Concert Pharmaceuticals (CNCE) 10-K2 Mar 152014 FY Annual reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
Document and Entity Information (USD $)	Dec. 31, 2014	Feb. 23, 2015	Jun. 30, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Trading Symbol	CNCE
Entity Registrant Name	CONCERT PHARMACEUTICALS, INC.
Entity Central Index Key	1367920
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		18,286,539
Entity Public Float			$98,050,000

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$13,396	$9,638
Investments, available for sale	65,836	23,039
Interest receivable	262	92
Accounts receivable	1,021	170
Prepaid expenses and other current assets	1,205	1,106
Total current assets	81,720	34,045
Property and equipment, net	2,284	2,473
Restricted cash	400	706
Other assets	50	2,549
Total assets	84,454	39,773
Current liabilities:
Accounts payable	560	971
Accrued expenses and other liabilities	5,002	2,475
Deferred revenue, current portion	5,955	4,321
Leasehold improvement loan, current portion		332
Loan payable, net of discount	7,101	7,818
Total current liabilities	18,618	15,917
Deferred revenue, net of current portion	9,866	15,310
Leasehold improvement loan, net of current portion		249
Deferred lease incentive, net of current portion	888	385
Deferred rent, net of current portion	257	208
Warrant to purchase redeemable securities		463
Loan payable, net of current portion and discount		7,101
Total liabilities	29,629	39,633
Commitments
Redeemable convertible preferred stock; $0.001 par value per share; 0 and 62,916,667 shares (Series A, B, C, D) authorized, 0 and 56,047,067 shares issued and outstanding in 2014 and 2013, respectively		112,244
Stockholders' equity (deficit):
Preferred stock, $0.001 par value per share; 5,000,000 shares authorized, no shares issued and outstanding in 2014
Common stock, $0.001 par value per share; 100,000,000 and 83,716,667 shares authorized, 18,234,068 and 1,298,300 shares issued and outstanding in 2014 and 2013, respectively	18	1
Additional paid-in capital	200,157	1,528
Accumulated other comprehensive income	-14	4
Accumulated deficit	-145,336	-113,637
Total stockholders' equity (deficit)	54,825	-112,104
Total liabilities, redeemable convertible preferred stock and stockholders' equity (deficit)	$84,454	$39,773

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Redeemable convertible preferred stock (Series A, B, C, D), par value	$0.00	$0.00
Redeemable convertible preferred stock (Series A, B, C, D), shares authorized	0	62,916,667
Redeemable convertible preferred stock (Series A, B, C, D), shares issued	0	56,047,067
Redeemable convertible preferred stock (Series A, B, C, D), shares outstanding	0	56,047,067
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	5,000,000
Preferred stock, shares issued	0
Preferred stock, shares outstanding	0
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	100,000,000	83,716,667
Common stock, shares issued	18,234,068	1,298,300
Common stock, shares outstanding	18,234,068	1,298,300

Consolidated_Statements_of_Ope

Consolidated Statements of Operations and Comprehensive Loss (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue:
License and research and development revenue	$6,576	$23,408	$11,349
Milestone revenue	2,000	2,000	1,500
Total revenue	8,576	25,408	12,849
Operating expenses:
Research and development	27,474	21,790	24,193
General and administrative	11,700	8,028	7,266
Total operating expenses	39,174	29,818	31,459
Loss from operations	-30,598	-4,410	-18,610
Investment income	49	21	22
Interest and other expense	-1,150	-1,667	-1,856
Net loss	-31,699	-6,056	-20,444
Other comprehensive loss:
Unrealized loss on investments	-18		-5
Comprehensive loss	-31,717	-6,056	-20,449
Reconciliation of net loss to net loss applicable to common stockholders:
Net loss	-31,699	-6,056	-20,444
Accretion on redeemable convertible preferred stock	-55	-396	-388
Net loss applicable to common stockholders-basic and diluted	($31,754)	($6,452)	($20,832)
Net loss per share applicable to common stockholders-basic and diluted	($2)	($4.99)	($16.15)
Weighted-average number of common shares used in net loss per share applicable to common stockholders-basic and diluted	15,842	1,292	1,290

Consolidated_Statements_of_Red

Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (USD $)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]	Redeemable Convertible Preferred Stock [Member]
In Thousands, except Share data	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]	Redeemable Convertible Preferred Stock [Member]
Beginning balance at Dec. 31, 2011	($86,718)	$1	$409	$9	($87,137)	$111,460
Beginning balance, shares at Dec. 31, 2011		1,290,238				56,047,067
Accretion of redeemable convertible preferred stock to redemption value	-388		-388			388
Unrealized gain (loss) on short-term investments	-5			-5
Stock-based compensation expense	868		868
Net loss	-20,444				-20,444
Ending balance at Dec. 31, 2012	-106,687	1	889	4	-107,581	111,848
Ending balance, shares at Dec. 31, 2012		1,290,238				56,047,067
Accretion of redeemable convertible preferred stock to redemption value	-396		-396			396
Exercise of stock options, value	32		32
Exercise of stock options, shares		8,062
Stock-based compensation expense	1,003		1,003
Net loss	-6,056				-6,056
Ending balance at Dec. 31, 2013	-112,104	1	1,528	4	-113,637	112,244
Ending balance, shares at Dec. 31, 2013		1,298,300				56,047,067
Accretion of redeemable convertible preferred stock to redemption value	-55		-55			55
Proceeds from IPO, net of underwriting discounts and offering expenses	83,119	7	83,112
Proceeds from IPO, net of underwriting discounts and offering expenses , shares		6,649,690
Conversion of preferred stock into common stock, value	112,299	10	112,289			-112,299
Conversion of preferred stock into common stock, shares		9,919,821				-56,047,067
Reclassification of warrant, value	581		581
Reclassification of warrant, shares	0	0	0	0	0	0
Exercise of stock options, value	1,009		1,009
Exercise of stock options, shares		366,257
Unrealized gain (loss) on short-term investments	-18			-18
Stock-based compensation expense	1,693		1,693
Net loss	-31,699				-31,699
Ending balance at Dec. 31, 2014	$54,825	$18	$200,157	($14)	($145,336)
Ending balance, shares at Dec. 31, 2014		18,234,068

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities
Net loss	($31,699)	($6,056)	($20,444)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	1,052	1,346	1,452
Stock-based compensation expense	1,693	1,003	868
Accretion of premiums and discounts on investments	833	302	365
Amortization of discount on loan payable	98	97	96
Amortization of deferred financing costs	38	38	39
Re-measurement of warrant to purchase redeemable securities	117	4	291
Amortization of deferred lease incentive	-367	-513	-513
Changes in operating assets and liabilities:
Accounts receivable	-851	-157	487
Interest receivable	-170	10	26
Prepaid expenses and other current assets	-137	32	-364
Restricted cash	306
Other assets	82	69	5
Accounts payable	-32	158	-764
Accrued expenses and other liabilities	2,863	-15	432
Landlord lease incentive	350
Deferred rent	-126	-181	-131
Deferred revenue	-3,810	16,881	-8,272
Net cash (used in) provided by operating activities	-29,760	13,018	-26,427
Investing activities
Purchases of property and equipment	-804	-363	-468
Purchases of investments	-89,188	-29,929	-38,398
Maturities of investments	45,540	26,655	37,666
Net cash used in investing activities	-44,452	-3,637	-1,200
Financing activities
Proceeds from issuance of loan payable, net of issuance costs			12,500
Principal payments on loan payable	-7,916	-4,909
Repayment of leasehold improvement loan	-266	-332	-332
Proceeds from initial public offering, net of underwriting discounts and commissions	86,579
Proceeds from issuance of common stock	1,009	32
Payment of initial public offering costs	-1,436	-2,024
Net cash provided by (used in) financing activities	77,970	-7,233	12,168
Net increase (decrease) in cash and cash equivalents	3,758	2,148	-15,459
Cash and cash equivalents at beginning of period	9,638	7,490	22,949
Cash and cash equivalents at end of period	13,396	9,638	7,490
Supplemental cash flow information:
Cash paid for interest	992	1,601	1,339
Property and equipment included in accrued expenses and other liabilities	60
Initial public offering costs incurred but unpaid at period end		$475

Nature_of_Business

Nature of Business	12 Months Ended
Nature of Business	Dec. 31, 2014
Accounting Policies [Abstract]
Nature of Business	1. Nature of Business

	Concert Pharmaceuticals, Inc., or Concert or the Company, was incorporated on April 12, 2006 as a Delaware corporation with operations based in Lexington, Massachusetts. The Company is a clinical stage biopharmaceutical company that applies its extensive knowledge of deuterium chemistry to discover and develop novel small molecule drugs. The Company’s approach starts with approved drugs, advanced clinical candidates or previously studied compounds that the Company believes can be improved with deuterium substitution to provide better pharmacokinetic or metabolic properties, enhancing clinical safety, tolerability or efficacy. The Company believes this approach may enable drug discovery and clinical development that is more efficient and less expensive than conventional small molecule drug research and development. The Company’s pipeline includes five clinical-stage candidates and a number of preclinical compounds that it is actively assessing.

	In the first quarter of 2014, the Company closed its initial public offering, or IPO, in which the Company sold 6,649,690 shares of common stock, including shares sold under the underwriters’ over-allotment option, at a price to the public of $14.00 per share. The Company’s net proceeds from the IPO were $83.1 million after deducting underwriting discounts and commissions and offering expenses. In preparation for the IPO, the Company’s Board of Directors and stockholders approved a one-for-5.65 reverse stock split of the Company’s common stock that was effected on January 29, 2014. All share and per share amounts in the consolidated financial statements and notes thereto have been retroactively adjusted, where necessary, to give effect to this reverse stock split. In conjunction with the IPO, all outstanding shares of the Company’s preferred stock automatically converted into 9,919,821 shares of common stock and the outstanding warrant to purchase 400,000 shares of Series C redeemable convertible preferred stock converted into a warrant to purchase 70,796 shares of common stock at an exercise price of $14.13 per share. As of December 31, 2014, there were 18,234,068 shares of common stock outstanding. The significant increase in shares of common stock outstanding in the first quarter of 2014 is expected to impact the year-over-year comparability of the Company’s net earnings (loss) per share calculations until the first quarter of 2015.

	The Company had cash and cash equivalents and investments of $79.2 million at December 31, 2014. The Company believes that its existing cash and cash equivalents and investments will be sufficient to allow the Company to fund its current operating plan for at least the next 12 months. Management expects the Company to continue to incur losses for the foreseeable future. The Company’s ability to achieve profitability in the future is dependent upon the successful development, approval, and commercialization of its product candidates and achieving a level of revenues adequate to support the Company’s cost structure. The Company may never achieve profitability, and unless and until it does, the Company will continue to need to raise additional capital. Management intends to fund future operations through additional private or public debt or equity offerings, and may seek additional capital through arrangements with collaborators or from other sources. There can be no assurances, however, that additional funding will be available on terms acceptable to the Company, or at all.

	Unless otherwise indicated, all amounts are in thousands except share and per share amounts.

Basis_of_Presentation_and_Sign

Basis of Presentation and Significant Accounting Policies	12 Months Ended
Basis of Presentation and Significant Accounting Policies	Dec. 31, 2014
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	2. Basis of Presentation and Significant Accounting Policies

	The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or GAAP. Management has determined that the Company operates in one segment: the development of pharmaceutical products on its own behalf or in collaboration with others. All material long-lived assets of the Company reside in the United States.

	The accompanying consolidated financial statements include the accounts of Concert Pharmaceuticals, Inc. and its wholly owned subsidiary, Concert Pharmaceuticals Securities Corporation, which is a Massachusetts subsidiary created to buy, sell and hold securities. All intercompany transactions and balances have been eliminated.



	The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure.

	Cash, Cash Equivalents and Investments

	Cash equivalents include all highly liquid investments maturing within 90 days from the date of purchase. Investments consist of securities with original maturities greater than 90 days when purchased. The Company classifies these investments as available-for-sale and records them at fair value in the accompanying consolidated balance sheets. Unrealized gains or losses are included in accumulated other comprehensive income. Premiums or discounts from par value are amortized to investment income over the life of the underlying investment.

	Cash, cash equivalents and investments included the following at December 31, 2014 and 2013 (in thousands):



			Average			Amortized			Unrealized				Unrealized			Fair
			maturity			cost			gains				losses			value
	December 31, 2014
	Cash					$	1,492		$	—			$	—		$	1,492
	Money market funds						11,904			—				—			11,904

	Cash and cash equivalents					$	13,396		$	—			$	—		$	13,396

	U.S. Treasury obligations			171 days		$	12,037		$	(2	)		$	—		$	12,035
	Government agency securities			194 days			53,813			3				(15	)		53,801

	Investments					$	65,850		$	1			$	(15	)	$	65,836




			Average			Amortized			Unrealized				Unrealized			Fair
			maturity			cost			gains				losses			value
	December 31, 2013
	Cash					$	2,188		$	—			$	—		$	2,188
	Money market funds						7,450			—				—			7,450

	Cash and cash equivalents					$	9,638		$	—			$	—		$	9,638

	U.S. Treasury obligations			301 days		$	500		$	—			$	—		$	500
	Government agency securities			324 days			22,535			4				—			22,539

	Investments					$	23,035		$	4			$	—		$	23,039


	Although available to be sold to meet operating needs or otherwise, securities are generally held through maturity. The cost of securities sold is determined based on the specific identification method for purposes of recording realized gains and losses. During 2014 and 2013, there were no realized gains or losses on sales of investments, and no investments were adjusted for other than temporary declines in fair value.

	Fair Value of Financial Measurements

	The Company measures certain financial assets and liabilities at fair value on a recurring basis (principally cash equivalents, investments and the preferred stock warrant liability) that have been classified as Level 1, 2 or 3 within the fair value hierarchy as described below. Fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access. Fair values determined by Level 2 inputs utilize data points that are observable, such as quoted prices, interest rates and yield curves. Fair values determined by Level 3 inputs utilize unobservable data points for the asset or liability. The Company’s investments in money market funds, U.S. treasury obligations and government agency securities have been classified as Level 1 because their fair values are based on quoted market prices. The preferred stock warrant liability was classified as Level 3 because certain inputs to the valuation of the warrant are based on unobservable inputs.

	As of December 31, 2014 and December 31, 2013, the Company’s financial assets and liabilities recognized at fair value consisted of the following:



			Level 1			Level 2			Level 3				Total
	December 31, 2014
	Money market funds, included in cash equivalents		$	11,904		$	—		$	—			$	11,904
	Investments, available for sale:
	U.S. Treasury obligations			12,035			—			—				12,035
	Government agency securities			53,801			—			—				53,801

Total		$	77,740		$	—		$	—			$	77,740




		Level 1			Level 2			Level 3				Total
December 31, 2013
Assets:
Money market funds, included in cash equivalents		$	7,450		$	—		$	—			$	7,450
Investments, available for sale:
U.S. Treasury obligations			500			—			—				500
Government agency securities			22,539			—			—				22,539

Total		$	30,489		$	—		$	—			$	30,489

Liabilities:
Warrant to purchase redeemable securities		$	—		$	—		$	463			$	463

The fair value of the preferred stock warrant liability was determined based on Level 3 inputs utilizing the Black-Scholes-Merton option pricing model. On February 19, 2014, upon completion of the IPO, the Company’s outstanding warrant to purchase preferred stock converted into a warrant to purchase common stock and the Company reclassified the fair value of the warrant as of February 19, 2014 to additional paid-in capital. The assumptions used to value the warrant are more fully described in Note 12.

The carrying amount of financial instruments not carried at fair value, including the loan payable and leasehold improvement loan, approximate fair value. The carrying value of the Company’s loan payable and leasehold improvement loan approximated fair value because the interest rate yields for the loans approximate current market yields. The disclosed fair values of the Company’s loan payable and leasehold improvement loan are Level 3 liabilities within the fair value hierarchy.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to concentration of credit risk consist principally of money market funds and investments and accounts receivable. The Company has not experienced any credit losses in these accounts and does not believe it is exposed to any significant credit risk on these funds. The Company has no foreign exchange contracts, option contracts or other foreign exchange hedging arrangements. At December 31, 2014 and 2013, substantially all of the Company’s cash was deposited in accounts at two highly rated financial institutions, thus limiting the amount of credit exposure to any one financial institution. These amounts at times may exceed federally insured limits.

Accounts receivable represent amounts due from collaboration partners. The Company monitors economic conditions to identify facts or circumstances that may indicate that any of its accounts receivable are at risk of collection.

