAK4. The development candidate is CA-4948, an orally available small molecule inhibitor of IRAK4. 2. PD1/VISTA Program - an immuno-oncology program of small molecule antagonists of PD1 and VISTA immune checkpoint pathways. The development candidate is CA-170, an orally available small molecule antagonist of VISTA and PDL1. 3. PD1/TIM3 Program - an immuno-oncology program of small molecule antagonists of PD1 and TIM3 immune checkpoint pathways. The development candidate is CA-327, an orally available small molecule antagonist of PDL1 and TIM3. 4. In March 2018, the Company exercised its option to license a fourth program, which is an immuno-oncology program. For each of the licensed programs (as described above) the Company is obligated to use commercially reasonable efforts to develop, obtain regulatory approval for, and commercialize at least one product in each of the U.S., specified countries in the European Union and Japan, and Aurigene is obligated to use commercially reasonable efforts to perform its obligations under the development plan for such licensed program in an expeditious manner. Since January 2015, the Company has paid $14.5 million in research payments and Aurigene has waived $19.5 million in milestone payments under the terms of the collaboration agreement. For each of the IRAK4, PD1/VISTA, PD1/TIM3 programs, and the fourth immuno-oncology program, the Company has remaining unpaid or unwaived payment obligations of $42.5 million per program, related to regulatory approval and commercial sales milestones, plus specified additional payments for approvals for additional indications, if any. In addition to the collaboration agreement, in June 2017, the Company entered into a master development and manufacturing agreement with Aurigene for the supply of drug substance and drug product, under which it has made cash payments to Aurigene of $1.0 million in 2020 and $1.4 million in 2019. (c) ImmuNext On January 6, 2020, the Company entered into an Option and License Agreement with ImmuNext (the “ImmuNext Agreement”). Under the terms of the ImmuNext Agreement, the Company agreed to engage in a collaborative effort with ImmuNext, and to conduct a Phase 1a/1b clinical trial of CI-8993. In exchange, ImmuNext granted the Company an exclusive option, exercisable until the earlier of (a) four years after January 6, 2020 and (b) 90 days after database lock for the first Phase 1a/1b trial in which the endpoints are satisfied (the “Option Period”), to obtain an exclusive, worldwide license to develop and commercialize certain VISTA antagonizing compounds and products containing these compounds (the “VISTA Compounds and Products”) in the field of oncology. A joint steering committee composed of representatives from each of the parties will manage the non-clinical and clinical development of the VISTA Compounds and Products during the Option Period, including, but not limited to, the approval of the plan for the Phase 1a/1b trial. During the Option Period, the Company will conduct the Phase 1a/1b trial and ImmuNext will conduct certain agreed upon non-clinical research activities to support the Phase 1a/1b trial. Additionally, the Company will assign to ImmuNext all right, title and interest in and to, inventions made by the Company alone or jointly with ImmuNext in conducting clinical and non-clinical activities under the ImmuNext Agreement and any patent rights covering those inventions. If the option is exercised, ImmuNext will assign to the Company (i) all such inventions that were made solely by the Company and any patent rights covering those inventions that were assigned by the Company to ImmuNext during the Option Period and (ii) a joint ownership interest in all such inventions that were made jointly by the Company and ImmuNext and patent rights covering those inventions that were assigned by the Company to ImmuNext during the Option Period, except for any of those inventions that relates to certain compounds to which ImmuNext has retained exclusive rights. In consideration of the grant of the option, the Company made an upfront payment to ImmuNext of $1.3 million which is included in research and development expense as the acquired intellectual property is not yet completed. If the Company elects to exercise the option, the Company has agreed to pay to ImmuNext an option exercise fee of $20.0 million. If the Company elects to exercise the option, ImmuNext will be eligible to receive up to $4.6 million in potential development milestones, up to $84.3 million in potential regulatory approval milestones, and up to $125.0 million in potential sales milestone payments from the Company. In addition, ImmuNext is eligible to receive tiered royalties on annual net sales on a product-by-product and country-by-country basis, at percentage rates ranging from high single digits to low double digits, subject to specified adjustments. The royalty payment obligations under the ImmuNext Agreement with respect to a product in a country will expire on the later of (i) expiration of the last-to-expire valid claim of the ImmuNext patents or jointly owned patents covering the manufacture, use or sale of such product in such country, (ii) the expiration of all regulatory exclusivity for such product in such country, and (iii) 10 years from the first commercial sale of such product in such country. In partial consideration for drug substance, technical advice, and maintenance of ImmuNext’s existing IND and access to ImmuNext’s technology, the Company has agreed to make semi-annual maintenance fee payments of $0.4 million to ImmuNext during the Option Period. In addition, the Company has agreed to reimburse ImmuNext for certain documented external costs and expenses incurred by ImmuNext in carrying out non-clinical research activities approved by the joint steering committee, up to $0.3 million per calendar year, unless otherwise agreed to by both parties in writing. In addition, the Company has agreed to pay ImmuNext a low double-digit percentage of sublicense revenue received by the Company or its Affiliates.

Stock Plans and Stock-Based Com

Stock Plans and Stock-Based Compensation	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock Plans and Stock-Based Compensation	Stock Plans and Stock-Based Compensation As of December 31, 2020, the Company had two shareholder-approved, stock-based compensation plans: (i) the Amended and Restated 2010 Employee Stock Purchase Plan, (“ESPP”), adopted by the Board of Directors in April 2017 and approved by shareholders in June 2017, and (ii) the Third Amended and Restated 2010 Stock Incentive Plan, (“2010 Plan”). New employees are typically issued options as an inducement equity award under Nasdaq Listing Rule 5635(c)(4) outside of the 2010 Plan. The Third Amended and Restated 2010 Stock Incentive Plan The 2010 Plan permits the granting of incentive and non-qualified stock options and stock awards to employees, officers, directors, and consultants of the Company and its subsidiaries at prices determined by the Company’s Board of Directors. On June 4, 2020, the Company's stockholders approved an amendment to the Company's Third Amended and Restated 2010 Stock Incentive Plan to reserve an additional 1,300,000 shares of common stock for issuance under the 2010 Plan. The Company can issue up to 12,190,000 shares of its common stock pursuant to awards granted under the 2010 Plan. Options become exercisable as determined by the Board of Directors and expire up to ten years from the date of grant. The 2010 Plan uses a “fungible share” concept under which each share of stock subject to awards granted as options and stock appreciation rights (“SARs”), will cause one share per share under the award to be removed from the available share pool, while each share of stock subject to awards granted as restricted stock, restricted stock units, other stock-based awards or performance awards where the price charged for the award is less than 100% of the fair market value of the Company’s common stock will cause 1.3 shares per share under the award to be removed from the available share pool. As of December 31, 2020, the Company had only granted options to purchase shares of the Company’s common stock with an exercise price equal to the closing market price of the Company’s common stock on the Nasdaq Global Market on the grant date. As of December 31, 2020, 3,765,515 shares remained available for grant under the 2010 Plan. During the year ended December 31, 2020, the Company’s board of directors granted options to purchase 2,398,150 shares of the Company’s common stock to officers and employees of the Company under the 2010 Plan. These options vest and become exercisable as to 25% of the shares underlying the award after the first year and as to an additional 6.25% of the shares underlying the award in each subsequent quarter, based upon continued employment over a four-year period, and are exercisable at a price equal to the closing price of the Company’s common stock on the Nasdaq Global Market on the grant dates. During the first quarter of 2020, the Company’s board of directors granted options to its non-employee directors to purchase 720,000 shares of common stock under the 2010 Plan, which will vest and become exercisable in one year from the date of grant. These options were granted at an exercise price that equaled the closing market price of the Company’s common stock on the Nasdaq Global Market on the grant date. During the year ended December 31, 2020, the Company’s board of directors did not grant any restricted stock awards (“RSA”) to officers of the Company. There remain RSAs for an aggregate amount of 20,624 shares outstanding of the Company's common stock previously issued under the 2010 Plan. These RSAs will vest as to 25% of the shares underlying the RSA on the first anniversary of the date of grant and as to an additional 25% annually thereafter until all such shares become vested, based upon continued service to the Company over a four-year period. Nonstatutory Inducement Grants For certain new employees the Company issued options as an inducement equity award under Nasdaq Listing Rule 5635(c)(4) outside of the 2010 Plan. The option will vest as to 25% of the shares underlying the option on the first anniversary of the grant date, and as to an additional 6.25% of the shares underlying the option on each successive three-month period thereafter. During the year ended December 31, 2020, the Company’s board of directors granted inducement equity awards of 250,000 shares of common stock. These options were granted at a weighted average exercise price of $1.33, which is based on the closing market price of the Company’s common stock on the Nasdaq Global Market on the grant date. Employee and Director Grants Vesting Tied to Service Conditions In determining the fair value of stock options, the Company generally uses the Black-Scholes option pricing model. The Black-Scholes option pricing model employs the following key assumptions for employee and director options awarded during each of the following years: For the Year Ended 2020 2019 Expected term (years) 5.5 5.5 Risk-free interest rate 0.4-1.7% 1.5-2.6% Expected volatility 80-81% 76-79% Expected dividend yield None None The following table summarizes details regarding stock options granted under the Company's equity incentive plans for the year ended December 31, 2020: Number of Weighted Weighted Aggregate Intrinsic Value Outstanding, December 31, 2019 6,158,026 $ 3.43 8.33 Granted 3,368,150 1.27 Exercised (391,122) 1.86 Canceled (467,049) 2.55 Outstanding, December 31, 2020 8,668,005 $ 2.71 7.98 $ 51,339 Exercisable at December 31, 2020 3,437,551 $ 4.68 6.88 $ 15,821 Vested and unvested expected to vest 8,039,167 $ 2.81 7.91 $ 47,024 At December 31, 2020, the weighted average fair values of stock options granted with standard vesting terms during the years ended December 31, 2020 and December 31, 2019 were $0.84 and $0.85 per share of common stock underlying such stock options, respectively. As of December 31, 2020, there was approximately $3.0 million, including the impact of estimated forfeitures, of unrecognized compensation cost related to unvested employee stock option awards outstanding under the Company’s 2010 Plan that is expected to be recognized as expense over a weighted average period of 2.2 years. The intrinsic value of employee stock options exercised during the year ended December 31, 2020 was $2.0 million. The following table presents a summary of outstanding RSAs under the 2010 Plan as of December 31, 2020: Number of Weighted Unvested, December 31, 2019 30,937 $ 3.45 Awarded — — Vested (10,313) 3.45 Forfeited — — Unvested, December 31, 2020 20,624 $ 3.45 As of December 31, 2020, there were 20,624 shares outstanding covered by RSAs that are expected to vest. The weighted average grant date fair value of these shares of restricted stock was $3.45 per share and the aggregate fair value of these shares of restricted stock was approximately $0.1 million. As of December 31, 2020, there were approximately $0.1 million of unrecognized compensation costs, net of estimated forfeitures, related to RSAs granted to officers and non-employee directors, which are expected to be recognized as expense over a remaining weighted average period of 1.06 years. Second Amended and Restated 2010 Employee Stock Purchase Plan (ESPP) The Company has reserved 2,000,000 of its shares of common stock for issuance under the ESPP. Eligible employees may purchase shares of the Company’s common stock at 85% of the lower closing market price of the common stock at the beginning of the enrollment period or ending date of the any purchase period within a two-year enrollment period, as defined. The Company has four six-month purchase periods per each two-year enrollment period. If, within any one of the four purchase periods in an enrollment period, the purchase period ending stock price is lower than the stock price at the beginning of the enrollment period, the two-year enrollment resets at the new lower stock price. This aspect of the plan was amended in 2017. Prior to 2017, the plan included two six-month purchase period per year with no defined enrollment period. As of December 31, 2020, 402,610 shares were issued under the ESPP, of which 80,544 were issued during the year ended December 31, 2020. As of December 31, 2020, there were 1,597,390 shares available for future purchase under the ESPP. For the years ended December 31, 2020 and December 31, 2019, the Company recorded compensation expense related to its ESPP and calculated the fair value of shares expected to be purchased under the ESPP using the Black-Scholes models with the following assumptions: For the Year Ended December 31, 2020 2019 Compensation expense recognized under ESPP (in thousands)_ $ 56 $ 49 Expected term 6-24 months 6-24 months Risk-free interest rate 0.1-0.2% 1.5-2.1% Volatility 97-219% 92-97% Dividends None None Employee Stock-Based Compensation Expense Stock-based compensation for employee and director stock option grants for the years ended December 31, 2020 and December 31, 2019 of $2.7 million and $2.7 million, respectively, was calculated using the above valuation models and has been included in the Company’s results of operations. The total fair value of vested stock options for the years ended December 31, 2020 and December 31, 2019 was $2.7 million and $2.0 million, respectively. Total Stock-Based Compensation Expense For the years ended December 31, 2020 and December 31, 2019, the Company recorded employee and non-employee stock-based compensation expense to the following line items in its Costs and Expenses section of the Consolidated Statements of Operations and Comprehensive Loss: For the Year Ended December 31, 2020 2019 Research and development expenses $ 731 $ 575 General and administrative expenses 1,967 2,083 Total stock-based compensation expense $ 2,698 $ 2,658

