Concert Pharmaceuticals (CNCE) 10-K 28 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Feb. 22, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	CNCE
Entity Registrant Name	CONCERT PHARMACEUTICALS, INC.
Entity Central Index Key	1,367,920
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Small Business	true
Entity Common Stock, Shares Outstanding		23,529,253
Entity Public Float			$ 257,489

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 17,770	$ 27,665
Investments, available for sale	135,544	175,500
Marketable equity securities	7,525	0
Interest receivable	556	628
Accounts receivable	15	155
Contract asset (Note 12)	16,000	0
Prepaid expenses and other current assets	2,739	1,786
Total current assets	180,149	205,734
Property and equipment, net	8,919	2,165
Restricted cash	1,157	1,557
Other assets	0	34
Income taxes receivable	2,322	2,246
Total assets	192,547	211,736
Current liabilities:
Accounts payable	1,277	658
Accrued expenses and other liabilities	5,669	4,299
Income taxes payable	390	46
Deferred revenue, current portion	1,413	1,442
Total current liabilities	8,749	6,445
Deferred revenue, net of current portion	9,120	8,859
Deferred lease incentive, net of current portion	4,088	0
Deferred rent, net of current portion	2,850	0
Total liabilities	24,807	15,304
Commitments (Note 11)
Stockholders’ equity:
Preferred stock, $0.001 par value per share; 5,000,000 shares authorized; no shares issued and outstanding in 2018 and 2017, respectively	0	0
Common stock, $0.001 par value per share; 100,000,000 shares authorized; 23,518,690 and 23,147,779 shares issued and 23,437,587 and 23,140,378 outstanding in 2018 and 2017, respectively	23	23
Additional paid-in capital	284,369	273,059
Accumulated other comprehensive loss	(137)	(407)
Accumulated deficit	(116,515)	(76,243)
Total stockholders’ equity	167,740	196,432
Total liabilities and stockholders’ equity	$ 192,547	$ 211,736

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	23,518,690	23,147,779
Common stock, shares outstanding (in shares)	23,437,587	23,140,378

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue:
Total revenue	$ 10,505,000	$ 143,891,000	$ 174,000
Operating expenses:
Research and development	43,149,000	30,223,000	36,983,000
General and administrative	22,940,000	21,019,000	14,358,000
Total operating expenses	66,089,000	51,242,000	51,341,000
(Loss) Income from operations	(55,584,000)	92,649,000	(51,167,000)
Investment income	2,787,000	1,336,000	447,000
Other income (Note 14)	12,000	3,601,000	0
Interest and other expense	0	(815,000)	0
Loss on extinguishment of debt (Note 13)	0	(1,432,000)	0
Unrealized loss on marketable equity securities (Note 12)	(2,926,000)	0	0
(Loss) Income before income taxes	(55,711,000)	95,339,000	(50,720,000)
Provision (Benefit) for income taxes	313,000	(300,000)	0
Net loss	(56,024,000)	95,639,000	(50,720,000)
Other comprehensive income (loss):
Unrealized gain (loss) on investments, net of tax of $76 in 2018	270,000	(400,000)	11,000
Comprehensive (loss) income	(55,754,000)	95,239,000	(50,709,000)
Net (loss) income attributable to common stockholders:
Basic	(56,024,000)	95,195,000	(50,720,000)
Diluted	$ (56,024,000)	$ 95,210,000	$ (50,720,000)
Net (loss) income per share attributable to common stockholders:
Basic (in dollars per share)	$ (2.40)	$ 4.20	$ (2.28)
Diluted (in dollars per share)	$ (2.40)	$ 4.06	$ (2.28)
Weighted-average number of common shares used in net (loss) income per share attributable to common stockholders:
Basic (in shares)	23,370	22,641	22,233
Diluted (in shares)	23,370	23,442	22,233
License and Research and Development Revenue
Revenue:
Total revenue	$ 10,505,000	$ 62,000	$ 174,000
Product and Service, Other
Revenue:
Total revenue	$ 0	$ 143,829,000	$ 0

Consolidated Statements of Op_2

Consolidated Statements of Operations and Comprehensive Income (Loss) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Income Statement [Abstract]
Unrealized gain (loss) on investments, tax	$ 76

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	In Treasury	Additional paid-in capital	Accumulated other comprehensive income	Accumulated deficit
Beginning balance (in shares) at Dec. 31, 2015		22,167	2
Beginning balance at Dec. 31, 2015	$ 130,635	$ 22		$ 251,793	$ (18)	$ (121,162)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		153	1
Exercise of stock options	601	$ 0		601
Unrealized gain on short-term investments	11				11
Stock-based compensation expense	5,067			5,067
Net income (loss)	(50,720)					(50,720)
Ending balance (in shares) at Dec. 31, 2016		22,320	3
Ending balance at Dec. 31, 2016	85,594	$ 22		257,461	(7)	(171,882)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		828	5
Exercise of stock options	6,587	$ 1		6,586
Unrealized gain on short-term investments	(400)				(400)
Stock-based compensation expense	8,500			8,500
Issuance of stock warrants	512			512
Net income (loss)	95,639					95,639
Ending balance (in shares) at Dec. 31, 2017		23,148	8
Ending balance at Dec. 31, 2017	196,432	$ 23		273,059	(407)	(76,243)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		197	21
Exercise of stock options	1,016	$ 0		1,016
Release of restricted stock units (in shares)		174	52
Release of restricted stock units	(1,206)			(1,206)
Unrealized gain on short-term investments	270				270
Stock-based compensation expense	11,500			11,500
Net income (loss)	(56,024)					(56,024)
Ending balance (in shares) at Dec. 31, 2018		23,519	81
Ending balance at Dec. 31, 2018	$ 167,740	$ 23		$ 284,369	$ (137)	$ (116,515)

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Statement of Stockholders' Equity [Abstract]
Unrealized gain (loss) on investments, tax	$ 76