Property and Equipment

Property and equipment are recognized at cost and depreciated over their estimated useful lives using the straight-line method. Repair and maintenance costs are expensed as incurred, whereas major improvements are capitalized as additions to property and equipment. Potential impairment is assessed when there is evidence that events or circumstances indicate that the carrying amount of an asset may not be recovered. No such impairment losses have been recorded through December 31, 2014.

Rent Expense

The Company’s operating lease for its Lexington, Massachusetts facility provides for scheduled annual rent increases throughout the lease term. The Company recognizes the effects of the scheduled rent increases on a straight-line basis over the full term of the lease, which expires in 2018. Additionally, the Company has received certain lease incentives in connection with the Lexington, Massachusetts facility lease, which are recognized as a reduction to rent expense over the remaining lease term. Refer to Note 9 for additional details regarding the Company’s operating lease.

Contingencies

The Company records liabilities for legal and other contingencies when information available to the Company indicates that it is probable that a liability has been incurred and the amount of loss can be reasonably estimated. Legal costs in connection with legal and other contingencies are expensed as costs are incurred.

Revenue Recognition

The Company has primarily generated revenue through arrangements with collaborators and nonprofit organizations for the development and commercialization of product candidates.

The Company recognizes revenue in accordance with Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 605, Revenue Recognition (ASC 605). Accordingly, revenue is recognized when all of the following criteria are met:


•		Persuasive evidence of an arrangement exists;


•		Delivery has occurred or services have been rendered;


•		The seller’s price to the buyer is fixed or determinable; and


•		Collectability is reasonably assured.

Amounts received prior to satisfying the revenue recognition criteria are recognized as deferred revenue in the Company’s consolidated balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, current portion. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion.

The Company’s revenue is currently generated through collaborative research and development and licensing agreements. The terms of these agreements typically contain multiple elements, or deliverables, which may include licenses, or options to obtain licenses, to product candidates, referred to as exclusive licenses, as well as research and development activities to be performed by the Company on behalf of the collaboration partner related to the licensed product candidates. The terms of these agreements may include payments to the Company of one or more of the following: a nonrefundable, upfront payment; milestone payments; payment of license exercise or option fees with respect to product candidates; fees for research and development services rendered; and royalties on commercial sales of licensed product candidates, if any. To date, the Company has received upfront payments, several milestone payments and certain research and development service payments but has not received any license exercise or option fees or earned royalty revenue as a result of product sales.

When evaluating multiple element arrangements, the Company considers whether the deliverables under the arrangement represent separate units of accounting. This evaluation requires subjective determinations and requires management to make judgments about the individual deliverables and whether such deliverables are separable from the other aspects of the contractual relationship. In determining the units of accounting, management evaluates certain criteria, including whether the deliverables have standalone value, based on the consideration of the relevant facts and circumstances for each arrangement. The consideration received is allocated among the separate units of accounting using the relative selling price method, and the applicable revenue recognition criteria are applied to each of the separate units.

The Company determines the estimated selling price for deliverables within each agreement using vendor-specific objective evidence, or VSOE, of selling price, if available, third-party evidence, or TPE, of selling price if VSOE is not available, or best estimate of selling price, or BESP, if neither VSOE nor TPE is available. Determining the BESP for a deliverable requires significant judgment. The Company has used its BESP to estimate the selling price for licenses to the Company’s proprietary technology, since the Company does not have VSOE or TPE of selling price for these deliverables. In those circumstances where the Company utilizes BESP to determine the estimated selling price of a license to the Company’s proprietary technology, the Company considers market conditions as well as entity-specific factors, including those factors contemplated in negotiating the agreement, estimated development costs, and the probability of success and the time needed to commercialize a product candidate pursuant to the license. In validating the Company’s BESP, the Company evaluates whether changes in the key assumptions used to determine the BESP will have a significant effect on the allocation of arrangement consideration between multiple deliverables.

The Company’s multiple-element revenue arrangements may include the following:

Exclusive Licenses. The deliverables under the Company’s collaboration agreements generally include exclusive licenses to develop, manufacture and commercialize one or more deuterated compounds. To account for this element of the arrangement, management evaluates whether the exclusive license has standalone value from the undelivered elements based on the consideration of the relevant facts and circumstances of each arrangement, including the research and development capabilities of the collaboration partner. The Company may recognize the arrangement consideration allocated to licenses upon delivery of the license if facts and circumstances indicate that the license has standalone value from the undelivered elements, which generally include research and development services. The Company defers arrangement consideration allocated to licenses if facts and circumstances indicate that the delivered license does not have standalone value from the undelivered elements.



When management believes the license does not have stand-alone value from the other deliverables to be provided in the arrangement, the Company generally recognizes revenue attributed to the license on a straight-line basis over the Company’s contractual or estimated performance period, which is typically the term of the Company’s research and development obligations. If management cannot reasonably estimate when the Company’s performance obligation ends, then revenue is deferred until management can reasonably estimate when the performance obligation ends. The periods over which revenue should be recognized are subject to estimates by management and may change over the course of the research and development and licensing agreement. Such a change could have a material impact on the amount of revenue the Company records in future periods.

Research and Development Services. The deliverables under the Company’s collaboration and license agreements may include deliverables related to research and development services to be performed by the Company on behalf of the collaboration partner.

Payments or reimbursements resulting from the Company’s research and development efforts are recognized as the services are performed and presented on a gross basis because the Company is the principal for such efforts, so long as there is persuasive evidence of an arrangement, the fee is fixed or determinable, and collection of the related amount is reasonably assured.

Option Agreements. The Company’s arrangements may provide a collaborator with the right to select a deuterated compound for licensing within an initial pre-defined selection period. Under these agreements, a fee would be due to the Company upon the exercise of an option to acquire a license. The accounting for option arrangements is dependent on the nature of the option granted to the collaboration partner. An option is considered substantive if, at the inception of the arrangement, the Company is at risk as to whether the collaboration partner will choose to exercise the option to secure exclusive licenses. Factors that the Company considers in evaluating whether an option is substantive include the overall objective of the arrangement, the benefit the collaborator might obtain from the arrangement without exercising the option, the cost to exercise the option relative to the total upfront consideration and the additional financial commitments or economic penalties imposed on the collaborator as a result of exercising the option. For arrangements under which an option to secure a license is considered substantive, the Company does not consider the license underlying the option to be a deliverable at the inception of the arrangement. For arrangements under which the option to secure a license is not considered substantive, the Company considers the license underlying the option to be a deliverable at the inception of the arrangement and, upon delivery of the license, would apply the multiple-element revenue arrangement criteria to the license and any other deliverables to determine the appropriate revenue recognition. A significant and incremental discount included in an otherwise substantive option is considered to be a separate deliverable at the inception of the arrangement.

Milestone Revenue. The Company’s collaboration agreements generally include contingent milestone payments related to specified development milestones, regulatory milestones and sales-based milestones. Development milestones are typically payable when a product candidate initiates or advances in clinical trial phases or achieves defined clinical events such as proof-of-concept. Regulatory milestones are typically payable upon submission for marketing approval with regulatory authorities or upon receipt of actual marketing approvals for a compound, approvals for additional indications, upon commercial launch or upon the first commercial sale. Sales-based milestones are typically payable when annual sales reach specified levels.

At the inception of each arrangement that includes milestone payments, the Company evaluates whether each milestone is substantive and at risk to both parties on the basis of the contingent nature of the milestone. This evaluation includes an assessment of whether (a) the consideration is commensurate with either (i) the entity’s performance to achieve the milestone or (ii) the enhancement of the value of the delivered item(s) as a result of a specific outcome resulting from the entity’s performance to achieve the milestone; (b) the consideration relates solely to past performance; and (c) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company evaluates factors such as the scientific, regulatory, commercial and other risks that must be overcome to achieve the respective milestone, the level of effort and investment required to achieve the respective milestone and whether the milestone consideration is reasonable relative to all deliverables and payment terms in the arrangement in making this assessment. Milestones that are not considered substantive are accounted for as license payments and recognized on a straight-line basis over the remaining period of performance.

Research and Development Costs

Research and development costs are expensed as incurred.

Research and development expenses are comprised of costs incurred in providing research and development activities, including salaries and benefits, facilities costs, overhead costs, contract research and development services, and other outside costs. Nonrefundable advance payments for goods and services that will be used in future research and development activities are expensed when the activity has been performed or when the goods have been received rather than when the payment is made.

Direct research and development expenses associated with the Company’s programs include clinical trial site costs, clinical manufacturing costs, costs incurred for consultants and other outside services, such as data management and statistical analysis support, and materials and supplies used in support of the clinical programs. Indirect costs of the Company’s clinical program include salaries, stock based compensation, and an allocation of the Company’s facility costs. When third-party service providers’ billing terms do not coincide with the Company’s period-end, the Company is required to make estimates of its obligations to those third parties, including clinical trial and pharmaceutical development costs, contractual services costs and costs for supply of its drug candidates, incurred in a given accounting period and record accruals at the end of the period. The Company bases its estimates on its knowledge of the research and development programs, services performed for the period, past history for related activities and the expected duration of the third-party service contract, where applicable.

Accounting for Stock-Based Compensation

The Company issues stock options to certain employees, officers and directors. The Company accounts for stock compensation using the fair value method, which results in the recognition of compensation expense over the vesting period of the awards. See Note 7 for additional information.

Prior to the Company’s IPO, the estimated fair value of its common stock was determined by the Company’s board of directors based on contemporaneous and retrospective valuation estimates provided by management and prepared in accordance with the framework of the American Institute of Certified Public Accountants’ Technical Practice Aid, Valuation of Privately-Held-Company Equity Securities Issued as Compensation, as well as independent third-party valuations. The Company’s valuations of its common stock were based on a number of objective and subjective factors, including external market conditions affecting the biotechnology industry sector and the prices at which it sold shares of preferred stock, the superior rights and preferences of securities senior to its common stock at the time of each grant and the likelihood of achieving a liquidity event such as an IPO. Following the Company’s IPO, the fair value of the shares of common stock underlying stock options has been the closing price on the option grant date.



Income Taxes

The Company provides deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the Company’s financial statement carrying amounts and the tax basis of assets and liabilities using enacted tax rates expected to be in effect in the years in which the differences are expected to reverse. A valuation allowance is provided to reduce the deferred tax assets to the amount that will more likely than not be realized.

The Company evaluates tax positions taken, or expected to be taken, in the course of preparing its tax returns to determine whether the tax positions are “more likely than not” of being sustained by the applicable tax authority. Tax positions not deemed to meet the more-likely-than-not threshold would be recognized as a tax expense.

Guarantees

As permitted under Delaware law, the Company indemnifies its officers and directors for certain events or occurrences while the officer or director is, or was, serving at the Company’s request in such capacity. The term of the indemnification is for the officer’s or director’s lifetime. The maximum potential amount of future payments the Company could be required to make is unlimited; however, the Company has directors’ and officers’ insurance coverage that limits its exposure and enables it to recover a portion of any future amounts paid.

The Company leases office space under a non-cancelable operating lease which is further described in Note 9, Commitments. The Company has a standard indemnification arrangement under the lease that requires it to indemnify the landlord against all costs, expenses, fines, suits, claims, demands, liabilities, and actions directly resulting from any breach, violation, or non-performance of any covenant or condition of the Company’s lease.

As of December 31, 2014 and 2013, the Company had not experienced any material losses related to these indemnification obligations, and no material claims with respect thereto were outstanding. The Company does not expect significant claims related to these indemnification obligations and, consequently, concluded that the fair value of these obligations is negligible, and no related reserves were established.

Comprehensive Loss

Comprehensive loss is comprised of net loss and other comprehensive income or loss. Other comprehensive income or loss consists of unrealized gains and losses on investments.

Earnings (Loss) Per Share

Basic earnings (loss) per share is computed by dividing income (loss) allocable to common stockholders, computed as the sum of net income (loss) and accretion on the Company’s redeemable convertible preferred stock, by the weighted average number of common shares outstanding. During periods of income where participating securities are outstanding, participating securities are allocated a proportional share of income determined by dividing total weighted-average participating securities by the sum of the total weighted-average common shares and participating securities (the “two-class method”). Prior to its automatic conversion into common stock upon the closing of the IPO, the Company’s redeemable convertible preferred stock was entitled to participate in any dividends declared by the Company and was therefore considered to constitute participating securities. Participating securities have the effect of diluting both basic and diluted earnings per share during periods of income. During periods of loss, no loss is allocated to participating securities since they have no contractual obligation to share in the losses of the Company. Diluted earnings (loss) per share is computed after giving consideration to the dilutive effect of stock options and a warrant that are outstanding during the periods, except where such securities would be anti-dilutive.



In the first quarter of 2014, the Company issued an additional 6,649,690 shares of common stock in connection with its IPO and 9,919,821 shares of common stock in connection with the automatic conversion of its redeemable convertible preferred stock upon the closing of the IPO. The issuance of these shares resulted in a significant increase in the Company’s weighted-average shares of common stock outstanding for the year ended December 31, 2014 when compared to the prior year periods and is expected to continue to impact the year-over-year comparability of the Company’s earnings (loss) per share calculations until the first quarter of 2015.

The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect (in thousands):



		Year ended
		December 31,
		2014			2013			2012
Preferred stock			—			9,920			9,920
Warrant			71			71			71
Outstanding stock options			2,689			1,953			1,960

			2,760			11,944			11,951


Recent Accounting Pronouncements

In May 2014, the FASB issued Accounting Standards Update, or ASU, No. 2014-09, Revenue from Contracts with Customers (Topic 606), or ASU 2014-09, which stipulates that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this core principle, ASU 2014-09 provides that an entity should apply the following steps: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract and (5) recognize revenue when (or as) the entity satisfies a performance obligation. This update will be effective for the Company retrospectively beginning in the first quarter of fiscal 2017 with early adoption not permitted. The Company is currently assessing the impact of this ASU on its consolidated financial statements.

In August 2014, the FASB issued ASU No. 2014-15, Disclosure of Uncertainties About an Entity’s Ability to Continue as a Going Concern, or ASU 2014-15 ASU 2014-15 amends FASB Accounting Standards Codification, or ASC, 205-40, Presentation of Financial Statements – Going Concern, by providing guidance on determining when and how reporting entities must disclose going-concern uncertainties in their financial statements, including requiring management to perform interim and annual assessments of an entity’s ability to continue as a going concern within one year of the date of issuance of the entity’s financial statements and providing certain disclosures if there is substantial doubt about the entity’s ability to continue as a going concern. ASU 2014-15 will be effective for the Company’s fiscal year 2016 and for interim periods beginning in the first quarter of fiscal 2017. The Company is still evaluating the impact of this ASU on its financial statement disclosures.

Restricted_Cash

Restricted Cash	12 Months Ended
Restricted Cash	Dec. 31, 2014
Cash and Cash Equivalents [Abstract]
Restricted Cash	3. Restricted Cash
Restricted Cash	At December 31, 2014 and 2013, $0.4 million and $0.7 million, respectively, of the Company’s cash is restricted by a bank as collateral for a stand-by letter of credit issued by the Company to its landlord in connection with the lease of the Company’s Lexington, Massachusetts facility.

Property_and_Equipment

Property and Equipment	12 Months Ended
Property and Equipment	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property and Equipment	4. Property and Equipment

	Property and equipment consists of the following at December 31, 2014 and 2013 (in thousands):



		Estimated useful life		December 31,			December 31,
		(in years)		2014			2013
	Laboratory equipment		5	$	1,544		$	2,062
	Computer, telephone and office equipment		3		175			143
	Software		3		88			66
	Leasehold improvements		Lesser of useful life		6,392			5,848
	Leasehold improvements		or remaining lease term		6,392			5,848

					8,199			8,119
	Less accumulated depreciation and amortization				(5,915	)		(5,646	)

				$	2,284		$	2,473


	Depreciation and amortization expense was charged to operations in the amounts of $1.1 million, $1.3 million and $1.5 million for the years ended December 31, 2014, 2013 and 2012, respectively.

