Curis (CRIS) 10-K 8 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Mar. 02, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	CRIS
Entity Registrant Name	CURIS INC
Entity Central Index Key	1,108,205
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		165,628,371
Entity Public Float			$ 146.6

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Cash and cash equivalents	$ 38,288	$ 26,038
Investments	21,944	18,447
Accounts receivable	3,073	2,459
Prepaid expenses and other current assets	989	1,257
Total current assets	64,294	48,201
Property and equipment, net	366	413
Long-term investment—restricted	153	153
Goodwill	8,982	8,982
Other assets	3	3
Total assets	73,798	57,752
Current Liabilities:
Accounts payable	5,423	5,883
Accrued liabilities	2,793	2,725
Current portion of long-term debt, net	5,886	4,939
Total current liabilities	14,102	13,547
Long-term debt, net	35,669	14,921
Other long-term liabilities	34	18
Total liabilities	49,805	28,486
Stockholders’ Equity:
Common stock, $0.01 par value—225,000,000 shares authorized at December 31, 2017 and 2016, respectively; 165,379,967 shares issued and 164,157,121 shares outstanding at December 31, 2017, respectively; 142,346,871 shares issued and 141,124,025 shares outstanding at December 31, 2016	1,654	1,423
Additional paid-in capital	976,130	928,319
Treasury stock (at cost, 1,222,846 shares at December 31, 2017 and 2016, respectively)	(1,524)	(1,524)
Accumulated deficit	(952,265)	(898,948)
Accumulated other comprehensive loss	(2)	(4)
Total stockholders’ equity	23,993	29,266
Total liabilities and stockholders’ equity	$ 73,798	$ 57,752

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	225,000,000	225,000,000
Common stock, shares issued (in shares)	165,379,967	142,346,871
Common stock, shares outstanding (in shares)	164,157,121	141,124,025
Treasury stock, at cost (in shares)	1,222,846	1,222,846

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Royalties	$ 9,849	$ 7,810	$ 8,031
Research and development, net	49	(283)	(153)
Total revenues	9,898	7,527	7,878
Costs and Expenses:
Cost of royalties	496	399	406
Research and development	45,096	31,590	26,699
In-process research and development	0	17,989	24,348
General and administrative	14,066	15,588	12,906
Total costs and expenses	59,658	65,566	64,359
Loss from operations	(49,760)	(58,039)	(56,481)
Other (Expense) Income:
Interest income	513	406	277
Other (expense) income	(104)	(1)	548
Interest expense	(3,966)	(2,777)	(3,325)
Total other expense, net	(3,557)	(2,372)	(2,500)
Net loss	$ (53,317)	$ (60,411)	$ (58,981)
Net Loss per Common Share (Basic and Diluted) (in dollars per share)	$ (0.36)	$ (0.45)	$ (0.48)
Weighted Average Common Shares (Basic and Diluted) (in shares)	149,133,466	132,785,687	123,365,195
Net Loss	$ (53,317)	$ (60,411)	$ (58,981)
Other comprehensive gain/(loss), net of tax:
Unrealized gain/(loss) on marketable securities	2	(32)	39
Comprehensive loss	$ (53,315)	$ (60,443)	$ (58,942)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Deficit	Accumulated Other Comprehensive Income/(Loss)	IPO	IPOCommon Stock	IPOAdditional Paid-in Capital	At-The-Market Offering	At-The-Market OfferingCommon Stock	At-The-Market OfferingAdditional Paid-in Capital
Beginning Balance at Dec. 31, 2014	$ 29,783	$ 873	$ 810,001	$ (1,524)	$ (779,556)	$ (11)
Beginning Balance (in shares) at Dec. 31, 2014		87,253,657
Issuances of common pursuant to sales of shares							$ 64,620	$ 251	$ 64,369
Issuances of common pursuant to sales of shares (in shares)								25,090,908
Issuance of common stock in consideration for rights granted under the Aurigene collaboration agreement	23,968	$ 171	23,797
Issuance of common stock in consideration for rights granted under the Aurigene collaboration agreement (in shares)		17,120,131
Issuances of common stock upon the exercise of stock options and for purchases under the ESPP	1,206	$ 7	1,199
Issuances of common stock upon the exercise of stock options, for purchases under the ESPP (in shares)		748,528
Recognition of employee stock-based compensation	3,582		3,582
Non-employee stock-based compensation expense, including mark-to-market	293		293
Other comprehensive gain (loss)	39					39
Net loss	(58,981)				(58,981)
Ending Balance at Dec. 31, 2015	64,510	$ 1,302	903,241	(1,524)	(838,537)	28
Ending Balance (in shares) at Dec. 31, 2015		130,213,224
Issuance of common stock in consideration for rights granted under the Aurigene collaboration agreement	17,967	$ 102	17,865
Issuance of common stock in consideration for rights granted under the Aurigene collaboration agreement (in shares)		10,208,333
Issuances of common stock upon the exercise of stock options and for purchases under the ESPP	2,907	$ 19	2,888
Issuances of common stock upon the exercise of stock options, for purchases under the ESPP (in shares)		1,925,314
Recognition of employee stock-based compensation	4,294		4,294
Non-employee stock-based compensation expense, including mark-to-market	31		31
Other comprehensive gain (loss)	(32)					(32)
Net loss	(60,411)				(60,411)
Ending Balance at Dec. 31, 2016	$ 29,266	$ 1,423	928,319	(1,524)	(898,948)	(4)
Ending Balance (in shares) at Dec. 31, 2016	142,346,871	142,346,871
Issuances of common pursuant to sales of shares							$ 35,331	$ 200	$ 35,131	$ 6,215	$ 21	$ 6,194
Issuances of common pursuant to sales of shares (in shares)								20,000,000			2,103,981
Issuances of common stock upon the exercise of stock options and for purchases under the ESPP	$ 1,179	$ 10	$ 1,169
Issuances of common stock upon the exercise of stock options, for purchases under the ESPP (in shares)		953,501
Exercise of stock options settled in shares	$ (42)	$ (42)
Exercise of stock options settled in shares (in shares)	(780,135)		(24,386)
Recognition of employee stock-based compensation	$ 5,365		$ 5,365
Non-employee stock-based compensation expense, including mark-to-market	(6)		(6)
Other comprehensive gain (loss)	2					2
Net loss	(53,317)				(53,317)
Ending Balance at Dec. 31, 2017	$ 23,993	$ 1,654	$ 976,130	$ (1,524)	$ (952,265)	$ (2)
Ending Balance (in shares) at Dec. 31, 2017	165,379,967	165,379,967

Consolidated Statements of Sto6

Consolidated Statements of Stockholders' Equity (Parenthetical) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Issuance costs	$ 4.4
IPO
Issuance costs	0.3
At-The-Market Offering
Issuance costs	$ 0.2

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows from Operating Activities:
Net loss	$ (53,317)	$ (60,411)	$ (58,981)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	235	193	161
Stock-based compensation expense	5,359	4,325	3,875
Issuance of common stock in consideration for rights granted under the Aurigene collaboration agreement (see Note 3(b))	0	17,989	23,968
Amortization of debt issuance costs	144	48	56
Non-cash interest (income)/expense	(53)	168	149
Gain on sale of fixed assets	0	0	(22)
Changes in operating assets and liabilities:
Accounts receivable	(614)	(353)	(145)
Prepaid expenses and other assets	267	(85)	(726)
Accounts payable and accrued and other liabilities	(376)	2,315	1,774
Total adjustments	4,962	24,600	29,090
Net cash used in operating activities	(48,355)	(35,811)	(29,891)
Cash Flows from Investing Activities:
Purchases of investments	(51,121)	(57,639)	(123,240)
Sales/maturities of investments	47,679	88,092	116,822
Decrease in restricted cash/investments	0	0	14
Expenditures for property and equipment	(188)	(329)	(48)
Proceeds from sale of fixed assets	0	0	24
Net cash (used in)/provided by investing activities	(3,630)	30,124	(6,428)
Cash Flows from Financing Activities:
Proceeds from issuance of common stock associated with offerings, net of issuance costs (see Note 11)	41,546	0	64,620
Proceeds from issuance of common stock under the Company’s share-based compensation plans	1,138	2,907	1,206
Proceeds from new credit agreement with HealthCare Royalty	45,000	0	0
Payment of debt issuance costs	(192)	0	0
Payment on termination of former credit agreement with BioPharma	(18,303)	0	0
Payments made on Curis Royalty’s debt	(4,954)	(4,273)	(4,163)
Net cash provided by/(used in) financing activities	64,235	(1,366)	61,663
Net increase/(decrease) in cash and cash equivalents	12,250	(7,053)	25,344
Cash and cash equivalents, beginning of period	26,038	33,091	7,747
Cash and cash equivalents, end of period	38,288	26,038	33,091
Supplemental cash flow data:
Cash paid for interest	$ 3,942	$ 2,787	$ 3,303