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Net (loss) income	$ (56,024)	$ 95,639	$ (50,720)
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization	1,247	1,008	893
Stock-based compensation expense	11,500	8,500	5,067
Accretion of premiums and discounts on investments	(469)	90	504
Amortization of discount on loan payable	0	166	0
Amortization of deferred lease incentive	(703)	(324)	(315)
Noncash license consideration (Note 12)	(10,451)	0	0
Other noncash items	(77)	0	0
Unrealized loss on marketable equity securities (Note 12)	2,926	0	0
Loss on disposal of asset	52	46	2
Loss on extinguishment of debt	0	1,432	0
Changes in operating assets and liabilities:
Accounts receivable	119	(107)	43
Interest receivable	72	(464)	17
Prepaid expenses and other current assets	(953)	(433)	314
Other assets	34	33	11
Accounts payable	435	113	44
Accrued expenses and other liabilities	1,265	436	(957)
Income taxes receivable	(76)	(2,246)	0
Income taxes payable	344	46	(75)
Deferred rent	2,746	(102)	(51)
Deferred revenue	(16)	251	(120)
Net cash (used in) provided by operating activities	(48,029)	104,084	(45,343)
Investing activities
Purchases of property and equipment	(2,869)	(947)	(770)
Purchases of investments	(99,435)	(206,207)	(132,344)
Maturities of investments	140,207	85,847	125,901
Net cash provided by (used in) investing activities	37,903	(121,307)	(7,213)
Financing activities
Proceeds from loan, net	0	29,659	0
Repayment of loan	0	(30,745)	0
Repurchase of common stock pursuant to share surrender	(1,206)	0	0
Proceeds from exercise of stock options	1,037	6,576	601
Net cash (used in) provided by financing activities	(169)	5,490	601
Net decrease in cash, cash equivalents and restricted stock	(10,295)	(11,733)	(51,955)
Cash, cash equivalents and restricted stock at beginning of period	29,222	40,955	92,910
Cash, cash equivalents and restricted stock at end of period	18,927	29,222	40,955
Supplemental cash flow information:
Cash paid for income taxes	123	1,900	75
Cash paid for interest	0	648	0
Purchases of property and equipment unpaid at period end	188	65	20
Tenant Improvements paid by landlord (Note 11)	4,996	0	0
Issuance of stock warrants	$ 0	$ 512	$ 0

Nature of Business

Nature of Business	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Nature of Business	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 previously studied compounds, including approved drugs, 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 multiple clinical-stage candidates and a number of preclinical compounds that it is currently assessing. In March 2015, the Company sold 3,300,000 shares of common stock in a public offering at a price to the public of $15.15 per share, resulting in net proceeds to the Company of approximately $46.7 million after deducting underwriting discounts and commissions and offering expenses. In June 2015, the Company received a one-time payment of $50.2 million from Auspex Pharmaceuticals, Inc., or Auspex, pursuant to a patent assignment agreement between Concert and Auspex. Concert became eligible to receive the payment due to a change of control of Auspex, which was acquired by Teva Pharmaceutical Industries Ltd. in May 2015 (see Note 12). On March 3, 2017, the Company entered into an Asset Purchase Agreement (the "Asset Purchase Agreement") with Vertex Pharmaceuticals, Inc., through Vertex Pharmaceuticals (Europe) Limited ("Vertex"), pursuant to which the Company agreed to sell and assign CTP-656, now known as VX-561, and other cystic fibrosis assets of the Company, for up to $250 million subject to the satisfaction of certain closing conditions. On July 25, 2017, the transaction contemplated by the Asset Purchase Agreement closed and Vertex paid the Company $160 million in cash consideration, with $16 million to be held in escrow. Additional information concerning the sale of CTP-656 is discussed further in Note 12. The Company had cash and cash equivalents and investments of $153.3 million at December 31, 2018. The Company believes that its cash and cash equivalents and investments at December 31, 2018 will be sufficient to allow the Company to fund its current operating plan for at least the next twelve months from the date of issuance of the financial statements. The Company may pursue additional cash resources through public or private financings and by establishing collaborations with or licensing its technology to other companies and through other arrangements. Since its inception, the Company has generated an accumulated deficit of $116.5 million through December 31, 2018. The Company's operating results may fluctuate significantly from year to year, depending on the timing and magnitude of clinical trial and other development activities under its current development programs. Substantially all the Company's net losses have resulted from costs incurred in connection with its research and development programs and from general and administrative costs associated with its operations. The Company expects to continue to incur significant expenses and increasing operating losses for at least the next several years. The Company is subject to risks common to companies in the biotechnology industry, including, but not limited to, risks of failure or unsatisfactory results of nonclinical studies and clinical trials, the need to obtain additional financing to fund the future development of its pipeline, the need to obtain marketing approval for its product candidates, the need to successfully commercialize and gain market acceptance of its product candidates, dependence on key personnel, protection of proprietary technology, compliance with government regulations, development by competitors of technological innovations and ability to transition from pilot-scale manufacturing to large-scale production of products. Unless otherwise indicated, all amounts are in thousands except share and per share amounts.