Accrued_Expenses_and_Other_Lia

Accrued Expenses and Other Liabilities	12 Months Ended
Accrued Expenses and Other Liabilities	Dec. 31, 2014
Payables and Accruals [Abstract]
Accrued Expenses and Other Liabilities	5. Accrued Expenses and Other Liabilities

	Accrued expenses and other liabilities consist of the following (in thousands):



		December 31,		December 31,
		2014		2013
	Accrued professional fees and other	$	916	$	569
	Employee compensation and benefits		1,606		290
	Research and development expenses		2,104		860
	Deferred lease incentive, current portion		308		513
	Deferred rent, current portion		68		243

		$	5,002	$	2,475

Redeemable_Convertible_Preferr

Redeemable Convertible Preferred Stock	12 Months Ended
Redeemable Convertible Preferred Stock	Dec. 31, 2014
Equity [Abstract]
Redeemable Convertible Preferred Stock	6. Redeemable Convertible Preferred Stock

	From time to time prior to the Company’s IPO, the Company issued Series A, Series B, Series C and Series D redeemable convertible preferred stock, or collectively, the Convertible Preferred Stock. The Company classified the Convertible Preferred Stock outside of stockholders’ equity (deficit) because the shares contained contingent redemption features that were not solely within the Company’s control. In connection with the closing of the Company’s IPO on February 19, 2014, all of the outstanding Convertible Preferred Stock converted into 9,919,821 shares of common stock.

	Subsequent to the closing of the Company’s IPO, the Company is authorized to issue up to 5,000,000 shares of preferred stock in one or more series and to fix the powers, designations, preferences and relative participating, option or other rights thereof, including dividend rights, conversion rights, voting rights, redemption terms, liquidation preferences and the number of shares constituting any series, without any further vote or action by the Company’s stockholders. As of December 31, 2014, the Company had no shares of preferred stock issued or outstanding.



	Convertible Preferred Stock consisted of the following as of December 31, 2013 (in thousands):



		Preferred		Preferred		Redemption		Carrying		Common
		shares		shares		value /		value		stock
		authorized		issued		liquidation				issuable
				and		preference				upon
				outstanding						conversion
	Series A		10,000		10,000	$	10,000	$	9,993		1,770
	Series B		24,250		24,250		48,500		48,488		4,292
	Series C		22,000		15,130		37,826		37,809		2,678
	Series D		6,667		6,667		16,667		15,954		1,180

			62,917		56,047	$	112,993	$	112,244		9,920

Stock_Compensation

Stock Compensation	12 Months Ended
Stock Compensation	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Compensation	7. Stock Compensation

	Stock incentive plan

	The Company previously sponsored an Amended and Restated 2006 Stock Option and Grant Plan, or the 2006 Plan, which provided for the issuance of a total of 2,212,389 shares of common stock in the form of incentive stock options, nonstatutory stock options, awards of stock and direct stock purchase opportunities to directors, officers, employees and consultants of the Company.

	In January 2014, in preparation for the Company’s IPO, the 2006 Plan was replaced by the Company’s 2014 Stock Incentive Plan, or the 2014 Plan. The 2014 Plan became effective in February 2014.

	The 2014 Plan provides for the grant of incentive stock options, nonstatutory stock options, restricted stock awards, restricted stock units, stock appreciation rights and other stock-based awards. Upon the closing of the Company’s IPO on February 19, 2014, 2,249,911 shares of common stock were reserved for issuance under the 2014 Plan. The number of shares reserved under the 2014 Plan is subject to further increase by the number of shares of common stock subject to outstanding awards under the 2006 Plan that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased. In addition, the 2014 Plan includes an “evergreen provision” that allows for an annual increase in the number of shares of common stock available for issuance under the 2014 Plan. The annual increase will be added on the first day of each year beginning in 2015 and each subsequent anniversary until 2024, equal to the lowest of 2,000,000 shares of common stock, 4.0% of the number of shares of common stock outstanding on January 1 of each such fiscal year and an amount determined by the board of directors. Effective January 1, 2015, 729,363 shares were added to the 2014 Plan for future issuance pursuant to this evergreen provision.

	The following table is a roll-forward of shares available for future grant under the 2014 Plan:



			Shares
			Available for
			Grant
	Shares reserved for future grant at February 19, 2014			2,249,911
	Add: stock options and restricted stock awards forfeited or expired under plans			68,186
	Less: stock options and awards granted from February 19, 2014 to December 31, 2014			(1,182,143	)

	Shares reserved for future grant at December 31, 2014			1,135,954




	Stock Options

	The weighted-average fair value of options granted during the years ended December 31, 2014, 2013 and 2012 based on fair values estimated as of the applicable grant dates using the Black-Scholes-Merton option pricing model, was $6.69, $13.77 and $6.53 per option share, respectively.

	For the years ended December 31, 2014, 2013 and 2012, the fair values of options granted were estimated using the Black-Scholes-Merton option pricing model using the following weighted-average assumptions:



			Year ended December 31,
			2014				2013				2012
	Expected volatility			80.94	%			70.1	%			72.8	%
	Expected term			6.0 years				6.0 years				6.0 years
	Risk-free interest rate			1.9	%			1.69	%			0.95	%
	Expected dividend yield			0	%			0	%			0	%

	Expected volatility. Because there had been no public market for the Company’s common stock prior to its IPO, the Company believes that it has insufficient data from its limited public trading history to appropriately utilize company-specific historical and implied volatility information. Accordingly, the Company utilizes data from a representative group of publicly traded companies to estimate expected stock price volatility. The Company selected representative companies from the biopharmaceutical industry with similar characteristics as the Company, including stage of product development and therapeutic focus.

	Expected term. The expected term of awards represents the period of time that the awards are expected to be outstanding. The expected term was determined using the simplified method as prescribed by the Securities and Exchange Commission Staff Accounting Bulletin No. 107, Share-Based Payment as the Company does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term of stock options granted to employees.

	Risk-free interest rate. For the years ended December 31, 2014, 2013 and 2012, the risk-free interest rate was estimated using an average of treasury bill interest rates over a period commensurate with the expected term of the option at the time of grant.

	Expected dividend yield. The expected dividend yield is zero as the Company has not paid any dividends to date and has no current intention of paying cash dividends.

	Forfeiture rate. The Company is required to estimate potential forfeiture of stock grants and adjust compensation cost recorded accordingly. The estimate of forfeitures is adjusted over the requisite service period to the extent that actual forfeitures differ, or are expected to differ, from such estimates. Changes in estimated forfeitures are recognized through a cumulative catch-up in the period of change and impact the amount of stock compensation expense to be recognized in future periods. For the years ended December 31, 2014, 2013 and 2012, the Company estimated a forfeiture rate of 5%.

	During the years ended December 31, 2014, 2013 and 2012, the total intrinsic value of stock options exercised was $2.4 million, $0.1 million and $0, respectively. Cash received from option exercises for the years ended December 31, 2014, 2013 and 2012 was $1.0 million, $32 thousand and $0, respectively.

	The total grant date fair value of stock options that vested during the years ended December 31, 2014, 2013 and 2012 was $0.6 million, $0.9 million and $0.9 million, respectively.



	The following is a summary of option activity under the 2006 Plan and 2014 Plan:



			Number of				Weighted				Weighted			Aggregate
			Option Shares				Average				Average			Intrinsic
							Exercise				Remaining			Value
			Price per				Contractual
			Share				Term
											(In years)			(In thousands)
Outstanding at December 31, 2013				1,952,578			$	3.14
Granted			1,182,143			$	9.68
Exercised			(366,258	)		$	2.76
Forfeited or expired			(79,526	)		$	4.08

Outstanding at December 31, 2014			2,688,937			$	6.04				6.79			19,699

Exercisable at December 31, 2014			1,425,925			$	3.27				4.59			14,329

Vested and expected to vest at December 31, 2014 (1)			2,594,803			$	5.92				6.7			19,315



-1	This represents the number of vested options as of December 31, 2014, plus the number of unvested options expected to vest as of December 31, 2014, based on the unvested options at December 31, 2014, adjusted for the estimated forfeiture rate of 5%.

The aggregate intrinsic values in the preceding table represent the total pre-tax intrinsic value (the difference between the Company’s common stock price on the last day of the reporting period and the exercise price, multiplied by the number of in-the-money stock options) that would have been received by the stock option holders had all stock option holders exercised their stock options at the end of the reporting period. The amount of aggregate intrinsic value will change based on the fair value of the Company’s common stock.

Stock-based compensation expense

Total compensation cost recognized for all stock-based compensation awards in the consolidated statements of operations and comprehensive loss is as follows (in thousands):



		For the Year Ended December 31,
		2014				2013				2012
Research and development		$	802			$	583			$	564
General and administrative			891				420				304

Total stock-based compensation expense		$	1,693			$	1,003			$	868


As of December 31, 2014 there was $7.2 million of total unrecognized compensation cost related to unvested options. Total unrecognized compensation cost will be adjusted for future changes in forfeitures. The Company expects to recognize that cost over a weighted-average period of 3.1 years.



Reserved Shares

The Company had reserved the following shares of common stock as of December 31, 2014 for the potential exercise of outstanding warrants and stock options:



		December 31,
		2014
Warrants			70,796
Common stock options			3,824,891

Shares reserved for issuance at December 31, 2014			3,895,687

Income_Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	8. Income Taxes

	During fiscal years 2014, 2013 and 2012, the Company did not record a benefit for income taxes related to its operating losses. The Company has provided a full valuation allowance against its net deferred tax assets, as the Company believes that it is more likely than not that the deferred tax assets will not be realized.

	A reconciliation of the federal statutory income tax rate and the Company’s effective income tax rate is as follows:



		Year ended December 31,
		2014			2013			2012
	Federal statutory income tax rate		34.0	%		34	%		34	%
	State income taxes		5.3			5.3			5.3
	Change in valuation allowance		(41.0	)		(43.3	)		(34.9	)
	Research and development credits		4.5			31.7			1.2
	Permanent items		(0.7	)		(5.9	)		(1.8	)
	Expiring state net operating loss carryforward		(2.1	)		(21.8	)		(3.8	)

	Effective income tax rate		0.0	%		0	%		0	%


	The significant components of the Company’s net deferred tax assets consist of the following (in thousands):



		December 31,
		2014			2013
	Net operating loss carryforwards	$	44,186		$	38,585
	Deferred revenue		6,215			1,081
	Research and development credit carryforwards		7,728			6,277
	Other		1,863			1,043

			59,992			46,986
	Valuation allowance		(59,992	)		(46,986	)

	Net deferred tax assets	$	—		$	—


	At December 31, 2014, the Company had federal net operating loss carryforwards of $119.5 million and state net operating loss carryforwards of $67.6 million available to reduce future taxable income, which expire at various dates beginning in 2015 through 2035. The Company also had federal and state research and development tax credit carryforwards of $6.0 million and $2.6 million, respectively, available to reduce future tax liabilities, which expire at various dates through 2035.



	Realization of the future tax benefits is dependent on many factors, including the Company’s ability to generate taxable income within the net operating loss carryforward period. The Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets and concluded that it is more likely than not that the Company will not realize the benefit of its deferred tax assets. As a result, the deferred tax assets have been fully reserved at December 31, 2014 and 2013. Under the provisions of the Internal Revenue Code Section 382, the net operating loss and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. Net operating loss and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders over a three-year period in excess of 50 percent, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the value of the company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. The Company has completed several financings since its inception which may have resulted in a change in control as defined by Sections 382 and 383 of the Internal Revenue Code, or could result in a change in control in the future.

	At December 31, 2014, the Company had no unrecognized tax benefits. The Company has not conducted a study of its research and development credit carryforwards. A study may result in an adjustment to the Company’s research and development credit carryforwards; however, until a study is completed and any adjustment is known, no amounts will be presented as an uncertain tax position. A full valuation allowance has been provided against the Company’s research and development credit carryforwards 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.

	Interest and penalty charges, if any, related to unrecognized tax benefits would be classified as income tax expense in the accompanying statement of operations. As of December 31, 2014, the Company had no accrued interest related to uncertain tax positions.

	The Company is currently open to examination under the statute of limitations by the Internal Revenue Service and state jurisdictions for the tax years ended 2011 through 2013. Carryforward tax attributes generated in years prior to 2011 may still be adjusted upon future examination if they have or will be used in a future period. The Company is currently not under examination by the Internal Revenue Service or any other jurisdictions for any tax years. Since the Company is in a loss carryforward position, the Company is generally subject to examination by the U.S. federal, state and local income tax authorities for all tax years in which a loss carryforward is available.

Commitments

Commitments	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments	9. Commitments

	In February 2008, the Company entered into a seven-year, non-cancelable operating lease for approximately 45,000 square feet of office and laboratory space, or the 2008 Lease Agreement, in Lexington, Massachusetts, which serves as the Company’s headquarters.

	The 2008 Lease Agreement included certain lease incentives in the form of two tenant improvement allowances. The first tenant improvement allowance of $3.7 million was for general improvements to the facility’s office space and HVAC systems. The Company capitalized the improvements made with the first tenant improvement allowance into fixed assets and established a liability in the accompanying balance sheet under the caption “deferred lease incentive”.

	The second tenant improvement allowance of $2.3 million was for improvements to be made to build laboratory space to the Company’s specifications. The second tenant improvement allowance was similar to the first, except that the Company was required to repay the reimbursements to the landlord monthly over the lease term, plus interest at a 10% annual rate. The Company capitalized the improvements made with the second tenant improvement allowance into fixed assets and established a liability, exclusive of interest, in the accompanying balance sheet under the caption “leasehold improvement loan”.

	In August 2014, the Company entered into an amendment of its 2008 Lease Agreement, or the Amendment of Lease, pursuant to which the Company will lease through September 30, 2018 the approximately 45,000 square feet of office and laboratory space that was covered by the 2008 Lease Agreement as well as an additional 5,000 square feet of office space. A tenant improvement allowance of $0.4 million was provided by the landlord under the Amendment of Lease for general improvements. The Amendment of Lease also provides for the waiver of the remaining monthly payments due under the Company’s outstanding leasehold improvement loan, totaling $0.3 million as of December 31, 2014, and a reduction in the letter of credit the Company delivered under the 2008 Lease Agreement from $0.7 million to $0.4 million. Waiver of the leasehold improvement loan will occur on a monthly basis from October 1, 2014 through September 30, 2015 and was considered to represent a lease incentive. Accordingly, the remaining principal balance of the leasehold improvement loan as of December 31, 2014 has been classified as a component of deferred lease incentive in the accompanying balance sheet and will be recognized over the remainder of the extended lease term. The Company capitalized the improvements made with the tenant improvement allowance provided in the Amendment of Lease and established a liability in the accompanying balance sheet under the caption “deferred lease incentive.”

	The Company is amortizing all leasehold improvement assets and deferred incentives over the remaining lease term, as amended.

	The Amendment of Lease provides for escalating rent payments over the lease term. The Company is recognizing rental expense under the Amendment of Lease on a straight-line basis after considering the escalating rent payments and the remaining deferred rent under the 2008 Lease Agreement.

	The future minimum lease payments under the 2008 Lease Agreement, as amended, is as follows (in thousands):



		Base rent obligations
	At December 31, 2014
	2015	$	1,540
	2016		1,522
	2017		1,573
	2018		1,208

	Total minimum lease payments	$	5,843


	Rent expense for the years ended December 31, 2014, 2013 and 2012 was $1.0 million, $0.7 million and $0.7 million, respectively.

	Employment agreements

	Five of the Company’s employees are covered by employment agreements, covering salary, certain benefits and incentive compensation. Under these agreements, the executives could be entitled to severance pay up to 12 months of base salary, paid COBRA insurance coverage for 12 months and acceleration of stock option vesting (assuming for such acceleration a termination without cause or on death or disability or resignation for good reason within one year after a change in control). During 2013, the Company accrued $0.3 million in severance and benefit obligations in connection with the departure of its Chief Medical Officer, with the associated costs allocated to research and development expenses on the statement of operations and comprehensive loss. Approximately $69 thousand of cash payments related to these obligations were made during 2013, resulting in a total recorded liability of $0.3 million related to this obligation as of December 31, 2013, which was subsequently paid in 2014.

Collaboration_Agreements

Collaboration Agreements	12 Months Ended
Collaboration Agreements	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration Agreements	10. Collaboration Agreements

	Celgene

	In April 2013, the Company entered into a master development and license agreement with Celgene Corporation and Celgene International Sàrl, referred to together as Celgene, which is primarily focused on the research, development and commercialization of specified deuterated compounds targeting inflammation or cancer. The collaboration is initially focused on one program, but has the potential to encompass up to four programs.