Nature of Business

Nature of Business	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	Nature of Business Curis, Inc. is a biotechnology company seeking to develop and commercialize innovative drug candidates for the treatment of human cancers. As used throughout these consolidated financial statements, the term “the Company” refers to the business of Curis, Inc. and its wholly owned subsidiaries, except where the context otherwise requires, and the term “Curis” refers to Curis, Inc. The Company conducts its research and development programs both internally and through strategic collaborations. The Company’s clinical stage drug candidates are CUDC-907, which is being investigated in clinical studies in patients with MYC-altered diffuse large B-cell lymphoma and solid tumors, and CA-170, for which it is currently conducting a Phase 1 study in patients with advanced solid tumors and lymphomas, and CA-4948, for which, in January 2018 it initiated a Phase 1 trial in patients with advanced non-Hodgkin lymphomas, including those with MYD88 alterations. The Company’s pipeline also includes CA-327, which is a pre-IND stage oncology drug candidate. The Company expects to file an IND application with the FDA for clinical testing of CA-327 in 2018. The Company is party to a collaboration with F. Hoffmann-La Roche Ltd, or Roche, and Genentech Inc., or Genentech, a member of the Roche Group, under which Roche and Genentech are commercializing Erivedge, a first-in-class orally-administered small molecule Hedgehog signaling pathway inhibitor. Erivedge® (vismodegib) is approved for the treatment of advanced basal cell carcinoma, or BCC. In January 2015, and as amended in September 2016, the Company entered into a collaboration, option and license agreement focused on immuno-oncology and selected precision oncology targets with Aurigene Discovery Technologies Limited, or Aurigene. In September 2016, the Company entered into an amendment to this agreement, pursuant to which Aurigene received 10,208,333 shares of the Company's common stock in lieu of receiving up to $24.5 million of milestone and other payments from Curis (see Note 3(b)). The collaboration with Aurigene is comprised of multiple programs, and Curis has the option to exclusively license each program, including data, intellectual property and compounds associated therewith, once a development candidate is nominated within such program. In October 2015, the Company exercised options to license two programs under this collaboration. The first licensed program is in the immuno-oncology field and the Company has named CA-170, an orally-available small molecule antagonist of two immune checkpoints, programmed death ligand-1 (PDL1) and V domain Ig suppressor of T-cell activation (VISTA), as the development candidate from this program. The second licensed program is in the precision oncology field and the Company has named CA-4948, an orally-available small molecule inhibitor of Interleukin-1 receptor-associated kinase 4 (IRAK4) as the development candidate. In October 2016, the Company exercised its option to license a third program in the collaboration, and designated CA-327, a distinct orally available small molecule antagonist of two immune checkpoints PDL1 and T-cell immunoglobulin and mucin domain containing protein-3 (TIM3) as the development candidate from this program. In March 2018, we exercised the option to license a fourth program, which is an immuno-oncology program. The Company operates in a single reportable segment, which is the research and development of innovative cancer therapeutics. 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. 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 advance and expand its research and development programs; the Company’s reliance on Aurigene to successfully discover and preclinically develop 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 Company’s ability to obtain adequate financing to fund its operations; the ability of the Company and its wholly owned subsidiary, Curis Royalty, LLC, or Curis Royalty, to satisfy the terms of its credit agreement with HealthCare Royalty Partners III, L.P, a Delaware limited partnership managed by HealthCare Royalty Management, LLC, or HealthCare Royalty; the Company’s ability to obtain and maintain necessary intellectual property protection; development by the Company’s competitors of new or better technological innovations; dependence on key personnel; the Company’s ability to comply with regulatory requirements; and the Company’s ability to execute on its overall business strategies. 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 makes under its current and potential future collaborations. The results of the Company’s operations may 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 successfully discover and develop preclinical programs under the Company’s collaboration with Aurigene, as well as the Company’s decision to exclusively license and further develop programs under this collaboration; Roche and Genentech’s ability to successfully commercialize Erivedge; and positive results in Roche and Genentech’s ongoing clinical trials. The Company has incurred losses and negative cash flows from operations since its inception. As of December 31, 2017 , the Company had an accumulated deficit of approximately $952.3 million . The Company anticipates that its $60.2 million of existing cash, cash equivalents and investments at December 31, 2017 should enable it to maintain its planned operations for at least the next twelve months from the issuance date of the financial statements. We will need to raise additional capital or incur indebtedness to continue to fund our operations in the future. 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, we may have to delay, reduce the scope of, or eliminate some of our development programs, potentially delaying the time to market for any of our product candidates.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies (a) USE OF ESTIMATES 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 of 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 intangible assets; 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. (b) CONSOLIDATION The accompanying consolidated financial statements include the Company and its wholly owned subsidiaries, Curis Royalty (see Note 9) and Curis Securities Corporation, Inc. The Company has eliminated all intercompany transactions in each of the years ended December 31, 2017 , 2016 and 2015 . (c) 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. The Company follows the provisions of the Financial Accounting Standards Board, or FASB, Codification Topic 605, Revenue Recognition . License Fees and Multiple Element Arrangements Non-refundable license fees are recognized as revenue when the Company has a contractual right to receive such payment, the contract price is fixed or determinable, the collection of the resulting receivable is reasonably assured and the Company has no further performance obligations under the license agreement. Multiple element arrangements, such as license and development arrangements are analyzed to determine whether the deliverables, which often include a license and performance obligations such as research and steering committee services, can be separated or whether they must be accounted for as a single unit of accounting in accordance with generally accepted accounting principles, or GAAP. The Company recognizes up-front license payments as revenue upon delivery of the license only if the license has stand-alone value. If the license is considered not to have stand-alone value, the arrangement would then be accounted for as a single unit of accounting and the license payments and payments for performance obligations are recognized as revenue over the estimated period of when the performance obligations are performed. 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 determined to be 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. Whenever the Company determines that an arrangement should be accounted for as a single unit of accounting, it must determine the period over which the performance obligations will be performed and revenue will be recognized. Revenue will be recognized using either a relative performance or straight-line method. The Company recognizes revenue using the relative performance method provided that the Company can reasonably estimate the level of effort required to complete its performance obligations under an arrangement and such performance obligations are provided on a best-efforts basis. Direct labor hours or full-time equivalents are typically used as the measure of performance. Revenue recognized under the relative performance method would be determined by multiplying the total payments under the contract, excluding royalties and payments contingent upon achievement of substantive milestones, by the ratio of level of effort incurred to date to estimated total level of effort required to complete the Company’s performance obligations under the arrangement. Revenue is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the relative performance method, as of each reporting period. If the Company cannot reasonably estimate the level of effort required to complete its performance obligations under an arrangement, the performance obligations are provided on a best-efforts basis and the Company can reasonably estimate when the performance obligation ceases or the remaining obligations become inconsequential and perfunctory, then the total payments under the arrangement, excluding royalties and payments contingent upon achievement of substantive milestones, would be recognized as revenue on a straight-line basis over the period the Company expects to complete its performance obligations. Revenue is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the straight-line basis, as of the period ending date. If the Company cannot reasonably estimate when its performance obligation either ceases or becomes inconsequential and perfunctory, then revenue is deferred 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. Substantive Milestone Payments Collaboration agreements that contain substantive milestone payments are recognized upon achievement of the milestone only if: • such milestone is commensurate with either of the following: a) the Company’s performance to achieve the milestone (for example, the achievement of the milestone involves a degree of risk and was not reasonably assured at the inception of the arrangement); or b) the enhancement of the value of the deliverable as a result of a specific outcome resulting from the Company’s performance to achieve the milestone (or substantive Company effort is involved in achieving the milestone); • such milestone relates solely to past performance; and • the amount of the milestone payment is reasonable relative to all deliverables and payment terms in the arrangement. Determination as to whether a payment meets the aforementioned conditions involves management’s judgment. If any of these conditions are not met, the resulting payment would not be considered a substantive milestone, and the resulting payment would be recognized as revenue as performance obligations are performed under either the relative performance or straight-line methods, as applicable, and in accordance with these policies as described above. In addition, the determination that one such payment was not a substantive milestone could prevent the Company from concluding that subsequent milestone payments were substantive milestones and, as a result, any additional milestone payments could also be considered part of the consideration for the single unit of accounting and would be recognized as revenue as such performance obligations are performed under either the relative performance or straight-line methods, as applicable. Milestones that are tied to regulatory approval are not considered probable of being achieved until such approval is received. Milestones tied to counterparty performance are not included in the Company’s revenue model until the performance conditions are met. Reimbursement of Costs Reimbursement of research and development costs by third party collaborators is recognized as revenue provided the Company has determined that it is acting primarily as a principal in the transaction according to the provisions outlined in the FASB Codification Topic 605-45, Revenue Recognition, Principal Agent Considerations , the amounts are determinable and collection of the related receivable is reasonably assured. Royalty Revenue Since the first quarter of 2012, the Company has recognized royalty revenues related to Genentech’s and Roche’s sales of Erivedge. Royalty revenue is recognized upon the sale of the related products based on contractual terms, provided that the royalty amounts are fixed or determinable, collection of the related receivable is reasonably assured and the Company has no remaining performance obligations under the arrangement. If royalties are received when the Company has remaining performance obligations, it expects to attribute the royalty payments to the services being provided under the arrangement and therefore to recognize such royalty payments as such performance obligations are performed under either the relative performance or straight-line methods, as applicable, and in accordance with these policies as described above. The Company expects to recognize royalty revenue in future quarters 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 Notes 3(a) and 9). However, Erivedge royalties will service Curis Royalty’s debt until this debt is repaid in full (see Note 9). Summary During the years ended December 31, 2017 , 2016 and 2015 , total gross revenues are 100% from the Company’s collaboration with Genentech. (d) 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. For the year ended December 31, 2017, the Company did not recognize any in-process research and development expenses. The Company incurred in-process research and development expenses of $18.0 million during the year ended December 31, 2016 representing the value of common stock issued to Aurigene pursuant to the September 2016 amendment to the collaboration and $24.3 million during the year ended December 31, 2015 representing partial consideration for the rights granted to the Company under the original collaboration agreement with Aurigene in January 2015 (see Note 3(b)). The Company expenses research and development costs as they are incurred. 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. (e) CASH EQUIVALENTS AND INVESTMENTS Cash equivalents consist of short-term, highly liquid investments purchased with original maturities of three months or less. All other liquid investments are classified as marketable securities. The Company’s short-term investments are marketable 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 securities with original maturities of greater than twelve months from the balance sheet. Marketable securities consist of commercial paper, corporate bonds and notes, and government obligations. All of the Company’s investments have been designated available-for-sale and are stated at fair value with any unrealized holding gains or losses included as a component of stockholders’ equity and any realized gains and losses recorded in the statement of operations in the period during which the securities are sold. Unrealized gains and temporary losses on investments are included in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity. Realized gains and losses, dividends and interest income are included in other income (expense). Any premium or discount arising at purchase is amortized and/or accreted to interest income. (f) LONG-LIVED ASSETS OTHER THAN GOODWILL Long-lived assets other than goodwill consist of property and equipment. The aggregate net balances for these long-lived assets were $0.4 million and $0.4 million as of December 31, 2017 and 2016 , respectively. 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 impairment charges for the years ended December 31, 2017 , 2016 or 2015 . 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: Asset Classification Estimated Useful Life Laboratory equipment, computers and software 3-5 years Leasehold improvements Lesser of life of the lease or the life of the asset Office furniture and equipment 5 years (g) GOODWILL As of both December 31, 2017 and 2016 , 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 2017 , 2016 and 2015 , 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, 2017 , 2016 and 2015 . (i) TREASURY STOCK On May 31, 2002, the Company announced that its Board of Directors had approved the repurchase of up to $3.0 million of the Company’s common stock. The Company accounted for its common stock repurchases as treasury stock under the cost method. In 2002, the Company repurchased 1,047,707 shares of its common stock at a cost of $0.9 million pursuant to this repurchase program. Each of the Company’s now-expired 2000 Stock Incentive Plan and the current Amended and Restated 2010 Stock Incentive Plan generally allow participants to purchase common stock upon the exercise of a stock option by delivery of shares of Company common stock held directly by the participant, with such shares of common stock valued at the closing price on the Nasdaq Global Market, or NASDAQ, on the date of exercise. On certain instances in the past, the Company has accounted for the value of the common stock remitted to the Company in satisfaction of the exercise price as treasury stock under the cost method. As of December 31, 2017 , the Company had repurchased an aggregate of 1,222,846 shares of its common stock at a total cost of $1.5 million . (j) 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. Antidilutive securities consist of stock options outstanding as of the respective reporting period. Antidilutive securities as of December 31, 2017 , 2016 and 2015 consisted of the following For the Year Ended December 31, 2017 2016 2015 Stock options outstanding 16,034,181 13,752,157 13,290,844 Total antidilutive securities 16,034,181 13,752,157 13,290,844 (k) STOCK-BASED COMPENSATION The Company records stock-based compensation in accordance with FASB Codification Topic 718, Compensation—Stock Compensation , or ASC 718, which requires that the fair value of such equity instruments be recognized as an expense in the financial statements as services are performed. (l) OPERATING LEASES The Company currently has one facility located at 4 Maguire Road in Lexington, Massachusetts under a noncancellable operating lease agreement for office and laboratory space. The rent payments for this facility escalate over the lease term and the Company expenses its obligations under this lease agreement on a straight-line basis over the term of the lease (see Note 10(a)). (m) CONCENTRATION OF RISK Financial instruments, which potentially subject the Company to concentrations of credit risk, consist principally of cash and cash equivalents, short- and long-term investments. The Company invests directly in commercial paper of financial institutions and corporations with A-/Aa3 or better long-term ratings and A-1/P-1 short term debt ratings and U.S. Treasury securities. 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. The Company’s accounts receivable at December 31, 2017 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 CUDC-907, CA-170, CA-4948 and CA-327, 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. (n) 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. (o) NEW ACCOUNTING PRONOUNCEMENTS In September 2017, the FASB issued ASU 2017-13, which further clarified ASU 2016-02 issued in February 2016, Leases . The standard requires organizations that lease assets to recognize on the balance sheet assets or liabilities, as applicable, for the rights and obligations created by those leases. Additionally, the guidance modifies current guidance for lessor accounting and leveraged leases, and is effective for fiscal years beginning after December 15, 2018, and interim periods within such years. Early adoption is permitted, but the Company does not anticipate electing early adoption. The Company is currently evaluating the impact of the adoption of this guidance on its consolidated financial statements. In May 2017, the Financial Accounting Standard Board (FASB) issued Accounting Standard Update (ASU) 2017-09, Scope of Modification Accounting , which clarifies the scope under which modification accounting should be applied to a share-based payment award under Codification Topic 718. The standard will be effective for annual reporting periods and interim periods within those annual periods, beginning after December 15, 2017, and early adoption was permitted for interim or annual reporting periods beginning after January 1, 2017. The Company does not expect this guidance to have a material impact on its consolidated financial statements. In January 2017, the Financial Accounting Standard Board (FASB) issued Accounting Standard Update (ASU) 2017-04, Simplifying the Test for Goodwill Impairment , which simplifies the subsequent measurement of goodwill under the current standard in testing the interim or annual impairment of goodwill. The standard will be effective for annual reporting periods and interim periods within those annual periods beginning after December 15, 2019, and early adoption is now permitted for interim or annual reporting periods that began after January 1, 2017. The Company does not expect the impact of this guidance to be material to its consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments , which helps to clarify the diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows under Codification Topic 230, Statement of Cash Flows, by addressing eight specific cash flow issues. The standard became effective for annual reporting periods and interim periods within those annual periods, beginning after December 15, 2017. The Company does not expect this guidance to have a material impact on its consolidated financial statements. In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities , which amends prior guidance on accounting for equity investments and financial liabilities. The new standard amends certain aspects of accounting and disclosure requirements for financial instruments, including the requirement that equity investments with readily determinable fair values be measured at fair value with changes in fair value recognized in results of operations. The new standard does not apply to investments accounted for under the equity method of accounting or those that result in consolidation of the investee. Equity investments that do not have readily determinable fair values may be measured at fair value or at cost minus impairment adjusted for changes in observable prices. A financial liability that is measured at fair value in accordance with the fair value option is required to be presented separately in other comprehensive income for the portion of the total change in the fair value resulting from change in the instrument-specific credit risk. In addition, a valuation allowance should be evaluated on deferred tax assets related to available-for-sale debt securities in combination with other deferred tax assets. The guidance is effective for fiscal years beginning after December 15, 2017, and interim periods within such years. Early adoption is permitted but the Company does not anticipate electing early adoption. The Company does not expect the adoption of this guidance to have a material impact on its consolidated financial statements. In May 2014, the FASB issued new revenue recognition guidance in ASC 606, Revenue from Contracts with Customers , for entities, providing a single, comprehensive model to account for revenue arising from contracts with customers. In addition, The FASB recently issued ASUs 2016-08, 2016-10, 2016-12, 2016-20, 2017-13 and 2017-14 all of which are further clarifying amendments to ASU 2014-09.This new standard provides a five-step framework whereby revenue is recognized when promised goods or services are transferred to a customer at an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new standard also requires significantly expanded disclosures regarding the qualitative and quantitative information of an entity’s nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. Two adoption methods are permitted: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU recognized at the date of initial application. The Company plans to use the modified retrospective method for its adoption. To date, the Company’s sources of collaboration and other revenue have primarily been collaboration agreements. The most significant differences between Topic 606 and previous guidance for license and collaboration revenue are: (i) allocating consideration to performance obligations; and (ii) estimating and determining the timing of recognition of variable consideration received from licensees, including up-front license payments, contingent milestones and royalties. The guidance is effective for interim and annual periods beginning after December 15, 2017 and early adoption is permitted. The guidance is anticipated to be effective for the Company as of January 1, 2018. The Company has evaluated the potential impact that ASU 2014-09 may have on the financial position and results of operations and expects the adoption of this guidance to have no material impact on its consolidated financial statements. (p) SEGMENT REPORTING The Company is engaged solely in the discovery and development of innovative drug candidates for the treatment of human cancers. Accordingly, the Company has determined that it operates in one operating segment.

Research and Development Collab

Research and Development Collaborations	12 Months Ended
	Dec. 31, 2017
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 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 United States 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, 2017 . In addition to these payments and pursuant to the 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 United States sales of Erivedge as a result of the first commercial sale of Odomzo® in the United States. In November 2012, the Company formed a wholly owned subsidiary, Curis Royalty, to receive a $30.0 million loan, at an annual interest rate of 12.25% pursuant to a credit agreement between Curis Royalty and BioPharma-II (see Note 9). In connection with the loan, the Company transferred to Curis Royalty its right to receive royalty and royalty-related payments that it receives from Genentech. The loan and accrued interest was an obligation of Curis Royalty, with no recourse to Company to be repaid using the royalty and royalty-related payments from Genentech. In March 2017, the Company and Curis Royalty entered into a new credit agreement with HealthCare Royalty Partners III, L.P., or HealthCare Royalty, for the purpose of refinancing 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 Company considers its arrangement with Genentech to be a revenue arrangement with multiple deliverables. The Company’s deliverables under this collaboration include an exclusive license to its Hedgehog signaling pathway inhibitor technologies, research and development services for the first two years of the collaboration, and participation on the joint steering committee. The Company applied the provisions of the FASB Codification Topic 605-25, Revenue Recognition, Multiple Element Arrangement to determine whether the performance obligations under this collaboration should be accounted for separately or should be accounted for as a single unit of account. The Company determined that the deliverables, specifically, the license, research and development services and steering committee participation, represented a single unit of account because the Company believes that the license, although delivered at the inception of the arrangement, did not have stand-alone value to Genentech without the Company’s research and development services and steering committee participation. During 2007, the Company reassessed its participation on the joint steering committee and concluded that its participation in the joint steering committee had become inconsequential and perfunctory. As a result, the Company determined that it had no further performance obligations under this collaboration and consideration received after this date is recognized in the Company’s financial statements in the period in which it was earned. As a result of its licensing agreements with various universities, the Company is obligated to make payments to these university licensors when certain non-royalty payments are received from Genentech. Through December 31, 2017 , the Company has incurred aggregate research and development expenses over the term of this collaboration of $4.4 million related to payments made to these university licensors in connection with the Company’s receipt of cash payments from Genentech for research, development and regulatory objectives achieved related to such university licensing agreements. The Company recognized $9.8 million , $7.8 million and $8.0 million in royalty revenue under the Genentech collaboration during the year ended December 31, 2017 , 2016 and 2015 , respectively. The Company also recorded $0.5 million , $0.4 million and $0.4 million , respectively, 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 2% direct net sales in Australia (subject to decrease to 5% of royalties on expiration of the patent in April 2019), that the Company is obligated to pay to university licensors. During the years ended December 31, 2017 , 2016 and 2015 , the Company also recognized “research and development” revenue of $0.2 million , $0.2 million and $0.3 million , respectively, related to expenses incurred on behalf of Genentech that were incurred by the Company and for which Genentech is obligated to reimburse the Company. During the years ended December 31, 2017 and 2016 , Genentech incurred expenses of $0.2 million and $0.5 million , respectively, under this collaboration which the Company is obligated to reimburse to Genentech, and which the Company has recorded as contra-revenues which have been net against research and development 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 FASB Codification Topic 605-45 are met. The Company had recorded as amounts receivable from Genentech under this collaboration, comprised primarily of Erivedge royalties earned in the fourth quarters of 2017 and 2016 , of $3.0 million and $2.5 million , as of December 31, 2017 and 2016 , 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. During 2015, the Company exercised options to license the first two programs under this collaboration, resulting in an aggregate one-time payment of $6.0 million (satisfying the $3.0 million option exercise fee for each program) by the Company to Aurigene. Effective October 2015, the Company agreed to make additional payments to Aurigene totaling up to $2.0 million for supplemental research, development and/or manufacturing activities in support of these two programs. The Company incurred and recognized $1.0 million of such costs in 2015, which was paid in 2016. The remaining $1.0 million was incurred and recognized and paid in 2016. All payments have been recorded within research and development expense in the Company's Consolidated Statement of Operations and Comprehensive Loss. Also in 2015, the Company selected a preclinical program for potential further development within the immuno-oncology part of the collaboration resulting in a one-time payment of $2.0 million . In October 2016, the Company licensed the program and designated CA-327 as the development candidate as described in Note 1, resulting in a one-time payment of $1.5 million . In connection with the collaboration agreement, the Company issued to Aurigene 17,120,131 shares of its common stock valued at $24.3 million at the time of issuance in partial consideration for the rights granted to the Company under the collaboration agreement. 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 10,208,333 shares of its common stock, Aurigene waived $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, e.g. 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. As of December 31, 2017 , the Company has exercised its option to license the following three 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 PDL1 and VISTA. 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. In March 2018, the Company exercised its option to license a fourth program, which is an immuno-oncology program. For each option to license (as described above) exercised by the Company, 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 United States, 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. Subject to specified exceptions, Aurigene and the Company agreed to collaborate exclusively with each other on the discovery, research, development and commercialization of programs and compounds within immuno-oncology for an initial period of approximately two years from the effective date of the collaboration agreement. At the Company’s option, and subject to specified conditions, it may extend such exclusivity for up to three additional one -year periods by paying to Aurigene additional exclusivity option fees on an annual basis. The Company exercised the first one-year exclusivity option fee in 2017. The fee for this exclusivity option exercise was $7.5 million , which the Company paid in two equal installments in 2017 . The Company has elected not to further exercise its exclusivity option and thus will not make the $10.0 million payment required for this additional exclusivity in 2018. As a result of the Company’s election to not further exercise its exclusivity option, Curis is no longer operating under broad immuno-oncology exclusivity with Aurigene. The Company has, however, as provided in the agreement, elected to exercise its option to extend exclusivity on a program-by-program, year-by-year, basis for the IRAK4 Program and the PD1/VISTA Program, both of the licensed programs currently in clinical trials. Since January 2015, Curis has paid $14.5 million in research payments, option exercise fees and milestone payments to Aurigene, and have waived $15.5 million in milestone payments as part of the 2016 amendment. For each of the IRAK4, PD1/VISTA,PD1/TIM3 programs, and the fourth program: Curis 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. Under the terms of the amendment, the value of common stock issued to Aurigene equaled $18.0 million based on the closing share price of the Company’s common stock of $1.76 per share on September 6, 2016, which was the last closing price prior to execution of the amendment. As a result, the Company recognized in-process research and development expense of $18.0 million within its consolidated statement of operations and comprehensive loss for the year ended December 31, 2016 in recognition of the fact that any compounds that have been and may be licensed from Aurigene are in clinical or preclinical development and will require substantial development, regulatory and marketing approval efforts in order to reach technological feasibility. 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 totaling $0.8 million .