Retirement Savings Plan

Retirement Savings Plan	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Retirement Savings Plan	Retirement Savings PlanThe Company has a 401(k) retirement savings plan covering substantially all of the Company’s employees. For each of the years ended December 31, 2020 and December 31, 2019, the Company made matching contributions of $0.2 million and $0.2 million respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes For the years ended December 31, 2020 and December 31, 2019, the Company did not record any federal or state income tax expense given its continued operating losses. A reconciliation between income tax benefit and the expected tax benefit at the statutory rate for the years ended December 31, 2020 and December 31, 2019 are as follows: For the Year Ended 2020 2019 Statutory federal income tax rate 21.0 % 21.0 % State income taxes, net of federal benefit 6.1 % 6.1 % Research and development tax credits 4.1 % 2.7 % Orphan drug tax credits 2.3 % 4.6 % Expiration of NOLs/Credits (29.8) % (4.0) % Permanent adjustments and other 0.3 % (0.6) % Change in valuation allowance (4.0) % (29.8) % Effective income tax rate — % — % The principle components of the Company’s deferred tax assets at December 31, 2020 and December 31, 2019, respectively, are as follows: December 31, 2020 2019 Deferred Tax Assets: NOL carryforwards $ 60,759 $ 58,654 Research and development tax credit carryforwards 14,923 15,408 Orphan drug tax credit carryforwards 18,778 18,088 Depreciation and amortization 8,478 9,671 Capitalized research and development expenditures 34,832 34,487 Stock options 6,584 6,329 Accrued expenses and other 708 131 Oberland agreement 15,872 17,022 Lease liability ASC 842 1,846 45 Total gross deferred tax asset 162,780 159,835 Valuation allowance (160,987) (159,794) Net deferred tax asset $ 1,793 $ 41 Deferred tax liabilities: Right of use asset ASC 842 (1,793) (41) Total gross deferred tax liabilities $ (1,793) $ (41) Net deferred tax assets (liabilities) $ — $ — For the years ended December 31, 2020 and 2019, the Company had federal net operating losses (“NOL”), of $251.3 and $251.2 million, respectively. The operating losses generated prior to 2021 will expire in years 2021 through 2037, unless previously utilized. The federal operating loss carryforward generated in 2021 and later can be carried forward indefinitely and can be used to offset up to 80% of taxable income of each future tax year. For the years ended December 31, 2020 and 2019, the Company had state NOLs of $126.5 and $93.6 million, respectively. The operating losses will expire in years 2021 through 2039, unless previously utilized. For the years ended December 31, 2020 and 2019, the Company had federal research and development credit carryforwards of $11.4 million and $11.9 million, respectively. The credits will expire in the years 2021 through 2040. For the years ended December 31, 2020 and 2019, the Company had state research and development credit carryforwards of $4.5 million and $4.4 million, respectively. The credits will expire in the years 2021 through 2035, unless previously utilized. For the years ended December 31, 2020 and 2019, the Company had orphan drug tax credit carryforwards of $18.8 million and $18.1 million, these credits, if any, relate to qualified expenses incurred for CUDC-907 since receiving the Orphan Drug designation. As required by U.S. GAAP, the Company’s management has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets, and has determined that it is more likely than not that the Company will not recognize the benefits of the deferred tax assets. Accordingly, a valuation allowance of approximately $161.0 million has been established at December 31, 2020. The valuation allowance increased approximately $1.2 million and $9.6 million during the years ended December 31, 2020 and 2019. The increases in the valuation allowance are primarily due to an increase in net deferred tax assets with an offsetting valuation allowance related to income recorded for tax related to the Oberland royalty purchase agreement. Utilization of the NOL may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986 due to ownership change limitations that have occurred previously or that could occur in the future. These ownership changes may limit the amount of NOL carryforwards that can be utilized annually to offset future taxable income and tax, respectively. The Company completed a §382 study in 2019 and determined no ownership changes have occurred and no limitation on NOLs through December 31, 2018. There could be additional ownership changes in the future, which may result in additional limitations in the utilization of the carryforward NOLs and credits, and the Company does not expect to have any taxable income for the foreseeable future. An individual tax position must satisfy for some or all of the benefits of that position to be recognized in a company’s financial statements. At December 31, 2020 and 2019, the Company had no unrecognized tax benefits. The Company has not, as yet, conducted a study of its 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 under FASB Codification Topic 740 Income Taxes . 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 tax years 2005 through 2020 remain open to examination by major taxing jurisdictions to which the Company is subject, which are primarily in the U.S., as carryforward attributes generated in years past may still be adjusted upon examination by the Internal Revenue Service (“IRS”) or state tax authorities if they have or will be used in a future period. The Company is currently not under examination by the IRS or any other jurisdictions for any tax years. The Company recognizes both accrued interest and penalties related to unrecognized benefits in income tax expense. The Company has not recorded any interest or penalties on any unrecognized tax benefits since its inception.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Agreement with Head of Research and Development - Robert E. Martell, M.D., Ph.D. On October 17, 2018, the Company entered into an exclusive option and license agreement with Epi-Cure Pharmaceuticals, Inc., (“Epi-Cure”) a privately held early-stage biotechnology company. Robert E. Martell, M.D., Ph.D., the Company’s Head of Research and Development and a former director of the Company, is a founder of Epi-Cure, was formerly an officer and director of Epi-Cure, and is currently a holder of a convertible promissory note to Epi-Cure. Under the terms of the option and license agreement, Epi-Cure has granted Curis an exclusive option to certain program compounds that may arise during the initial research and development period, and any extension thereof. Upon execution of the option and license agreement, the Company provided Epi-Cure an upfront payment of $0.1 million for legal and consulting costs incurred by Epi-Cure in connection with the transaction. In July 2019, the Company extended the research and development period of the program until April 2020, as permitted under the terms of the agreement.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	Selected Quarterly Financial Data (Unaudited) The following are selected quarterly financial data for the years ended December 31, 2020 and December 31, 2019: Quarter Ended (in thousands, except share and per share amounts) March 31, June 30, September 30, December 31, 2020 Revenues $ 2,709 $ 2,360 $ 2,742 $ 3,024 Loss from operations (8,482) (5,430) (4,711) (6,275) Net loss (9,709) (6,708) (5,974) (7,517) Net loss per common share (basic and diluted) $ (0.28) $ (0.17) $ (0.11) $ (0.11) Weighted average common shares (basic and diluted) 34,453,189 39,517,045 54,554,129 66,363,229 Quarter Ended (in thousands, except share and per share amounts) March 31, June 30, September 30, December 31, 2019 Revenues $ 1,767 $ 2,094 $ 2,856 $ 3,287 Loss from operations (5,558) (6,141) (5,323) (7,334) Net loss (9,884) (7,213) (6,436) (8,609) Net loss per common share (basic and diluted) $ (0.30) $ (0.22) $ (0.19) $ (0.26) Weighted average common shares (basic and diluted) 33,150,869 33,154,566 33,202,871 33,209,217