	For the initial program, the Company granted Celgene an exclusive worldwide license to develop, manufacture and commercialize deuterated analogs of a selected non-deuterated compound and certain close chemical derivatives thereof. The Company further granted Celgene licenses with respect to two additional programs and an option with respect to a third additional program. The Company and Celgene have agreed on the non-deuterated compounds for each of the two additional license programs. For the option program, Celgene may select the non-deuterated compound at a later time, which, unless otherwise agreed by the Company, will be limited to a compound for which Celgene possesses exclusive rights. With respect to the two additional license programs, the Company granted Celgene an upfront exclusive worldwide license to develop, manufacture and commercialize deuterated products that contain deuterated analogs of the agreed non-deuterated compounds. Celgene is restricted from utilizing their research, development and commercialization rights under each of these upfront licenses, unless, within seven years after the effective date of the agreement, Celgene pays the Company a license exercise fee. If Celgene does not elect to pay the license exercise fee during the seven year period, the license will expire. With respect to the option program, once a compound is selected, Celgene may exercise its option by paying the Company an option exercise fee within seven years of the effective date of the agreement, and upon Celgene’s exercise of the option the Company will grant to Celgene an exclusive worldwide license to develop, manufacture and commercialize deuterated products that contain deuterated analogs of the selected non-deuterated compound.

	The Company is responsible for conducting and funding research and early development activities for the initial program at its own expense pursuant to mutually agreed upon development plans. This includes the completion of single and multiple ascending dose Phase 1 clinical trials and any mutually agreed upon additional Phase 1 clinical trials, as set forth in the development plan and approved by the joint steering committee for the collaboration.

	Under the terms of the agreement, the Company received a non-refundable upfront payment of $35.0 million. In addition, the Company is eligible to earn up to $23.0 million in development milestone payments, including $8.0 million related to the completion of a Phase 1 clinical trial, up to $247.5 million in regulatory milestone payments and up to $50.0 million in sales-based milestone payments related to products within the initial program. The next milestone payment the Company may be entitled to receive under the initial program is $8.0 million related to the completion of Phase 1 clinical trials of CTP-730. If Celgene exercises its rights with respect to either of the two additional license programs, the Company will receive a license exercise fee for the applicable program of $30.0 million and will also be eligible to earn up to $23.0 million in development milestone payments and up to $247.5 million in regulatory milestone payments for that program. Additionally, with respect to one of the additional license programs, the Company is eligible to receive up to $100.0 million in sales-based milestone payments based on net sales of products, and with respect to the other additional license program, the Company is eligible to receive up to $50.0 million in sales-based milestone payments based on net sales of products. If Celgene exercises its option with respect to the option program, in respect of a compound to be identified at a later time, the Company will receive an option exercise fee of $10.0 million and will be eligible to earn up to $23.0 million in development milestone payments and up to $247.5 million in regulatory milestone payments.

	In addition, with respect to each program, Celgene is required to pay the Company royalties on worldwide net sales of each licensed product at defined percentages ranging from the mid-single digits to low double digits below 20%. The royalty term for each licensed product in each country is the period commencing with first commercial sale of the applicable licensed product in the applicable country and ending on the latest of expiration of specified patent coverage, expiration of regulatory exclusivity or 10 years following commercial launch. The royalty rate is reduced on a country-by-country basis during any period within the royalty term when there is no patent claim or regulatory exclusivity covering the licensed product in the particular country.

	The Company’s arrangement with Celgene contains the following deliverables: (i) an exclusive worldwide license to develop, manufacture and commercialize deuterated analogs of a selected compound related to the initial program, or the License Deliverable, (ii) obligations to perform research and development services associated with the initial program, or the R&D Services Deliverable, (iii) obligation to supply preclinical and clinical trial material related to the initial program, or the Supply Deliverable, (iv) participation on the JSC during the term of the initial program, or the JSC Deliverable, (v) significant and incremental discount related to the first additional license program for which the non-deuterated compound has been selected, or the First Discount Deliverable and (vi) significant and incremental discount related to the second additional license program for which the non-deuterated compound has been selected, or the Second Discount Deliverable.

	Allocable arrangement consideration at inception was limited to the $35.0 million non-refundable upfront payment. The Company allocated the arrangement consideration for the collaboration among the separate units of accounting using the relative selling price method as follows: (i) $17.0 million to the License Deliverable; (ii) $8.7 million to the R&D Services Deliverable for the initial program; (iii) $3.2 million to the Supply Deliverable for the initial program; (iv) $0.1 million to the JSC Deliverable for the initial program; (v) $3.0 million to the First Discount Deliverable for the first additional program; and (vi) $3.0 million to the Second Discount Deliverable for the second additional program.

	The arrangement consideration allocated to the License Deliverable was recognized upon delivery. Amounts allocated to the R&D Services Deliverable and Supply Deliverable are recognized under the proportional performance method over the expected period of performance, or 39 months. The amount allocated to the JSC Deliverable is recognized ratably over the expected period of performance, or 39 months. Amounts allocated to the First Discount Deliverable and the Second Discount Deliverable are deferred and will be recognized at the earlier of when the associated license rights are exercised and licenses are delivered or upon lapsing of the underlying right, if the respective right expires unexercised. The Company reassesses the estimated periods of performance for each unit of accounting at the end of each reporting period.

	During the years ended December 31, 2014 and 2013, the Company recognized revenue of $1.8 million and $0.7 million for the R&D Services Deliverable and $1.9 million and $0.6 million for the Supply Deliverable, respectively. Additionally, during the years ended December 31, 2014 and 2013, the Company recognized revenue of $32 thousand and $24 thousand, respectively, related to the JSC Deliverable. The revenue was classified as license and research and development revenue in the accompanying consolidated statement of operations and comprehensive loss.

	As of December 31, 2014, there was $12.9 million of deferred revenue related to the Company’s collaboration with Celgene, $5.8 million of which was classified as current and $7.1 million of which was classified as noncurrent, in the accompanying consolidated balance sheet.

	Jazz Pharmaceuticals

	In February 2013, the Company entered into a development and license agreement with Jazz Pharmaceuticals, Inc., or Jazz Pharmaceuticals, to research, develop and commercialize products containing deuterated sodium oxybate, or D-SXB. The Company is initially focusing on one analog, designated as JZP-386. Under the terms of the agreement, the Company granted Jazz Pharmaceuticals an exclusive, worldwide, royalty-bearing license under intellectual property controlled by us to develop, manufacture and commercialize D-SXB products including, but not limited to, JZP-386.

	The Company, together with Jazz Pharmaceuticals, is conducting certain development activities for a Phase 1 clinical trial with respect to JZP-386 pursuant to an agreed upon development plan. The Company is responsible under the development plan for conducting a Phase 1 clinical trial with respect to JZP-386. Thereafter, the Company’s obligations to conduct further development activities are subject to mutual agreement. Jazz Pharmaceuticals has assumed all manufacturing responsibilities. Pursuant to the agreement, the Company’s costs for activities under the development plan, including pass-through costs and the costs of the Company’s employees’ time at a rate per full-time equivalent year of its employees’ time, which the Company and Jazz Pharmaceuticals mutually agreed to, are reimbursed by Jazz Pharmaceuticals, except for the costs of an additional Phase 1 clinical trial that was initiated in the first quarter of 2015, which will be shared between Jazz Pharmaceuticals and the Company. This reimbursement is subject to limitations specified in the agreement, including adherence within a particular percentage to the development budget. Under the agreement, Jazz Pharmaceuticals is subject to specified diligence obligations regarding the development and commercialization of licensed products.

	Under the agreement, the Company received a non-refundable upfront payment of $4.0 million and is eligible to earn an aggregate of up to $8.0 million in development milestone payments, up to $35.0 million in regulatory milestone payments and up to $70.0 million in sales milestone payments based on net product sales of licensed products. The next milestone payment that the Company may be entitled to receive is $4.0 million related to the successful completion of a Phase 1 clinical trial or clinical advancement of JZP-386, a deuterated analog of sodium oxybate.

	In addition, Jazz Pharmaceuticals is required to pay the Company royalties at defined percentages ranging from the mid-single digits to low double digits below 20%, on a country-by-country and licensed product-by-licensed product basis, on worldwide net product sales of licensed products. The royalty term for each licensed product in each country is the period commencing with first commercial sale of the applicable licensed product in the applicable country and ending on the later of the expiration of specified patent coverage or 10 years following commercial launch. The royalty rate is lowered, on a country by country basis, under certain circumstances as specified in the agreement.

	The Company determined that there were three deliverables under the agreement: (i) an exclusive, royalty-bearing, sub-licensable worldwide license to develop and commercialize D-SXB compounds, or the License Deliverable, (ii) participation on a joint steering committee, or the JSC Deliverable, and (iii) a deliverable to direct external patent activities and bear a portion of the external patent fees, or the Patent Support Deliverable.



	The Company allocated arrangement consideration of $3.7 million to the License Deliverable, $0.1 million to the JSC Deliverable and $0.2 million to the Patent Support Deliverable. The Company recognized the arrangement consideration allocated to the License Deliverable upon delivery and will recognize revenue related to the JSC Deliverable and the Patent Support Deliverable over the respective periods of performance, which are each estimated to be 46 months.

	For the years ended December 31, 2014 and 2013, the Company recognized revenue of $2.6 million and $1.1 million related to the performance of development support services, respectively. For the year ended December 31, 2013 the Company recognized revenue of $3.7 million upon delivery of the License Deliverable. Additionally, for the years ended December 31, 2014 and 2013, the Company recognized revenue of $56 thousand and $61 thousand, respectively, related to the JSC and Patent Support deliverables.

	Avanir

	In February 2012, the Company entered into a development and license agreement with Avanir Pharmaceuticals, Inc., or Avanir, under which the Company granted Avanir an exclusive worldwide license to develop, manufacture and commercialize deuterated dextromethorphan containing products. Subsequent to the Company’s agreement, Avanir was acquired by Otsuka Pharmaceutical Co., Ltd. and it is now a wholly owned subsidiary of Otsuka America, Inc. Avanir is initially focused on developing AVP-786, which is a combination of a deuterated dextromethorphan analog and an ultra-low dose of quinidine, for the treatment of neurologic and psychiatric disorders.

	Under the agreement, the Company received a non-refundable upfront payment of $2.0 million, a milestone payment of $2.0 million in 2013 and a milestone payment of $2.0 million in 2014. The Company is also eligible to earn, with respect to licensed products comprising a combination of deuterated dextromethorphan and quinidine, up to $2.0 million in development milestone payments related to initiation of dosing in a Phase 3 clinical trial for AVP-786, up to $37.0 million in regulatory and commercial launch milestone payments and up to $125.0 million in sales-based milestone payments. The next milestone that the Company may be entitled to earn is $2.0 million related to the initiation of dosing in a Phase 3 clinical trial for AVP-786. In addition, the Company is eligible for higher development milestones, up to an additional $43.0 million, for licensed products that do not require quinidine. Avanir is currently developing deuterated dextromethorphan only in combination with quinidine.

	Avanir also is required to pay the Company royalties at defined percentages ranging from the mid-single digits to low double digits below 20% on worldwide net sales of licensed products. The royalty term for each licensed product in each country is the period commencing with first commercial sale of the applicable licensed product in the applicable country and ending on the later of expiration of specified patent coverage or 10 years following commercial launch. The royalty rate is reduced, on a country-by-country basis, during any period within the royalty term when there is no patent claim covering the licensed product in the particular country.

	The Company determined that the deliverables under the agreement were the exclusive, royalty-bearing sub-licensable license to deuterated dextromethorphan delivered at the inception of the arrangement as well as participation on a joint steering committee through a first IND filing. The Company allocated arrangement consideration of $2.0 million to the license and an insignificant amount to the Company’s participation on the joint steering committee. Accordingly, the Company recognized the $2.0 million non-refundable upfront fee as revenue upon delivery of the deuterated dextromethorphan license in March 2012.

	During the year ended December 31, 2014, the Company recognized as revenue a $2.0 million milestone payment received from Avanir based on the initiation of dosing in a Phase 2 clinical trial of AVP-786. Since June 2012, Avanir has elected to conduct all research and development activities, including manufacturing activities; however, the Company has continued to receive intellectual property cost reimbursements. The Company recognized $0.2 million for the year ended December 31, 2014 for intellectual property cost reimbursements, the cost of which was recorded within general and administrative expense.

	During the year ended December 31, 2013, the Company recognized as revenue a $2.0 million milestone payment received from Avanir based on positive data from Avanir’s Phase 1 clinical trial of AVP-786. The Company also recognized $0.2 million for the year ended December 31, 2013 for intellectual property cost reimbursements.

	During the year ended December 31, 2012, the Company recognized as revenue a $2.0 million non-refundable upfront license fee upon delivery of the deuterated dextromethorphan license and $0.2 million for intellectual property cost reimbursements.

	GSK

	In May 2009, the Company entered into a research and development collaboration and license agreement with Glaxo Group Limited, or GSK, to research, develop and commercialize multiple products containing deuterated compounds, including CTP-499. The agreement with GSK, as subsequently amended, expired in May 2012 after GSK opted out of further development under the agreement and made a $2.75 million payment to the Company. The rights to the product candidates developed under the agreement have reverted to the Company and it is free to pursue them without further obligation to GSK other than to repay GSK an amount of up to $2.75 million if the Company commercializes CTP-499 or if, prior to a specified date in 2018, the Company re-licenses or transfers rights to CTP-499 to a third party. The $2.75 million payment was classified as deferred revenue and will not be recognized as revenue until all repayment obligations lapse.

Sponsored_Research_Agreement

Sponsored Research Agreement	12 Months Ended
Sponsored Research Agreement	Dec. 31, 2014
Research and Development [Abstract]
Sponsored Research Agreement	11. Sponsored Research Agreement

	In February 2012, the Company entered into a sponsored research agreement with Fast Forward LLC, or Fast Forward, the National Multiple Sclerosis Society’s subsidiary devoted to research and drug development. Under the research agreement, Fast Forward provided $0.8 million of funding for the preclinical advancement of CTP-354, a deuterated subtype-selective GABAA modulator developed by Concert with the therapeutic potential of treating spasticity. Concert received the funding as it met certain preclinical milestones.

	In certain circumstances, the Company is obligated to make milestone payments to Fast Forward not in excess of a low-single digit multiple of the funding amount. As of December 31, 2014 and 2013, it was not probable any milestone payments would be owed to Fast Forward.

	The Company did not receive any payments from Fast Forward during the year ended December 31, 2014. During the years ended December 31, 2013 and 2012, the Company received payments totaling $45 thousand and $0.7 million, respectively, from Fast Forward, which were recognized as revenue within license and research and development revenue in the accompanying statement of operations and comprehensive loss. The revenue recognized is commensurate with the services performed in 2013 and 2012, and such payments are non-refundable as the Company has incurred costs in excess of the amounts funded.

Loan_Payable_and_Warrant_to_Pu

Loan Payable and Warrant to Purchase Redeemable Securities	12 Months Ended
Loan Payable and Warrant to Purchase Redeemable Securities	Dec. 31, 2014
Debt Disclosure [Abstract]
Loan Payable and Warrant to Purchase Redeemable Securities	12. Loan Payable and Warrant to Purchase Redeemable Securities

	On December 22, 2011, the Company entered into a Loan and Security Agreement, or the Loan and Security Agreement, with Hercules Technology Growth Capital, Inc., or Hercules. The Loan and Security Agreement provides for aggregate advances of up to $20 million in two tranches. Under the first tranche, the Company obtained an advance on December 22, 2011 totaling $7.5 million, or the December 2011 Advance. Under the second tranche, the Company obtained an advance on March 29, 2012 totaling $12.5 million, or the March 2012 Advance. The Company incurred $0.2 million in loan issuance costs paid directly to the lenders, which have been offset against the loan proceeds as a loan discount.

	Each advance made under the Loan and Security Agreement bears interest at a variable rate of the greater of 8.5% and an amount equal to 8.5% plus the prime rate of interest minus 5.25%, provided however, that the per annum interest rate shall not exceed 11%. Through December 31, 2014, each of the December 2011 Advance and the March 2012 Advance had an interest rate of 8.5%. Interest-only payments were due monthly on the first day of each month beginning the month after the date of the respective advance until April 30, 2013. Thereafter the aggregate principal balance outstanding became payable in 30 equal monthly installments of principal and interest beginning May 1, 2013 and continuing through the maturity date of October 1, 2015.