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company discloses fair value measurements based on a framework outlined by GAAP which requires expanded disclosures regarding fair value measurements. GAAP also defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Market participants are buyers and sellers in the principal market that are (i) independent, (ii) knowledgeable, (iii) able to transact, and (iv) willing to transact. The FASB Codification Topic 820, Fair Value Measurements and Disclosures, requires the use of valuation techniques that are consistent with the market approach, the income approach and/or the cost approach. The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets and liabilities. The income approach uses valuation techniques to convert future amounts, such as cash flows or earnings, to a single present amount on a discounted basis. The cost approach is based on the amount that currently would be required to replace the service capacity of an asset (replacement cost). Valuation techniques should be consistently applied. GAAP also establishes a fair value hierarchy which requires an entity to maximize the use of observable inputs, where available, and minimize the use of unobservable inputs when measuring fair value. The standard describes three levels of inputs that may be used to measure fair value: 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, 2017 and 2016 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, 2017 and 2016 . Quoted Prices in Active Markets (Level 1) Other Observable Inputs (Level 2) Unobservable Inputs (Level 3) Fair Value (in thousands) As of December 31, 2017 Cash equivalents: Money market funds $ 35,308 $ — $ — $ 35,308 Municipal bonds — 260 — 260 Short-term investments: Corporate commercial paper, stock, bonds and notes — 21,944 — 21,944 Total assets at fair value $ 35,308 $ 22,204 $ — $ 57,512 Quoted Prices in Active Markets (Level 1) Other Observable Inputs (Level 2) Unobservable Inputs (Level 3) Fair Value (in thousands) As of December 31, 2016 Cash equivalents: Money market funds $ 24,542 $ — $ — $ 24,542 Municipal bonds — 330 — 330 Short- and long-term investments: Corporate commercial paper, stock, bonds and notes — 18,447 — 18,447 Total assets at fair value $ 24,542 $ 18,777 $ — $ 43,319

Investments

Investments	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Investments	Investments Cash equivalents consist of short-term, highly liquid investments purchased with original maturities of three months or less. All other liquid investments are classified as marketable securities. The Company’s short-term investments are marketable 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 securities with original maturities of greater than twelve months from the balance sheet. Marketable securities consist of commercial paper, corporate bonds and notes, and government obligations. All of the Company’s investments have been designated available-for-sale and are stated at fair value with any unrealized holding gains or losses included as a component of stockholders’ equity and any realized gains and losses recorded in the statement of operations in the period during which the securities are sold. Unrealized gains and temporary losses on investments are included in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity. Realized gains and losses, dividends and interest income are included in other income (expense). Any premium or discount arising at purchase is amortized and/or accreted to interest income. The amortized cost, unrealized gains and losses and fair value of investments available-for-sale as of December 31, 2017 are as follows: Amortized Cost Unrealized Gain Unrealized Loss Fair Value Corporate bonds and notes—short-term $ 21,946 $ — $ (2 ) $ 21,944 Total investments $ 21,946 $ — $ (2 ) $ 21,944 Short-term investments have maturities ranging from one and twelve months with a weighted average maturity of 0.2 years at December 31, 2017 . The amortized cost, unrealized gains and losses and fair value of investments available-for-sale as of December 31, 2016 are as follows: Amortized Cost Unrealized Gain Unrealized Loss Fair Value Corporate bonds and notes—short-term $ 18,451 $ 2 $ (6 ) $ 18,447 Total investments $ 18,451 $ 2 $ (6 ) $ 18,447 Short-term investments have maturities ranging from one and twelve months with a weighted average maturity of 0.2 years at December 31, 2016 . At December 31, 2017 , Curis held one debt security that had been in an unrealized loss position for less than 12 months. The fair value of this security was $1.5 million at December 31, 2017 . Curis 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 one debt security as of December 31, 2017 to be primarily attributable to current economic and market conditions. The Company will likely not be required to sell this security, and does not intend to sell this security before the recovery of its amortized cost bases, which recovery is expected within the next 12 months. Based on the Company's analysis, it does not consider this investment to be other-than-temporarily impaired as of December 31, 2017 .

Stock Plans and Stock Based Com

Stock Plans and Stock Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Plans and Stock Based Compensation	Stock Plans and Stock Based Compensation As of December 31, 2017 , the Company had two shareholder-approved, share-based compensation plans: (i) the Second Amended and Restated 2010 Stock Incentive Plan, or the 2010 Plan, adopted by the Board of Directors in April and approved by shareholders in June 2017 and (ii) the Amended and Restated 2010 Employee Stock Purchase Plan, or the ESPP, adopted by the Board of Directors in April 2017 and approved by shareholders in June 2017. In the first quarter of 2010, the Company’s 2000 Stock Incentive Plan expired in accordance with its terms, and its 2000 Director Stock Option Plan had no available shares remaining under the plan. No additional awards will be made under these plans, although all outstanding awards under these plans will remain in effect until they are exercised or they expire in accordance with their terms. The Second 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. The Company can issue up to 19,000,000 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 10 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, 2017 , 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, 2017 , 5,502,567 shares remained available for grant under the 2010 Plan. During the year ended December 31, 2017 , the Company’s board of directors granted options to purchase 4,629,000 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 year ended December 31, 2017 , the Company’s board of directors also granted options to its non-employee directors to purchase 840,000 shares of common stock under the 2010 Plan. Of these options, 840,000 will vest and become exercisable in equal monthly installments over a period of one year from the date of grant. All options issued to non-employee directors 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. Nonstatutory Inducement Grants For certain new employees we 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, 2017 , the Company’s board of directors granted inducement equity awards of 644,000 shares of common stock. These options were granted at a weighted average exercise price of $2.61 , 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. As discussed below, for employee stock options with market performance conditions, the Company uses a Monte Carlo simulation valuation 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 December 31, 2017 2016 2015 Expected term (years)—Employees 5.5 6.0 6.0 Expected term (years)—Officers 5.5 7.0 7.0 Expected term (years)—Directors 6.3 7.0 7.0 Risk-free interest rate 2.0-2.1% 1.4-1.9% 1.5-1.9% Expected volatility 63-64% 63-70% 68-70% Expected dividend yield None None None 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. A summary of stock option activity under the Second Amended and Restated 2010 Plan, the 2000 Stock Incentive Plan, the 2000 Director Stock Option Plan, and Nonstatutory Inducement Grants is summarized as follows: Number of Shares Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Life Aggregate Intrinsic Value Outstanding, December 31, 2016 13,752,157 $ 2.30 Granted 6,113,000 2.51 Exercised (780,135 ) 1.36 Canceled (3,050,841 ) 2.33 Outstanding, December 31, 2017 16,034,181 $ 2.42 6.57 $ — Exercisable at December 31, 2017 8,771,728 $ 2.54 4.92 $ — Vested and unvested expected to vest 15,498,301 $ 2.42 6.49 $ — At December 31, 2017 , the weighted average grant-date fair values of stock options granted with standard vesting terms during the years ended December 31, 2017 , 2016 and 2015 were $1.43 , $1.11 and $1.71 per share of common stock underlying such stock options, respectively. As of December 31, 2017 , there was approximately $7.4 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 2.5 years . The intrinsic value of employee stock options exercised during the years ended December 31, 2017 , 2016 and 2015 were $1.0 million , $2.1 million and $0.8 million , respectively. Vesting Tied to Market Conditions Monte Carlo simulation models were used to value stock options to purchase an aggregate of 1,040,000 shares of common stock granted to the Company’s officers during the year ended December 31, 2014. Of this amount, options to purchase 640,000 shares of common stock were granted in February 2014 with an exercise price of $3.09 and options to purchase 400,000 shares of common stock were granted in June 2014 with an exercise price of $1.75 per share that contained specific market conditions. The key assumptions used in these Monte Carlo simulation models and resulting valuations are noted in the following table: Market Market Expected life (years)—officers 6 6 Risk-free interest rate 1.9% 2.1% Volatility 70% 65% Dividends None None Number of options granted 640,000 400,000 Fair value per share $1.20 $0.34 Based on the above, the Monte Carlo simulation models calculated an aggregate fair value of $0.9 million , excluding forfeitures, related to these grants that are being recognized on a straight-line basis over the estimated vesting periods of the separate tranches. These awards accounted for an immaterial amount of the employee stock-based compensation expense recorded by the Company for the year ended December 31, 2016 , with no expense recognized for the year ended December 31, 2017 . As of December 31, 2017 , all of the options with market conditions had been canceled. Second Amended and Restated 2010 Employee Stock Purchase Plan (ESPP) The Company has reserved 10,000,000 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, 2017 , 647,542 shares were issued under the ESPP, of which 173,366 were issued during 2017 . As of December 31, 2017 , there were 9,352,458 shares available for future purchase under the ESPP. For the years ended December 31, 2017 , 2016 and 2015 , 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, 2017 2016 2015 Compensation expense recognized under ESPP $ 268 $ 48 $ 30 Expected term 6-24 months 6 months 6 months Risk-free interest rate 1.1-1.8% 0.4-0.7% 0.06-0.5% Volatility 65-76% 64-78% 55-78% Dividends None None None Employee Stock-Based Compensation Expense Stock-based compensation for employee and director stock option grants for the years ended December 31, 2017 , 2016 and 2015 of $5.4 million , $4.3 million and $3.6 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, 2017 , 2016 and 2015 was $3.6 million , $3.6 million and $2.7 million , respectively. Total Stock-Based Compensation Expense For the years ended December 31, 2017 , 2016 and 2015 , 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, 2017 2016 2015 Research and development expenses $ 1,486 $ 762 $ 1,023 General and administrative expenses 3,873 3,563 2,852 Total stock-based compensation expense $ 5,359 $ 4,325 $ 3,875 No income tax benefits have been recorded for the years ended December 31, 2017 , 2016 or 2015 , as the Company has recorded a full valuation allowance and management has concluded that it is more likely than not that the net deferred tax assets will not be realized (see Note 12).

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property and Equipment, net	Property and Equipment, net Property and equipment consist of the following: December 31, 2017 2016 Laboratory equipment, computers and software $ 1,736 $ 1,624 Leasehold improvements 185 185 Office furniture and equipment 354 371 2,275 2,180 Less—Accumulated depreciation and amortization (1,909 ) (1,767 ) Total $ 366 $ 413 The Company recorded depreciation and amortization expense of $0.2 million , $0.2 million and $0.2 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. During the years ended December 31, 2017 , 2016 and 2015 , the Company identified certain of its fully depreciated assets no longer being used. As a result, the Company wrote off gross assets and related accumulated depreciation, totaling $0.1 million , $0.4 million and $0.1 million for the years ended December 31, 2017 , 2016 and 2015 , respectively.