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	Basis of Presentation and Significant Accounting Policies Basis of Presentation 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 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 subsidiaries. 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. Estimates and Uncertainties The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, equity, revenue, expenses and the disclosure of contingent assets and liabilities and the Company's ability to continue as a going concern. In preparing the consolidated financial statements, management used estimates in the following areas, among others: revenue recognition; income tax expense; stock-based compensation expense; accrued expenses; and the evaluation of the existence of conditions and events that raise substantial doubt regarding the Company’s ability to continue as a going concern. Actual results could differ from those estimates. 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 (loss). Premiums or discounts from par value are amortized to investment income over the life of the underlying investment. Although available to be sold to meet operating needs or otherwise, securities are generally held through maturity. The Company classifies all investments as current assets as these assets are readily available for use in current operations. The cost of securities sold is determined based on the specific identification method for purposes of recording realized gains and losses. During 2018 and 2017, there were no realized gains or losses on sales of investments, and no investments were adjusted for other than temporary declines in fair value. The Company reviews available-for-sale securities for other-than-temporary impairment whenever the fair value of an available-for-sale security is less than the amortized cost and evidence indicates that an available-for-sale security’s carrying amount is not recoverable within a reasonable period of time. Other-than-temporary impairments of investments are recognized in the consolidated statements of operations if the Company has experienced a credit loss, has the intent to sell the security, or if it is more likely than not that the Company will be required to sell the security before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with the Company’s investment policy, the severity and the duration of the impairment and changes in value subsequent to the end of the period. Marketable Equity Securities Marketable equity securities consist of the fair value of common shares of Processa held by the Company, as discussed further in Note 12. As discussed below in this Note 2, effective January 1, 2018 the Company prospectively adopted ASU 2016-01, resulting in the recognition of the effects of changes in fair value of equity securities within net income. The Company reviews investments in marketable securities for other-than-temporary impairment whenever the fair value of the investment is less than the cost and evidence indicates that an investment’s carrying amount is not recoverable within a reasonable period of time. To determine whether an impairment is other-than-temporary, the Company considers whether it has an intent to sell, or whether it is more likely than not that the Company will be required to sell, the investment before recovery of the investment’s cost basis. Evidence considered in this assessment includes reasons for the impairment, the severity and the duration of the impairment and changes in value subsequent to year-end. Fair Value of Financial Measurements The Company has certain financial assets and liabilities that are recorded at fair value which have been classified as Level 1, 2 or 3 within the fair value hierarchy as described in the accounting standards for fair value measurements: • Level 1—quoted prices for identical instruments in active markets; • Level 2—quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all significant inputs and significant value drivers are observable in active markets; and • Level 3—valuations derived from valuation techniques in which one or more significant value drivers are unobservable. For additional information related to fair value measurements, please read Note 3 to the consolidated financial statements. Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentration of credit risk consist principally of money market funds, investments (including interest receivable), and accounts receivable. Our current investment policy is to maintain a diversified investment portfolio in U.S. government-backed securities and money market mutual funds consisting of U.S. government-backed securities. Our cash is deposited in and invested through highly rated financial institutions in North America. 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, 2018 and 2017, substantially all of the Company’s cash was deposited in accounts at two 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 generally 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. Leasehold improvements are amortized over the shorter of their useful life or the related lease term. 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, 2018. Rent Expense Rent expense for the year ended December 31, 2018 consists of the Company's previous facility at 99 Hayden Avenue, Lexington, Massachusetts, and the Company's new facility at 65 Hayden Avenue, Lexington, Massachusetts. The Company ceased recognizing rent expense for 99 Hayden Avenue when the lease expired on September 30, 2018. The Company began recognizing rent expense for 65 Hayden Avenue on January 1, 2018 when it obtained access to the premises. The Company's operating lease for its new facility at 65 Hayden Avenue in Lexington, Massachusetts 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 on January 1, 2029. Additionally, the Company has received certain lease incentives in connection with its existing Lexington, Massachusetts facility lease, which are recognized as a reduction to rent expense over the remaining lease term. Refer to Note 11 for additional details regarding the Company’s operating leases. Rent expense for the years ended December 31, 2018, 2017, and 2016 was $3.3 million , $1.1 million , and $1.2 million , respectively. 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. No liabilities for legal and other contingencies were accrued as of December 31, 2018 and 2017. Revenue Recognition The Company has generated revenue through arrangements with collaborators and nonprofit organizations for the development and commercialization of product candidates, a patent assignment agreement and an asset sale. On January 1, 2018, the Company adopted Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers and all related amendments ("ASC 606" or "the new revenue standard"). ASC 606 is a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most legacy revenue recognition guidance, including industry-s pecific guidance. The new revenue standard is based on the principle that an entity should recognize revenue to depict the transfer of 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, ASC 606 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. The new revenue standard also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts and costs to obtain or fulfill contracts. The Company applied ASC 606 on January 1, 2018 to all contracts using the modified retrospective approach. As a result of the adoption, the cumulative effect to retained earnings at January 1, 2018 was $15.8 million . The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The adoption of the new standard had an immaterial impact on the Company’s reported revenues, operating income and changes in operating cash flows for the twelve months ended December 31, 2018 as compared to what reported amounts would have been under legacy guidance. The cumulative effect of the changes made to the consolidated January 1, 2018 balance sheet for the adoption of the new revenue standard was as follows: (Amounts in thousands) Balance at December 31, 2017 ASC 606 Adjustments Opening Balance at January 1, 2018 Assets Contract Asset $ — $ 16,000 $ 16,000 Liabilities and Equity Deferred revenue, current portion $ 1,442 $ (14 ) $ 1,428 Deferred revenue, net of current portion 8,859 261 9,120 Retained earnings 76,243 15,753 60,490 The impact of adopting the new revenue standard primarily relates to the treatment of the consideration held in escrow under the Vertex Asset Purchase Agreement. Under previous authoritative guidance, the Company concluded that it would not recognize the Vertex escrow consideration until it was received. However, under ASC 606, the Vertex escrow consideration represents variable consideration and was included in the transaction price at contract inception, discussed further in Note 12. There was no material effect on the accounting for income taxes resulting from the adoption of ASC 606. 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. External research and development expenses associated with the Company’s programs include clinical trial site costs, research compounds and 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 and nonclinical programs. Internal costs of the Company’s clinical program include salaries, benefits, 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 and restricted-stock-units, or RSUs, 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 8 for additional information. 