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Consolidation	Basis of Presentation and Principles of ConsolidationThe accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the U.S. (“GAAP”) and include the accounts of our wholly owned subsidiaries.
Use of Estimates and Assumptions	Use of Estimates and Assumptions The preparation of the Company’s consolidated financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts and disclosure of revenue, expenses and certain assets and liabilities at the balance sheet date. Such estimates include revenue recognition, including estimates related to the performance obligations under the Company’s collaboration agreements; the estimated repayment term of the Company’s debt and related short and long-term classification; the collectability of receivables; the carrying value of property and equipment and goodwill; the assumptions used in the Company’s valuation of stock-based compensation and the value of certain investments and liabilities. Actual results may differ from such estimates. The extent to which COVID-19 has had and may continue to have impacts on the Company’s business and financial results will depend on numerous evolving factors including, but not limited to: the magnitude and duration of the COVID-19 pandemic, the extent to which it will impact worldwide macroeconomic conditions including interest rates, employment rates and health insurance coverage, the speed of the anticipated recovery, and governmental and business responses to the pandemic. The Company assessed certain accounting matters that generally require consideration of forecasted financial information in context with the information reasonably available to the Company and the unknown future impacts of COVID-19 as of December 31, 2020 and through the date of this report. The Company’s future assessment of the magnitude and duration of the COVID-19 pandemic, as well as other factors, could result in material impacts to the Company’s consolidated financial statements in future reporting periods.
Cash Equivalents, Restricted Cash, and Investments	Cash Equivalents, Restricted Cash, and Investments Cash equivalents consist of highly liquid investments purchased with original maturities of three months or less. All other liquid investments are classified as marketable securities. The Company classified $0.8 million and $1.0 million of its cash as restricted cash, as of December 31, 2020 and December 31, 2019. This amount represents the security deposit delivered to the respective landlords of the Company's current and former Lexington, Massachusetts headquarters. The Company's combined cash and restricted cash balances were $130.4 million and $16.4 million as of December 31, 2020 and December 31, 2019, as presented on the Company's Consolidated Statements of Cash Flows. The Company’s short-term investments are marketable debt securities with original maturities of greater than three months from the date of purchase, but less than twelve months from the balance sheet date, and long-term investments are marketable debt securities with original maturities of greater than twelve months from the balance sheet. Marketable securities consist of commercial paper, corporate bonds and notes, and/or government obligations. All of the Company’s investments have been designated available-for-sale and are stated at fair value. Unrealized gains and temporary losses on investments are included in accumulated other comprehensive income (loss) as a separate component of stockholders’ deficit. Realized gains and losses, dividends and interest income are included in other income (expense) in the period during which the securities are sold. Any premium or discount arising at purchase is amortized and/or accreted to interest income.
Concentrations and Significant Customer Information	Concentrations and Significant Customer Information Financial instruments which potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents, marketable securities, and accounts receivable. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. The Company’s credit risk related to investments is reduced as a result of the Company’s policy to limit the amount invested in any one issue. As of December 31, 2020, the Company did not have a material concentration in any single investment. The Company's operations are located entirely within the U.S. The Company focus is primarily on the development of first-in-class and innovative therapeutics for the treatment of cancer. The Company's customer, Genentech, accounted for 98% and 100% of the total gross revenues for December 31, 2020 and December 31, 2019, respectively. The Company’s accounts receivable at December 31, 2020 and December 31, 2019 represents amounts due from collaborators, primarily for royalties earned on sales of Erivedge by Genentech and Roche.
Long-Lived Assets Other than Goodwill	Long-Lived Assets Other than Goodwill Long-lived assets other than goodwill consist of property and equipment. The Company applies the guidance in FASB Codification Topic 360-10-05, Impairment or Disposal of Long-Lived Assets
Leases	Leases In February 2016 the FASB issued ASU No. 2016-02, Leases (Topic 842) , a standard issued to increase transparency and comparability among organizations related to their leasing activities. This standard established a right-of-use model that requires the recognition of right-of-use assets and lease liabilities for most leases as well as provides disclosure with respect to certain qualitative and quantitative information related to a company's leasing arrangements to meet the objective of allowing users of financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. The FASB subsequently issued the following amendments to ASU 2016-02 that have the same effective date and transition date: ASU No. 2018-10, Codification Improvements to Topic 842, Leases , ASU No. 2018-11, Leases (Topic 842): Targeted Improvements , and ASU No. 2019-01, Leases (Topic 842): Codification Improvements . The Company adopted these amendments with ASU 2016-02 (collectively, the new leasing standards) effective January 1, 2019. The Company adopted the leasing standards using the modified retrospective transition approach, as of January 1, 2019, with no restatement of prior periods or cumulative adjustment to retained earnings. Upon adoption, the Company elected the package of transition practical expedients, which allowed Curis to carry forward prior conclusions related to whether any expired or existing contracts are or contain leases, the lease classification for any expired or existing leases and initial direct costs for existing leases. The Company also made an accounting policy election to not recognize leases with an initial term of 12 months or less within its consolidated balance sheets and to recognize those lease payments on a straight-line basis in its consolidated statements of income over the lease term. Upon adoption of the leasing standard Curis recognized an operating lease asset of approximately $1.0 million and a corresponding operating lease liability of approximately $1.1 million. The adoption of the leasing standard did not have an impact on the consolidated statement of income. The Company determines if an arrangement is a lease at contract inception. Operating lease assets represent the Company's right to use an underlying asset for the lease term and operating lease liabilities represent its obligation to make lease payments arising from the lease. Operating lease assets and liabilities are recognized at the commencement date of the lease based upon the present value of lease payments over the lease term. When determining the lease term, the Company includes options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. As most of the Company's leases do not provide an implicit interest rate, the Company uses its incremental borrowing rate, which is based on rates that would be incurred to borrow on a collateralized basis over a term equal to the lease payments in a similar economic environment, in determining the present value of lease payments. Right-of-use assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The lease payment used to determine the operating lease asset may include lease incentives, stated rent increases and was recognized as an operating lease right-of-use asset in the consolidated balance sheets. The Company's lease agreements may include both lease and non-lease components, which are accounted for as a single lease component when the payments are fixed. Variable payments included in the lease agreement are expensed as incurred.
Goodwill	Goodwill As of both December 31, 2020 and December 31, 2019, the Company had recorded goodwill of $9.0 million. The Company applies the guidance in the FASB Codification Topic 350, Intangibles—Goodwill and Other
Revenue Recognition	Revenue Recognition The Company’s business strategy includes entering into collaborative license and development agreements with biotechnology and pharmaceutical companies for the development and commercialization of the Company’s drug candidates. The terms of the agreements typically include non-refundable license fees, funding of research and development, payments based upon achievement of clinical development and regulatory objectives, and royalties on product sales. License Fees and Multiple Element Arrangements If a license to its intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company will recognize revenues from non-refundable, up-front fees allocated to the license at such time as the license is transferred to the licensee and the licensee is able to use, and benefit from, the license. For licenses that are bundled 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 from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, will adjust the measure of performance and related revenue recognition. If the Company is involved in a steering committee as part of a multiple element arrangement, the Company assesses whether its involvement constitutes a performance obligation or a right to participate. Steering committee services that are not determined to be distinct performance obligations are combined with other research services or performance obligations required under an arrangement, if any, in determining the level of effort required in an arrangement and the period over which the Company expects to complete its aggregate performance obligations. Appropriate methods of measuring progress include output methods and input methods. In determining the appropriate method for measuring progress, the Company considers the nature of service that it promises to transfer to the customer. When the Company decides on a method of measurement, the Company will apply that single method of measuring progress for each performance obligation satisfied over time and will apply that method consistently to similar performance obligations and in similar circumstances. If the Company cannot reasonably measure its progress toward complete satisfaction of a performance obligation because the Company lacks reliable information that would be required to apply an appropriate method of measuring progress, but it can reasonably estimate when the performance ceases or the remaining obligations become inconsequential and perfunctory, then revenue is not recognized until the Company can reasonably estimate when the performance obligation ceases or becomes inconsequential. Revenue is then recognized over the remaining estimated period of performance. Significant management judgment is required in determining the level of effort required under an arrangement and the period over which the Company is expected to complete its performance obligations under an arrangement. Contingent Research Milestone Payments ASC 606 constrains the amount of variable consideration included in the transaction price in that either all, or a portion, of an amount of variable consideration should be included in the transaction price. The variable consideration amount should be included only to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. The assessment of whether variable consideration should be constrained is largely a qualitative one that has two elements: the likelihood of a change in estimate, and the magnitude thereof. Variable consideration is not constrained if the potential reversal of cumulative revenue recognized is not significant, for example. If the consideration in a contract includes a variable amount, a company will estimate the amount of consideration in exchange for transfer of promised goods or services. The consideration also can vary if a company’s entitlement to the consideration is contingent on the occurrence or