Accrued Liabilities

Accrued Liabilities	12 Months Ended
	Dec. 31, 2017
Other Liabilities Disclosure [Abstract]
Accrued Liabilities	Accrued Liabilities Accrued liabilities consist of the following: December 31, 2017 2016 Accrued compensation $ 2,187 $ 2,026 Professional fees 148 157 Accrued interest on debt (see Note 9) 193 194 Other 265 348 Total $ 2,793 $ 2,725

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt	Debt (a) BioPharma-II In December 2012, Curis’ wholly-owned subsidiary, Curis Royalty, received a $30.0 million loan at an annual interest rate of 12.25% pursuant to a credit agreement between Curis Royalty and BioPharma-II. In connection with the loan, Curis transferred to Curis Royalty its right to receive royalty and royalty-related payments on the commercial sales of Erivedge that it receives from Genentech (see Note 3(a)). The loan and accrued interest was being repaid by Curis Royalty using such royalty and royalty-related payments. To secure repayment of the loan, Curis Royalty granted a first priority lien and security interest (subject only to permitted liens) to BioPharma-II in all of its assets and all real, intangible and personal property, including all of its rights, title and interest in and to the royalty and royalty-related payments. The loan constituted an obligation of Curis Royalty, and was non-recourse to Curis. Under the terms of the loan, quarterly royalty payments received by Curis Royalty from Genentech were applied in the following order: to pay (i) escrow fees payable by Curis pursuant to an escrow agreement between Curis, Curis Royalty, BioPharma-II and Boston Private Bank and Trust Company, (ii) Curis’ royalty obligations to university licensors, (iii) certain expenses incurred by BioPharma-II in connection with the credit agreement and related transaction documents, including enforcement of its rights in the case of an event of default under the credit agreement and (iv) expenses incurred by Curis enforcing its right to indemnification under the collaboration agreement with Genentech. Remaining amounts were applied first to pay interest and second, to pay the principal on the loan. Curis remained entitled to receive any contingent payments upon achievement of clinical development objectives. Curis Royalty retained its right to royalty payments related to sales of Erivedge following repayment of the loan. The final maturity date of the loan was the earlier of the date when the principal was paid in full or the termination of Curis Royalty’s right to receive royalties under the collaboration agreement with Genentech. Because the repayment of the term loan was contingent upon the level of Erivedge royalties received, the short- and long-term classification of the debt was based on the Company’s estimate of the timing of amounts to be repaid. The Company could not estimate when the loan would be repaid as repayment was impacted by numerous factors, all of which are beyond the Company’s control. The repayment term may have been shortened or extended depending on the actual level of Erivedge royalties received. In addition, if Erivedge royalties were insufficient to pay the accrued interest on the outstanding loan, any unpaid interest outstanding would have been added to the principal on a quarterly basis. The length of the actual repayment period could have varied materially to the extent that the royalty payments Curis Royalty receives were lower than the Company’s current estimates, which could have arisen due to factors beyond the Company’s control, such as the sale of competing products that result in a lowering of the royalty rates that Curis Royalty is entitled to receive, decreased market acceptance or a failure by Genentech and/or Roche to successfully commercialize Erivedge in territories where it has received regulatory approval. At any time after January 1, 2017, Curis Royalty may have, subject to certain limitations, prepaid the outstanding principal of the loan in whole or in part, at a price equal to 105% of the outstanding principal on the loan, plus accrued but unpaid interest. The obligations of Curis Royalty under the credit agreement to repay the loan may have been accelerated upon the occurrence of an event of default as defined in the credit agreement. (b) HealthCare Royalty Partners III On March 6, 2017, the Company and Curis Royalty entered into a credit agreement, referred to herein as the credit agreement, with HealthCare Royalty for the purpose of refinancing Curis’ and Curis Royalty’s existing royalty financing arrangement with BioPharma-II, referred to herein as the prior loan, with BioPharma-II. On March 22, 2017, the Biopharma-II loan was terminated in its entirety. Pursuant to the credit agreement, HealthCare Royalty made a $45.0 million loan at an annual interest rate of 9.95% to Curis Royalty, which was used to pay off $18.4 million in remaining loan obligations to Biopharma-II under the prior loan. The remaining proceeds of $26.6 million were distributed to Curis as sole equity holder of Curis Royalty. The loan from HealthCare Royalty will be repaid from certain Erivedge royalty and royalty-related payments owed by Genentech under the Genentech collaboration agreement, the rights to which were transferred from Curis to Curis Royalty in 2012. Under the terms of the credit agreement with HealthCare Royalty, quarterly Erivedge royalty and royalty-related payments from Genentech will first be applied to pay: (i) escrow fees payable by the Company pursuant to an escrow agreement, (ii) the Company’s royalty obligations to academic institutions, (iii) certain expenses incurred by HealthCare Royalty in connection with the credit agreement and related transaction documents, including enforcement of its rights in the case of an event of default under the credit agreement and (iv) expenses incurred by the Company enforcing its right to indemnification under the collaboration agreement. Subsequently, remaining amounts will be applied first, to pay interest and second, to pay principal on the loan. If royalties owed under the Genentech collaboration agreement are insufficient to pay the accrued interest on the outstanding loan, the unpaid interest outstanding will be added to the loan principal on a quarterly basis. (c) Respective Debt Payments to BioPharma-II and HealthCare Royalty Partners III During the years ended December 31, 2017 and 2016 , Curis Royalty made payments totaling $8.9 million and $7.1 million , respectively, of which $5.0 million and $4.3 million have been applied to the principal, respectively, with the remainder applied to accrued interest. As of December 31, 2017 , the Company recorded short- and long-term debt of $5.9 million and $35.7 million , respectively, and at December 31, 2016 , the Company recorded short- and long-term debt of $4.9 million and $14.9 million , respectively, related to the loan, with such amounts recorded within the Company’s consolidated balance sheets. Curis Royalty is currently entitled to a royalty that escalates from 5% to 7.5% based on worldwide annual net sales of Erivedge ranging from less than $150.0 million to over $600.0 million . The royalty rate applicable to Erivedge may be decreased by 2% (such that the applicable royalty rate will range from 3% to 5.5% ) 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 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. During the third quarter of 2015, the FDA and CHMP approved Hedgehog signaling pathway inhibitor sonidegib, then marketed by Novartis (and now Sun Pharmaceuticals, Inc.), for use in locally advanced BCC. Genentech has advised us that Novartis recorded sales of sonidegib in the U.S. during the fourth quarter of 2015 and, accordingly, Genentech began reducing royalties on its net sales in the U.S. of Erivedge during the fourth quarter of 2015. At December 31, 2017 , the fair value of the principal portion of the debt is estimated as $41.2 million . Due to the assumptions required to estimate future Erivedge royalties, the expected repayment period, and weighting of various royalty projection scenarios, the fair value of the debt is measured using Level 3 inputs. For the year ended December 31, 2017 , the Company incurred debt issuance costs totaling $0.2 million in connection with the HealthCare Royalty transaction, all of which were incurred directly by the Company. For the year ended December 31, 2016 , the Company incurred debt issuance costs totaling $0.4 million in connection with the BioPharma-II loan transaction, of which $0.2 million related to expenses that the Company paid on behalf of BioPharma-II and the remaining $0.2 million were incurred directly by the Company. All debt issuance costs incurred directly by the Company were recorded as contra-debt, which were direct deductions from the carrying amount of the related debt liability in the Company’s condensed consolidated balance sheets as of December 31, 2017 and 2016 as detailed in the following table: As of December 31, 2017 2016 Debt, current 5,919 4,987 Debt issue costs, current (33 ) (48 ) Debt, current portion net of issuance costs $ 5,886 $ 4,939 Debt, long-term 35,802 14,992 Debt issue costs, long-term (133 ) (71 ) Debt, net of current portion and issuance costs $ 35,669 $ 14,921 All issuance costs are being amortized over the estimated term of the debt using the straight-line method which approximates the effective interest method. For the years ended December 31, 2017 , 2016 and 2015 , the Company recognized interest expense related to the loans with BioPharma-II and HealthCare Royalty of $3.9 million , $2.8 million and $3.3 million within the Company’s Consolidated Statement of Operations, comprised of interest accrued on the outstanding principal of the loan and amortization of debt issuance costs. The assumptions used in determining the expected repayment term of the debt and amortization period of the issuance costs requires management to make estimates that could impact the short- and long-term classification of these costs, as well as the period over which these costs will be amortized. In addition, the Company recorded related accrued interest on the debt of $0.2 million and $0.2 million as of December 31, 2017 and 2016 , respectively, with such amounts included in the Company’s accrued liabilities section of its consolidated balance sheets. Future payments of principal on the loan will require application of these same assumptions and will be used to estimate short- and long-term classification of the debt within the Company’s consolidated balance sheets, and these assumptions include a reduction in the Company’s forecasted royalties related to a competing product for the expected repayment term. At December 31, 2017 , the Company estimates that its future payments of principal on the loan are as follows: Principal 2018 $ 5,919 2019 6,923 2020 8,133 2021 9,438 2022 10,992 Thereafter 316 Total payments 41,721 Less current portion, gross (5,919 ) Total long-term debt obligations, gross $ 35,802

Commitments

Commitments	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments	Commitments (a) OPERATING LEASES The Company is party to a lease agreement with the Trustees of Lexington Office Realty Trust pursuant to which the Company leases 24,529 square feet of property that is used for office, research and laboratory space located at 4 Maguire Road in Lexington, Massachusetts. The term of the 4 Maguire Road lease agreement commenced on December 1, 2010, and was set to expire in February 2018 . The Company had the option to extend the term for one additional five -year period upon the Company’s written notice to the lessor at least one year and no more than 18 months in advance of the extension. On November 1, 2017, the Company entered into a second amendment to the lease agreement pursuant to which the Company agreed to extend the lease for an additional two -year period. The term of the lease amendment commences on March 1, 2018, and expires on February 29, 2020. The amendment provides for no option to extend the term beyond the two -year period, nor does it provide an option for early termination of the lease. The total cash obligations for the base rent over the initial term of the lease agreement and the extended term of the lease agreement were approximately $4.4 million and $2.0 million , respectively. In addition to the base rent, the Company is also responsible for its share of operating expenses and real estate taxes, in accordance with the terms of the lease agreement. The Company has provided a security deposit to the lessor in the form of an irrevocable letter of credit in the original amount of $0.3 million . The original deposit has been reduced throughout the lease term since its inception to $0.2 million during 2017 and 2016 , respectively, in accordance with the terms of the lease. These amounts have been classified as the restricted investments in the Company’s Consolidated Balance Sheet as of December 31, 2017 and 2016 . The Company’s remaining operating lease commitments for all leased facilities with an initial or remaining term of at least one year are as follows: Year Ending December 31, 2018 935 2019 1,001 2020 168 Total minimum payments $ 2,104 Rent expense for all operating leases was $0.7 million for the year ended December 31, 2017 and $0.6 million for each of the years ended December 31, 2016 and 2015 , respectively. The related deferred rent is included in accrued liabilities and other long-term liabilities in the Company’s consolidated balance sheet as of December 31, 2017 and 2016 . (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 incurred 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, 2017 , 2016 and 2015 , of $7.5 million , $5.5 million and $9.8 million , respectively. Of the aggregate amount recognized for the year ended December 31, 2017 , $7.5 million related to payments the Company made pursuant to its Aurigene collaboration (see Note 3(b)). For the years ended December 31, 2017 , 2016 and 2015 , the Company also recognized $0.5 million , $0.4 million and $0.4 million as cost of royalty revenues in its Consolidated Statements of Operations and Comprehensive Loss related to such obligations (see Note 3(a)). During the year ended December 31, 2016 and 2015 , pursuant to the amendment and original collaboration agreement with Aurigene, the Company also recognized expense of $18.0 million and $24.3 million , respectively, related to partial consideration for the rights granted to the Company under the amendment to the collaboration agreement and the original collaboration agreement within the in-process research and development expense line item of the consolidated statements of operations and comprehensive loss (see Note 3(b)).

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Common Stock	Common Stock (a) 2017 Public Offering of Common Stock On September 18, 2017, the Company entered into an underwriting agreement with Robert W. Baird & Co., Incorporated, or Baird, as underwriter, pursuant to which the Company sold and issued 20,000,000 shares of the Company’s common stock. The underwriter agreed to purchase the shares from the Company pursuant to the underwriting agreement at a price of $1.78 , per share, offering price to the public was $1.85 per share. Under the terms of the underwriting agreement, the Company also granted the underwriter an option, exercisable for 30 days, to purchase up to an additional 3,000,000 shares of common stock at the public offering price per share less underwriting discounts and commissions. The underwriter's option was not exercised. The Company received net proceeds from the sale of the shares, after deducting the underwriting discounts and commissions and estimated offering expenses, of $35.3 million . The Company incurred offering expenses of $0.3 million related to this transaction. (b) 2015 Public Offering of Common Stock On February 25, 2015, the Company entered into an underwriting agreement with Cowen and Company, or Cowen, acting for itself and as representative of the named underwriters, relating to an underwritten public offering of 21,818,181 shares of the Company’s common stock. The offering price to the public was $2.75 per share, and the underwriters agreed to purchase the shares from the Company pursuant to the underwriting agreement at a price of $2.585 per share. Under the terms of the underwriting agreement, the Company granted the underwriters an option, exercisable for 30 days , to purchase up to an additional 3,272,727 shares of common stock at the public offering price per share less the underwriting discounts and commissions. The underwriters exercised this option in full on February 25, 2015. On March 2, 2015, the Company completed the public offering of 25,090,908 shares of common stock. The Company received net proceeds from the sale of the shares, after deducting the underwriting discounts and commissions and estimated offering expenses, of $64.6 million . (c) 2015 Sales Agreement with Cowen On July 2, 2015, the Company entered into a sales agreement with Cowen, pursuant to which the Company may 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 will act as sales agent. Subject to the terms and conditions of the sales agreement, Cowen may sell the common stock by methods deemed to be an “at-the-market” offering as defined in Rule 415 promulgated under the Securities Act of 1933, as amended, 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, Cowen may also sell the common stock by any other method permitted by law, including in negotiated transactions. Cowen will use its commercially reasonable efforts consistent with its normal trading and sales practices and applicable state and federal laws, rules and regulations and the rules of the NASDAQ Global Market to sell on the Company’s behalf all of the shares requested to be sold by the Company. The Company has no obligation to sell any of the common stock under the sales agreement. Either the Company or Cowen may at any time suspend solicitations and offers under the sales agreement upon notice to the other party. The sales agreement may be terminated at any time by either the Company or Cowen upon written notice to the other party as specified in the sales agreement. The aggregate compensation payable to Cowen shall be 3% of the gross sales price of the common stock sold by Cowen pursuant to the sales agreement. Each party has 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 shares to be sold under the sales agreement, if any, may be sold and issued pursuant to the currently-effective universal shelf registration statement on Form S-3, filed with the Securities and Exchange Commission on July 2, 2015. The Company sold 2,103,981 shares of common stock under this sales agreement for net proceeds of $6.2 million during the year ended December 31, 2017 .