	Additionally, the advances are to be repaid in full immediately upon an event of default, as defined. The Loan and Security Agreement defines events of default, including the occurrence of an event that results in a material adverse effect upon the Company’s business operations, properties, assets or condition (financial or otherwise), its ability to perform its obligations under and in accordance with the terms of the new loan agreement, or upon the ability of the lenders to enforce any of their rights or remedies with respect to such obligations, or upon the collateral under the Loan and Security Agreement or upon the liens of the lenders on such collateral or upon the priority of such liens. The Company does not believe that any events have occurred that could reasonably be deemed to have a material adverse effect. Substantially all assets of the Company are pledged as collateral, with the exception of intellectual property, which is the subject of a negative pledge under the Loan and Security Agreement. The lenders’ security interest in the collateral is a first priority security interest. The Company does not have any financial covenants under the Loan and Security Agreement.

	As of December 31, 2014, the future minimum payments due under the Loan and Security Agreement are as follows (in thousands):



		Year			Minimum
		Year			Payments
			2015			7,462
	Less amounts representing interest					(287	)

	Present value of minimum payments					7,175
	Less discount					(74	)

	Loan payable and unamortized discount				$	7,101


	In connection with the Loan and Security Agreement, the Company granted Hercules a warrant, the Warrant, to purchase up to 200,000 shares of Series C Preferred Stock at an exercise price of $2.50 per share which vested immediately upon the December 2011 Advance. Upon the draw of the March 2012 Advance, the Warrant became exercisable for an additional 200,000 shares of Series C Preferred Stock at an exercise price of $2.50 per share. Upon completion of the Company’s IPO in February 2014 the Warrant became exercisable for an aggregate of 70,796 shares of the Company’s common stock at an exercise price of $14.13 per share.

	Pursuant to ASC Topic 480, Distinguishing Liabilities from Equity, for periods prior to the Company’s IPO the Warrant was classified as a liability and was re-measured to the-then current value at each balance sheet date. The Warrant liability was determined based on Level 3 inputs utilizing the Black-Scholes-Merton option pricing model. On February 19, 2014, upon completion of the IPO, the Warrant converted into a warrant to purchase common stock and the Company reclassified the fair value of the Warrant as of February 19, 2014 to additional paid-in capital. The following table sets forth a summary of changes in the fair value of the Warrant during each period presented (in thousands):



		Year ended
		December 31,
		2014			2013			2012
	Beginning balance	$	463		$	459		$	168
	Change in fair value		117			4			291
	Reclassification to additional paid-in capital in connection with IPO		(580	)		—			—

	Ending balance	$	—		$	463		$	459




	The Warrant expires on the earlier of: (i) ten years from the effective date of the Loan and Security Agreement or (ii) five years after the closing of an IPO.

	The Company measured the fair value of the Warrant as of December 31, 2012 and December 31, 2013 using a hybrid method that is consistent with the manner in which the Company estimated the fair value of its common stock on those dates. Using the hybrid method, the Company used the Black-Scholes-Merton option pricing method to value the Warrant based on the results of the initial public offering scenarios and the option pricing method to value the Warrant based on the results of the other assumed scenarios (sale or liquidation). The results of those valuations were then weighted consistent with the weightings used in the Company’s common stock valuation to determine the fair value of the Warrant. The significant assumptions used in estimating the fair value of the Warrant include the volatility of the stock underlying the warrant, risk-free interest rate, estimated fair value of the preferred stock underlying the warrant, and the estimated life of the warrant.

	As of February 19, 2014, upon completion of the IPO, the Warrant converted to a warrant to purchase common stock and the Company remeasured the Warrant using the Black-Scholes-Merton option pricing method based upon the closing price of the Company’s common stock on February 19, 2014.

	Where the fair value of the Warrant was estimated using the Black-Scholes-Merton option pricing model, the Company used the following weighted-average assumptions:



		Year ended
		December 31,
		2014			2013			2012
	Expected volatility		70	%		70	%		70	%
	Expected term		5.0 years			5.3 years			7.9 years
	Risk-free interest rate		1.53	%		1.75	%		0.95	%
	Expected dividend yield		0.0	%		0	%		0	%

	Expected volatility

	The Company estimated the expected volatility based on actual historical volatility of the stock price of similar companies with publicly-traded equity securities. The Company calculated the historical volatility of the selected companies by using daily closing prices over a period of the expected term of the Warrant. The companies were selected based on their enterprise value, risk profiles, position within the industry, and with historical share price information sufficient to meet the expected term of the associated award.

Expected term

The Company based the expected term on the actual remaining contractual term as of each respective measurement date.

Risk-free interest rate

The Company estimated the risk-free interest rate in reference to the yield on U.S. Treasury securities with a maturity date commensurate with the expected term of the Warrant.

Expected dividend yield

The Company estimated the expected dividend yield based on consideration of its historical dividend experience and future dividend expectations. The Company has not historically declared or paid dividends to stockholders. Moreover, it does not intend to pay dividends in the future, but instead expects to retain any earnings to invest in the continued growth of the business. Accordingly, the Company assumed an expected dividend yield of 0.0%.

401k_Retirement_Plan

401(k) Retirement Plan	12 Months Ended
401(k) Retirement Plan	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
401(k) Retirement Plan	13. 401(k) Retirement Plan

	In January 2008, the Company established the Concert Pharmaceuticals 401(k) Retirement Plan (the 401(k) Plan) in which substantially all of its permanent employees are eligible to contribute a percentage of base wages up to an amount not to exceed an annual statutory maximum. The Company matches 50% of the first 6% of an employee’s contributions subject to statutory limits.

	The Company made matching contributions under the 401(k) Plan of $0.2 million, $0.2 million and $0.2 million for the years ended December 31, 2014, 2013 and 2012, respectively.

Quarterly_Financial_Informatio

Quarterly Financial Information (unaudited)	12 Months Ended
Quarterly Financial Information (unaudited)	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (unaudited)	14. Quarterly Financial Information (unaudited)



		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2014			2014			2014			2014
		(in thousands, except per share data)
		(unaudited)
	Revenue	$	1,613		$	1,235		$	4,418		$	1,310
	Operating expenses		8,132			8,961			12,026			10,055

	Loss from operations		(6,519	)		(7,726	)		(7,608	)		(8,745	)
	Other expense, net		(431	)		(264	)		(224	)		(182	)

	Net loss	$	(6,950	)	$	(7,990	)	$	(7,832	)	$	(8,927	)

	Net loss per share—basic and diluted	$	(0.76	)	$	(0.45	)	$	(0.43	)	$	(0.49	)



		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2013			2013			2013			2013
		(in thousands, except per share data)
		(unaudited)
	Revenue	$	5,873		$	17,441		$	681		$	1,413
	Operating expenses		7,003			8,026			7,797			6,992

	(Loss) income from operations		(1,130	)		9,415			(7,116	)		(5,579	)
	Other expense, net		(649	)		(650	)		(11	)		(336	)

	Net (loss) income	$	(1,779	)	$	8,765		$	(7,127	)	$	(5,915	)

	Net loss per share—basic and diluted	$	(1.46	)	$	0		$	(5.59	)	$	(4.64	)

Basis_of_Presentation_and_Sign1

Basis of Presentation and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Cash, Cash Equivalents and Investments	Cash, Cash Equivalents and Investments

	Cash equivalents include all highly liquid investments maturing within 90 days from the date of purchase. Investments consist of securities with original maturities greater than 90 days when purchased. The Company classifies these investments as available-for-sale and records them at fair value in the accompanying consolidated balance sheets. Unrealized gains or losses are included in accumulated other comprehensive income. Premiums or discounts from par value are amortized to investment income over the life of the underlying investment.

	Cash, cash equivalents and investments included the following at December 31, 2014 and 2013 (in thousands):



		Average		Amortized		Unrealized			Unrealized			Fair
		maturity		cost		gains			losses			value
	December 31, 2014
	Cash			$	1,492	$	—		$	—		$	1,492
	Money market funds				11,904		—			—			11,904

	Cash and cash equivalents			$	13,396	$	—		$	—		$	13,396

	U.S. Treasury obligations		171 days	$	12,037	$	(2	)	$	—		$	12,035
	Government agency securities		194 days		53,813		3			(15	)		53,801

	Investments			$	65,850	$	1		$	(15	)	$	65,836




		Average		Amortized		Unrealized			Unrealized			Fair
		maturity		cost		gains			losses			value
	December 31, 2013
	Cash			$	2,188	$	—		$	—		$	2,188
	Money market funds				7,450		—			—			7,450

	Cash and cash equivalents			$	9,638	$	—		$	—		$	9,638

	U.S. Treasury obligations		301 days	$	500	$	—		$	—		$	500
	Government agency securities		324 days		22,535		4			—			22,539

	Investments			$	23,035	$	4		$	—		$	23,039


	Although available to be sold to meet operating needs or otherwise, securities are generally held through maturity. The cost of securities sold is determined based on the specific identification method for purposes of recording realized gains and losses. During 2014 and 2013, there were no realized gains or losses on sales of investments, and no investments were adjusted for other than temporary declines in fair value.
Fair Value of Financial Measurements	Fair Value of Financial Measurements

	The Company measures certain financial assets and liabilities at fair value on a recurring basis (principally cash equivalents, investments and the preferred stock warrant liability) that have been classified as Level 1, 2 or 3 within the fair value hierarchy as described below. Fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access. Fair values determined by Level 2 inputs utilize data points that are observable, such as quoted prices, interest rates and yield curves. Fair values determined by Level 3 inputs utilize unobservable data points for the asset or liability. The Company’s investments in money market funds, U.S. treasury obligations and government agency securities have been classified as Level 1 because their fair values are based on quoted market prices. The preferred stock warrant liability was classified as Level 3 because certain inputs to the valuation of the warrant are based on unobservable inputs.

	As of December 31, 2014 and December 31, 2013, the Company’s financial assets and liabilities recognized at fair value consisted of the following:



		Level 1		Level 2		Level 3			Total
	December 31, 2014
	Money market funds, included in cash equivalents	$	11,904	$	—	$	—		$	11,904
	Investments, available for sale:
	U.S. Treasury obligations		12,035		—		—			12,035
	Government agency securities		53,801		—		—			53,801

	Total	$	77,740	$	—	$	—		$	77,740




		Level 1		Level 2		Level 3			Total
	December 31, 2013
	Assets:
	Money market funds, included in cash equivalents	$	7,450	$	—	$	—		$	7,450
	Investments, available for sale:
	U.S. Treasury obligations		500		—		—			500
	Government agency securities		22,539		—		—			22,539

	Total	$	30,489	$	—	$	—		$	30,489

	Liabilities:
	Warrant to purchase redeemable securities	$	—	$	—	$	463		$	463

	The fair value of the preferred stock warrant liability was determined based on Level 3 inputs utilizing the Black-Scholes-Merton option pricing model. On February 19, 2014, upon completion of the IPO, the Company’s outstanding warrant to purchase preferred stock converted into a warrant to purchase common stock and the Company reclassified the fair value of the warrant as of February 19, 2014 to additional paid-in capital. The assumptions used to value the warrant are more fully described in Note 12.

	The carrying amount of financial instruments not carried at fair value, including the loan payable and leasehold improvement loan, approximate fair value. The carrying value of the Company’s loan payable and leasehold improvement loan approximated fair value because the interest rate yields for the loans approximate current market yields. The disclosed fair values of the Company’s loan payable and leasehold improvement loan are Level 3 liabilities within the fair value hierarchy.
Concentrations of Credit Risk	Concentrations of Credit Risk

	Financial instruments that potentially subject the Company to concentration of credit risk consist principally of money market funds and investments and accounts receivable. The Company has not experienced any credit losses in these accounts and does not believe it is exposed to any significant credit risk on these funds. The Company has no foreign exchange contracts, option contracts or other foreign exchange hedging arrangements. At December 31, 2014 and 2013, substantially all of the Company’s cash was deposited in accounts at two highly rated financial institutions, thus limiting the amount of credit exposure to any one financial institution. These amounts at times may exceed federally insured limits.

	Accounts receivable represent amounts due from collaboration partners. The Company monitors economic conditions to identify facts or circumstances that may indicate that any of its accounts receivable are at risk of collection.
Property and Equipment	Property and Equipment

	Property and equipment are recognized at cost and depreciated over their estimated useful lives using the straight-line method. Repair and maintenance costs are expensed as incurred, whereas major improvements are capitalized as additions to property and equipment. Potential impairment is assessed when there is evidence that events or circumstances indicate that the carrying amount of an asset may not be recovered. No such impairment losses have been recorded through December 31, 2014.
Rent Expense	Rent Expense

	The Company’s operating lease for its Lexington, Massachusetts facility provides for scheduled annual rent increases throughout the lease term. The Company recognizes the effects of the scheduled rent increases on a straight-line basis over the full term of the lease, which expires in 2018. Additionally, the Company has received certain lease incentives in connection with the Lexington, Massachusetts facility lease, which are recognized as a reduction to rent expense over the remaining lease term. Refer to Note 9 for additional details regarding the Company’s operating lease.
Contingencies	Contingencies

	The Company records liabilities for legal and other contingencies when information available to the Company indicates that it is probable that a liability has been incurred and the amount of loss can be reasonably estimated. Legal costs in connection with legal and other contingencies are expensed as costs are incurred.
Revenue Recognition	Revenue Recognition

	The Company has primarily generated revenue through arrangements with collaborators and nonprofit organizations for the development and commercialization of product candidates.

	The Company recognizes revenue in accordance with Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 605, Revenue Recognition (ASC 605). Accordingly, revenue is recognized when all of the following criteria are met:


	•	Persuasive evidence of an arrangement exists;


	•	Delivery has occurred or services have been rendered;


	•	The seller’s price to the buyer is fixed or determinable; and


	•	Collectability is reasonably assured.

	Amounts received prior to satisfying the revenue recognition criteria are recognized as deferred revenue in the Company’s consolidated balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, current portion. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion.

	The Company’s revenue is currently generated through collaborative research and development and licensing agreements. The terms of these agreements typically contain multiple elements, or deliverables, which may include licenses, or options to obtain licenses, to product candidates, referred to as exclusive licenses, as well as research and development activities to be performed by the Company on behalf of the collaboration partner related to the licensed product candidates. The terms of these agreements may include payments to the Company of one or more of the following: a nonrefundable, upfront payment; milestone payments; payment of license exercise or option fees with respect to product candidates; fees for research and development services rendered; and royalties on commercial sales of licensed product candidates, if any. To date, the Company has received upfront payments, several milestone payments and certain research and development service payments but has not received any license exercise or option fees or earned royalty revenue as a result of product sales.

	When evaluating multiple element arrangements, the Company considers whether the deliverables under the arrangement represent separate units of accounting. This evaluation requires subjective determinations and requires management to make judgments about the individual deliverables and whether such deliverables are separable from the other aspects of the contractual relationship. In determining the units of accounting, management evaluates certain criteria, including whether the deliverables have standalone value, based on the consideration of the relevant facts and circumstances for each arrangement. The consideration received is allocated among the separate units of accounting using the relative selling price method, and the applicable revenue recognition criteria are applied to each of the separate units.

	The Company determines the estimated selling price for deliverables within each agreement using vendor-specific objective evidence, or VSOE, of selling price, if available, third-party evidence, or TPE, of selling price if VSOE is not available, or best estimate of selling price, or BESP, if neither VSOE nor TPE is available. Determining the BESP for a deliverable requires significant judgment. The Company has used its BESP to estimate the selling price for licenses to the Company’s proprietary technology, since the Company does not have VSOE or TPE of selling price for these deliverables. In those circumstances where the Company utilizes BESP to determine the estimated selling price of a license to the Company’s proprietary technology, the Company considers market conditions as well as entity-specific factors, including those factors contemplated in negotiating the agreement, estimated development costs, and the probability of success and the time needed to commercialize a product candidate pursuant to the license. In validating the Company’s BESP, the Company evaluates whether changes in the key assumptions used to determine the BESP will have a significant effect on the allocation of arrangement consideration between multiple deliverables.

	The Company’s multiple-element revenue arrangements may include the following:

	Exclusive Licenses. The deliverables under the Company’s collaboration agreements generally include exclusive licenses to develop, manufacture and commercialize one or more deuterated compounds. To account for this element of the arrangement, management evaluates whether the exclusive license has standalone value from the undelivered elements based on the consideration of the relevant facts and circumstances of each arrangement, including the research and development capabilities of the collaboration partner. The Company may recognize the arrangement consideration allocated to licenses upon delivery of the license if facts and circumstances indicate that the license has standalone value from the undelivered elements, which generally include research and development services. The Company defers arrangement consideration allocated to licenses if facts and circumstances indicate that the delivered license does not have standalone value from the undelivered elements.