nonoccurrence of a future event. The Company considers contingent research milestone payments to fall under the scope of variable consideration, which should be estimated for revenue recognition purposes at the inception of the contract and reassessed ongoing at the end of each reporting period. The Company assesses whether contingent research milestones should be considered variable consideration that should be constrained and thus not part of the transaction price. This includes an assessment of the probability that all or some of the milestone revenues could be reversed when the uncertainty around whether or not the achievement of each milestone is resolved, and the amount of reversal could be significant. GAAP provides factors to consider when assessing whether variable consideration should be constrained. All of the factors should be considered, and no factor is determinative. The Company considers all relevant factors. Reimbursement of Costs Reimbursement of research and development costs by third-party collaborators is recognized as revenue over time provided the Company has determined that it transfers control (i.e. performs the services) of a service over time and, therefore, satisfies a performance obligation according to the provisions outlined in ASC 606-10-25-27, Revenue Recognition . Royalty Revenue Since the first quarter of 2012, the Company has recognized royalty revenues related to Genentech’s and Roche’s sales of Erivedge. For arrangements that include sales based royalties, including milestone payments based on the level of sales, and where 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). The Company expects to continue recognizing royalty revenue from Genentech’s sales of Erivedge in the U.S. and in other markets where Genentech and Roche successfully obtain marketing approval, if any (see Note 11). However, a portion of potential Erivedge royalties will be paid to the Purchasers pursuant to the Oberland Purchase Agreement (see Note 9). Contra Revenue, Net Contra revenue, net represents shared costs, primarily related to intellectual property, with the Company's collaboration partners, and reserves for potential royalty reductions. With respect to each of the foregoing areas of revenue recognition, the Company exercises significant judgment in determining whether an arrangement contains multiple elements, and, if so, how much revenue is allocable to each element. In addition, the Company exercises its judgment in determining when its significant obligations have been met under such agreements and the specific time periods over which the Company recognized revenue, such as non-refundable, up-front license fees. To the extent that actual facts and circumstances differ from the Company's initial judgments, its revenue recognition with respect to such transactions would change accordingly and any such change could affect the Company's reported financial results.
Cost of Royalties	Cost of RoyaltiesThe Company recognizes cost of royalties on Erivedge royalty revenue earned from Genentech related to obligations to third-party university licensors. The Company is also incurring research and development expenses under this collaboration related to the maintenance of these third-party licenses to certain background technologies. In addition, the Company records research and development expense for obligations to certain third-party university licensors upon earning payments from Genentech related to the achievement of clinical development and regulatory objectives under this collaboration.
Research and Development	Research and DevelopmentResearch and development expense consists of costs incurred to discover, research and develop drug candidates. These expenses primarily include: (1) salaries and related expenses for personnel including stock-based compensation expense; (2) outside service costs, including clinical research organizations and contract manufacturing costs, among others; (3) sublicense payments; and (4) the costs of supplies and reagents, consulting, and occupancy and depreciation charges. The Company expenses research and development costs as they are incurred.
Basic and Diluted Loss Per Common Share	Basic and Diluted Loss per Common ShareBasic and diluted net losses per share were determined by dividing net loss by the weighted average number of common shares outstanding during the period. Diluted net loss per common share is the same as basic net loss per common share for all periods presented, as the effect of the potential common stock equivalents is antidilutive due to the Company’s net loss position for all periods presented.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation transactions using a grant-date fair-value based method under FASB Codification Topic 718, Compensation-Stock Compensation . The Company measures compensation cost for stock-based compensation at fair value, including an estimate of forfeitures and recognizes the expense as compensation expense over the period that the recipient is required to provide service in exchange for the award, which generally is the vesting period. The Company uses the Black-Scholes option pricing model to measure the fair value of stock options. This model requires significant estimates related to the award’s expected life and future stock price volatility of the underlying equity security. In determining the amount of expense to be recorded, the Company also estimates forfeiture rates for awards, based on the probability that employees will complete the required service period. The Company estimates the forfeiture rate based on historical experience. If actual forfeitures differ significantly from the Company’s estimates, additional adjustments to compensation expense may be required in future periods. Ultimately, the actual expense recognized over the vesting period will only be for those shares that vest. The expected volatility is based on the annualized daily historical volatility of the Company’s stock price for a time period consistent with the expected term of each grant. Management believes that the historical volatility of the Company’s stock price best represents the future volatility of the stock price. The risk-free rate is based on the U.S. Treasury yield in effect at the time of grant for the expected term of the respective grant. The Company has not historically paid cash dividends, and does not expect to pay cash dividends in the foreseeable future. The stock price volatility and expected terms utilized in the calculation involve management’s best estimates at that time, both of which impact the fair value of the option calculated under the Black-Scholes methodology and, ultimately, the expense that will be recognized over the life of the option. GAAP also requires that the Company recognize compensation expense for only the portion of options that are expected to vest. Therefore, management calculated an estimated annual pre-vesting forfeiture rate that is derived from historical employee termination behavior since the inception of the Company, as adjusted. If the actual number of forfeitures differs from those estimated by management, additional adjustments to compensation expense may be required in future periods.
Comprehensive Loss	Comprehensive LossComprehensive loss is comprised of net loss and other comprehensive income (loss). Other comprehensive income (loss) includes unrealized holding gains and losses arising during the period on available-for-sale securities that are not other-than-temporarily impaired.
Segment Reporting	Segment ReportingThe Company has determined that it operates in a single reportable segment, which is the research and development of innovative drug candidates for the treatment of human cancer. The Company expects that any products that are successfully developed and commercialized would be used in the healthcare industry and would be regulated in the United States by the FDA and in overseas markets by similar regulatory authorities.
Interest Expense on Liability related to the Sale of Future Royalties	Interest Expense on Liability related to the Sale of Future RoyaltiesIn March 2019 the Company entered into the Oberland Purchase Agreement with Oberland Capital. Pursuant to the terms of the Oberland Purchase Agreement the Company sold to Oberland a portion of its rights to receive royalties from Genentech on potential net sales of Erivedge. As a result of the obligation to pay future royalties to Oberland, the Company recorded the proceeds from this transaction as a liability on its Consolidated Balance Sheet that is accounted for using the interest method over the estimated life of the Oberland Purchase Agreement. As a result, the Company imputes interest on the transaction and records imputed interest expense at the estimated interest rate. The Company's estimate of the interest rate under the agreement is based on the amount of royalty payments expected to be received by Oberland over the life of the arrangement. On a quarterly basis, the Company assesses the expected royalty payments to Curis Royalty from Genentech using a combination of historical results and forecasts from market data sources. To the extent such payments are greater or less than the initial estimates or the timing of such payments is materially different than the original estimates, the Company will prospectively adjust the amortization of the liability.
New Accounting Pronouncements	New Accounting Pronouncements Recently Adopted In August 2018, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2018-13, Fair Value Measurement, which modified the disclosure requirements for fair value measurement under ASC 820. The standard was effective for annual reporting periods and interim periods within those annual periods, beginning after December 15, 2019, with early adoption permitted. The Company adopted the standard effective January 1, 2020 with no material impact to its Consolidated Financial Statements. Issued, Not Yet Adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. This standard requires that for most financial assets, losses be based on an expected loss approach which includes estimates of losses over the life of exposure that considers historical, current and forecasted information. Expanded disclosures related to the methods used to estimate the losses as well as a specific disaggregation of balances for financial assets are also required. The targeted transition relief standard allows filers an option to irrevocably elect the fair value option of ASC 825-10, Financial Instruments-Overall, applied on an instrument-by-instrument basis for eligible instruments. In November 2019 the effective date for smaller reporting companies was extended to January 1, 2023 with the issuance of ASU 2019-10 Financial Instruments-Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842) Effective Dates. The Company is currently evaluating the effects of this standard and does not expect that adoption of this standard will have a material impact on its consolidated financial statements.
Fair Value of Financial Instruments	The Company applies the provisions of ASC Topic 820, Fair Value Measurements (“ASC 820”) for its financial assets and liabilities that are re-measured and reported at fair value each reporting period and the non-financial assets and liabilities that are re-measured and reported at fair value on a non-recurring basis. Fair value is the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value, the Company considers the principal or most advantageous market in which it would transact and consider assumptions that market participants would use when pricing the asset or liability. ASC 820 establishes a three-level valuation hierarchy for disclosure of fair value measurements. Financial assets and liabilities are categorized within the valuation hierarchy based upon the lowest level of input that is significant to the measurement of fair value. The three levels of the hierarchy are defined as follows: Level 1 Quoted prices in active markets for identical assets or liabilities. Level 2 Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Estimated Useful Lives of Long-Lived Assets Other Than Goodwill	Depreciation and amortization are provided on the straight-line method over the estimated useful lives of the related assets or the remaining terms of the leases, whichever is shorter, as follows: Useful Life Laboratory equipment, computers and software 3-5 years Leasehold improvements Lesser of lease or asset life Office furniture and equipment 5 years
Summary of Antidilutive Securities	For the Year Ended December 31, 2020 2019 Stock options outstanding 8,668,005 6,158,026 Total antidilutive securities 8,668,005 6,158,026