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes For the years ended December 31, 2017 , 2016 and 2015 , the Company did not record any federal or state income tax expense given its continued operating losses. On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act ("Tax Reform Act"). The legislation significantly changes U.S. tax law by, among other things, lowering corporate income tax rates, implementing a territorial tax systems and imposing a repatriation tax on deemed repatriated earnings of foreign subsidiaries. The Tax Reform Act permanently reduces the U.S. corporate income tax rate from a maximum of 35% to a flat 21% rate, effective January 1, 2018. The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to reverse. As a result of the reduction in the U.S. corporate income tax rate from the maximum 35% to 21% under the Tax Reform Act, the Company revalued its ending deferred tax assets and liabilities at December 31, 2017. This revaluation resulted in a reduction to the Company’s deferred tax asset of $55.6 million . Due to the Company's full valuation allowance, no provisional tax expense or benefit associated with the remeasurement was recognized in the Company's consolidated statement of income for the year ended December 31, 2017 . However, the reduction of the U.S. federal corporate tax rate from the maximum 35% to 21% resulted in increases to the amounts reflected “Change in valuation allowance” and “Deferred rate change” captions for the year ended December 31, 2017 in the Company’s tax reconciliation table below compared to those amounts disclosed for the year ended December 31, 2016. The change in the U.S. federal corporate tax rate, which is effective January 1, 2018, is also reflected in the Company’s deferred tax table below. The provision for income taxes for continuing operations was at rates different from the U.S. federal statutory income tax rate for the following reasons: For the Year Ended December 31, 2017 2016 2015 Statutory federal income tax rate 34.0 % 34.0 % 34.0 % State income taxes, net of federal benefit 4.4 % 5.0 % 5.1 % Research and development tax credits 2.7 % 1.3 % 1.4 % Orphan drug tax credits 10.9 % 10.5 % — % Deferred compensation (0.8 )% (0.5 )% (0.4 )% Interest expense (0.5 )% (0.4 )% (0.5 )% Deferred rate change (104.4 )% — % — % Permanent adjustments and other (5.2 )% (0.2 )% 0.1 % Change in valuation allowance 58.9 % (49.7 )% (39.7 )% Effective income tax rate — — — The principle components of the Company’s deferred tax assets at December 31, 2017 and 2016 , respectively, are as follows: December 31, 2017 2016 Deferred Tax Assets: NOL carryforwards $ 63,688 $ 92,012 Research and development tax credit carryforwards 15,340 13,404 Orphan drug tax credit carryforwards 15,580 10,148 Depreciation and amortization 11,663 18,242 Capitalized research and development expenditures 32,550 35,848 Stock options 4,948 5,507 Accrued expenses and other 155 176 Total Gross Deferred Tax Asset 143,924 175,337 Valuation Allowance (143,924 ) (175,337 ) Net Deferred Tax Asset $ — $ — The classification of the above deferred tax assets is as follows: December 31, 2017 2016 Deferred Tax Assets: Current deferred tax assets $ — $ — Non-current deferred tax assets 143,924 175,337 Valuation Allowance (143,924 ) (175,337 ) Net Deferred Tax Asset $ — $ — As of December 31, 2017 , the Company had federal and state net operating losses, or NOLs, of $273.5 million and $98.6 million , respectively, and federal and state research and experimentation credit carryforwards of approximately $11.6 million and $4.7 million , respectively, which will expire at various dates starting in 2018 through 2036 . As of December 31, 2017 , the Company also had orphan drug tax credit carryforwards of $15.6 million , these credits 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 $143.9 million has been established at December 31, 2017 . The benefit of deductions from the exercise of stock options is included in the NOL carryforwards. The valuation allowance (decreased)/increased approximately $(31.4) million , $30.0 million and $23.4 million during the years ended December 31, 2017 , 2016 and 2015 . The current year decrease in the valuation allowance is primarily due to the impact of the Tax Reform Act on the ending deferred assets which offset the current year increase in net operating loss carryforwards. The increase in 2016 and 2015 is due primarily to the increase in net operating loss carryforwards and tax credits. Utilization of the NOL and research and development, or R&D, credit carryforwards 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 and R&D credit carryforwards that can be utilized annually to offset future taxable income and tax, respectively. The Company has not completed a study to assess whether a change of control has occurred or whether there have been multiple changes of control since the Company’s formation because the Company continues to maintain a full valuation allowance on its NOL and R&D credit carryforwards. In addition, 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, 2017 and 2016 , 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 Topic 740. 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 2002 through 2017 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, or 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. On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 ("SAB 118") to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Reform Act. The Company has recognized the provisional tax impacts related to the revaluation of the deferred tax assets and liabilities and included these amounts in its consolidated financial statements for the year ended December 31, 2017 . The ultimate impact may differ from these provisional amounts due to, among other things, additional analysis, changes in interpretations and assumptions the Company has made, additional regulatory guidance that may be issued, and actions the Company may take as a result of the Tax Reform Act. The accounting is expected to be complete when the 2017 U.S. corporate income tax return is filed in 2018.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions (a) Agreements with Daniel R. Passeri On June 2, 2014 , Daniel R. Passeri resigned as Chief Executive Officer of the Company and the Board of Directors appointed Mr. Passeri to serve as the Vice Chairman of the Board of Directors. Also on June 2, 2014, the Company and Mr. Passeri entered into a consulting agreement. The agreement was for an initial term of one year , subject to renewal or earlier termination by the parties. The agreement was renewed by the parties through May 31, 2016, after which the agreement between Mr. Passeri and the Company was terminated. Pursuant to the terms of the agreement, Mr. Passeri was paid an hourly fee or a monthly retainer as consideration for the services rendered by Mr. Passeri to the Company. During the five months ended May 31, 2016, Mr. Passeri provided consulting services to the Company on intellectual property, corporate and strategic matters in exchange for payments of $30,000 per month. On September 2, 2016, the Company and Mr. Passeri entered into a letter agreement pursuant to which Mr. Passeri resigned as director and Vice Chairman of the Company's board of directors, which became effective on September 14, 2016. Pursuant to the terms of the Letter Agreement, and in recognition of his many years of service to the Company in varying roles, including as a director and Vice Chairman of the Board, and formerly as Chief Executive Officer, President, and as a consultant, the Board authorized a $0.3 million recognition bonus payment to Mr. Passeri and also approved a modification to Mr. Passeri’s vested common stock options such that the exercise period for all such options shall be 24 months. Mr. Passeri agreed to provide continued assistance to the Company, without further remuneration, for up to twenty-four months, if and when requested by the Board of Directors or the Chief Executive Officer. The letter agreement also contains other customary terms and conditions relating to Mr. Passeri’s end of service with the Company. The Company recognized expenses related to the consulting and letter agreements of $0.4 million and $0.2 million during the years ended December 31, 2016 and 2015 , respectively. (b) Agreement with Director - Lori A. Kunkel On November 11, 2016 , the Company's board of directors elected Lori A. Kunkel, M.D., to serve as a class II director until the 2019 Annual Meeting of Stockholders and thereafter until her successor is duly elected and qualified. Prior to Dr. Kunkel’s election as a director, the Company were party to a consulting agreement dated August 21, 2013 with D2D, LLC, a limited liability company owned by Dr. Kunkel, under which Dr. Kunkel provided consulting services to the Company related to oncology clinical evaluation and development. The Company and Dr. Kunkel terminated the D2D consulting agreement on June 30, 2015 , and entered into a new consulting agreement on July 1, 2015 . The Company and Dr. Kunkel terminated the July 2015 consulting agreement in connection with her election as a member of the Board of Directors. From January 1, 2015 until Dr. Kunkel’s election to the Company's board of directors, Dr. Kunkel has received aggregate payments from the Company of $0.1 million and received options in connection with her July 2015 consulting agreement to purchase an aggregate of 150,000 shares of our common stock at a weighted average exercise price of $3.33 per share. The Company recognized expenses related to the consulting and letter agreements of $0.1 million during the year ended December 31, 2016 .

Retirement Savings Plan

Retirement Savings Plan	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Retirement Savings Plan	Retirement Savings Plan The Company has a 401(k) retirement savings plan covering substantially all of the Company’s employees. For the years ended December 31, 2017 , 2016 and 2015 , the Company made matching contributions of $0.3 million , $0.2 million and $0.2 million , respectively.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2017
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, 2017 and 2016 : Quarter Ended March 31, June 30, September 30, December 31, 2017 Revenues $ 2,131 $ 2,061 $ 2,444 $ 3,262 Loss from operations (15,053 ) (13,109 ) (14,471 ) (7,127 ) Net loss (15,742 ) (14,090 ) (15,457 ) (8,028 ) Net loss per common share (basic and diluted) $ (0.11 ) $ (0.10 ) $ (0.11 ) $ (0.05 ) Weighted average common shares (basic and diluted) 142,011,776 143,786,705 146,514,196 164,008,252 Quarter Ended March 31, June 30, September 30, December 31, 2016 Revenues $ 1,726 $ 1,680 $ 1,759 $ 2,362 Loss from operations (8,807 ) (10,680 ) (27,789 ) (10,763 ) Net loss (9,441 ) (11,290 ) (28,345 ) (11,335 ) Net loss per common share (basic and diluted) $ (0.07 ) $ (0.09 ) $ (0.21 ) $ (0.08 ) Weighted average common shares (basic and diluted) 129,019,984 129,270,639 132,065,947 140,715,621 The net loss amounts presented for the quarters ended March 31, 2017 and September 30, 2017 include milestone payments of $3.8 million made under the Company’s collaboration with Aurigene, which were recognized as research and development expenses (see Note 3(b)).