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. On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act (“TCJA”). This legislation made broad and complex changes to the U.S. tax code, including, but not limited to, (i) reducing the U.S. federal statutory tax rate from 35% to 21%; (ii) eliminating the corporate alternative minimum tax (AMT) and changing how existing AMT credits can be realized; (iii) changing rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017, and (iv) modifying the officer’s compensation limitation. The Company recognized the effects of changes in tax law, including the TCJA, in the period the law is enacted. Accordingly, the effects of the TCJA were recognized in the financial statements for the year ended December 31, 2017. For additional details regarding the accounting for income taxes, see Note 10. 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 non-cancelable operating leases which are further described in Note 11. The Company has standard indemnification arrangements under the leases that requires it to indemnify the landlords 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 leases. Pursuant to the Asset Purchase Agreement, discussed further in Note 12, the Company agreed to indemnify Vertex for certain matters, including breaches of specified representations and warranties, covenants included in the Asset Purchase Agreement and specified tax claims. Representations and warranties, other than certain fundamental representations and warranties, survived for a period of eighteen months following the Closing and the maximum liability of the Company for claims by Vertex related to the breaches of such representations and warranties, with limited exceptions, was limited to the escrow amount, or $16 million . In January 2019, the escrow period expired and the escrow of $16.0 million was released to the Company in February 2019. As of December 31, 2018 and 2017, 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. Other Income In the fiscal year ended December 31, 2017, the Company received $3.6 million due to a disgorgement of short-swing profits arising from sales of the Company's stock by a 10% stockholder pursuant to Section 16(b) of the Securities and Exchange Act of 1934. The Company has classified the proceeds from the disgorgement as other income in the accompanying consolidated financial statements in fiscal year 2017. Comprehensive (Loss) Income Comprehensive (loss) income is comprised of net (loss) income and other comprehensive income or loss. Other comprehensive income or loss consists of unrealized gains and losses on investments. Recently Adopted Accounting Pronouncements On January 1, 2018, the Company adopted ASU 2014-09, Revenue from Contracts with Customers and all related amendments. For further discussion, see the Revenue Recognition discussion appearing elsewhere in this Note 2. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows - Restricted Cash (Topic 230). This standard requires companies to include amounts generally described as restricted cash and restricted cash equivalents in cash and cash equivalents when reconciling beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The Company adopted this standard on January 1, 2018. The adoption of ASU 2016-18 resulted in the Company's cash, cash equivalents and restricted cash being included in the beginning and ending amounts for the periods shown on the statement of cash flows and was applied retroactively and reflected in the balances presented for any prior periods. The Company believes that the adoption of this guidance did not have a significant impact on its consolidated financial statements and related disclosures. Restricted cash as of December 31, 2018 and 2017 is held as collateral for stand-by letters of credit issued by the Company to its landlords in connection with the leases of both the Company's current facility at 65 Hayden Avenue, Lexington, Massachusetts, as well as its previous facility at 99 Hayden Avenue, Lexington, Massachusetts. Cash, cash equivalents and restricted cash consisted of the following: December 31, December 31, Cash and cash equivalents $ 17,770 $ 27,665 Restricted cash 1,157 1,557 $ 18,927 $ 29,222 In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities, which revises the classification and measurement of investments in equity securities. ASU 2016-01 generally requires that equity investments, except for those accounted for under the equity method of accounting, be measured at fair value and changes in fair value are recognized in net income. Unrealized gains or losses from other investments, including debt securities, continue to be included in accumulated other comprehensive income (loss). Effective January 1, 2018, the Company prospectively adopted this new standard resulting in the recognition of the effects of changes in fair value of equity securities within net income (loss) in the consolidated statement of operations and comprehensive loss. Refer to Note 12 for discussion of the Company's marketable equity securities holdings. Pending Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). ASU 2016-02 requires lessees to recognize assets and liabilities on the balance sheet for the rights and obligations created by all leases with terms of more than 12 months. ASU 2016-02 will also require certain qualitative and quantitative disclosures designed to give financial statement users information on the amount, timing, and uncertainty of cash flows arising from leases. ASU 2016-02 will be effective for the Company on January 1, 2019. The Company plans to adopt the new standard with a cumulative-effect adjustment to the opening balance of retained earnings at that date and no restatement of comparative periods’ financial information, as recently allowed by the FASB. The Company is currently evaluating the effect of adopting the requirements of ASU 2016-02 as it relates to the accounting for its facility lease at 65 Hayden Avenue, Lexington, Massachusetts, which was executed in December 2017 and is discussed further in Note 11. The Company has performed a preliminary evaluation of other material contracts to determine if any contain embedded leases, and has not identified any to date. The Company's lease for its 99 Hayden Avenue, Lexington, Massachusetts facility expired in September 2018 and as a result will not be evaluated under the scope of ASU 2016-02. The Company expects to elect certain relief options offered in ASU 2016-02 including the package of practical expedients, the option not to separate lease and non-lease components and instead to account for them as a single lease component, and the option not to recognize right-of-use assets and lease liabilities that arise from short-term leases (i.e., leases with terms of twelve months or less). In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326)-Measurement of Credit Losses on Financial Instruments, or ASU 2016-13. The new standard requires entities to measure all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions and reasonable and supportable forecasts. ASU 2016-13 will become effective for the Company for fiscal years beginning after December 15, 2019, with early adoption permitted. The Company is currently evaluating the impact ASU 2016-13 will have on its financial statements and related disclosures. In June 2018, the FASB issued ASU 2018-07 (Topic 718) - Improvements to Nonemployee Share-Based Payment Accounting that expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. ASU 2018-07 provides that an entity should apply the requirements of Topic 718 to nonemployee awards except for certain exemptions specified in the amendment. The guidance is effective for fiscal years beginning after December 15, 2018, including interim reporting periods within that fiscal year. Early adoption is permitted, but no earlier than an entity’s adoption date of ASC 606. The Company believes that this guidance will not have a significant impact on its consolidated financial statements and related disclosures.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The tables below present information about the Company’s financial assets and liabilities that are measured and carried at fair value as of December 31, 2018 and 2017 (in thousands) and indicate the level within the fair value hierarchy where each measurement is classified. Level 1 Level 2 Level 3 Total December 31, 2018 Cash equivalents: Money market funds $ 7,643 $ — $ — $ 7,643 U.S. Treasury obligations 1,748 — — 1,748 Investments, available for sale: U.S. Treasury obligations 34,103 746 — 34,849 Government agency securities 64,733 35,962 — 100,695 Marketable equity securities: Corporate equity securities (Note 12) 7,525 — — 7,525 Total $ 115,752 $ 36,708 $ — $ 152,460 Level 1 Level 2 Level 3 Total December 31, 2017 Cash equivalents: Money market funds $ 8,108 $ — $ — $ 8,108 Investments, available for sale: U.S. Treasury obligations 53,910 — — 53,910 Government agency securities 88,651 32,939 — 121,590 Total $ 150,669 $ 32,939 $ — $ 183,608