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	In accordance with the fair value hierarchy, the following table shows the fair value as of December 31, 2020 and December 31, 2019 of those financial assets and liabilities that are measured at fair value on a recurring basis, according to the valuation techniques the Company used to determine their fair value. No financial assets or liabilities are measured at fair value on a nonrecurring basis at December 31, 2020 and December 31, 2019. Quoted Prices in Other Unobservable Fair Value (in thousands) As of December 31, 2020 Cash equivalents: Money market funds $ 115,278 $ — $ — $ 115,278 Short-term investments: Corporate commercial paper, bonds and notes — 38,884 — 38,884 Long-term investments: Corporate commercial paper, bonds and notes — 14,564 — 14,564 Total assets at fair value $ 115,278 $ 53,448 $ — $ 168,726 Quoted Prices in Other Unobservable Fair Value (in thousands) As of December 31, 2019 Cash equivalents: Money market funds $ 10,684 $ — $ — $ 10,684 US government obligations — 550 — 550 Corporate commercial paper, stock, bonds and notes — 300 — 300 Municipal bonds — 90 — 90 Short-term investments: Corporate commercial paper, stock, bonds and notes — 5,113 — 5,113 Total assets at fair value $ 10,684 $ 6,053 $ — $ 16,737

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Schedule of Amortized Cost, Unrealized Gains and Losses and Fair Value of Investments Available-for-Sale	The amortized cost, unrealized gains and losses and fair value of investments available-for-sale as of December 31, 2020 are as follows: (in thousands) Amortized Unrealized Unrealized Fair Value Corporate bonds and notes—short-term $ 38,888 $ — $ (4) $ 38,884 Corporate bonds and notes—long-term 14,563 1 — 14,564 Total investments $ 53,451 $ 1 $ (4) $ 53,448 The amortized cost, unrealized gains and losses and fair value of investments available-for-sale as of December 31, 2019 are as follows: (in thousands) Amortized Unrealized Unrealized Fair Value Corporate bonds and notes—short-term $ 5,113 $ — $ — $ 5,113 Total investments $ 5,113 $ — $ — $ 5,113

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consist of the following: December 31, (in thousands) 2020 2019 Laboratory equipment, computers and software $ 1,736 $ 1,725 Leasehold improvements 214 185 Office furniture and equipment 779 331 2,729 2,241 Less—Accumulated depreciation and amortization (2,066) (2,087) Total $ 663 $ 154

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Other Liabilities Disclosure [Abstract]
Summary of Accrued Liabilities	Accrued liabilities consist of the following: December 31, (in thousands) 2020 2019 Accrued compensation $ 2,638 $ 1,413 Accrued license fees 375 — Professional fees 307 289 Other 305 208 Total $ 3,625 $ 1,910

Leases and Commitments (Tables)

Leases and Commitments (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Balance Sheet Information for Operating Leases	All of the Company's leases qualify as operating leases. The following table summarizes the presentation in the Company's consolidated balance sheet for the operating leases: Balance sheet location ( in thousands) As of December 31, 2020 As of December 31, 2019 Assets: Operating lease right-of-use asset $ 6,578 $ 149 Liabilities: Operating lease liability - short-term $ 1,731 $ 166 Operating lease liability - long-term $ 5,040 $ — Total operating liability $ 6,771 $ 166
Lease Cost	The following table summarized the effect of lease costs in our consolidated statements of income. Income statement location ( in thousands) Year ended Year ended Operating lease cost Research and development $ 1,061 $ 651 General and administrative 275 351 1,336 $ 1,002
Lease Maturity Schedule	The Company’s lease payments for the next five years and thereafter is expected to be as follows: Year Ending December 31, (in thousands) 2021 $ 2,256 2022 1,144 2023 1,178 2024 1,213 2025 1,250 Thereafter 1,721 Total lease payments $ 8,762 Less: interest 1,991 Present value of operating lease liabilities $ 6,771

Liability Related to the Sale_2

Liability Related to the Sale of Future Royalties (Tables)	12 Months Ended
	Dec. 31, 2020
Nonmonetary Transactions [Abstract]
Schedule of Liability Due to Non-Cash Transaction	The following table shows the activity with respect to the liability related to the sale of future royalties during the year ended December 31, 2020: (in thousands) Carrying value of liability related to the sale of future royalties at January 1, 2020 $ 62,477 Amortization of capitalized issuance costs 61 Imputed interest expense recognized for the year ended December 31, 2020 5,034 Less: payments to Oberland Capital, LLC (9,337) Carrying value of liability related to the sale of future royalties at December 31, 2020 $ 58,235 The following table shows the activity with respect to the liability related to the sale of future royalties during the year ended December 31, 2019: (in thousands) Liability related to the sale of future royalties at March 22, 2019 $ 65,000 Capitalized issuance costs, net (584) Imputed interest expense recognized for the year ended December 31, 2019 4,055 Less: payments to Oberland Capital, LLC (5,994) Carrying value of liability related to the sale of future royalties at December 31, 2019 $ 62,477

Stock Plans and Stock-Based C_2

Stock Plans and Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Valuation Assumptions Used to Calculate Fair Value of Employee Options Awarded	The Black-Scholes option pricing model employs the following key assumptions for employee and director options awarded during each of the following years: For the Year Ended 2020 2019 Expected term (years) 5.5 5.5 Risk-free interest rate 0.4-1.7% 1.5-2.6% Expected volatility 80-81% 76-79% Expected dividend yield None None
Summary of Stock Option Activity	The following table summarizes details regarding stock options granted under the Company's equity incentive plans for the year ended December 31, 2020: Number of Weighted Weighted Aggregate Intrinsic Value Outstanding, December 31, 2019 6,158,026 $ 3.43 8.33 Granted 3,368,150 1.27 Exercised (391,122) 1.86 Canceled (467,049) 2.55 Outstanding, December 31, 2020 8,668,005 $ 2.71 7.98 $ 51,339 Exercisable at December 31, 2020 3,437,551 $ 4.68 6.88 $ 15,821 Vested and unvested expected to vest 8,039,167 $ 2.81 7.91 $ 47,024
Nonvested Restricted Stock Shares Activity	The following table presents a summary of outstanding RSAs under the 2010 Plan as of December 31, 2020: Number of Weighted Unvested, December 31, 2019 30,937 $ 3.45 Awarded — — Vested (10,313) 3.45 Forfeited — — Unvested, December 31, 2020 20,624 $ 3.45
Summary of Compensation Expense Related to ESPP	For the years ended December 31, 2020 and December 31, 2019, the Company recorded compensation expense related to its ESPP and calculated the fair value of shares expected to be purchased under the ESPP using the Black-Scholes models with the following assumptions: For the Year Ended December 31, 2020 2019 Compensation expense recognized under ESPP (in thousands)_ $ 56 $ 49 Expected term 6-24 months 6-24 months Risk-free interest rate 0.1-0.2% 1.5-2.1% Volatility 97-219% 92-97% Dividends None None
Employee and Non-Employee Stock-Based Compensation Expense Allocation	For the years ended December 31, 2020 and December 31, 2019, the Company recorded employee and non-employee stock-based compensation expense to the following line items in its Costs and Expenses section of the Consolidated Statements of Operations and Comprehensive Loss: For the Year Ended December 31, 2020 2019 Research and development expenses $ 731 $ 575 General and administrative expenses 1,967 2,083 Total stock-based compensation expense $ 2,698 $ 2,658

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation	A reconciliation between income tax benefit and the expected tax benefit at the statutory rate for the years ended December 31, 2020 and December 31, 2019 are as follows: For the Year Ended 2020 2019 Statutory federal income tax rate 21.0 % 21.0 % State income taxes, net of federal benefit 6.1 % 6.1 % Research and development tax credits 4.1 % 2.7 % Orphan drug tax credits 2.3 % 4.6 % Expiration of NOLs/Credits (29.8) % (4.0) % Permanent adjustments and other 0.3 % (0.6) % Change in valuation allowance (4.0) % (29.8) % Effective income tax rate — % — %
Components of Deferred Tax Assets	The principle components of the Company’s deferred tax assets at December 31, 2020 and December 31, 2019, respectively, are as follows: December 31, 2020 2019 Deferred Tax Assets: NOL carryforwards $ 60,759 $ 58,654 Research and development tax credit carryforwards 14,923 15,408 Orphan drug tax credit carryforwards 18,778 18,088 Depreciation and amortization 8,478 9,671 Capitalized research and development expenditures 34,832 34,487 Stock options 6,584 6,329 Accrued expenses and other 708 131 Oberland agreement 15,872 17,022 Lease liability ASC 842 1,846 45 Total gross deferred tax asset 162,780 159,835 Valuation allowance (160,987) (159,794) Net deferred tax asset $ 1,793 $ 41 Deferred tax liabilities: Right of use asset ASC 842 (1,793) (41) Total gross deferred tax liabilities $ (1,793) $ (41) Net deferred tax assets (liabilities) $ — $ —

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Data	The following are selected quarterly financial data for the years ended December 31, 2020 and December 31, 2019: Quarter Ended (in thousands, except share and per share amounts) March 31, June 30, September 30, December 31, 2020 Revenues $ 2,709 $ 2,360 $ 2,742 $ 3,024 Loss from operations (8,482) (5,430) (4,711) (6,275) Net loss (9,709) (6,708) (5,974) (7,517) Net loss per common share (basic and diluted) $ (0.28) $ (0.17) $ (0.11) $ (0.11) Weighted average common shares (basic and diluted) 34,453,189 39,517,045 54,554,129 66,363,229 Quarter Ended (in thousands, except share and per share amounts) March 31, June 30, September 30, December 31, 2019 Revenues $ 1,767 $ 2,094 $ 2,856 $ 3,287 Loss from operations (5,558) (6,141) (5,323) (7,334) Net loss (9,884) (7,213) (6,436) (8,609) Net loss per common share (basic and diluted) $ (0.30) $ (0.22) $ (0.19) $ (0.26) Weighted average common shares (basic and diluted) 33,150,869 33,154,566 33,202,871 33,209,217

Nature of Business (Details)