Summary of Significant Accoun23

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Use of Estimates	USE OF ESTIMATES 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 of 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 intangible assets; 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.
Consolidation	CONSOLIDATION The accompanying consolidated financial statements include the Company and its wholly owned subsidiaries, Curis Royalty (see Note 9) and Curis Securities Corporation, Inc. The Company has eliminated all intercompany transactions in each of the years ended December 31, 2017 , 2016 and 2015 .
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. The Company follows the provisions of the Financial Accounting Standards Board, or FASB, Codification Topic 605, Revenue Recognition . License Fees and Multiple Element Arrangements Non-refundable license fees are recognized as revenue when the Company has a contractual right to receive such payment, the contract price is fixed or determinable, the collection of the resulting receivable is reasonably assured and the Company has no further performance obligations under the license agreement. Multiple element arrangements, such as license and development arrangements are analyzed to determine whether the deliverables, which often include a license and performance obligations such as research and steering committee services, can be separated or whether they must be accounted for as a single unit of accounting in accordance with generally accepted accounting principles, or GAAP. The Company recognizes up-front license payments as revenue upon delivery of the license only if the license has stand-alone value. If the license is considered not to have stand-alone value, the arrangement would then be accounted for as a single unit of accounting and the license payments and payments for performance obligations are recognized as revenue over the estimated period of when the performance obligations are performed. 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 determined to be 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. Whenever the Company determines that an arrangement should be accounted for as a single unit of accounting, it must determine the period over which the performance obligations will be performed and revenue will be recognized. Revenue will be recognized using either a relative performance or straight-line method. The Company recognizes revenue using the relative performance method provided that the Company can reasonably estimate the level of effort required to complete its performance obligations under an arrangement and such performance obligations are provided on a best-efforts basis. Direct labor hours or full-time equivalents are typically used as the measure of performance. Revenue recognized under the relative performance method would be determined by multiplying the total payments under the contract, excluding royalties and payments contingent upon achievement of substantive milestones, by the ratio of level of effort incurred to date to estimated total level of effort required to complete the Company’s performance obligations under the arrangement. Revenue is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the relative performance method, as of each reporting period. If the Company cannot reasonably estimate the level of effort required to complete its performance obligations under an arrangement, the performance obligations are provided on a best-efforts basis and the Company can reasonably estimate when the performance obligation ceases or the remaining obligations become inconsequential and perfunctory, then the total payments under the arrangement, excluding royalties and payments contingent upon achievement of substantive milestones, would be recognized as revenue on a straight-line basis over the period the Company expects to complete its performance obligations. Revenue is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the straight-line basis, as of the period ending date. If the Company cannot reasonably estimate when its performance obligation either ceases or becomes inconsequential and perfunctory, then revenue is deferred 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. Substantive Milestone Payments Collaboration agreements that contain substantive milestone payments are recognized upon achievement of the milestone only if: • such milestone is commensurate with either of the following: a) the Company’s performance to achieve the milestone (for example, the achievement of the milestone involves a degree of risk and was not reasonably assured at the inception of the arrangement); or b) the enhancement of the value of the deliverable as a result of a specific outcome resulting from the Company’s performance to achieve the milestone (or substantive Company effort is involved in achieving the milestone); • such milestone relates solely to past performance; and • the amount of the milestone payment is reasonable relative to all deliverables and payment terms in the arrangement. Determination as to whether a payment meets the aforementioned conditions involves management’s judgment. If any of these conditions are not met, the resulting payment would not be considered a substantive milestone, and the resulting payment would be recognized as revenue as performance obligations are performed under either the relative performance or straight-line methods, as applicable, and in accordance with these policies as described above. In addition, the determination that one such payment was not a substantive milestone could prevent the Company from concluding that subsequent milestone payments were substantive milestones and, as a result, any additional milestone payments could also be considered part of the consideration for the single unit of accounting and would be recognized as revenue as such performance obligations are performed under either the relative performance or straight-line methods, as applicable. Milestones that are tied to regulatory approval are not considered probable of being achieved until such approval is received. Milestones tied to counterparty performance are not included in the Company’s revenue model until the performance conditions are met. Reimbursement of Costs Reimbursement of research and development costs by third party collaborators is recognized as revenue provided the Company has determined that it is acting primarily as a principal in the transaction according to the provisions outlined in the FASB Codification Topic 605-45, Revenue Recognition, Principal Agent Considerations , the amounts are determinable and collection of the related receivable is reasonably assured. Royalty Revenue Since the first quarter of 2012, the Company has recognized royalty revenues related to Genentech’s and Roche’s sales of Erivedge. Royalty revenue is recognized upon the sale of the related products based on contractual terms, provided that the royalty amounts are fixed or determinable, collection of the related receivable is reasonably assured and the Company has no remaining performance obligations under the arrangement. If royalties are received when the Company has remaining performance obligations, it expects to attribute the royalty payments to the services being provided under the arrangement and therefore to recognize such royalty payments as such performance obligations are performed under either the relative performance or straight-line methods, as applicable, and in accordance with these policies as described above. The Company expects to recognize royalty revenue in future quarters 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 Notes 3(a) and 9). However, Erivedge royalties will service Curis Royalty’s debt until this debt is repaid in full (see Note 9).
License Fees and Multiple Element Arrangement	License Fees and Multiple Element Arrangements Non-refundable license fees are recognized as revenue when the Company has a contractual right to receive such payment, the contract price is fixed or determinable, the collection of the resulting receivable is reasonably assured and the Company has no further performance obligations under the license agreement. Multiple element arrangements, such as license and development arrangements are analyzed to determine whether the deliverables, which often include a license and performance obligations such as research and steering committee services, can be separated or whether they must be accounted for as a single unit of accounting in accordance with generally accepted accounting principles, or GAAP. The Company recognizes up-front license payments as revenue upon delivery of the license only if the license has stand-alone value. If the license is considered not to have stand-alone value, the arrangement would then be accounted for as a single unit of accounting and the license payments and payments for performance obligations are recognized as revenue over the estimated period of when the performance obligations are performed. 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 determined to be 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. Whenever the Company determines that an arrangement should be accounted for as a single unit of accounting, it must determine the period over which the performance obligations will be performed and revenue will be recognized. Revenue will be recognized using either a relative performance or straight-line method. The Company recognizes revenue using the relative performance method provided that the Company can reasonably estimate the level of effort required to complete its performance obligations under an arrangement and such performance obligations are provided on a best-efforts basis. Direct labor hours or full-time equivalents are typically used as the measure of performance. Revenue recognized under the relative performance method would be determined by multiplying the total payments under the contract, excluding royalties and payments contingent upon achievement of substantive milestones, by the ratio of level of effort incurred to date to estimated total level of effort required to complete the Company’s performance obligations under the arrangement. Revenue is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the relative performance method, as of each reporting period. If the Company cannot reasonably estimate the level of effort required to complete its performance obligations under an arrangement, the performance obligations are provided on a best-efforts basis and the Company can reasonably estimate when the performance obligation ceases or the remaining obligations become inconsequential and perfunctory, then the total payments under the arrangement, excluding royalties and payments contingent upon achievement of substantive milestones, would be recognized as revenue on a straight-line basis over the period the Company expects to complete its performance obligations. Revenue is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the straight-line basis, as of the period ending date. If the Company cannot reasonably estimate when its performance obligation either ceases or becomes inconsequential and perfunctory, then revenue is deferred 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.
Royalty Revenue	Royalty Revenue Since the first quarter of 2012, the Company has recognized royalty revenues related to Genentech’s and Roche’s sales of Erivedge. Royalty revenue is recognized upon the sale of the related products based on contractual terms, provided that the royalty amounts are fixed or determinable, collection of the related receivable is reasonably assured and the Company has no remaining performance obligations under the arrangement. If royalties are received when the Company has remaining performance obligations, it expects to attribute the royalty payments to the services being provided under the arrangement and therefore to recognize such royalty payments as such performance obligations are performed under either the relative performance or straight-line methods, as applicable, and in accordance with these policies as described above. The Company expects to recognize royalty revenue in future quarters 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 Notes 3(a) and 9). However, Erivedge royalties will service Curis Royalty’s debt until this debt is repaid in full (see Note 9).
Research and Development	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. For the year ended December 31, 2017, the Company did not recognize any in-process research and development expenses. The Company incurred in-process research and development expenses of $18.0 million during the year ended December 31, 2016 representing the value of common stock issued to Aurigene pursuant to the September 2016 amendment to the collaboration and $24.3 million during the year ended December 31, 2015 representing partial consideration for the rights granted to the Company under the original collaboration agreement with Aurigene in January 2015 (see Note 3(b)). The Company expenses research and development costs as they are incurred. 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.
Cash Equivalents and Investments	CASH EQUIVALENTS AND INVESTMENTS Cash equivalents consist of short-term, highly liquid investments purchased with original maturities of three months or less. All other liquid investments are classified as marketable securities. The Company’s short-term investments are marketable 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 securities with original maturities of greater than twelve months from the balance sheet. Marketable securities consist of commercial paper, corporate bonds and notes, and government obligations. All of the Company’s investments have been designated available-for-sale and are stated at fair value with any unrealized holding gains or losses included as a component of stockholders’ equity and any realized gains and losses recorded in the statement of operations in the period during which the securities are sold. Unrealized gains and temporary losses on investments are included in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity. Realized gains and losses, dividends and interest income are included in other income (expense). Any premium or discount arising at purchase is amortized and/or accreted to interest income.
Long-Lived Assets Other than Goodwill	LONG-LIVED ASSETS OTHER THAN GOODWILL Long-lived assets other than goodwill consist of property and equipment. The aggregate net balances for these long-lived assets were $0.4 million and $0.4 million as of December 31, 2017 and 2016 , respectively. 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 impairment charges for the years ended December 31, 2017 , 2016 or 2015 . 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: Asset Classification Estimated Useful Life Laboratory equipment, computers and software 3-5 years Leasehold improvements Lesser of life of the lease or the life of the asset Office furniture and equipment 5 years
Goodwill	The Company applies the guidance in the FASB Codification Topic 350, Intangibles—Goodwill and Other. During each of December 2017 , 2016 and 2015 , 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.
Treasury Stock	TREASURY STOCK On May 31, 2002, the Company announced that its Board of Directors had approved the repurchase of up to $3.0 million of the Company’s common stock. The Company accounted for its common stock repurchases as treasury stock under the cost method. In 2002, the Company repurchased 1,047,707 shares of its common stock at a cost of $0.9 million pursuant to this repurchase program. Each of the Company’s now-expired 2000 Stock Incentive Plan and the current Amended and Restated 2010 Stock Incentive Plan generally allow participants to purchase common stock upon the exercise of a stock option by delivery of shares of Company common stock held directly by the participant, with such shares of common stock valued at the closing price on the Nasdaq Global Market, or NASDAQ, on the date of exercise. On certain instances in the past, the Company has accounted for the value of the common stock remitted to the Company in satisfaction of the exercise price as treasury stock under the cost method.
Basic and Diluted Loss Per Common Share	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.
Stock-Based Compensation	STOCK-BASED COMPENSATION The Company records stock-based compensation in accordance with FASB Codification Topic 718, Compensation—Stock Compensation , or ASC 718, which requires that the fair value of such equity instruments be recognized as an expense in the financial statements as services are performed.
Operating Leases	OPERATING LEASES The Company currently has one facility located at 4 Maguire Road in Lexington, Massachusetts under a noncancellable operating lease agreement for office and laboratory space. The rent payments for this facility escalate over the lease term and the Company expenses its obligations under this lease agreement on a straight-line basis over the term of the lease
Concentration of Risk	CONCENTRATION OF RISK Financial instruments, which potentially subject the Company to concentrations of credit risk, consist principally of cash and cash equivalents, short- and long-term investments. The Company invests directly in commercial paper of financial institutions and corporations with A-/Aa3 or better long-term ratings and A-1/P-1 short term debt ratings and U.S. Treasury securities. 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. The Company’s accounts receivable at December 31, 2017 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 CUDC-907, CA-170, CA-4948 and CA-327, 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.
Comprehensive Loss	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.
New Accounting Pronouncements	NEW ACCOUNTING PRONOUNCEMENTS In September 2017, the FASB issued ASU 2017-13, which further clarified ASU 2016-02 issued in February 2016, Leases . The standard requires organizations that lease assets to recognize on the balance sheet assets or liabilities, as applicable, for the rights and obligations created by those leases. Additionally, the guidance modifies current guidance for lessor accounting and leveraged leases, and is effective for fiscal years beginning after December 15, 2018, and interim periods within such years. Early adoption is permitted, but the Company does not anticipate electing early adoption. The Company is currently evaluating the impact of the adoption of this guidance on its consolidated financial statements. In May 2017, the Financial Accounting Standard Board (FASB) issued Accounting Standard Update (ASU) 2017-09, Scope of Modification Accounting , which clarifies the scope under which modification accounting should be applied to a share-based payment award under Codification Topic 718. The standard will be effective for annual reporting periods and interim periods within those annual periods, beginning after December 15, 2017, and early adoption was permitted for interim or annual reporting periods beginning after January 1, 2017. The Company does not expect this guidance to have a material impact on its consolidated financial statements. In January 2017, the Financial Accounting Standard Board (FASB) issued Accounting Standard Update (ASU) 2017-04, Simplifying the Test for Goodwill Impairment , which simplifies the subsequent measurement of goodwill under the current standard in testing the interim or annual impairment of goodwill. The standard will be effective for annual reporting periods and interim periods within those annual periods beginning after December 15, 2019, and early adoption is now permitted for interim or annual reporting periods that began after January 1, 2017. The Company does not expect the impact of this guidance to be material to its consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments , which helps to clarify the diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows under Codification Topic 230, Statement of Cash Flows, by addressing eight specific cash flow issues. The standard became effective for annual reporting periods and interim periods within those annual periods, beginning after December 15, 2017. The Company does not expect this guidance to have a material impact on its consolidated financial statements. In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities , which amends prior guidance on accounting for equity investments and financial liabilities. The new standard amends certain aspects of accounting and disclosure requirements for financial instruments, including the requirement that equity investments with readily determinable fair values be measured at fair value with changes in fair value recognized in results of operations. The new standard does not apply to investments accounted for under the equity method of accounting or those that result in consolidation of the investee. Equity investments that do not have readily determinable fair values may be measured at fair value or at cost minus impairment adjusted for changes in observable prices. A financial liability that is measured at fair value in accordance with the fair value option is required to be presented separately in other comprehensive income for the portion of the total change in the fair value resulting from change in the instrument-specific credit risk. In addition, a valuation allowance should be evaluated on deferred tax assets related to available-for-sale debt securities in combination with other deferred tax assets. The guidance is effective for fiscal years beginning after December 15, 2017, and interim periods within such years. Early adoption is permitted but the Company does not anticipate electing early adoption. The Company does not expect the adoption of this guidance to have a material impact on its consolidated financial statements. In May 2014, the FASB issued new revenue recognition guidance in ASC 606, Revenue from Contracts with Customers , for entities, providing a single, comprehensive model to account for revenue arising from contracts with customers. In addition, The FASB recently issued ASUs 2016-08, 2016-10, 2016-12, 2016-20, 2017-13 and 2017-14 all of which are further clarifying amendments to ASU 2014-09.This new standard provides a five-step framework whereby revenue is recognized when promised goods or services are transferred to a customer at an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new standard also requires significantly expanded disclosures regarding the qualitative and quantitative information of an entity’s nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. Two adoption methods are permitted: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU recognized at the date of initial application. The Company plans to use the modified retrospective method for its adoption. To date, the Company’s sources of collaboration and other revenue have primarily been collaboration agreements. The most significant differences between Topic 606 and previous guidance for license and collaboration revenue are: (i) allocating consideration to performance obligations; and (ii) estimating and determining the timing of recognition of variable consideration received from licensees, including up-front license payments, contingent milestones and royalties. The guidance is effective for interim and annual periods beginning after December 15, 2017 and early adoption is permitted. The guidance is anticipated to be effective for the Company as of January 1, 2018. The Company has evaluated the potential impact that ASU 2014-09 may have on the financial position and results of operations and expects the adoption of this guidance to have no material impact on its consolidated financial statements.
Segment Reporting	SEGMENT REPORTING The Company is engaged solely in the discovery and development of innovative drug candidates for the treatment of human cancers. Accordingly, the Company has determined that it operates in one operating segment.
Fair Value Measurements	The Company discloses fair value measurements based on a framework outlined by GAAP which requires expanded disclosures regarding fair value measurements. GAAP also defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Market participants are buyers and sellers in the principal market that are (i) independent, (ii) knowledgeable, (iii) able to transact, and (iv) willing to transact. The FASB Codification Topic 820, Fair Value Measurements and Disclosures, requires the use of valuation techniques that are consistent with the market approach, the income approach and/or the cost approach. The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets and liabilities. The income approach uses valuation techniques to convert future amounts, such as cash flows or earnings, to a single present amount on a discounted basis. The cost approach is based on the amount that currently would be required to replace the service capacity of an asset (replacement cost). Valuation techniques should be consistently applied. GAAP also establishes a fair value hierarchy which requires an entity to maximize the use of observable inputs, where available, and minimize the use of unobservable inputs when measuring fair value. The standard describes three levels of inputs that may be used to measure fair value: 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 Accoun24

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
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: Asset Classification Estimated Useful Life Laboratory equipment, computers and software 3-5 years Leasehold improvements Lesser of life of the lease or the life of the asset Office furniture and equipment 5 years
Summary of Antidilutive Securities	Antidilutive securities as of December 31, 2017 , 2016 and 2015 consisted of the following For the Year Ended December 31, 2017 2016 2015 Stock options outstanding 16,034,181 13,752,157 13,290,844 Total antidilutive securities 16,034,181 13,752,157 13,290,844

Fair Value of Financial Instr25

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017 and 2016 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, 2017 and 2016 . Quoted Prices in Active Markets (Level 1) Other Observable Inputs (Level 2) Unobservable Inputs (Level 3) Fair Value (in thousands) As of December 31, 2017 Cash equivalents: Money market funds $ 35,308 $ — $ — $ 35,308 Municipal bonds — 260 — 260 Short-term investments: Corporate commercial paper, stock, bonds and notes — 21,944 — 21,944 Total assets at fair value $ 35,308 $ 22,204 $ — $ 57,512 Quoted Prices in Active Markets (Level 1) Other Observable Inputs (Level 2) Unobservable Inputs (Level 3) Fair Value (in thousands) As of December 31, 2016 Cash equivalents: Money market funds $ 24,542 $ — $ — $ 24,542 Municipal bonds — 330 — 330 Short- and long-term investments: Corporate commercial paper, stock, bonds and notes — 18,447 — 18,447 Total assets at fair value $ 24,542 $ 18,777 $ — $ 43,319

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017 are as follows: Amortized Cost Unrealized Gain Unrealized Loss Fair Value Corporate bonds and notes—short-term $ 21,946 $ — $ (2 ) $ 21,944 Total investments $ 21,946 $ — $ (2 ) $ 21,944 The amortized cost, unrealized gains and losses and fair value of investments available-for-sale as of December 31, 2016 are as follows: Amortized Cost Unrealized Gain Unrealized Loss Fair Value Corporate bonds and notes—short-term $ 18,451 $ 2 $ (6 ) $ 18,447 Total investments $ 18,451 $ 2 $ (6 ) $ 18,447

Stock Plans and Stock Based C27

Stock Plans and Stock Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [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 December 31, 2017 2016 2015 Expected term (years)—Employees 5.5 6.0 6.0 Expected term (years)—Officers 5.5 7.0 7.0 Expected term (years)—Directors 6.3 7.0 7.0 Risk-free interest rate 2.0-2.1% 1.4-1.9% 1.5-1.9% Expected volatility 63-64% 63-70% 68-70% Expected dividend yield None None None The key assumptions used in these Monte Carlo simulation models and resulting valuations are noted in the following table: Market Market Expected life (years)—officers 6 6 Risk-free interest rate 1.9% 2.1% Volatility 70% 65% Dividends None None Number of options granted 640,000 400,000 Fair value per share $1.20 $0.34
Summary of Stock Option Activity	A summary of stock option activity under the Second Amended and Restated 2010 Plan, the 2000 Stock Incentive Plan, the 2000 Director Stock Option Plan, and Nonstatutory Inducement Grants is summarized as follows: Number of Shares Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Life Aggregate Intrinsic Value Outstanding, December 31, 2016 13,752,157 $ 2.30 Granted 6,113,000 2.51 Exercised (780,135 ) 1.36 Canceled (3,050,841 ) 2.33 Outstanding, December 31, 2017 16,034,181 $ 2.42 6.57 $ — Exercisable at December 31, 2017 8,771,728 $ 2.54 4.92 $ — Vested and unvested expected to vest 15,498,301 $ 2.42 6.49 $ —
Summary of Compensation Expense Related to ESPP	For the years ended December 31, 2017 , 2016 and 2015 , 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, 2017 2016 2015 Compensation expense recognized under ESPP $ 268 $ 48 $ 30 Expected term 6-24 months 6 months 6 months Risk-free interest rate 1.1-1.8% 0.4-0.7% 0.06-0.5% Volatility 65-76% 64-78% 55-78% Dividends None None None
Employee and Non-Employee Share Based Compensation Expense Allocation	For the years ended December 31, 2017 , 2016 and 2015 , 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, 2017 2016 2015 Research and development expenses $ 1,486 $ 762 $ 1,023 General and administrative expenses 3,873 3,563 2,852 Total stock-based compensation expense $ 5,359 $ 4,325 $ 3,875

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consist of the following: December 31, 2017 2016 Laboratory equipment, computers and software $ 1,736 $ 1,624 Leasehold improvements 185 185 Office furniture and equipment 354 371 2,275 2,180 Less—Accumulated depreciation and amortization (1,909 ) (1,767 ) Total $ 366 $ 413

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Other Liabilities Disclosure [Abstract]
Summary of Accrued Liabilities	Accrued liabilities consist of the following: December 31, 2017 2016 Accrued compensation $ 2,187 $ 2,026 Professional fees 148 157 Accrued interest on debt (see Note 9) 193 194 Other 265 348 Total $ 2,793 $ 2,725

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Debt Issuance Costs	debt issuance costs incurred directly by the Company were recorded as contra-debt, which were direct deductions from the carrying amount of the related debt liability in the Company’s condensed consolidated balance sheets as of December 31, 2017 and 2016 as detailed in the following table: As of December 31, 2017 2016 Debt, current 5,919 4,987 Debt issue costs, current (33 ) (48 ) Debt, current portion net of issuance costs $ 5,886 $ 4,939 Debt, long-term 35,802 14,992 Debt issue costs, long-term (133 ) (71 ) Debt, net of current portion and issuance costs $ 35,669 $ 14,921
Schedule of Future Payments of Principal on Loan	At December 31, 2017 , the Company estimates that its future payments of principal on the loan are as follows: Principal 2018 $ 5,919 2019 6,923 2020 8,133 2021 9,438 2022 10,992 Thereafter 316 Total payments 41,721 Less current portion, gross (5,919 ) Total long-term debt obligations, gross $ 35,802