Cash, Cash Equivalents, Investm

Cash, Cash Equivalents, Investments and Marketable Equity Securities	12 Months Ended
	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents, Investments and Marketable Equity Securities	Cash, Cash Equivalents, Investments and Marketable Equity Securities Cash, cash equivalents, available for sale investments, and marketable equity securities included the following at December 31, 2018 and 2017: Average maturity Amortized cost Unrealized gains Unrealized losses Fair value December 31, 2018 Cash $ 8,379 $ — $ — $ 8,379 Money market funds 7,643 — — 7,643 U.S. Treasury obligations 31 days 1,748 — — 1,748 Cash and cash equivalents $ 17,770 $ — $ — $ 17,770 U.S. Treasury obligations 151 days $ 34,856 $ 2 $ (9 ) $ 34,849 Government agency securities 153 days 100,748 7 (60 ) 100,695 Investments, available for sale $ 135,604 $ 9 $ (69 ) $ 135,544 December 31, 2018 Acquisition value Unrealized gains Unrealized losses Fair value Marketable equity securities (Note 12) $ 10,451 $ — $ (2,926 ) $ 7,525 Average maturity Amortized cost Unrealized gains Unrealized losses Fair value December 31, 2017 Cash $ 19,557 $ — $ — $ 19,557 Money market funds 8,108 — — 8,108 Cash and cash equivalents $ 27,665 $ — $ — $ 27,665 U.S. Treasury obligations 184 days $ 54,004 $ — $ (94 ) $ 53,910 Government agency securities 229 days 121,903 — (313 ) 121,590 Investments, available for sale $ 175,907 $ — $ (407 ) $ 175,500

Restricted Cash

Restricted Cash	12 Months Ended
	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Restricted Cash	Restricted Cash At December 31, 2018 and 2017, restricted cash was $1.2 million and $1.6 million , respectively. Restricted cash as of December 31, 2018 and 2017 is held as collateral for stand-by letters of credit issued by the Company to its landlords in connection with the leases of both the Company's current facility at 65 Hayden Avenue, Lexington, Massachusetts, as well as its previous facility at 99 Hayden Avenue, Lexington, Massachusetts. For additional information regarding the Company's leases, please reference Note 11. December 31, December 31, 2017 Letter of Credit: 99 Hayden Avenue, Lexington, Massachusetts $ — $ 400 Letter of Credit: 65 Hayden Avenue, Lexington, Massachusetts 1,157 1,157 $ 1,157 $ 1,557

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment Property and equipment consists of the following at December 31, 2018 and 2017 (in thousands): Estimated useful life (in years) December 31, 2018 December 31, Laboratory equipment 5 $ 3,484 $ 2,674 Computer, telephone and office equipment 3 875 147 Software 3 206 160 Leasehold improvements Lesser of useful life or remaining lease term 5,866 6,551 10,431 9,532 Less accumulated depreciation and amortization (1,512 ) (7,367 ) $ 8,919 $ 2,165 Depreciation and amortization expense was charged to operations in the amounts of $1.2 million , $1.0 million , and $0.9 million for the years ended December 31, 2018, 2017, and 2016, respectively.

Accrued Expenses and Other Liab

Accrued Expenses and Other Liabilities	12 Months Ended
	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued Expenses and Other Liabilities	Accrued Expenses and Other Liabilities Accrued expenses and other liabilities consist of the following (in thousands): December 31, 2018 December 31, Accrued professional fees and other $ 672 $ 628 Employee compensation and benefits 3,067 2,797 Research and development expenses 1,476 521 Deferred lease incentive, current portion 454 249 Deferred rent, current portion — 104 $ 5,669 $ 4,299