Nature of Business (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ 1,046,889				$ 1,016,981				$ 1,046,889	$ 1,016,981
Net loss	7,517	$ 5,974	$ 6,708	$ 9,709	$ 8,609	$ 6,436	$ 7,213	$ 9,884	29,908	32,141
Net cash used in operating activities									25,739	$ 26,205
Cash, cash equivalents, and investments	$ 183,100								$ 183,100

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2020USD ($)numberOfSecurities	Dec. 31, 2019USD ($)	May 01, 2020USD ($)	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)
Significant Accounting Policies [Line Items]
Restricted cash	$ 800,000	$ 1,000,000
Cash and cash equivalents, restricted cash and restricted cash equivalents	130,426,000	16,399,000			$ 23,789,000
Operating lease right-of-use asset	6,578,000	149,000
Total operating liability	6,771,000	166,000	$ 8,200,000
Goodwill	8,982,000	8,982,000
Goodwill impairment charges	$ 0	$ 0
Number of reportable segments | numberOfSecurities	1
Customer concentration risk | Genentech, Inc.
Significant Accounting Policies [Line Items]
Total gross revenue	98.00%	100.00%
Accounting Standards Update 2016-02
Significant Accounting Policies [Line Items]
Operating lease right-of-use asset				$ 1,000,000
Total operating liability				$ 1,100,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Estimated Useful Lives of Long-Lived Assets (Details)	12 Months Ended
	Dec. 31, 2020
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Useful Life	5 years
Minimum | Laboratory equipment, computers and software
Property, Plant and Equipment [Line Items]
Useful Life	3 years
Maximum | Laboratory equipment, computers and software
Property, Plant and Equipment [Line Items]
Useful Life	5 years

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Antidilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total antidilutive securities (in shares)	8,668,005	6,158,026
Stock options outstanding
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total antidilutive securities (in shares)	8,668,005	6,158,026

Fair Value of Financial Instr_3

Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Investments, Fair Value Disclosure [Abstract]
Corporate commercial paper, stock, bonds and notes	$ 53,448	$ 5,113
Fair value, measurements, recurring
Investments, Fair Value Disclosure [Abstract]
Total assets at fair value	168,726	16,737
Fair value, measurements, recurring | Corporate commercial paper, bonds and notes
Investments, Fair Value Disclosure [Abstract]
Corporate commercial paper, stock, bonds and notes	38,884	5,113
Fair value, measurements, recurring | Money market funds
Cash equivalents:
Cash equivalents	115,278	10,684
Fair value, measurements, recurring | US government obligations
Cash equivalents:
Cash equivalents		550
Fair value, measurements, recurring | Municipal bonds
Cash equivalents:
Cash equivalents		90
Fair value, measurements, recurring | Corporate commercial paper, bonds and notes
Cash equivalents:
Cash equivalents		300
Investments, Fair Value Disclosure [Abstract]
Corporate commercial paper, stock, bonds and notes	14,564
Fair value, measurements, recurring | Quoted Prices in Active Markets (Level 1)
Investments, Fair Value Disclosure [Abstract]
Total assets at fair value	115,278	10,684
Fair value, measurements, recurring | Quoted Prices in Active Markets (Level 1) | Corporate commercial paper, bonds and notes
Investments, Fair Value Disclosure [Abstract]
Corporate commercial paper, stock, bonds and notes	0	0
Fair value, measurements, recurring | Quoted Prices in Active Markets (Level 1) | Money market funds
Cash equivalents:
Cash equivalents	115,278	10,684
Fair value, measurements, recurring | Quoted Prices in Active Markets (Level 1) | US government obligations
Cash equivalents:
Cash equivalents		0
Fair value, measurements, recurring | Quoted Prices in Active Markets (Level 1) | Municipal bonds
Cash equivalents:
Cash equivalents		0
Fair value, measurements, recurring | Quoted Prices in Active Markets (Level 1) | Corporate commercial paper, bonds and notes
Cash equivalents:
Cash equivalents		0
Investments, Fair Value Disclosure [Abstract]
Corporate commercial paper, stock, bonds and notes	0
Fair value, measurements, recurring | Other Observable Inputs (Level 2)
Investments, Fair Value Disclosure [Abstract]
Total assets at fair value	53,448	6,053
Fair value, measurements, recurring | Other Observable Inputs (Level 2) | Corporate commercial paper, bonds and notes
Investments, Fair Value Disclosure [Abstract]
Corporate commercial paper, stock, bonds and notes	38,884	5,113
Fair value, measurements, recurring | Other Observable Inputs (Level 2) | Money market funds
Cash equivalents:
Cash equivalents	0	0
Fair value, measurements, recurring | Other Observable Inputs (Level 2) | US government obligations
Cash equivalents:
Cash equivalents		550
Fair value, measurements, recurring | Other Observable Inputs (Level 2) | Municipal bonds
Cash equivalents:
Cash equivalents		90
Fair value, measurements, recurring | Other Observable Inputs (Level 2) | Corporate commercial paper, bonds and notes
Cash equivalents:
Cash equivalents		300
Investments, Fair Value Disclosure [Abstract]
Corporate commercial paper, stock, bonds and notes	14,564
Fair value, measurements, recurring | Unobservable Inputs (Level 3)
Investments, Fair Value Disclosure [Abstract]
Total assets at fair value	0	0
Fair value, measurements, recurring | Unobservable Inputs (Level 3) | Corporate commercial paper, bonds and notes
Investments, Fair Value Disclosure [Abstract]
Corporate commercial paper, stock, bonds and notes	0	0
Fair value, measurements, recurring | Unobservable Inputs (Level 3) | Money market funds
Cash equivalents:
Cash equivalents	0	0
Fair value, measurements, recurring | Unobservable Inputs (Level 3) | US government obligations
Cash equivalents:
Cash equivalents		0
Fair value, measurements, recurring | Unobservable Inputs (Level 3) | Municipal bonds
Cash equivalents:
Cash equivalents		0
Fair value, measurements, recurring | Unobservable Inputs (Level 3) | Corporate commercial paper, bonds and notes
Cash equivalents:
Cash equivalents		$ 0
Investments, Fair Value Disclosure [Abstract]
Corporate commercial paper, stock, bonds and notes	$ 0

Investments (Details)

Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 53,451	$ 5,113
Unrealized Gain	1	0
Unrealized Loss	(4)	0
Fair Value	$ 53,448	5,113
Corporate bonds and notes—long-term
Debt Securities, Available-for-sale [Line Items]
Weighted average maturity of short-term investments	1 year 6 months
Corporate Debt Securities | Corporate bonds and notes—short-term
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 38,888	5,113
Unrealized Gain	0	0
Unrealized Loss	(4)	0
Fair Value	38,884	$ 5,113
Corporate Debt Securities | Corporate bonds and notes—long-term
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	14,563
Unrealized Gain	1
Unrealized Loss	0
Fair Value	$ 14,564
Minimum | Corporate bonds and notes—short-term
Debt Securities, Available-for-sale [Line Items]
Range of maturities	1 month	1 month
Weighted average maturity of short-term investments	7 months 6 days
Maximum | Corporate bonds and notes—short-term
Debt Securities, Available-for-sale [Line Items]
Range of maturities	12 months	12 months
Weighted average maturity of short-term investments		1 month 6 days

Property and Equipment, Net - S

Property and Equipment, Net - Schedule (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment	$ 2,729	$ 2,241
Less—Accumulated depreciation and amortization	(2,066)	(2,087)
Total	663	154
Laboratory equipment, computers and software
Property, Plant and Equipment [Line Items]
Property and equipment	1,736	1,725
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	214	185
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment	$ 779	$ 331

Property and Equipment, Net - N

Property and Equipment, Net - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 144	$ 125

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Other Liabilities Disclosure [Abstract]
Accrued compensation	$ 2,638	$ 1,413
Accrued license fees	375	0
Professional fees	307	289
Other	305	208
Total	$ 3,625	$ 1,910

Leases and Commitments - Narrat

Leases and Commitments - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	May 01, 2020
Leases [Abstract]
Discount rate (percent)	9.95%
Lease term	7 years
Total operating liability	$ 6,771	$ 166	$ 8,200
Operating lease expense	700
Cost of royalties	$ 534	$ 503

Leases and Commitments - Balanc

Leases and Commitments - Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2020	May 01, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease right-of-use asset	$ 6,578		$ 149
Current portion of operating lease liability	1,731		166
Operating lease liability - long-term	5,040		0
Total operating liability	$ 6,771	$ 8,200	$ 166

Leases and Commitments - Lease

Leases and Commitments - Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 1,336	$ 1,002
Research and development expenses
Lessee, Lease, Description [Line Items]
Operating lease cost	1,061	651
General and administrative expenses
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 275	$ 351

Leases and Commitments - Leas_2

Leases and Commitments - Lease Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	May 01, 2020	Dec. 31, 2019
Future Lease Payments (Topic 842)
2021	$ 2,256
2022	1,144
2023	1,178
2024	1,213
2025	1,250
Thereafter	1,721
Total lease payments	8,762
Less: interest	1,991
Present value of operating lease liabilities	$ 6,771	$ 8,200	$ 166

Debt (Details)

Debt (Details) - USD ($)	Dec. 31, 2020	Apr. 21, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Unsecured loan		$ 900,000	$ 0
Current portion long-term debt	$ 557,000		0
Silicon Valley Bank | Cares Act PPP Loan | Commercial paper
Debt Instrument [Line Items]
Unsecured loan term (months)		24 months
Unsecured loan interest rate (percent)		1.00%
Current portion long-term debt	$ 600,000		$ 300,000