Commitments (Tables)

Commitments (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of Operating Lease Commitments	The Company’s remaining operating lease commitments for all leased facilities with an initial or remaining term of at least one year are as follows: Year Ending December 31, 2018 935 2019 1,001 2020 168 Total minimum payments $ 2,104

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation	The provision for income taxes for continuing operations was at rates different from the U.S. federal statutory income tax rate for the following reasons: For the Year Ended December 31, 2017 2016 2015 Statutory federal income tax rate 34.0 % 34.0 % 34.0 % State income taxes, net of federal benefit 4.4 % 5.0 % 5.1 % Research and development tax credits 2.7 % 1.3 % 1.4 % Orphan drug tax credits 10.9 % 10.5 % — % Deferred compensation (0.8 )% (0.5 )% (0.4 )% Interest expense (0.5 )% (0.4 )% (0.5 )% Deferred rate change (104.4 )% — % — % Permanent adjustments and other (5.2 )% (0.2 )% 0.1 % Change in valuation allowance 58.9 % (49.7 )% (39.7 )% Effective income tax rate — — —
Components of Deferred Tax Assets	The principle components of the Company’s deferred tax assets at December 31, 2017 and 2016 , respectively, are as follows: December 31, 2017 2016 Deferred Tax Assets: NOL carryforwards $ 63,688 $ 92,012 Research and development tax credit carryforwards 15,340 13,404 Orphan drug tax credit carryforwards 15,580 10,148 Depreciation and amortization 11,663 18,242 Capitalized research and development expenditures 32,550 35,848 Stock options 4,948 5,507 Accrued expenses and other 155 176 Total Gross Deferred Tax Asset 143,924 175,337 Valuation Allowance (143,924 ) (175,337 ) Net Deferred Tax Asset $ — $ —
Classification of Deferred Tax Assets	The classification of the above deferred tax assets is as follows: December 31, 2017 2016 Deferred Tax Assets: Current deferred tax assets $ — $ — Non-current deferred tax assets 143,924 175,337 Valuation Allowance (143,924 ) (175,337 ) Net Deferred Tax Asset $ — $ —

Selected Quarterly Financial 33

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Data	The following are selected quarterly financial data for the years ended December 31, 2017 and 2016 : Quarter Ended March 31, June 30, September 30, December 31, 2017 Revenues $ 2,131 $ 2,061 $ 2,444 $ 3,262 Loss from operations (15,053 ) (13,109 ) (14,471 ) (7,127 ) Net loss (15,742 ) (14,090 ) (15,457 ) (8,028 ) Net loss per common share (basic and diluted) $ (0.11 ) $ (0.10 ) $ (0.11 ) $ (0.05 ) Weighted average common shares (basic and diluted) 142,011,776 143,786,705 146,514,196 164,008,252 Quarter Ended March 31, June 30, September 30, December 31, 2016 Revenues $ 1,726 $ 1,680 $ 1,759 $ 2,362 Loss from operations (8,807 ) (10,680 ) (27,789 ) (10,763 ) Net loss (9,441 ) (11,290 ) (28,345 ) (11,335 ) Net loss per common share (basic and diluted) $ (0.07 ) $ (0.09 ) $ (0.21 ) $ (0.08 ) Weighted average common shares (basic and diluted) 129,019,984 129,270,639 132,065,947 140,715,621

Nature of Business (Details)

Nature of Business (Details) $ in Thousands	1 Months Ended	36 Months Ended
	Sep. 30, 2016USD ($)shares	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015program	Oct. 31, 2015program	Jan. 31, 2015program
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accumulated deficit		$ (952,265)	$ (898,948)
Cash, cash equivalents, and investments		60,200
Aurigene Discovery Technologies Limited
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Shares issued of common stock in exchange for waived payment (in shares) | shares	10,208,333
Waived payment of milestone and other payments (up to)	$ 15,500	$ 14,500
Collaboration agreement, number of programs licensed | program				2	2	2

Summary of Significant Accoun35

Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2017USD ($)segmentleaseshares	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2002USD ($)shares	May 31, 2002USD ($)
Significant Accounting Policies [Line Items]
In-process research and development expenses		$ 18,000,000
Long-lived assets	$ 366,000	413,000
Goodwill	8,982,000	8,982,000
Goodwill impairment charges	0	0	$ 0
Approved repurchase of common stock					$ 3,000,000
Number of shares of common stock repurchased (in shares) | shares				1,047,707
Cost of repurchased stock				$ 900,000
Total cost of repurchased stock	$ 1,524,000	1,524,000
Facility under noncancellable operating lease agreement | lease	1
Number of operating segments | segment	1
In-process research and development	$ 0	$ 17,989,000	$ 24,348,000
Amended and Restated 2010 Stock Incentive Plan
Significant Accounting Policies [Line Items]
Number of shares of common stock repurchased (in shares) | shares	1,222,846
Total cost of repurchased stock	$ 1,500,000
Customer concentration risk | Genentech, Inc.
Significant Accounting Policies [Line Items]
Total gross revenue	100.00%	100.00%	100.00%

Summary of Significant Accoun36

Summary of Significant Accounting Policies - Estimated Useful Lives of Long-Lived Assets (Details)	12 Months Ended
	Dec. 31, 2017
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 Accoun37

Summary of Significant Accounting Policies - Antidilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total antidilutive securities (in shares)	16,034,181	13,752,157	13,290,844
Stock options outstanding
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total antidilutive securities (in shares)	16,034,181	13,752,157	13,290,844

Research and Development Coll38

Research and Development Collaborations (Details)	Mar. 06, 2017USD ($)	Sep. 07, 2016USD ($)	Apr. 30, 2019	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Oct. 31, 2016USD ($)	Sep. 30, 2016USD ($)shares	Jan. 31, 2015USD ($)productpaymenttermprogramshares	Jun. 30, 2003USD ($)	Sep. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2015USD ($)program	Dec. 31, 2017USD ($)shares	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)program	Dec. 31, 2017USD ($)shares	Sep. 06, 2016$ / shares	Oct. 31, 2015USD ($)program	Dec. 31, 2012USD ($)	Nov. 30, 2012USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Residual proceeds	$ 26,600,000				$ 26,600,000
Recognized royalty revenue													$ 9,849,000	$ 7,810,000	$ 8,031,000
Cost of royalty revenues													496,000	399,000	406,000
Accounts receivable													$ 3,073,000	2,459,000		$ 3,073,000
Option fees								$ 7,500,000
Research and development expenses														$ 18,000,000
Common stock, shares issued (in shares) | shares													165,379,967	142,346,871		165,379,967
Value of shares of common stock issued													$ 1,654,000	$ 1,423,000		$ 1,654,000
Number of optional additional terms | term								3
Optional additional term								1 year
Number of payments | payment								2
Exclusivity payment													10,000,000
Closing share price of common stock (in dollars per share) | $ / shares																	$ 1.76
Credit agreement with BioPharma-II | Curis Royalty
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Principal loan amount																			$ 30,000,000	$ 30,000,000
Interest rate on loan																			12.25%	12.25%
Genentech, Inc.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount received for specified clinical development and regulatory objectives													59,000,000			59,000,000
Period of time of collaboration and exclusive license									2 years
Research and development expense related to licensors													4,400,000
Recognized royalty revenue													9,800,000	7,800,000	8,000,000
Cost of royalty revenues													$ 500,000	400,000	400,000
Percentage of cash payments received from recorded research and development expenses													5.00%
Accounts receivable													$ 3,000,000	2,500,000		3,000,000
Genentech, Inc. | Drug development royalty
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development revenue													200,000	200,000	$ 300,000
Research and development expenses													$ 200,000	500,000
Genentech, Inc. | Forecast
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Subject to a decreased percentage of royalties on expiration of patent			5.00%
Genentech, Inc. | Australia
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of royalty rate decrease									2.00%
Percentage of direct net sales													2.00%
Genentech, Inc. | United States
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of royalty rate decrease												2.00%
Genentech, Inc. | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [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 Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of royalty on net sales									5.00%
Aurigene Discovery Technologies Limited
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration agreement, number of programs licensed | program								2				2			2			2
Collaboration agreement payment										$ 3,800,000	$ 3,800,000				$ 6,000,000
Option fees															3,000,000
Additional payments made under collaborative arrangements																		$ 2,000,000
Research and development expenses												$ 1,000,000		1,000,000
Payment for preclinical program for potential further development															$ 2,000,000
Payment for license and designation as the development candidate						$ 1,500,000
Common stock, shares issued (in shares) | shares								17,120,131
Value of shares of common stock issued								$ 24,300,000
Shares issued of common stock in exchange for waived payment (in shares) | shares							10,208,333
Waived payment of milestone and other payments (up to)							$ 15,500,000									$ 14,500,000
Number of products required to commercialize (at least) | product								1
Collaboration agreement period								2 years
Value of common stock issued		$ 18,000,000												$ 18,000,000
Aurigene Discovery Technologies Limited | Third and Fourth Programs [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional funding										$ 2,000,000
Aurigene Discovery Technologies Limited | IRAK4, PD1/VISTA,PD1/TIM3 Program
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Waived payment of milestone and other payments (up to)							42,500,000
Aurigene Discovery Technologies Limited | Master Development And Manufacturing Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration agreement payment				$ 800,000
Aurigene Discovery Technologies Limited | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Waived payment of milestone and other payments (up to)							$ 24,500,000
Curis Royalty, LLC | HealthCare Royalty Partners III, L.P.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Principal loan amount	$ 45,000,000				$ 45,000,000						$ 45,000,000
Interest rate on loan	9.95%				9.95%						9.95%
Remaining loan obligation	$ 18,400,000				$ 18,400,000						$ 18,400,000

Fair Value of Financial Instr39

Fair Value of Financial Instruments (Details) - Fair value, measurements, recurring - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	$ 57,512	$ 43,319
Short-term investments | Corporate commercial paper, stock, bonds and notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate commercial paper, stock, bonds and notes	21,944	18,447
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	35,308	24,542
Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	260	330
Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	35,308	24,542
Quoted Prices in Active Markets (Level 1) | Short-term investments | Corporate commercial paper, stock, bonds and notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate commercial paper, stock, bonds and notes	0	0
Quoted Prices in Active Markets (Level 1) | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	35,308	24,542
Quoted Prices in Active Markets (Level 1) | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	22,204	18,777
Other Observable Inputs (Level 2) | Short-term investments | Corporate commercial paper, stock, bonds and notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate commercial paper, stock, bonds and notes	21,944	18,447
Other Observable Inputs (Level 2) | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Other Observable Inputs (Level 2) | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	260	330
Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	0	0
Unobservable Inputs (Level 3) | Short-term investments | Corporate commercial paper, stock, bonds and notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate commercial paper, stock, bonds and notes	0	0
Unobservable Inputs (Level 3) | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Unobservable Inputs (Level 3) | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 0	$ 0

Investments (Details)

Investments (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)security	Dec. 31, 2016USD ($)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 21,946	$ 18,451
Unrealized Gain	0	2
Unrealized Loss	(2)	(6)
Fair Value	$ 21,944	$ 18,447
Number of investments in a continuous unrealized loss position for 12 months or longer (in securities) | security	0
Debt securities
Schedule of Available-for-sale Securities [Line Items]
Number of securities in an unrealized loss position for less than 12 months | security	1
Fair value of securities in an unrealized loss position for less than 12 months	$ 1,500
Short-term investments
Schedule of Available-for-sale Securities [Line Items]
Weighted average maturity of short-term investments	2 months	2 months
Short-term investments | Corporate bonds and notes—short-term
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 21,946	$ 18,451
Unrealized Gain	0	2
Unrealized Loss	(2)	(6)
Fair Value	$ 21,944	$ 18,447

Stock Plans and Stock Based C41

Stock Plans and Stock Based Compensation - Narrative (Details) $ / shares in Units, $ in Thousands	Jun. 02, 2014$ / sharesshares	Feb. 18, 2014$ / sharesshares	Jun. 30, 2014$ / sharesshares	Feb. 28, 2014$ / sharesshares	Dec. 31, 2017USD ($)planpurchase_period$ / sharesshares	Dec. 31, 2016USD ($)$ / shares	Dec. 31, 2015USD ($)$ / shares	Dec. 31, 2014shares	Mar. 31, 2010shares
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shareholder-approved, share-based compensation plans | plan					2
Additional awards (in shares)					0
Number of options granted (in shares)					6,113,000
Options that will vest (in shares)					15,498,301
Number of inducement equity awards granted (in shares)					644,000
Weighted average exercise price (in dollars per share) | $ / shares					$ 2.61
Weighted average grant-date fair values of stock options (in dollars per share) | $ / shares	$ 0.34	$ 1.20			$ 1.43	$ 1.11	$ 1.71
Unrecognized compensation cost, including impact of estimated forfeitures | $					$ 7,400
Intrinsic values of employee stock options exercised | $					$ 1,000	$ 2,100	$ 800
Shares granted (in shares)								1,040,000
Number of shares granted (in shares)	400,000	640,000	400,000	640,000
Exercise price (in dollars per share) | $ / shares			$ 1.75	$ 3.09	$ 2.51
Amount of stock-based compensation expense recorded | $					$ 5,359	4,325	3,875
Fair values of vested stock options | $					$ 3,600	3,600	2,700
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%
Amended and Restated 2010 Stock Incentive Plan
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares available under plan (in shares)					5,502,567
Number of shares available for issue (up to)					19,000,000
Period of time options are exercisable					10 years
Number of shares under award to be removed from share pool					1.3
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]
Number of options granted (in shares)					4,629,000
Vesting period					4 years
2010 Plan | Non-employee director
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of options granted (in shares)					840,000
Options that will vest (in shares)					840,000
Options that will become exercisable (in shares)					840,000
Vesting period					1 year
Weighted average period of when compensation expense is expected to be recognized					2 years 6 months
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)					647,542
Shares issued under ESPP during period (in shares)					173,366
Shares available for future purchase under ESPP (in shares)					9,352,458
2000 Director Stock Option Plan
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares available under plan (in shares)									0
Subject to market conditions
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Aggregate fair value, excluding forfeitures, of grants recognized on a straight-line basis | $					$ 900
Employee Stock Purchase Plan | 2010 Employee Stock Purchase Plan
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares available under plan (in shares)					10,000,000
Price charged for award based on fair market value percentage (less than)					85.00%
Enrollment period					2 years
Number of purchase periods per year | purchase_period					4
Term of purchase periods					6 months
Amount of stock-based compensation expense recorded | $					$ 268	48	30
Stock options outstanding
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Amount of stock-based compensation expense recorded | $					$ 5,400	$ 4,300	$ 3,600