Stock Compensation

Stock Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Compensation	Stock Compensation Stock incentive plans The Company previously sponsored an Amended and Restated 2006 Stock Option and Grant Plan, or the 2006 Plan, which provided for the issuance of 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. The 2006 Plan was replaced by the Company’s 2014 Stock Incentive Plan, or the 2014 Plan, which 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. 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. Effective January 1, 2019, 937,503 shares were added to the 2014 Plan for future issuance pursuant to this evergreen provision. The 2006 Plan has no shares remaining available for grant, although existing stock options granted under the 2006 Plan remain outstanding. As of December 31, 2018, 1,488,976 shares were available for future grant under the 2014 Plan. Stock options Stock options are granted with an exercise price equal to the closing market price of the Company’s common stock on the date of grant. Stock options generally vest ratably over three or four years and have contractual terms of ten years. Stock options are valued using the Black-Scholes-Merton option valuation model and compensation cost is recognized based on such fair value over the period of vesting. The following table provides certain information related to the Company's outstanding stock options: Year ended December 31, 2018 2017 2016 (in thousands, except per share data) Weighted average fair value of options granted, per option $ 17.74 $ 7.67 $ 10.42 Aggregate grant date fair value of options vested during the year $ 7,755 $ 6,212 $ 4,614 Total cash received from exercises of stock options $ 1,037 $ 6,576 $ 601 Total intrinsic value of stock options exercised $ 2,599 $ 8,692 $ 1,160 The weighted average fair value of options granted in the years ended December 31, 2018, 2017 and 2016, reflect the following weighted-average assumptions: Year ended December 31, 2018 2017 2016 Expected volatility 77.22 % 78.15 % 78.29 % Expected term 6.0 years 6.0 years 6.0 years Risk-free interest rate 2.64 % 2.07 % 1.36 % Expected dividend yield — % — % — % Expected volatility. For the years ended December 31, 2018 and 2017, expected volatility was estimated using a weighted-average of the Company's historical volatility of its common stock and the historical volatility of the common stock of a representative group of publicly traded companies from the biopharmaceutical industry with similar characteristics as the Company, including stage of product development and therapeutic focus. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available. For year ended December 31, 2016, the Company estimated expected volatility using only the historical volatility from a representative group of publicly traded companies from the biopharmaceutical industry with similar characteristics 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, 2018, 2017 and 2016, 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 elected 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, 2018, 2017 and 2016, the Company assumed forfeiture rates of approximately 7% , 7% , and 6% , respectively. The following is a summary of option activity under the 2006 Plan and 2014 Plan: Number of Option Shares Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (In years) (In thousands) Outstanding at December 31, 2017 2,889,722 $ 11.25 Granted 968,043 $ 26.01 Exercised (196,861 ) $ 7.27 Forfeited or expired (103,498 ) $ 19.20 Outstanding at December 31, 2018 3,557,406 $ 15.26 6.97 5,834 Exercisable at December 31, 2018 2,134,434 $ 12.27 6.05 5,052 Vested and expected to vest at December 31, 2018 (1) 3,444,612 $ 15.06 6.92 5,780 (1) This represents the number of vested stock option shares as of December 31, 2018, plus the number of unvested stock option shares that the Company estimated as of December 31, 2018 would vest, based on the unvested stock option shares at December 31, 2018 and an estimated forfeiture rate of 7% . As of December 31, 2018 there was $16.9 million of total unrecognized compensation cost related to stock options that are expected to vest. Total unrecognized compensation cost will be adjusted for future changes in forfeitures. The stock option costs are expected to be recognized over a weighted-average remaining vesting period of 2.3 years. Restricted Stock units On July 6, 2017, the Company granted 0.5 million restricted stock units, or RSUs, to executives and employees. The awards granted to employees are service-based, whereas the awards granted to executives are a blend of service-based and performance-based. Assuming all service and performance conditions were achieved, fifty percent of the RSUs would vest on March 31, 2018, and the remaining fifty percent of the RSUs would vest on March 31, 2019. Certain executive awards were subject to the achievement of defined performance criteria prior to March 31, 2018, including the closing of the Asset Purchase Agreement with Vertex and the institution by the Patent Trial and Appeal Board ("PTAB") of the Post Grant Review ("PGR") petition filed by the Company against Incyte Corporation. In January 2018, the PTAB decided not to institute the PGR petition and, as a result, the corresponding performance-based awards will not vest. The Company is using the accelerated attribution method to recognize expense over the required service period based on its estimate of the number of performance-based awards that will vest. If there is a change in the estimate of the number of performance-based awards that are probable of vesting, the Company will cumulatively adjust compensation expense in the period that the change in estimate is made. RSUs are not included in issued and outstanding common stock until the shares are vested and released. As of December 31, 2018, 174,050 RSUs had vested. The fair value of an RSU is measured based on the market price of the underlying common stock as of the date of grant. The following is a summary of RSU activity, including both time-based and performance-based restricted stock units for the year ended December 31, 2018: Number of RSU Shares Weighted Average Grant Date Fair Value Outstanding at December 31, 2017 517,300 $ 13.87 Granted — $ — Released (174,050 ) $ 13.87 Forfeited (115,100 ) $ 13.87 Outstanding at December 31, 2018 228,150 $ 13.87 As of December 31, 2018, there was $0.6 million of unrecognized compensation cost related to restricted stock units that are expected to vest. This amount excludes compensation cost related to restricted stock units where the performance conditions are not considered probable of being satisfied. The costs from restricted stock units that are considered probable of vesting are expected to be recognized over a weighted average remaining vesting period of 0.3 year. Stock-based compensation expense Total compensation cost recognized for all stock-based compensation awards in the consolidated statements of operations and comprehensive income (loss) is as follows (in thousands): For the Year Ended December 31, 2018 2017 2016 Research and development $ 5,221 $ 3,708 $ 2,147 General and administrative 6,279 4,792 2,920 Total stock-based compensation expense $ 11,500 $ 8,500 $ 5,067

Earnings (Loss) Per Share

Earnings (Loss) Per Share	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Earnings (Loss) Per Share	Earnings (Loss) Per Share Basic net earnings (loss) per common share is calculated by dividing net income (loss) allocable to common stockholders by the weighted-average common shares outstanding during the period, without consideration of common stock equivalents. For periods with net income, diluted net earnings per share is calculated by either (i) adjusting the weighted-average shares outstanding for the dilutive effect of common stock equivalents, including warrants, stock options and restricted stock units outstanding for the period as determined using the treasury stock method or (ii) the two-class method considering common stock equivalents, whichever is more dilutive. For purposes of the diluted net loss per share calculation, common stock equivalents are excluded from the calculation if their effect would be anti-dilutive. As such, basic and diluted net loss per share applicable to common stockholders are the same for periods with a net loss. The two-class method is an earnings allocation formula that treats a participating security as having rights to earnings that otherwise would have been available to common stockholders. The Company has outstanding warrants, including those issued in connection with the Loan and Security Agreement described in Note 13, that are deemed to be participating securities. The two-class method was not applied for the years ended December 31, 2018 and 2016 as the Company’s participating securities do not have any obligation to absorb net losses. The Company applied the two-class method to calculate basic and diluted net earnings per share of common stock for the year ended December 31, 2017. The following table illustrates the determination of earnings (loss) per share for each period presented. For the Year Ended December 31, 2018 2017 2016 Basic Earnings per Share (in thousands, except per share amounts) Numerator: Net (loss) income $ (56,024 ) $ 95,639 $ (50,720 ) Income attributable to participating securities - basic — 444 — (Loss) income attributable to common stockholders - basic (56,024 ) 95,195 (50,720 ) Denominator: Weighted average shares outstanding 23,370 22,641 22,233 Net (loss) income per share applicable to common stockholders - basic $ (2.40 ) $ 4.20 $ (2.28 ) Diluted Earnings per Share Numerator: Net (loss) income (56,024 ) 95,639 (50,720 ) Income attributable to participating securities - diluted — 429 — (Loss) income attributable to common stockholders - diluted (56,024 ) 95,210 (50,720 ) Denominator: Weighted average shares outstanding 23,370 22,641 22,233 Dilutive impact from: Stock options — 688 — Restricted stock units — 113 — Weighted average shares outstanding - diluted 23,370 23,442 22,233 Net (loss) income per share applicable to common stockholders - diluted $ (2.40 ) $ 4.06 $ (2.28 ) Anti-dilutive potential common stock equivalents excluded from the calculation of net (loss) income per share: Stock options 666 1,833 620 Restricted stock units 185 408 — Warrants 132 — 71