Liability Related to the Sale_3

Liability Related to the Sale of Future Royalties (Details) - USD ($) $ in Thousands	Mar. 22, 2019	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Nonmonetary Transaction [Line Items]
Proceeds from royalty interest purchase agreement with Oberland Capital Management			$ 0	$ 65,000
Non-cash interest rate (percent)			8.20%
Transaction fees	$ 600
Nonmonetary Transaction [Roll Forward]
Carrying value of liability related to the sale of future royalties at January 1, 2020		$ 65,000	$ 62,477
Amortization of capitalized issuance costs			61
Capitalized issuance costs, net		(584)
Imputed interest expense recognized for the year ended December 31, 2020		4,055	5,034
Less: payments to Oberland Capital, LLC		(5,994)	(9,337)
Carrying value of liability related to the sale of future royalties at December 31, 2020	65,000	$ 62,477	$ 58,235	$ 62,477
Oberland Capital
Nonmonetary Transaction [Line Items]
Proceeds from royalty interest purchase agreement with Oberland Capital Management	65,000
Cash proceeds from royalty purchase agreement	70,700
Purchaser default option period (days)			180 days
Royalty Amounts In 2021 | Oberland Capital
Nonmonetary Transaction [Line Items]
Cash proceeds from royalty purchase agreement	17,200
Royalty amount threshold	18,000
Aggregate Net Royalties Prior To 2027 | Oberland Capital
Nonmonetary Transaction [Line Items]
Cash proceeds from royalty purchase agreement	53,500
Royalty amount threshold	$ 117,000

Common Stock (Details)

Common Stock (Details) - USD ($)	Dec. 09, 2020	Feb. 26, 2020	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Mar. 16, 2021	Jun. 04, 2020	Jun. 03, 2020	Mar. 04, 2020	May 23, 2019	May 22, 2019	Jul. 02, 2015
Common Stock And Warrant Liability [Line Items]
Common stock, shares authorized (in shares)			151,875,000		151,875,000	101,250,000		151,875,000	101,250,000		101,250,000	67,500,000
Proceeds from issuance of common stock					$ 159,447,000	$ 0
Common stock, shares issued (in shares)			91,502,461		91,502,461	33,241,793
Value of shares of common stock issued			$ 915,000		$ 915,000	$ 332,000
Private Placement
Common Stock And Warrant Liability [Line Items]
Proceeds from direct offering			169,600,000	$ 17,500,000
Fees payable expenses			$ 10,200,000	1,000,000
Other estimated offering expenses payable expense				$ 500,000
Over-Allotment Option [Member]
Common Stock And Warrant Liability [Line Items]
Number of shares sold (in shares)			3,847,826
Common Stock
Common Stock And Warrant Liability [Line Items]
Sale price per share (in dollars per share)			$ 5.75		$ 5.75
Common Stock | Subsequent Event
Common Stock And Warrant Liability [Line Items]
Common stock authorized (in shares)							$ 100,000,000
Common Stock | Private Placement
Common Stock And Warrant Liability [Line Items]
Common stock issued (in shares)			29,500,000	14,000,000
Sale price per share (in dollars per share)				$ 1.25
Demand Sales Agreement
Common Stock And Warrant Liability [Line Items]
Proceeds from issuance of common stock					$ 8,176,000	0
Demand Sales Agreement | Common Stock
Common Stock And Warrant Liability [Line Items]
Proceeds from direct offering	$ 8,300,000
Common stock authorized (in shares)										$ 30,000,000
Compensation fee (percent of gross proceeds)										3.00%
Number of shares sold (in shares)	6,298,648
Remaining purchase program amount	$ 21,700,000
Proceeds from issuance of common stock	$ 7,900,000
Aspire Capital Fund, LLC
Common Stock And Warrant Liability [Line Items]
Proceeds from issuance of common stock		$ 3,000,000			8,099,000	$ 0
Common stock, shares issued (in shares)		2,693,965
Additional shares authorized under the plan (in shares)		4,650,000
Value of shares of common stock issued		$ 5,400,000
Aspire Capital Fund, LLC | Common Stock
Common Stock And Warrant Liability [Line Items]
Authorized purchase program amount		$ 30,000,000
Commitment fee (in shares)		646,551
Sale of stock remaining authorized amount			$ 21,600,000		$ 21,600,000
Stock purchase program, authorized per day (in shares)			150,000		150,000
Stock purchase program, authorized per day, after mutual agreement (in shares)			2,000,000		2,000,000
Cowen | Maximum | At-the-market Agreement
Common Stock And Warrant Liability [Line Items]
Planned proceeds from sale of stock (up to)													$ 30,000,000

Research and Development Coll_2

Research and Development Collaborations (Details)	Sep. 07, 2016USD ($)shares	Jun. 30, 2020	Apr. 30, 2019	Mar. 31, 2017USD ($)	Sep. 30, 2016program	Jun. 30, 2003USD ($)	Dec. 31, 2020USD ($)product	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2020USD ($)productprogram	Dec. 31, 2019USD ($)	Dec. 31, 2015USD ($)shares	Apr. 21, 2020USD ($)	Feb. 29, 2020	Jan. 06, 2020USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Unsecured loan											$ 0					$ 0		$ 900,000
Residual proceeds				$ 26,600,000
Revenues							$ 3,024,000	$ 2,742,000	$ 2,360,000	$ 2,709,000	3,287,000	$ 2,856,000	$ 2,094,000	$ 1,767,000	$ 10,835,000	10,004,000
Cost of royalty revenues															534,000	503,000
Accounts receivable							3,043,000				3,244,000				3,043,000	3,244,000
Value of shares of common stock issued							915,000				332,000				$ 915,000	332,000
Number of programs licensed | program					4										4
Research and Development, Net
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenues															$ 100,000	100,000
Genentech, Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Amount received for specified clinical development and regulatory objectives							59,000,000								59,000,000
Percentage of royalty rate decrease						2.00%
Cost of royalty revenues															$ 500,000
Cost and expenses of percentage of aggregate royalty earned															5.00%
Subject to a decreased percentage of royalties on expiration of patent			5.00%
Accounts receivable							$ 3,000,000				$ 3,200,000				$ 3,000,000	3,200,000
Genentech, Inc. | Gross Royalty Revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenues															$ 10,700,000	10,400,000
Genentech, Inc. | Australia
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of direct net sales															5.00%
Genentech, Inc. | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Eligible to receive contingent cash milestone payments (up to)						$ 115,000,000
Percentage of royalty on net sales						7.50%
Genentech, Inc. | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of royalty on net sales						5.00%
Aurigene Discovery Technologies Limited
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock issued for collaboration agreement (shares) | shares																	3,424,026
Value of shares of common stock issued																	$ 24,300,000
Shares issued of common stock in exchange for waived payment (in shares) | shares	2,041,666
Waived payment of milestone and other payments (up to)	$ 24,500,000
Number of products required to commercialize (at least) | product							1								1
Milestone payments waived							$ 19,500,000								$ 19,500,000
Aurigene Discovery Technologies Limited | Third and Fourth Programs
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additional funding	$ 2,000,000
Payments for collaborative arrangements							$ 14,500,000								14,500,000
Aurigene Discovery Technologies Limited | IRAK4, PD1/VISTA,PD1/TIM3 Program
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Waived payment of milestone and other payments (up to)															42,500,000
Aurigene Discovery Technologies Limited | Master Development and Manufacturing Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement payment															1,000,000	1,400,000
Aurigene Discovery Technologies Limited | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalty fees receivable (as a percent)																			10.00%
ImmuNext
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment																				$ 1,300,000
Expiration period (years)		10 years
Semi-annual maintenance fee payment																				400,000
ImmuNext | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Option exercise fee																				20,000,000
Potential development milestone payments																				4,600,000
Potential regulatory approval milestone payments																				84,300,000
Potential sales milestone payments																				125,000,000
Reimbursable expenses																				$ 300,000
Curis Royalty, LLC | HealthCare Royalty Partners III, L.P.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Principal loan amount				$ 45,000,000
Unsecured loan interest rate (percent)				9.95%
Curis Royalty, LLC | BioPharma-II
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Unsecured loan				$ 18,400,000
Genentech, Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development collaboration expense															$ 200,000	$ 200,000