Stock Plans and Stock Based C42

Stock Plans and Stock Based Compensation - Key Assumptions (Details) - $ / shares	Jun. 02, 2014	Feb. 18, 2014	Jun. 30, 2014	Feb. 28, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Expected term	6 years	6 years
Risk-free interest rate	2.10%	1.90%
Risk-free interest rate, minimum					2.00%	1.40%	1.50%
Risk-free interest rate, maximum					2.10%	1.90%	1.90%
Volatility	65.00%	70.00%
Minimum volatility					63.00%	63.00%	68.00%
Maximum volatility					64.00%	70.00%	70.00%
Dividends	0.00%	0.00%			0.00%	0.00%	0.00%
Number of options granted (in shares)	400,000	640,000	400,000	640,000
Fair value per share (in dollars per share)	$ 0.34	$ 1.20			$ 1.43	$ 1.11	$ 1.71
Employees
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Expected term					5 years 6 months	6 years	6 years
Officers
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Expected term					5 years 6 months	7 years	7 years
Directors
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Expected term					6 years 4 months	7 years	7 years

Stock Plans and Stock Based C43

Stock Plans and Stock Based Compensation - Summary of Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Jun. 30, 2014	Feb. 28, 2014	Dec. 31, 2017
Number of Shares
Outstanding (beginning balance) (in shares)			13,752,157
Number of options granted (in shares)			6,113,000
Exercise of stock options settled in shares (in shares)			(780,135)
Canceled (in shares)			(3,050,841)
Outstanding (ending balance) (in shares)			16,034,181
Exercisable (in shares)			8,771,728
Vested and unvested expected to vest (in shares)			15,498,301
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding (beginning balance) (in dollars per share)			$ 2.30
Granted (in dollars per share)	$ 1.75	$ 3.09	2.51
Exercised (in dollars per share)			1.36
Canceled (in dollars per share)			2.33
Outstanding (ending balance) (in dollars per share)			2.42
Exercisable (in dollars per share)			2.54
Vested and unvested expected to vest (in dollars per share)			$ 2.42
Weighted Average Remaining Contractual Life and Aggregate Intrinsic Value
Outstanding			6 years 6 months 25 days
Exercisable			4 years 11 months
Vested and unvested expected to vest			6 years 5 months 25 days
Outstanding			$ 0
Exercisable			0
Vested and unvested expected to vest			$ 0

Stock Plans and Stock Based C44

Stock Plans and Stock Based Compensation - Summary of ESPP (Details) - USD ($) $ in Thousands	Jun. 02, 2014	Feb. 18, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense recognized under ESPP			$ 5,359	$ 4,325	$ 3,875
Expected term	6 years	6 years
Minimum risk-free interest rate			2.00%	1.40%	1.50%
Maximum risk-free interest rate			2.10%	1.90%	1.90%
Minimum volatility			63.00%	63.00%	68.00%
Maximum volatility			64.00%	70.00%	70.00%
Dividends	0.00%	0.00%	0.00%	0.00%	0.00%
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			$ 268	$ 48	$ 30
Expected term				6 months	6 months
Minimum risk-free interest rate			1.10%	0.40%	0.06%
Maximum risk-free interest rate			1.80%	0.70%	0.50%
Minimum volatility			65.00%	64.00%	55.00%
Maximum volatility			76.00%	78.00%	78.00%
Dividends			0.00%	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
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

Stock Plans and Stock Based C45

Stock Plans and Stock Based Compensation - Compensation Expense Allocation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Total stock-based compensation expense	$ 5,359	$ 4,325	$ 3,875
Research and development expenses
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Total stock-based compensation expense	1,486	762	1,023
General and administrative expenses
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Total stock-based compensation expense	$ 3,873	$ 3,563	$ 2,852

Property and Equipment, net - S

Property and Equipment, net - Schedule (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment	$ 2,275	$ 2,180
Less—Accumulated depreciation and amortization	(1,909)	(1,767)
Total	366	413
Laboratory equipment, computers and software
Property, Plant and Equipment [Line Items]
Property and equipment	1,736	1,624
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	185	185
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment	$ 354	$ 371

Property and Equipment, net - N

Property and Equipment, net - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 235	$ 193	$ 161
Wrote off gross assets and related accumulated depreciation	$ 100	$ 400	$ 100

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Liabilities Disclosure [Abstract]
Accrued compensation	$ 2,187	$ 2,026
Professional fees	148	157
Accrued interest on debt (see Note 9)	193	194
Other	265	348
Total	$ 2,793	$ 2,725

Debt - Narrative (Details)

Debt - Narrative (Details) - USD ($)	Mar. 06, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2012	Nov. 30, 2012
Debt Instrument [Line Items]
Residual proceeds	$ 26,600,000	$ 26,600,000
Payments on debt			$ 4,954,000	$ 4,273,000	$ 4,163,000
Current portion of long-term debt, net			5,886,000	4,939,000
Long-term debt, net			35,669,000	14,921,000
Total debt issuance costs			200,000	400,000
Interest expense related to loan			3,966,000	2,777,000	3,325,000
Accrued interest on debt			193,000	194,000
BioPharma-II
Debt Instrument [Line Items]
Total debt issuance costs				200,000
Interest expense related to loan			3,900,000	2,800,000	$ 3,300,000
Level 3
Debt Instrument [Line Items]
Fair value of debt, principal portion			$ 41,200,000
Genentech, Inc.
Debt Instrument [Line Items]
Percentage of royalty rate decrease			2.00%
Genentech, Inc. | Minimum
Debt Instrument [Line Items]
Entitled to receive royalty based on worldwide annual net sales			5.00%
Range of worldwide annual net sales for royalty entitlement (less than) (over)			$ 150,000,000
Royalty rate			3.00%
Genentech, Inc. | Maximum
Debt Instrument [Line Items]
Entitled to receive royalty based on worldwide annual net sales			7.50%
Range of worldwide annual net sales for royalty entitlement (less than) (over)			$ 600,000,000
Royalty rate			5.50%
Credit agreement with BioPharma-II
Debt Instrument [Line Items]
Payments on debt			$ 8,900,000	7,100,000
Credit agreement with BioPharma-II | Principal
Debt Instrument [Line Items]
Payments on debt			5,000,000	4,300,000
Curis Royalty
Debt Instrument [Line Items]
Total debt issuance costs				$ 200,000
Curis Royalty | BioPharma-II
Debt Instrument [Line Items]
Remaining loan obligation			41,721,000
Current portion of long-term debt, net			5,919,000
Long-term debt, net			$ 35,802,000
Curis Royalty | Credit agreement with BioPharma-II
Debt Instrument [Line Items]
Loan received						$ 30,000,000	$ 30,000,000
Stated interest rate						12.25%	12.25%
Prepayment price equal to the outstanding principal on the loan						105.00%
Curis Royalty, LLC | HealthCare Royalty Partners III, L.P.
Debt Instrument [Line Items]
Loan received	$ 45,000,000	$ 45,000,000
Stated interest rate	9.95%	9.95%
Remaining loan obligation	$ 18,400,000	$ 18,400,000

Debt - Schedule of Debt Issuanc

Debt - Schedule of Debt Issuance Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt [Line Items]
Debt, current	$ 5,919	$ 4,987
Debt, current portion net of issuance costs	5,886	4,939
Debt, long-term	35,802	14,992
Debt, net of current portion and issuance costs	35,669	14,921
Other current assets
Debt [Line Items]
Debt issue costs, current	(33)	(48)
Other assets
Debt [Line Items]
Debt issue costs, long-term	$ (133)	$ (71)

Debt - Schedule of Future Payme

Debt - Schedule of Future Payments of Principal on Loan (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Less current portion, gross	$ (5,886)	$ (4,939)
Total long-term debt obligations, gross	35,669	$ 14,921
Curis Royalty | BioPharma-II
Debt Instrument [Line Items]
2,018	5,919
2,019	6,923
2,020	8,133
2,021	9,438
2,022	10,992
Thereafter	316
Total payments	41,721
Less current portion, gross	(5,919)
Total long-term debt obligations, gross	$ 35,802

Commitments - Narrative (Detail

Commitments - Narrative (Details) $ in Thousands	Nov. 01, 2017USD ($)	Dec. 01, 2010USD ($)ft²	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
License Agreement [Line Items]
Square footage of property leased (in square feet) | ft²		24,529
Additional lease extension, period of time	2 years	5 years
Cash obligation for base rent over initial term	$ 2,000	$ 4,400
Current deposit			$ 200	$ 200
Rent expense for operating lease			700	600	$ 600
Cash paid to related party				18,000
Cost of royalty revenues			496	399	406
In-process research and development			0	17,989	24,348
Aurigene Discovery Technologies Limited
License Agreement [Line Items]
Cash paid to related party			7,500
Research and development
License Agreement [Line Items]
Cash paid to related party			7,500	$ 5,500	$ 9,800
Letter of credit
License Agreement [Line Items]
Security deposit in the form of an irrevocable letter of credit			$ 300
Minimum
License Agreement [Line Items]
Additional lease extension, period of time in which written notice is required		1 year
Maximum
License Agreement [Line Items]
Additional lease extension, period of time in which written notice is required		18 months

Commitments - Operating Lease (

Commitments - Operating Lease (Details) $ in Thousands	Dec. 31, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,018	$ 935
2,019	1,001
2,020	168
Total minimum payments	$ 2,104

Common Stock (Details)

Common Stock (Details) - USD ($)	Sep. 18, 2017	Jul. 02, 2015	Mar. 02, 2015	Feb. 25, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 06, 2016
Common Stock And Warrant Liability [Line Items]
Underwritten public offering of common stock (in shares)					165,379,967	142,346,871
Offering price to the public (in dollars per share)								$ 1.76
Period of time options are exercisable					4 years 11 months
Issuance of common stock (in shares)			25,090,908
Net proceeds from sale of shares			$ 64,600,000		$ 41,546,000	$ 0	$ 64,620,000
Cowen
Common Stock And Warrant Liability [Line Items]
Underwriting agreement at a price per share (in dollars per share)				$ 2.585
Underwritten public offering of common stock (in shares)				21,818,181
Offering price to the public (in dollars per share)				$ 2.75
Period of time options are exercisable				30 days
Issuance of common stock (in shares)				3,272,727
Cowen | At The Market Agreement
Common Stock And Warrant Liability [Line Items]
Number of shares sold (in shares)					2,103,981
Net proceeds from sale of shares					$ 6,200,000
Compensation payable, percentage of gross sales price of stock sold		3.00%
Cowen | Maximum | At The Market Agreement
Common Stock And Warrant Liability [Line Items]
Equity offering program (up to)		$ 30,000,000
At The Market Offering 2017
Common Stock And Warrant Liability [Line Items]
Number of shares sold (in shares)	20,000,000
Offering price (in dollars per share)	$ 1.85
Underwriting agreement at a price per share (in dollars per share)	$ 1.78
Exercise period	30 days
Proceeds	$ 35,300,000
Offering expense	$ 300,000
Over-Allotment Option
Common Stock And Warrant Liability [Line Items]
Number of shares sold (in shares)	3,000,000

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense	$ 55,600,000
Orphan drug tax credit carryforwards	15,580,000	$ 10,148,000
Valuation allowance	(143,924,000)	(175,337,000)
Increase (decrease) in valuation allowance	(31,400,000)	30,000,000	$ 23,400,000
Unrecognized tax benefits	0	$ 0
Uncertain tax position	0
Federal
Income Taxes [Line Items]
Net operating loss	273,500,000
Federal | Research and experimentation
Income Taxes [Line Items]
Research and experimentation credit carryforwards	11,600,000
State
Income Taxes [Line Items]
Net operating loss	98,600,000
State | Research and experimentation
Income Taxes [Line Items]
Research and experimentation credit carryforwards	$ 4,700,000

Income Taxes - Reconciliation (

Income Taxes - Reconciliation (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	34.00%	34.00%	34.00%
State income taxes, net of federal benefit	4.40%	5.00%	5.10%
Research and development tax credits	2.70%	1.30%	1.40%
Orphan drug tax credits	10.90%	10.50%	(0.00%)
Deferred compensation	(0.80%)	(0.50%)	(0.40%)
Interest expense	(0.50%)	(0.40%)	(0.50%)
Deferred rate change	(104.40%)	0.00%	0.00%
Permanent adjustments and other	(5.20%)	(0.20%)	0.10%
Change in valuation allowance	58.90%	(49.70%)	(39.70%)
Effective income tax rate	0.00%	0.00%	0.00%

Income Taxes - Principal Compon

Income Taxes - Principal Components (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets:
NOL carryforwards	$ 63,688	$ 92,012
Research and development tax credit carryforwards	15,340	13,404
Orphan drug tax credit carryforwards	15,580	10,148
Depreciation and amortization	11,663	18,242
Capitalized research and development expenditures	32,550	35,848
Stock options	4,948	5,507
Accrued expenses and other	155	176
Total Gross Deferred Tax Asset	143,924	175,337
Valuation Allowance	(143,924)	(175,337)
Net Deferred Tax Asset	$ 0	$ 0

Income Taxes - Classification o

Income Taxes - Classification of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets:
Current deferred tax assets	$ 0	$ 0
Non-current deferred tax assets	143,924	175,337
Valuation Allowance	(143,924)	(175,337)
Net Deferred Tax Asset	$ 0	$ 0

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($)	Sep. 02, 2016	Jul. 01, 2015	Jun. 02, 2014	May 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 11, 2016
Related Party Transaction [Line Items]
Number of options granted (in shares)					6,113,000
Weighted average exercise price (in dollars per share)					$ 2.42	$ 2.30
Daniel R. Passeri
Related Party Transaction [Line Items]
Initial term of agreement			1 year
Consulting fees per month				$ 30,000
Agreement to provide continued assistance, term (up to)	24 months
Expenses related to consulting and letter agreements						$ 400,000	$ 200,000
Daniel R. Passeri | Stock options outstanding
Related Party Transaction [Line Items]
Exercise period of options	24 months
Daniel R. Passeri | Bonus
Related Party Transaction [Line Items]
Authorized recognition bonus payment	$ 300,000
Lori A. Kunkel, M.D.
Related Party Transaction [Line Items]
Expenses related to consulting and letter agreements						$ 100,000
Payments made								$ 100,000
Number of options granted (in shares)		150,000
Weighted average exercise price (in dollars per share)		$ 3.33

Retirement Savings Plan (Detail

Retirement Savings Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Matching contribution	$ 0.3	$ 0.2	$ 0.2

Selected Quarterly Financial 61

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Commitments [Line Items]
Revenues	$ 3,262	$ 2,444	$ 2,061	$ 2,131	$ 2,362	$ 1,759	$ 1,680	$ 1,726	$ 9,898	$ 7,527	$ 7,878
Loss from operations	(7,127)	(14,471)	(13,109)	(15,053)	(10,763)	(27,789)	(10,680)	(8,807)	(49,760)	(58,039)	(56,481)
Net loss	$ (8,028)	$ (15,457)	$ (14,090)	$ (15,742)	$ (11,335)	$ (28,345)	$ (11,290)	$ (9,441)	$ (53,317)	$ (60,411)	$ (58,981)
Net loss per common share (basic and diluted) (in dollars per share)	$ (0.05)	$ (0.11)	$ (0.10)	$ (0.11)	$ (0.08)	$ (0.21)	$ (0.09)	$ (0.07)	$ (0.36)	$ (0.45)	$ (0.48)
Weighted average common shares (basic and diluted) (in shares)	164,008,252	146,514,196	143,786,705	142,011,776	140,715,621	132,065,947	129,270,639	129,019,984	149,133,466	132,785,687	123,365,195
Aurigene Discovery Technologies Limited
Other Commitments [Line Items]
Milestone payment		$ 3,800		$ 3,800							$ 6,000