	When management believes the license does not have stand-alone value from the other deliverables to be provided in the arrangement, the Company generally recognizes revenue attributed to the license on a straight-line basis over the Company’s contractual or estimated performance period, which is typically the term of the Company’s research and development obligations. If management cannot reasonably estimate when the Company’s performance obligation ends, then revenue is deferred until management can reasonably estimate when the performance obligation ends. The periods over which revenue should be recognized are subject to estimates by management and may change over the course of the research and development and licensing agreement. Such a change could have a material impact on the amount of revenue the Company records in future periods.

	Research and Development Services. The deliverables under the Company’s collaboration and license agreements may include deliverables related to research and development services to be performed by the Company on behalf of the collaboration partner.

	Payments or reimbursements resulting from the Company’s research and development efforts are recognized as the services are performed and presented on a gross basis because the Company is the principal for such efforts, so long as there is persuasive evidence of an arrangement, the fee is fixed or determinable, and collection of the related amount is reasonably assured.

	Option Agreements. The Company’s arrangements may provide a collaborator with the right to select a deuterated compound for licensing within an initial pre-defined selection period. Under these agreements, a fee would be due to the Company upon the exercise of an option to acquire a license. The accounting for option arrangements is dependent on the nature of the option granted to the collaboration partner. An option is considered substantive if, at the inception of the arrangement, the Company is at risk as to whether the collaboration partner will choose to exercise the option to secure exclusive licenses. Factors that the Company considers in evaluating whether an option is substantive include the overall objective of the arrangement, the benefit the collaborator might obtain from the arrangement without exercising the option, the cost to exercise the option relative to the total upfront consideration and the additional financial commitments or economic penalties imposed on the collaborator as a result of exercising the option. For arrangements under which an option to secure a license is considered substantive, the Company does not consider the license underlying the option to be a deliverable at the inception of the arrangement. For arrangements under which the option to secure a license is not considered substantive, the Company considers the license underlying the option to be a deliverable at the inception of the arrangement and, upon delivery of the license, would apply the multiple-element revenue arrangement criteria to the license and any other deliverables to determine the appropriate revenue recognition. A significant and incremental discount included in an otherwise substantive option is considered to be a separate deliverable at the inception of the arrangement.

	Milestone Revenue. The Company’s collaboration agreements generally include contingent milestone payments related to specified development milestones, regulatory milestones and sales-based milestones. Development milestones are typically payable when a product candidate initiates or advances in clinical trial phases or achieves defined clinical events such as proof-of-concept. Regulatory milestones are typically payable upon submission for marketing approval with regulatory authorities or upon receipt of actual marketing approvals for a compound, approvals for additional indications, upon commercial launch or upon the first commercial sale. Sales-based milestones are typically payable when annual sales reach specified levels.

	At the inception of each arrangement that includes milestone payments, the Company evaluates whether each milestone is substantive and at risk to both parties on the basis of the contingent nature of the milestone. This evaluation includes an assessment of whether (a) the consideration is commensurate with either (i) the entity’s performance to achieve the milestone or (ii) the enhancement of the value of the delivered item(s) as a result of a specific outcome resulting from the entity’s performance to achieve the milestone; (b) the consideration relates solely to past performance; and (c) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company evaluates factors such as the scientific, regulatory, commercial and other risks that must be overcome to achieve the respective milestone, the level of effort and investment required to achieve the respective milestone and whether the milestone consideration is reasonable relative to all deliverables and payment terms in the arrangement in making this assessment. Milestones that are not considered substantive are accounted for as license payments and recognized on a straight-line basis over the remaining period of performance.
Research and Development Costs	Research and Development Costs

	Research and development costs are expensed as incurred.

	Research and development expenses are comprised of costs incurred in providing research and development activities, including salaries and benefits, facilities costs, overhead costs, contract research and development services, and other outside costs. Nonrefundable advance payments for goods and services that will be used in future research and development activities are expensed when the activity has been performed or when the goods have been received rather than when the payment is made.

	Direct research and development expenses associated with the Company’s programs include clinical trial site costs, clinical manufacturing costs, costs incurred for consultants and other outside services, such as data management and statistical analysis support, and materials and supplies used in support of the clinical programs. Indirect costs of the Company’s clinical program include salaries, stock based compensation, and an allocation of the Company’s facility costs. When third-party service providers’ billing terms do not coincide with the Company’s period-end, the Company is required to make estimates of its obligations to those third parties, including clinical trial and pharmaceutical development costs, contractual services costs and costs for supply of its drug candidates, incurred in a given accounting period and record accruals at the end of the period. The Company bases its estimates on its knowledge of the research and development programs, services performed for the period, past history for related activities and the expected duration of the third-party service contract, where applicable.
Accounting for Stock-Based Compensation	Accounting for Stock-Based Compensation

	The Company issues stock options to certain employees, officers and directors. The Company accounts for stock compensation using the fair value method, which results in the recognition of compensation expense over the vesting period of the awards. See Note 7 for additional information.

	Prior to the Company’s IPO, the estimated fair value of its common stock was determined by the Company’s board of directors based on contemporaneous and retrospective valuation estimates provided by management and prepared in accordance with the framework of the American Institute of Certified Public Accountants’ Technical Practice Aid, Valuation of Privately-Held-Company Equity Securities Issued as Compensation, as well as independent third-party valuations. The Company’s valuations of its common stock were based on a number of objective and subjective factors, including external market conditions affecting the biotechnology industry sector and the prices at which it sold shares of preferred stock, the superior rights and preferences of securities senior to its common stock at the time of each grant and the likelihood of achieving a liquidity event such as an IPO. Following the Company’s IPO, the fair value of the shares of common stock underlying stock options has been the closing price on the option grant date.
Income Taxes	Income Taxes

	The Company provides deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the Company’s financial statement carrying amounts and the tax basis of assets and liabilities using enacted tax rates expected to be in effect in the years in which the differences are expected to reverse. A valuation allowance is provided to reduce the deferred tax assets to the amount that will more likely than not be realized.

	The Company evaluates tax positions taken, or expected to be taken, in the course of preparing its tax returns to determine whether the tax positions are “more likely than not” of being sustained by the applicable tax authority. Tax positions not deemed to meet the more-likely-than-not threshold would be recognized as a tax expense.
Guarantees	Guarantees

	As permitted under Delaware law, the Company indemnifies its officers and directors for certain events or occurrences while the officer or director is, or was, serving at the Company’s request in such capacity. The term of the indemnification is for the officer’s or director’s lifetime. The maximum potential amount of future payments the Company could be required to make is unlimited; however, the Company has directors’ and officers’ insurance coverage that limits its exposure and enables it to recover a portion of any future amounts paid.

	The Company leases office space under a non-cancelable operating lease which is further described in Note 9, Commitments. The Company has a standard indemnification arrangement under the lease that requires it to indemnify the landlord against all costs, expenses, fines, suits, claims, demands, liabilities, and actions directly resulting from any breach, violation, or non-performance of any covenant or condition of the Company’s lease.

	As of December 31, 2014 and 2013, the Company had not experienced any material losses related to these indemnification obligations, and no material claims with respect thereto were outstanding. The Company does not expect significant claims related to these indemnification obligations and, consequently, concluded that the fair value of these obligations is negligible, and no related reserves were established.
Comprehensive Loss	Comprehensive Loss

	Comprehensive loss is comprised of net loss and other comprehensive income or loss. Other comprehensive income or loss consists of unrealized gains and losses on investments.
Earnings (Loss) Per Share	Earnings (Loss) Per Share

	Basic earnings (loss) per share is computed by dividing income (loss) allocable to common stockholders, computed as the sum of net income (loss) and accretion on the Company’s redeemable convertible preferred stock, by the weighted average number of common shares outstanding. During periods of income where participating securities are outstanding, participating securities are allocated a proportional share of income determined by dividing total weighted-average participating securities by the sum of the total weighted-average common shares and participating securities (the “two-class method”). Prior to its automatic conversion into common stock upon the closing of the IPO, the Company’s redeemable convertible preferred stock was entitled to participate in any dividends declared by the Company and was therefore considered to constitute participating securities. Participating securities have the effect of diluting both basic and diluted earnings per share during periods of income. During periods of loss, no loss is allocated to participating securities since they have no contractual obligation to share in the losses of the Company. Diluted earnings (loss) per share is computed after giving consideration to the dilutive effect of stock options and a warrant that are outstanding during the periods, except where such securities would be anti-dilutive.



	In the first quarter of 2014, the Company issued an additional 6,649,690 shares of common stock in connection with its IPO and 9,919,821 shares of common stock in connection with the automatic conversion of its redeemable convertible preferred stock upon the closing of the IPO. The issuance of these shares resulted in a significant increase in the Company’s weighted-average shares of common stock outstanding for the year ended December 31, 2014 when compared to the prior year periods and is expected to continue to impact the year-over-year comparability of the Company’s earnings (loss) per share calculations until the first quarter of 2015.

	The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect (in thousands):



		Year ended
		December 31,
		2014		2013		2012
	Preferred stock		—		9,920		9,920
	Warrant		71		71		71
	Outstanding stock options		2,689		1,953		1,960

			2,760		11,944		11,951

Recent Accounting Pronouncements	Recent Accounting Pronouncements

	In May 2014, the FASB issued Accounting Standards Update, or ASU, No. 2014-09, Revenue from Contracts with Customers (Topic 606), or ASU 2014-09, which stipulates that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this core principle, ASU 2014-09 provides that an entity should apply the following steps: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract and (5) recognize revenue when (or as) the entity satisfies a performance obligation. This update will be effective for the Company retrospectively beginning in the first quarter of fiscal 2017 with early adoption not permitted. The Company is currently assessing the impact of this ASU on its consolidated financial statements.

	In August 2014, the FASB issued ASU No. 2014-15, Disclosure of Uncertainties About an Entity’s Ability to Continue as a Going Concern, or ASU 2014-15 ASU 2014-15 amends FASB Accounting Standards Codification, or ASC, 205-40, Presentation of Financial Statements – Going Concern, by providing guidance on determining when and how reporting entities must disclose going-concern uncertainties in their financial statements, including requiring management to perform interim and annual assessments of an entity’s ability to continue as a going concern within one year of the date of issuance of the entity’s financial statements and providing certain disclosures if there is substantial doubt about the entity’s ability to continue as a going concern. ASU 2014-15 will be effective for the Company’s fiscal year 2016 and for interim periods beginning in the first quarter of fiscal 2017. The Company is still evaluating the impact of this ASU on its financial statement disclosures.
Distinguishing Liabilities from Equity	Pursuant to ASC Topic 480, Distinguishing Liabilities from Equity, for periods prior to the Company’s IPO the Warrant was classified as a liability and was re-measured to the-then current value at each balance sheet date. The Warrant liability was determined based on Level 3 inputs utilizing the Black-Scholes-Merton option pricing model. On February 19, 2014, upon completion of the IPO, the Warrant converted into a warrant to purchase common stock and the Company reclassified the fair value of the Warrant as of February 19, 2014 to additional paid-in capital.

Basis_of_Presentation_and_Sign2

Basis of Presentation and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Cash, Cash Equivalents and Investments	Cash, cash equivalents and investments included the following at December 31, 2014 and 2013 (in thousands):



		Average		Amortized		Unrealized			Unrealized			Fair
		maturity		cost		gains			losses			value
	December 31, 2014
	Cash			$	1,492	$	—		$	—		$	1,492
	Money market funds				11,904		—			—			11,904

	Cash and cash equivalents			$	13,396	$	—		$	—		$	13,396

	U.S. Treasury obligations		171 days	$	12,037	$	(2	)	$	—		$	12,035
	Government agency securities		194 days		53,813		3			(15	)		53,801

	Investments			$	65,850	$	1		$	(15	)	$	65,836




		Average		Amortized		Unrealized			Unrealized			Fair
		maturity		cost		gains			losses			value
	December 31, 2013
	Cash			$	2,188	$	—		$	—		$	2,188
	Money market funds				7,450		—			—			7,450

	Cash and cash equivalents			$	9,638	$	—		$	—		$	9,638

	U.S. Treasury obligations		301 days	$	500	$	—		$	—		$	500
	Government agency securities		324 days		22,535		4			—			22,539

	Investments			$	23,035	$	4		$	—		$	23,039

Financial Assets and Liabilities Recognized at Fair Value	As of December 31, 2014 and December 31, 2013, the Company’s financial assets and liabilities recognized at fair value consisted of the following:



		Level 1		Level 2		Level 3			Total
	December 31, 2014
	Money market funds, included in cash equivalents	$	11,904	$	—	$	—		$	11,904
	Investments, available for sale:
	U.S. Treasury obligations		12,035		—		—			12,035
	Government agency securities		53,801		—		—			53,801

	Total	$	77,740	$	—	$	—		$	77,740




		Level 1		Level 2		Level 3			Total
	December 31, 2013
	Assets:
	Money market funds, included in cash equivalents	$	7,450	$	—	$	—		$	7,450
	Investments, available for sale:
	U.S. Treasury obligations		500		—		—			500
	Government agency securities		22,539		—		—			22,539

	Total	$	30,489	$	—	$	—		$	30,489

	Liabilities:
	Warrant to purchase redeemable securities	$	—	$	—	$	463		$	463
Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share	The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect (in thousands):



		Year ended
		December 31,
		2014		2013		2012
	Preferred stock		—		9,920		9,920
	Warrant		71		71		71
	Outstanding stock options		2,689		1,953		1,960

			2,760		11,944		11,951

Property_and_Equipment_Tables

Property and Equipment (Tables)	12 Months Ended
Property and Equipment (Tables)	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consists of the following at December 31, 2014 and 2013 (in thousands):



		Estimated useful life		December 31,			December 31,
		(in years)		2014			2013
	Laboratory equipment		5	$	1,544		$	2,062
	Computer, telephone and office equipment		3		175			143
	Software		3		88			66
	Leasehold improvements		Lesser of useful life		6,392			5,848
	Leasehold improvements		or remaining lease term		6,392			5,848

					8,199			8,119
	Less accumulated depreciation and amortization				(5,915	)		(5,646	)

				$	2,284		$	2,473

Accrued_Expenses_and_Other_Lia1

Accrued Expenses and Other Liabilities (Tables)	12 Months Ended
Accrued Expenses and Other Liabilities (Tables)	Dec. 31, 2014
Payables and Accruals [Abstract]
Accrued Expenses and Other Liabilities	Accrued expenses and other liabilities consist of the following (in thousands):


		December 31,		December 31,
		2014		2013
	Accrued professional fees and other	$	916	$	569
	Employee compensation and benefits		1,606		290
	Research and development expenses		2,104		860
	Deferred lease incentive, current portion		308		513
	Deferred rent, current portion		68		243

		$	5,002	$	2,475

Redeemable_Convertible_Preferr1

Redeemable Convertible Preferred Stock (Tables)	12 Months Ended
Redeemable Convertible Preferred Stock (Tables)	Dec. 31, 2014
Equity [Abstract]
Schedule of Convertible Preferred Stock	Convertible Preferred Stock consisted of the following as of December 31, 2013 (in thousands):


		Preferred		Preferred		Redemption		Carrying		Common
		shares		shares		value /		value		stock
		authorized		issued		liquidation				issuable
				and		preference				upon
				outstanding						conversion
	Series A		10,000		10,000	$	10,000	$	9,993		1,770
	Series B		24,250		24,250		48,500		48,488		4,292
	Series C		22,000		15,130		37,826		37,809		2,678
	Series D		6,667		6,667		16,667		15,954		1,180

			62,917		56,047	$	112,993	$	112,244		9,920

Stock_Compensation_Tables

Stock Compensation (Tables)	12 Months Ended
Stock Compensation (Tables)	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Shares Available for Future Grant Under 2014 Plan	The following table is a roll-forward of shares available for future grant under the 2014 Plan:



			Shares
			Available for
			Grant
	Shares reserved for future grant at February 19, 2014			2,249,911
	Add: stock options and restricted stock awards forfeited or expired under plans			68,186
	Less: stock options and awards granted from February 19, 2014 to December 31, 2014			(1,182,143	)

	Shares reserved for future grant at December 31, 2014			1,135,954

Estimated Weighted-Average Assumptions of Options Granted	For the years ended December 31, 2014, 2013 and 2012, the fair values of options granted were estimated using the Black-Scholes-Merton option pricing model using the following weighted-average assumptions:



			Year ended December 31,
			2014			2013			2012
	Expected volatility			80.94	%		70.1	%		72.8	%
	Expected term			6.0 years			6.0 years			6.0 years
	Risk-free interest rate			1.9	%		1.69	%		0.95	%
	Expected dividend yield			0	%		0	%		0	%
Summary of Stock Option Activity	The following is a summary of option activity under the 2006 Plan and 2014 Plan:



			Number of			Weighted			Weighted			Aggregate
			Option Shares			Average			Average			Intrinsic
						Exercise			Remaining			Value
						Price per			Contractual
						Share			Term
									(In years)			(In thousands)
	Outstanding at December 31, 2013			1,952,578		$	3.14
	Granted			1,182,143		$	9.68
	Exercised			(366,258	)	$	2.76
	Forfeited or expired			(79,526	)	$	4.08

	Outstanding at December 31, 2014			2,688,937		$	6.04			6.79			19,699

	Exercisable at December 31, 2014			1,425,925		$	3.27			4.59			14,329

	Vested and expected to vest at December 31, 2014 (1)			2,594,803		$	5.92			6.7			19,315



	-1	This represents the number of vested options as of December 31, 2014, plus the number of unvested options expected to vest as of December 31, 2014, based on the unvested options at December 31, 2014, adjusted for the estimated forfeiture rate of 5%.
Stock-Based Compensation Expense Related to All Stock-Based Awards Recognized in Statements of Operations and Comprehensive Loss	Total compensation cost recognized for all stock-based compensation awards in the consolidated statements of operations and comprehensive loss is as follows (in thousands):



			For the Year Ended December 31,
			2014			2013			2012
	Research and development		$	802		$	583		$	564
	General and administrative			891			420			304

	Total stock-based compensation expense		$	1,693		$	1,003		$	868

Schedule of Common Stock Reserved	The Company had reserved the following shares of common stock as of December 31, 2014 for the potential exercise of outstanding warrants and stock options:



			December 31,
			2014
	Warrants			70,796
	Common stock options			3,824,891

	Shares reserved for issuance at December 31, 2014			3,895,687

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Reconciliation of Federal Statutory Income Tax Rate and Effective Income Tax Rate	A reconciliation of the federal statutory income tax rate and the Company’s effective income tax rate is as follows:



		Year ended December 31,
		2014			2013			2012
	Federal statutory income tax rate		34.0	%		34	%		34	%
	State income taxes		5.3			5.3			5.3
	Change in valuation allowance		(41.0	)		(43.3	)		(34.9	)
	Research and development credits		4.5			31.7			1.2
	Permanent items		(0.7	)		(5.9	)		(1.8	)
	Expiring state net operating loss carryforward		(2.1	)		(21.8	)		(3.8	)

	Effective income tax rate		0.0	%		0	%		0	%

Significant Components of Net Deferred Tax Assets	The significant components of the Company’s net deferred tax assets consist of the following (in thousands):



		December 31,
		2014			2013
	Net operating loss carryforwards	$	44,186		$	38,585
	Deferred revenue		6,215			1,081
	Research and development credit carryforwards		7,728			6,277
	Other		1,863			1,043

			59,992			46,986
	Valuation allowance		(59,992	)		(46,986	)

	Net deferred tax assets	$	—		$	—

Commitments_Tables

Commitments (Tables)	12 Months Ended
Commitments (Tables)	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Lease Payments	The future minimum lease payments under the 2008 Lease Agreement, as amended, is as follows (in thousands):


		Base rent obligations
	At December 31, 2014
	2015	$	1,540
	2016		1,522
	2017		1,573
	2018		1,208

	Total minimum lease payments	$	5,843

Loan_Payable_and_Warrant_to_Pu1

Loan Payable and Warrant to Purchase Redeemable Securities (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Schedule of Future Minimum Payments Due Under Loan and Security Agreement	As of December 31, 2014, the future minimum payments due under the Loan and Security Agreement are as follows (in thousands):


		Year			Minimum
		Year			Payments
			2015			7,462
	Less amounts representing interest					(287	)

	Present value of minimum payments					7,175
	Less discount					(74	)

	Loan payable and unamortized discount				$	7,101

Summary of Changes in Fair value of Warrant	The following table sets forth a summary of changes in the fair value of the Warrant during each period presented (in thousands):



		Year ended
		December 31,
		2014			2013			2012
	Beginning balance	$	463		$	459		$	168
	Change in fair value		117			4			291
	Reclassification to additional paid-in capital in connection with IPO		(580	)		—			—

	Ending balance	$	—		$	463		$	459

Weighted-average Assumptions Used for Estimated Fair Value of Warrant Under Black-Scholes-Merton Option Pricing Model	Where the fair value of the Warrant was estimated using the Black-Scholes-Merton option pricing model, the Company used the following weighted-average assumptions:



		Year ended
		December 31,
		2014			2013			2012
	Expected volatility		70	%		70	%		70	%
	Expected term		5.0 years			5.3 years			7.9 years
	Risk-free interest rate		1.53	%		1.75	%		0.95	%
	Expected dividend yield		0.0	%		0	%		0	%

Quarterly_Financial_Informatio1

Quarterly Financial Information (unaudited) (Tables)	12 Months Ended
Quarterly Financial Information (unaudited) (Tables)	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (unaudited)
		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2014			2014			2014			2014
		(in thousands, except per share data)
		(unaudited)
	Revenue	$	1,613		$	1,235		$	4,418		$	1,310
	Operating expenses		8,132			8,961			12,026			10,055

	Loss from operations		(6,519	)		(7,726	)		(7,608	)		(8,745	)
	Other expense, net		(431	)		(264	)		(224	)		(182	)

	Net loss	$	(6,950	)	$	(7,990	)	$	(7,832	)	$	(8,927	)

	Net loss per share—basic and diluted	$	(0.76	)	$	(0.45	)	$	(0.43	)	$	(0.49	)


		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2013			2013			2013			2013
		(in thousands, except per share data)
		(unaudited)
	Revenue	$	5,873		$	17,441		$	681		$	1,413
	Operating expenses		7,003			8,026			7,797			6,992

	(Loss) income from operations		(1,130	)		9,415			(7,116	)		(5,579	)
	Other expense, net		(649	)		(650	)		(11	)		(336	)

	Net (loss) income	$	(1,779	)	$	8,765		$	(7,127	)	$	(5,915	)

	Net loss per share—basic and diluted	$	(1.46	)	$	0		$	(5.59	)	$	(4.64	)

Nature_of_Business_Additional_

Nature of Business - Additional Information (Detail) (USD $)	0 Months Ended		3 Months Ended	12 Months Ended
	Feb. 19, 2014	Jan. 29, 2014	Mar. 31, 2014	Dec. 31, 2014	Feb. 28, 2014	Dec. 31, 2013
Subsidiary, Sale of Stock [Line Items]
Net proceeds of IPO				$86,579,000
Reverse stock split of common stock, ratio		0.17699115
Conversion of preferred stock into shares of common stock	9,919,821		9,919,821
Common stock warrant issued upon on conversion of preferred stock			70,796
Warrants to purchase shares of common stock, exercise price per share			$14.13		$14.13
Common stock, shares outstanding				18,234,068		1,298,300
Cash and cash equivalents and investments				79,200,000
Series C Preferred Stock Warrants [Member]
Subsidiary, Sale of Stock [Line Items]
Number of stock converted			400,000
IPO [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, issued			6,649,690
Common stock price per share			$14
Net proceeds of IPO			$83,100,000

Basis_of_Presentation_and_Sign3

Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended	12 Months Ended
	Feb. 19, 2014	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
	Feb. 19, 2014	Mar. 31, 2014	Segment	Dec. 31, 2013
Schedule Of Accounting Policies [Line Items]
Number of segments			1
Cash equivalents, liquid investments maturity period			90 days
Realized gains or losses on sales of investments			$0	$0
Other than temporary impairment losses, investments			0	0
Impairment losses			$0
Lease expiration date			2018
Conversion of preferred stock into shares of common stock	9,919,821	9,919,821
IPO [Member]
Schedule Of Accounting Policies [Line Items]
Common stock, issued		6,649,690

Basis_of_Presentation_and_Sign4

Basis of Presentation and Significant Accounting Policies - Cash, Cash Equivalents and Investments (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$13,396	$9,638	$7,490	$22,949
Cash and cash equivalents, Fair value	13,396	9,638
Investments, Amortized cost	65,850	23,035
Investments, Unrealized gains	1	4
Investments, Unrealized losses	-15
Investments, Fair value	65,836	23,039
Cash [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	1,492	2,188
Cash and cash equivalents, Fair value	1,492	2,188
Money Market Funds Included in Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	11,904	7,450
Cash and cash equivalents, Fair value	11,904	7,450
U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Average maturity	171 days	301 days
Investments, Amortized cost	12,037	500
Investments, Unrealized gains	-2
Investments, Fair value	12,035	500
Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Average maturity	194 days	324 days
Investments, Amortized cost	53,813	22,535
Investments, Unrealized gains	3	4
Investments, Unrealized losses	-15
Investments, Fair value	$53,801	$22,539

Basis_of_Presentation_and_Sign5

Basis of Presentation and Significant Accounting Policies - Financial Assets and Liabilities Recognized at Fair Value (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, Fair value	$13,396	$9,638
Investments, available for sale	65,836	23,039
Financial assets at fair value	77,740	30,489
Money Market Funds Included in Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, Fair value	11,904	7,450
U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, available for sale	12,035	500
Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, available for sale	53,801	22,539
Warrant to Purchase Redeemable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities at fair value		463
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets at fair value	77,740	30,489
Level 1 [Member] \| Money Market Funds Included in Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, Fair value	11,904	7,450
Level 1 [Member] \| U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, available for sale	12,035	500
Level 1 [Member] \| Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, available for sale	53,801	22,539
Level 3 [Member] \| Warrant to Purchase Redeemable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities at fair value		$463

Basis_of_Presentation_and_Sign6

Basis of Presentation and Significant Accounting Policies - Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Detail)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of earning per share	2,760	11,944	11,951
Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of earning per share		9,920	9,920
Warrant [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of earning per share	71	71	71
Outstanding Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of earning per share	2,689	1,953	1,960

Restricted_Cash_Additional_Inf

Restricted Cash - Additional Information (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$400	$706
Stand-by Letter of Credit [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$400	$700

Property_and_Equipment_Schedul

Property and Equipment - Schedule of Property and Equipment (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$8,199	$8,119
Less accumulated depreciation and amortization	-5,915	-5,646
Total property, plant and equipment, net	2,284	2,473
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	5 years
Property, plant and equipment, gross	1,544	2,062
Computer, Telephone and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	3 years
Property, plant and equipment, gross	175	143
Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	3 years
Property, plant and equipment, gross	88	66
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	Lesser of useful life or remaining lease term
Property, plant and equipment, gross	$6,392	$5,848

Property_and_Equipment_Additio

Property and Equipment - Additional Information (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property Plant And Equipment Capitalized Interest Costs [Abstract]
Depreciation and amortization expense	$1,052	$1,346	$1,452

Accrued_Expenses_and_Other_Lia2

Accrued Expenses and Other Liabilities - Accrued Expenses and Other Liabilities (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Payables and Accruals [Abstract]
Accrued professional fees and other	$916	$569
Employee compensation and benefits	1,606	290
Research and development expenses	2,104	860
Deferred lease incentive, current portion	308	513
Deferred rent, current portion	68	243
Accrued expenses and other liabilities	$5,002	$2,475

Redeemable_Convertible_Preferr2

Redeemable Convertible Preferred Stock - Additional Information (Detail)	0 Months Ended	3 Months Ended
	Feb. 19, 2014	Mar. 31, 2014	Dec. 31, 2014
Temporary Equity [Line Items]
Conversion of preferred stock into shares of common stock	9,919,821	9,919,821
Preferred stock, shares authorized			5,000,000
Preferred stock, shares issued			0
Preferred stock, shares outstanding			0
IPO [Member]
Temporary Equity [Line Items]
Preferred stock, shares authorized	5,000,000

Redeemable_Convertible_Preferr3

Redeemable Convertible Preferred Stock - Schedule of Convertible Preferred Stock (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Temporary Equity [Line Items]
Preferred shares authorized	0	62,916,667
Preferred shares issued	0	56,047,067
Preferred shares outstanding	0	56,047,067
Redemption value		$112,993
Liquidation preference		112,993
Carrying value		112,244
Common stock issuable upon conversion		9,920,000
Series A Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred shares authorized		10,000,000
Preferred shares issued		10,000,000
Preferred shares outstanding		10,000,000
Redemption value		10,000
Liquidation preference		10,000
Carrying value		9,993
Common stock issuable upon conversion		1,770,000
Series B Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred shares authorized		24,250,000
Preferred shares issued		24,250,000
Preferred shares outstanding		24,250,000
Redemption value		48,500
Liquidation preference		48,500
Carrying value		48,488
Common stock issuable upon conversion		4,292,000
Series C Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred shares authorized		22,000,000
Preferred shares issued		15,130,000
Preferred shares outstanding		15,130,000
Redemption value		37,826
Liquidation preference		37,826
Carrying value		37,809
Common stock issuable upon conversion		2,678,000
Series D Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred shares authorized		6,667,000
Preferred shares issued		6,667,000
Preferred shares outstanding		6,667,000
Redemption value		16,667
Liquidation preference		16,667
Carrying value		$15,954
Common stock issuable upon conversion		1,180,000

Stock_Compensation_Additional_

Stock Compensation - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 19, 2014	Jan. 01, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value of options granted	$6.69	$13.77	$6.53
Expected dividend yield	0.00%	0.00%	0.00%
Estimated forfeiture rate	5.00%	5.00%	5.00%
Intrinsic value of stock options exercised	$2,400,000	$100,000	$0
Cash received from options exercised	1,000,000	32,000	0
Total grant date fair value of stock options that vested during the period	600,000	900,000	900,000
Total unrecognized compensation cost related to unvested options	$7,200,000
Total unrecognized compensation cost related to unvested options, weighted-average recognition period	3 years 1 month 6 days
2014 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance	1,135,954	2,249,911		2,249,911
Increase in shares of common stock				2,000,000
Percentage of common stock outstanding				4.00%
2014 Stock Incentive Plan [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for future issuance					729,363
Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for future issuance	2,212,389

Stock_Compensation_Schedule_of

Stock Compensation - Schedule of Shares Available for Future Grant Under 2014 Plan (Detail) (2014 Stock Incentive Plan [Member])	12 Months Ended
	Dec. 31, 2014	Feb. 19, 2014
2014 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future grant beginning balance	2,249,911	2,249,911
Add: stock options and restricted stock awards forfeited or expired under plans	68,186
Less: stock options and awards granted from February 19, 2014 to December 31, 2014	-1,182,143
Shares reserved for future grant Ending balance	1,135,954	2,249,911

Stock_Compensation_Estimated_W

Stock Compensation - Estimated Weighted-Average Assumptions of Options Granted (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Expected volatility	80.94%	70.10%	72.80%
Expected term (in years)	6 years	6 years	6 years
Risk-free interest rate	1.90%	1.69%	0.95%
Expected dividend yield	0.00%	0.00%	0.00%

Stock_Compensation_Summary_of_

Stock Compensation - Summary of Stock Option Activity (Detail) (2006 And 2014 Stock Incentive Plan [Member], USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014
2006 And 2014 Stock Incentive Plan [Member]
Number of options
Number of options, Outstanding beginning balance	1,952,578
Number of options, Granted	1,182,143
Number of options, Exercised	-366,258
Number of options, Forfeited or expired	-79,526
Number of options, Outstanding ending balance	2,688,937
Number of options, Exercisable	1,425,925
Number of options, Vested and expected to vest	2,594,803	[1]
Weighted average exercise price per share
Weighted average exercise price per share, Outstanding at beginning of year	$3.14
Weighted average exercise price per share, Granted	$9.68
Weighted average exercise price per share, Exercised	$2.76
Weighted average exercise price per share, Forfeited or expired	$4.08
Weighted average exercise price per share, Outstanding ending balance	$6.04
Weighted average exercise price per share, Exercisable	$3.27
Weighted average exercise price per share, Vested and expected to vest	$5.92	[1]
Weighted average remaining contractual term (Years)
Weighted average remaining contractual term, Outstanding	6 years 9 months 15 days
Weighted average remaining contractual term, Exercisable	4 years 7 months 2 days
Weighted average remaining contractual term, Vested and expected to vest	6 years 8 months 12 days	[1]
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding	$19,699
Aggregate Intrinsic Value, Exercisable	14,329
Aggregate Intrinsic Value, Vested and expected to vest	$19,315	[1]

[1]	This represents the number of vested options as of December 31, 2014, plus the number of unvested options expected to vest as of December 31, 2014, based on the unvested options at December 31, 2014, adjusted for the estimated forfeiture rate of 5%.