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes New Tax Legislation On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act (“TCJA”). This legislation made broad and complex changes to the U.S. tax code, including, but not limited to, (i) reducing the U.S. federal statutory tax rate from 35% to 21%; (ii) eliminating the corporate alternative minimum tax (AMT) and changing how existing AMT credits can be realized; (iii) modifying the officer’s compensation limitation, and (iv) changing rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017. Specifically, the TCJA limited the amount the Company is able to deduct for net operating loss carryforwards generated in taxable years beginning after December 31, 2017 to 80% of taxable income however these net operating loss carryforwards can be carried forward indefinitely. The Company recognizes the effects of changes in tax law, including the TCJA, in the period the law is enacted. Accordingly, the effects of the TCJA were recognized in the financial statements for the year ended December 31, 2017. As a result of the change in law, the Company recorded a reduction to its deferred tax assets of $8.6 million and a corresponding reduction to its valuation allowance due to the reduction in the U.S. federal statutory rate from 35% to 21%. In addition, the new legislation also repealed the corporate Alternative Minimum Tax (“AMT”) for years after 2017. Corporations that were previously subject to the AMT and have AMT tax credit carryforwards as of December 31, 2017, are eligible for a refund of these credits for tax years beginning after 2017 and before 2022. The Company was subject to AMT in the amount of $1.9 million in 2017. Since the AMT paid on its 2017 tax return generated an AMT credit that will be refundable between 2018 and 2022, the Company recorded a $1.9 million income tax receivable rather than a tax expense for 2017. Further, the Company also had a deferred tax asset for its AMT credit carryforward related to its AMT liability paid in 2015 in the amount of $0.3 million . This deferred tax asset was previously offset by a full valuation allowance. As a result of the change in law, the Company reclassified the 2015 AMT credit carryforward from deferred tax assets to income tax receivable during 2017. As of December 31, 2018, the Company has a $2.3 million income tax receivable related to AMT taxes in prior years. At December 31, 2018, the Company has completed its accounting for the tax effects of the enactment of the TCJA and no adjustments were recorded to the provisional amounts previously recorded. Income Taxes During the year ended December 31 2018, the Company recorded net loss before taxes of $55.7 million and, since it maintains a full valuation allowance on its deferred tax assets, the Company did not record an income tax benefit for the year ended December 31, 2018. On July 25, 2017, the transaction contemplated by the Asset Purchase Agreement with Vertex, as discussed in Note 12, closed and Vertex paid the Company $160 million in cash consideration, with $16 million to be held in escrow. For income tax purposes, the $16 million held in escrow is recognized under the installment method and is therefore deferred until the cash is received by the Company. Under the provisions of Section 453A of the Internal Revenue Code, the Company is required to recognize interest on the deferred tax liability with respect to the portion of the installment sale outstanding as of the close of each taxable year that exceeds $5 million . As a result, during 2018 the Company recorded a provision of $0.4 million , which includes $0.2 million of interest accrued for tax year 2017 and $0.2 million of interest accrued for tax year 2018. Additionally, during 2018 the Company recorded unrealized gains on its investments in available-for-sale securities in other comprehensive income. Intraperiod tax allocation rules require the Company to allocate its provision for income taxes between continuing operations and other categories of earnings, such as other comprehensive income. In periods in which the Company has a year-to-date pre-tax loss from continuing operations and pre-tax income in other categories of earnings, such as other comprehensive income, the Company must allocate the tax provision to the other categories of earnings. The Company then records a related tax benefit in continuing operations. As a result of these rules, the Company recorded a benefit of $0.1 million in continuing operations, with a corresponding reduction in other comprehensive income of $0.1 million , related to its unrealized gains on its investments in available-for-sale securities during 2018. During the year ended December 31 2017, the Company recorded net income before taxes of $95.3 million . As a result of the enactment of the TCJA, which allows for AMT to be refundable, the Company recorded a tax receivable of $2.2 million as of December 31, 2017 and a $0.3 million income tax benefit during the year ended December 31, 2017. The tax benefit is the result of the removal of its valuation allowance on its AMT credit carryforward as previously described. Income taxes that would otherwise have been due on the 2017 taxable income were offset with the tax benefit of net operating loss carryforwards which had previously had a full valuation allowance, except for $1.9 million of AMT incurred due to the limitation on use of net operating loss carryforwards when determining AMT. However, the 2017 AMT is also refundable under the Tax Cuts and Jobs Act of 2017 and thus we have not recorded a tax provision for this amount. The total amount of refundable AMT credits of $2.2 million is reflected as income tax receivable in the accompanying consolidated balance sheet as of December 31, 2017. We provide a full valuation allowance for any tax benefit related to net operating losses due to the uncertainty of the ability to realize such benefits. During the year ended December 31, 2016, the Company recorded a net loss of $50.7 million and, since it maintained a full valuation allowance on its deferred tax assets, the Company did not record an income tax benefit for the year ended December 31, 2016. The Company’s ability to use its operating loss carryforwards and tax credit carryforwards to offset taxable income is subject to restrictions under Sections 382 and 383 of the United States Internal Revenue Code (the “Internal Revenue Code”). Net operating loss and tax credit carryforwards are 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. Such changes would limit the Company’s use of its operating loss and tax credit carryforwards. In such a situation, the Company may be required to pay income taxes, even though significant operating loss and tax credit carryforwards exist. Additionally, any future