Stock Plans and Stock-Based C_3

Stock Plans and Stock-Based Compensation - Narrative (Details)	Jun. 04, 2020shares	May 29, 2018	Mar. 31, 2020shares	Dec. 31, 2020USD ($)purchase_periodplan$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018purchase_period
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shareholder-approved, share-based compensation plans | plan				2
Stock split ratio		0.2
Granted (in shares)				3,368,150
Awarded (in shares)				250,000
Awarded (dollars per share) | $ / shares				$ 1.33
Weighted average grant-date fair values of stock options (in dollars per share) | $ / shares				$ 0.84	$ 0.85
Unrecognized compensation cost, including impact of estimated forfeitures | $				$ 3,000,000
Weighted average period of when compensation expense is expected to be recognized				2 years 2 months 12 days
Intrinsic values of employee stock options exercised | $				$ 2,000,000
Amount of stock-based compensation expense recorded | $				2,698,000	$ 2,658,000
Fair values of vested stock options | $				2,700,000	2,000,000
Income tax benefit | $				$ 0	0
Tranche one
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Percentage of vested shares which are exercisable under stock option				25.00%
Tranche two
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Percentage of vested shares which are exercisable under stock option				6.25%
Vesting period (years)				3 months
Amended and Restated 2010 Stock Incentive Plan
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares available for issue (up to)				12,190,000
Period of time options are exercisable				10 years
Number of shares under award to be removed from share pool				3,765,515
Amended and Restated 2010 Stock Incentive Plan | Maximum
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Price charged for award based on fair market value percentage (less than)				100.00%
2010 Plan
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Granted (in shares)				2,398,150
Vesting period (years)				4 years
2010 Plan | Non-Employee Directors
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Granted (in shares)			720,000
Vesting period (years)			1 year
2010 Plan | Tranche one
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Percentage of vested shares which are exercisable under stock option				25.00%
2010 Plan | Tranche two
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Percentage of vested shares which are exercisable under stock option				6.25%
2010 Employee Stock Purchase Plan
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares issued under ESPP (in shares)				402,610
Shares issued under ESPP during period (in shares)				80,544
Shares available for future purchase under ESPP (in shares)				1,597,390
Employee Stock Purchase Plan | Amended and Restated 2010 Stock Incentive Plan
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Additional shares authorized under the plan (in shares)	1,300,000
Employee Stock Purchase Plan | 2010 Employee Stock Purchase Plan
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Price charged for award based on fair market value percentage (less than)				85.00%
Shares available under plan (in shares)				2,000,000
Enrollment period				2 years
Number of purchase periods per year | purchase_period				4		2
Term of purchase periods				6 months		6 months
Amount of stock-based compensation expense recorded | $				$ 56,000	$ 49,000
Stock Options, or Stock Appreciation Rights | Amended and Restated 2010 Stock Incentive Plan
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares removed from available share pool (per share) | $ / shares				$ 1
Restricted Stock, RSUs, Other Stock-Based Awards, or Performance Awards | Amended and Restated 2010 Stock Incentive Plan
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares removed from available share pool (per share) | $ / shares				$ 1.3
Restricted Stock
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Awarded (in shares)				0
Awarded (dollars per share) | $ / shares				$ 0
Outstanding RSAs expect to vest (in shares)				20,624	30,937
Weighted average fair value (dollars per share) | $ / shares				$ 3.45	$ 3.45
Aggregate fair value | $				$ 100,000
Restricted Stock | Officers
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Vesting period (years)				4 years
Awarded (in shares)				20,624
Restricted Stock | Officers and Non-Employee Directors
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Unrecognized compensation cost, including impact of estimated forfeitures | $				$ 100,000
Weighted average period of when compensation expense is expected to be recognized				1 year 21 days
Restricted Stock | Tranche two | Officers
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Percentage of vested shares which are exercisable under stock option				25.00%
Employee Stock Option
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Amount of stock-based compensation expense recorded | $				$ 2,700,000	$ 2,700,000

Stock Plans and Stock-Based C_4

Stock Plans and Stock-Based Compensation - Key Assumptions (Details) - Employees and Officers	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Expected term (years)	5 years 6 months	5 years 6 months
Minimum risk-free interest rate (percent)	0.40%	1.50%
Maximum risk-free interest rate (percent)	1.70%	2.60%
Minimum volatility (percent)	80.00%	76.00%
Maximum volatility (percent)	81.00%	79.00%
Dividends (percent)	0.00%	0.00%

Stock Plans and Stock-Based C_5

Stock Plans and Stock-Based Compensation - Summary of Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Number of Options
Outstanding (beginning balance) (in shares)	6,158,026
Granted (in shares)	3,368,150
Exercised (in shares)	(391,122)
Canceled (in shares)	(467,049)
Outstanding (ending balance) (in shares)	8,668,005	6,158,026
Exercisable (in shares)	3,437,551
Vested and unvested expected to vest (in shares)	8,039,167
Weighted Average Exercise Price per Share
Outstanding (beginning balance) (in dollars per share)	$ 3.43
Granted (in dollars per share)	1.27
Exercised (in dollars per share)	1.86
Canceled (in dollars per share)	2.55
Outstanding (ending balance) (in dollars per share)	2.71	$ 3.43
Exercisable (in dollars per share)	4.68
Vested and unvested expected to vest (in dollars per share)	$ 2.81
Weighted Average Remaining Contractual Life and Aggregate Intrinsic Value
Outstanding	7 years 11 months 23 days	8 years 3 months 29 days
Exercisable	6 years 10 months 17 days
Vested and unvested expected to vest	7 years 10 months 28 days
Outstanding	$ 51,339
Exercisable	15,821
Vested and unvested expected to vest	$ 47,024

Stock Plans and Stock-Based C_6

Stock Plans and Stock-Based Compensation - Summary of Activity RSU (Details)	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Awarded (in shares) | shares	250,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Awarded (dollars per share) | $ / shares	$ 1.33
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding, beginning of period (in shares) | shares	30,937
Awarded (in shares) | shares	0
Vested (in shares) | shares	(10,313)
Forfeited (in shares) | shares	0
Outstanding, end of period (in shares) | shares	20,624
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Outstanding, beginning of period (dollars per share) | $ / shares	$ 3.45
Awarded (dollars per share) | $ / shares	0
Vested (dollars per share) | $ / shares	3.45
Forfeited (dollars per share) | $ / shares	0
Outstanding, end of period (dollars per share) | $ / shares	$ 3.45

Stock Plans and Stock-Based C_7

Stock Plans and Stock-Based Compensation - Summary of ESPP (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense recognized under ESPP (in thousands)_	$ 2,698	$ 2,658
Employee Stock Purchase Plan | 2010 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense recognized under ESPP (in thousands)_	$ 56	$ 49
Minimum risk-free interest rate (percent)	0.10%
Maximum risk-free interest rate (percent)	0.20%	2.10%
Minimum volatility (percent)	97.00%	92.00%
Maximum volatility (percent)	219.00%	97.00%
Dividends	0.00%	0.00%
Minimum | Employee Stock Purchase Plan | 2010 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	6 months	6 months
Maximum | Employee Stock Purchase Plan | 2010 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	24 months	24 months

Stock Plans and Stock-Based C_8

Stock Plans and Stock-Based Compensation - Compensation Expense Allocation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Total stock-based compensation expense	$ 2,698	$ 2,658
Research and development expenses
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Total stock-based compensation expense	731	575
General and administrative expenses
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Total stock-based compensation expense	$ 1,967	$ 2,083

Retirement Savings Plan (Detail

Retirement Savings Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Retirement Benefits [Abstract]
Matching contribution	$ 0.2	$ 0.2

Income Taxes - Reconciliation (

Income Taxes - Reconciliation (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	21.00%	21.00%
State income taxes, net of federal benefit	6.10%	6.10%
Research and development tax credits	4.10%	2.70%
Orphan drug tax credits	2.30%	4.60%
Expiration of NOLs/Credits	(29.80%)	(4.00%)
Permanent adjustments and other	0.30%	(0.60%)
Change in valuation allowance	(4.00%)	(29.80%)
Effective income tax rate	0.00%	0.00%

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax Assets:
NOL carryforwards	$ 60,759	$ 58,654
Research and development tax credit carryforwards	14,923	15,408
Orphan drug tax credit carryforwards	18,778	18,088
Depreciation and amortization	8,478	9,671
Capitalized research and development expenditures	34,832	34,487
Stock options	6,584	6,329
Accrued expenses and other	708	131
Oberland agreement	15,872	17,022
Lease liability ASC 842	1,846	45
Total gross deferred tax asset	162,780	159,835
Valuation allowance	(160,987)	(159,794)
Net deferred tax asset	1,793	41
Deferred tax liabilities:
Right of use asset ASC 842	(1,793)	(41)
Total gross deferred tax liabilities	(1,793)	(41)
Net deferred tax assets (liabilities)	$ 0	$ 0

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Line Items]
Orphan drug tax credit carryforwards	$ 18,778,000	$ 18,088,000
Valuation allowance	160,987,000	159,794,000
Increase (decrease) in valuation allowance	1,200,000	9,600,000
Unrecognized tax benefits	0	0
Uncertain tax position	0
Federal
Income Taxes [Line Items]
Net operating loss	251,300,000	251,200,000
Federal | Research and experimentation
Income Taxes [Line Items]
Research and experimentation credit carryforwards	11,400,000	11,900,000
State
Income Taxes [Line Items]
Net operating loss	126,500,000	93,600,000
State | Research and experimentation
Income Taxes [Line Items]
Research and experimentation credit carryforwards	$ 4,500,000	$ 4,400,000

Related Party Transactions (Det

Related Party Transactions (Details) $ in Millions	Oct. 17, 2018USD ($)	Dec. 31, 2020USD ($)day	Dec. 31, 2019USD ($)
Related Party Transaction [Line Items]
Cash paid during period		$ 0.1	$ 0.3
Agreement With Head of Research and Development | Epi-Cure Pharmaceuticals, Inc. | Affiliated Entity
Related Party Transaction [Line Items]
Upfront payment to related party	$ 0.1
Research and development expense		$ 0.5
Days to exercise option to license program compounds | day		60

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 3,024	$ 2,742	$ 2,360	$ 2,709	$ 3,287	$ 2,856	$ 2,094	$ 1,767	$ 10,835	$ 10,004
Loss from operations	(6,275)	(4,711)	(5,430)	(8,482)	(7,334)	(5,323)	(6,141)	(5,558)	(24,898)	(24,356)
Net loss	$ (7,517)	$ (5,974)	$ (6,708)	$ (9,709)	$ (8,609)	$ (6,436)	$ (7,213)	$ (9,884)	$ (29,908)	$ (32,141)
Net loss per common share (basic and diluted) (in dollars per share)	$ (0.11)	$ (0.11)	$ (0.17)	$ (0.28)	$ (0.26)	$ (0.19)	$ (0.22)	$ (0.30)	$ (0.61)	$ (0.97)
Weighted average common shares (basic and diluted) (in shares)	66,363,229	54,554,129	39,517,045	34,453,189	33,209,217	33,202,871	33,154,566	33,150,869	48,670,381	33,180,516