Stock_Compensation_Summary_of_1

Stock Compensation - Summary of Stock Option Activity (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award Options [Line Items]
Estimated forfeiture rate	5.00%	5.00%	5.00%
2006 And 2014 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award Options [Line Items]
Estimated forfeiture rate	5.00%

Stock_Compensation_StockBased_

Stock Compensation - Stock-Based Compensation Expense Related to All Stock-Based Awards Recognized in Statements of Operations and Comprehensive Loss (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$1,693	$1,003	$868
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	802	583	564
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$891	$420	$304

Stock_Compensation_Schedule_of1

Stock Compensation - Schedule of Common Stock Reserved (Detail)	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance	3,895,687
Warrant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance	70,796
Common Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance	3,824,891

Income_Taxes_Reconciliation_of

Income Taxes - Reconciliation of Federal Statutory Income Tax Rate and Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	34.00%	34.00%	34.00%
State income taxes	5.30%	5.30%	5.30%
Change in valuation allowance	-41.00%	-43.30%	-34.90%
Research and development credits	4.50%	31.70%	1.20%
Permanent items	-0.70%	-5.90%	-1.80%
Expiring state net operating loss carryforward	-2.10%	-21.80%	-3.80%
Effective income tax rate	0.00%	0.00%	0.00%

Income_Taxes_Significant_Compo

Income Taxes - Significant Components of Net Deferred Tax Assets (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$44,186	$38,585
Deferred revenue	6,215	1,081
Research and development credit carryforwards	7,728	6,277
Other	1,863	1,043
Gross deferred tax assets	59,992	46,986
Valuation allowance	-59,992	-46,986
Net deferred tax assets	$0	$0

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
Income Taxes - Additional Information (Detail) (USD $)	Dec. 31, 2014
Schedule Of Income Taxes [Line Items]
Minimum percentage of ownership interest related to income tax annual limitation	50.00%
Unrecognized tax benefits	$0
Accrued interest related to uncertain tax positions	0
Minimum [Member]
Schedule Of Income Taxes [Line Items]
Years under examination	2011
Maximum [Member]
Schedule Of Income Taxes [Line Items]
Years under examination	2013
Federal [Member]
Schedule Of Income Taxes [Line Items]
Operating loss carryforwards	119,500,000
State [Member]
Schedule Of Income Taxes [Line Items]
Operating loss carryforwards	67,600,000
Research and Development [Member] \| Federal [Member]
Schedule Of Income Taxes [Line Items]
Tax credit carryforwards	6,000,000
Research and Development [Member] \| State [Member]
Schedule Of Income Taxes [Line Items]
Tax credit carryforwards	$2,600,000

Commitments_Additional_Informa

Commitments - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Aug. 31, 2014	Dec. 22, 2011
	Employees	Dec. 31, 2013	Dec. 31, 2012	sqft	Dec. 22, 2011
Commitments [Line Items]
Line of credit facility					$20,000,000
Rent expense	1,000,000	700,000	700,000
Accrued severance and benefit obligation		300,000
Number of employees covered by employment agreements	5
Cash payment related to obligation		69,000
liability related to obligation		300,000
Severance and benefit description	Under these agreements, the executives could be entitled to severance pay up to 12 months of base salary, paid COBRA insurance coverage for 12 months and acceleration of stock option vesting (assuming for such acceleration a termination without cause or on death or disability or resignation for good reason within one year after a change in control).
Two Thousand and Eight Lease Agreement [Member]
Commitments [Line Items]
Operating lease, area	45,000
Operating lease, term	7 years
Number of tenant allowances	2
Two Thousand and Eight Lease Agreement [Member] \| Office Space and HVAC Systems [Member]
Commitments [Line Items]
Tenant improvement allowance	3,700,000
Two Thousand and Eight Lease Agreement [Member] \| Laboratory [Member]
Commitments [Line Items]
Tenant improvement allowance	2,300,000
Lease interest rate	10.00%
Amendment of Lease [Member]
Commitments [Line Items]
Operating lease, area				45,000
Additional space for office				5,000
Lease expiration date				30-Sep-18
Leasehold improvement	300,000
Line of credit facility	400,000
Amendment of Lease [Member] \| Scenario, Previously Reported [Member]
Commitments [Line Items]
Line of credit facility	700,000
Amendment of Lease [Member] \| Property, Plant and Equipment, Other Types [Member]
Commitments [Line Items]
Tenant improvement allowance	$400,000

Commitments_Future_Minimum_Lea

Commitments - Future Minimum Lease Payments (Detail) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
2015	$1,540
2016	1,522
2017	1,573
2018	1,208
Total minimum lease payments	$5,843

Collaboration_Agreements_Celge

Collaboration Agreements - Celgene - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 30, 2013
				Option
				Licensed_Program
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue, current portion	$5,955,000	$4,321,000
Revenue recognized	2,000,000	2,000,000	1,500,000
Deferred revenue, net of current portion	9,866,000	15,310,000
Celgene [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of additional license program				2
Number of options for providing license program				1
Deferred revenue, current portion	5,800,000
Percentage of royalty on net sales required to pay under the agreement				20.00%
Royalty term				10 years
Arrangement consideration allocated to the License Deliverable, recognition period				39 months
Deferred revenue	12,900,000
Deferred revenue, net of current portion	7,100,000
Celgene [Member] \| Non-refundable Upfront Payment Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue, payment received				35,000,000
Celgene [Member] \| License Deliverable [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Allocated arrangement consideration				17,000,000
Celgene [Member] \| R&D Services Deliverable [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Allocated arrangement consideration				8,700,000
Revenue recognized	1,800,000	700,000
Celgene [Member] \| Supply Deliverable [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Allocated arrangement consideration				3,200,000
Revenue recognized	1,900,000	600,000
Celgene [Member] \| Joint Steering Committee Deliverable [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Allocated arrangement consideration				100,000
Revenue recognized	32,000	24,000
Celgene [Member] \| First Discount Deliverable [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Allocated arrangement consideration				3,000,000
Celgene [Member] \| Second Discount Deliverable [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Allocated arrangement consideration				3,000,000
Celgene [Member] \| Initial Program [Member] \| Phase 1 Clinical Trial [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				8,000,000
Celgene [Member] \| If Celgene Exercises its Option With Respect to the Option Program [Member] \| Sales-based Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue, current portion				10,000,000
Celgene [Member] \| If Celgene Exercises its Rights With Respect to Either of the Two Additional License Programs [Member] \| License Exercise Fee [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue, current portion				30,000,000
Celgene [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expiry period of license exercise fee				7 years
Non-refundable upfront payment				35,000,000
Celgene [Member] \| Maximum [Member] \| Initial Program [Member] \| Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				23,000,000
Celgene [Member] \| Maximum [Member] \| Initial Program [Member] \| Regulatory Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				247,500,000
Celgene [Member] \| Maximum [Member] \| Initial Program [Member] \| Sales-based Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				50,000,000
Celgene [Member] \| Maximum [Member] \| If Celgene Exercises its Option With Respect to the Option Program [Member] \| Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				23,000,000
Celgene [Member] \| Maximum [Member] \| If Celgene Exercises its Option With Respect to the Option Program [Member] \| Regulatory Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				247,500,000
Celgene [Member] \| Maximum [Member] \| One of the Additional License Programs [Member] \| Sales-based Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				50,000,000
Celgene [Member] \| Maximum [Member] \| If Celgene Exercises its Rights With Respect to Either of the Two Additional License Programs [Member] \| Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				23,000,000
Celgene [Member] \| Maximum [Member] \| If Celgene Exercises its Rights With Respect to Either of the Two Additional License Programs [Member] \| Regulatory Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				247,500,000
Celgene [Member] \| Maximum [Member] \| If Celgene Exercises its Rights With Respect to Either of the Two Additional License Programs [Member] \| Sales-based Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				100,000,000

Collaboration_Agreements_Jazz_

Collaboration Agreements - Jazz Pharmaceuticals - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 28, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized	$2,000,000	$2,000,000	$1,500,000
Jazz Pharmaceuticals [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of royalty on net sales required to pay under the agreement				20.00%
Royalty term				10 years
Arrangement consideration allocated to the License Deliverable, recognition period				46 months
Jazz Pharmaceuticals [Member] \| Phase 1 Clinical Trial [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				4,000,000
Jazz Pharmaceuticals [Member] \| Non-refundable Upfront Payment Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue, payment received				4,000,000
Jazz Pharmaceuticals [Member] \| License Deliverable [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Allocated arrangement consideration				3,700,000
Revenue recognized		3,700,000
Jazz Pharmaceuticals [Member] \| Joint Steering Committee Deliverable [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Allocated arrangement consideration				100,000
Revenue recognized	56,000	61,000
Jazz Pharmaceuticals [Member] \| Patent Support Deliverable [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Allocated arrangement consideration				200,000
Revenue recognized	56,000	61,000
Jazz Pharmaceuticals [Member] \| Development Milestone [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				8,000,000
Jazz Pharmaceuticals [Member] \| Regulatory Milestones [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				35,000,000
Jazz Pharmaceuticals [Member] \| Sales-based Milestone [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				70,000,000
Jazz Pharmaceuticals [Member] \| Development Support Services [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized	$2,600,000	$1,100,000

Collaboration_Agreements_Avani

Collaboration Agreements - Avanir - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 29, 2012	Mar. 31, 2012	31-May-12
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized	$2,000,000	$2,000,000	$1,500,000
Avanir Pharmaceuticals [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable	2,000,000	2,000,000
Percentage of royalty on net sales required to pay under the agreement				20.00%
Royalty term				10 years
Avanir Pharmaceuticals [Member] \| Phase 3 Clinical Trial [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				2,000,000
Avanir Pharmaceuticals [Member] \| Phase 2 Clinical Trial [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized	2,000,000
Avanir Pharmaceuticals [Member] \| Phase 1 Clinical Trial [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized		2,000,000
Avanir Pharmaceuticals [Member] \| Licensed Products [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				43,000,000
Avanir Pharmaceuticals [Member] \| Joint Steering Committee Deliverable [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Allocated arrangement consideration				2,000,000
Avanir Pharmaceuticals [Member] \| Reimbursements of Travel and Intellectual Property Expenses [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized	200,000	200,000	200,000
Avanir Pharmaceuticals [Member] \| Non-refundable Upfront Payment Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue, payment received				2,000,000
Avanir Pharmaceuticals [Member] \| Non-refundable Upfront Payment Arrangement [Member] \| Joint Steering Committee Deliverable [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized					2,000,000
Avanir Pharmaceuticals [Member] \| Revenue from Upfront License Fees [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized			2,000,000
Avanir Pharmaceuticals [Member] \| Maximum [Member] \| Development Milestone [Member] \| Phase 3 Clinical Trial [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				2,000,000
Avanir Pharmaceuticals [Member] \| Maximum [Member] \| Regulatory and Commercial Launch Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				37,000,000
Avanir Pharmaceuticals [Member] \| Maximum [Member] \| Sales-based Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payments receivable				125,000,000
GSK [Member] \| Amendment to GSK Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue, payment received						$2,750,000

Sponsored_Research_Agreement_A

Sponsored Research Agreement - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended
	Feb. 29, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Soft Dollar Arrangements [Abstract]
Fund provided for preclinical advancement	$800,000	$0	$45,000	$700,000

Loan_Payable_and_Warrant_to_Pu2

Loan Payable and Warrant to Purchase Redeemable Securities - Additional Information (Detail) (USD $)	0 Months Ended		1 Months Ended	12 Months Ended
	Mar. 29, 2012	Dec. 22, 2011	Feb. 28, 2014	Dec. 31, 2014	Mar. 31, 2014
	Mar. 29, 2012	Tranches	Feb. 28, 2014	MonthlyInstallments	Mar. 31, 2014
Debt Instrument [Line Items]
Aggregate advance provided under the agreement		$20,000,000
Number of tranches		2
Loan issuance cost paid to lenders	200,000
Debt instrument, annum interest rate				8.50%
Debt instrument, description of interest rate				Each advance made under the Loan and Security Agreement bears interest at a variable rate of the greater of 8.5% and an amount equal to 8.5% plus the prime rate of interest minus 5.25%, provided however, that the per annum interest rate shall not exceed 11%. Through December 31, 2014, each of the December 2011 Advance and the March 2012 Advance had an interest rate of 8.5%.
Debt instrument maturity date, start date				1-May-13
Debt instrument maturity date, end date				1-Oct-15
Debt instrument, number of equal monthly installments				30
Warrant to purchase preferred stock, shares					70,796
Warrant exercise price per share			$14.13		$14.13
Warrant exercisable			70,796
Warrant expiration description				(i) ten years from the effective date of the Loan and Security Agreement or (ii) five years after the closing of an IPO.
Expected dividend yield				0.00%
Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, annum interest rate				11.00%
Series C Preferred Stock [Member] \| December 2011 Advance [Member]
Debt Instrument [Line Items]
Warrant to purchase preferred stock, shares				200,000
Warrant exercise price per share				2.5
Series C Preferred Stock [Member] \| March 2012 Advance [Member]
Debt Instrument [Line Items]
Warrant to purchase preferred stock, shares				200,000
Warrant exercise price per share				2.5
Prime Rate [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, variable rate				8.50%
First Tranche [Member]
Debt Instrument [Line Items]
Advance made under the tranche		7,500,000
Second Tranche [Member]
Debt Instrument [Line Items]
Advance made under the tranche	$12,500,000

Loan_Payable_and_Warrant_to_Pu3

Loan Payable and Warrant to Purchase Redeemable Securities - Schedule of Future Minimum Payments Due Under Loan and Security Agreement (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014
Receivables [Abstract]
Minimum payments due 2015	$7,462
Less amounts representing interest	-287
Present value of minimum payments	7,175
Less discount	-74
Loan payable and unamortized discount	$7,101

Loan_Payable_and_Warrant_to_Pu4

Loan Payable and Warrant to Purchase Redeemable Securities - Summary of Changes in Fair value of Warrant (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity Method Investments And Cost Method Investments [Abstract]
Beginning balance	$463	$459	$168
Change in fair value	117	4	291
Reclassification to additional paid-in capital in connection with IPO	-580
Ending balance		$463	$459

Loan_Payable_and_Warrant_to_Pu5

Loan Payable and Warrant to Purchase Redeemable Securities - Estimated Weighted-Average Assumptions of Warrant (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Expected dividend yield	0.00%
Warrant [Member]
Schedule Of Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Expected volatility	70.00%	70.00%	70.00%
Expected term (in years)	5 years	5 years 3 months 18 days	7 years 10 months 24 days
Risk-free interest rate	1.53%	1.75%	0.95%
Expected dividend yield	0.00%	0.00%	0.00%

401k_Retirement_Plan_Additiona

401(k) Retirement Plan - Additional Information (Detail) (401(k) Plan [Member], USD $)	1 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jan. 31, 2008	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
401(k) Plan [Member]
Major Funded Pension Plans Postretirement And Other Employee Benefits [Line Items]
Matching contribution of employer	50.00%
Percentage of employees covered	6.00%
Contributions to employee benefits plan		$0.20	$0.20	$0.20

Quarterly_Results_of_Operation

Quarterly Results of Operations (Unaudited) - Unaudited Quarterly Results of Operations (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Revenue	$1,310	$4,418	$1,235	$1,613	$1,413	$681	$17,441	$5,873
Operating expenses	10,055	12,026	8,961	8,132	6,992	7,797	8,026	7,003	39,174	29,818	31,459
(Loss) income from operations	-8,745	-7,608	-7,726	-6,519	-5,579	-7,116	9,415	-1,130	-30,598	-4,410	-18,610
Other expense, net	-182	-224	-264	-431	-336	-11	-650	-649
Net loss	($8,927)	($7,832)	($7,990)	($6,950)	($5,915)	($7,127)	$8,765	($1,779)	($31,699)	($6,056)	($20,444)
Net loss per share-basic and diluted	($0.49)	($0.43)	($0.45)	($0.76)	($4.64)	($5.59)	$0	($1.46)	($2)	($4.99)	($16.15)