financing could result in a change in control, as defined by Sections 382 and 383, which could further limit the Company's use its operating loss and tax credit carryforwards. In determining the tax provisions for fiscal year 2018, we assessed our ability to use our net operating loss carryforwards in accordance with Sections 382 and 383 of the Internal Revenue Code. A reconciliation of the federal statutory income tax rate and the Company’s effective income tax rate is as follows: Year ended December 31, 2018 2017 2016 Federal statutory income tax rate 21.0 % (35.0 )% 34.0 % State income taxes 6.2 % (5.1 )% 4.5 % Change in valuation allowance (30.9 )% 46.2 % (40.3 )% Research and development and other credits 4.0 % 2.5 % 3.1 % Permanent items (0.3 )% 0.8 % (1.0 )% Alternative minimum tax — % — % — % Other (0.6 )% — % (0.3 )% Federal rate change — % (9.1 )% — % Effective income tax rate (0.6 )% 0.3 % — % The significant components of the Company’s net deferred tax assets consist of the following (in thousands): December 31, 2018 2017 Deferred tax assets: Net operating loss carryforwards $ 23,841 $ 11,670 Deferred revenue 2,878 2,733 Research and development and other credit carryforwards 15,597 13,399 Fixed assets — 236 Other 7,985 3,575 50,301 31,613 Valuation allowance (44,453 ) (31,613 ) Total deferred tax assets, net of valuation allowance $ 5,848 $ — Deferred tax liabilities: Fixed assets $ 1,477 $ — Gain deferred under installment method 4,371 — Total deferred tax liabilities $ 5,848 $ — Net deferred tax assets $ — $ — Subject to the limitations described above and the impacts of the TCJA, at December 31, 2018, the Company had gross federal net operating loss carryforwards of $99.5 million and state net operating loss carryforwards of $46.7 million available to reduce future taxable income, of which $54.8 million of the gross federal net operating loss carryforwards and $46.7 million of the state net operating loss carryforwards will expire at various dates beginning in 2034. Approximately $44.7 million of the federal net operating loss carryforwards will be carried forward indefinitely. The Company also had federal and state tax credit carryforwards of $11.7 million and $4.9 million , respectively, available to reduce future tax liabilities, which expire at various dates through 2038. The Company adopted ASU 2016-09, Improvements to Employee Share-Based Payment Accounting on January 1, 2017. As a result of adoption, the deferred tax assets associated with net operating losses as of December 31, 2016 have increased by $3.2 million . These amounts were offset by a corresponding increase in the valuation allowance. The adoption of ASU 2016-09 had no impact on the Company’s operations, financial position or cash flows. The Company adopted ASC 606 using the modified retrospective transition method as permissible for all contracts not yet completed as of January 1, 2018. This created approximately $4.3 million of deferred tax liabilities relating to federal and state deferred revenue that are fully offset by a corresponding decrease in the valuation allowance. As a result, there was no cumulative effect adjustment to accumulated deficit. Realization of the future tax benefits is dependent on many factors, including the Company’s ability to generate taxable income within the carryforward period. The Company currently has deferred tax assets in excess of its deferred tax liabilities, resulting in the Company having net deferred tax assets. The Company has evaluated the positive and negative evidence bearing upon the realizability of its net deferred tax assets and concluded that it is more likely than not that the Company will not realize the benefit of its net deferred tax assets. As a result, the net deferred tax assets have been fully reserved at December 31, 2018 and 2017. At December 31, 2018, 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, 2018, 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 2015 through 2017. Carryforward tax attributes generated in years prior to 2015 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, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments	Commitments The Company currently leases 55,522 square feet of office and laboratory space (the "Lease") located at 65 Hayden Avenue, Lexington, Massachusetts (the "Premises"). The Company occupied the Premises in the third quarter of 2018, however the Company gained access to the space on January 1, 2018 in order to start making certain tenant improvements. Accordingly, for accounting purposes the lease commencement date is January 1, 2018. The Lease term extends ten years following January 1, 2019. The Company is entitled to two five -year options to extend the Lease. The Lease is accounted for as an operating lease. The Lease provides for annual base rent of approximately $2.8 million in the first year following the Base Rent Commencement Date of January 1, 2019, which increases on a yearly basis by 3.0% (subject to an abatement of base rent of approximately $0.5 million at the beginning of the second year of the Lease term if the Company is not in default under the Lease). The Company is also obligated to pay the Landlord for certain costs, taxes and operating expenses related to the Premises, subject to certain exclusions. The Company is recognizing rental expense on a straight-line basis, beginning on the lease commencement date of January 1, 2018, over the term of the lease with corresponding rent differential accounted for as deferred rent. The Company received an improvement allowance from the Landlord of approximately $5.0 million for certain permitted costs related to the design of Company improvements to the Premises, consisting of normal tenant improvements. The Company is deemed to be the owner of these tenant improvements during the lease term. The Company is accounting for the tenant improvements funded by the Landlord as a lease incentive obligation to be amortized against operating lease expense on a straight-line basis over the term of the Lease. Leasehold improvements, including those funded by the Landlord and those funded by the Company, have been recognized as assets and are amortized on a straight-line basis over the term of the Lease. The Company provided a security deposit, in the form of a stand-by letter of credit, in the amount of approximately $1.2 million , which may be used by the Landlord to be applied for certain purposes upon the Company’s breach of any provisions under the Lease. The Lease contains customary provisions allowing the Landlord to terminate the Lease if the Company fails to remedy a breach of any of its obligations within specified time periods, or upon bankruptcy or insolvency of the Company. The Company previously leased approximately 50,000 square feet of office and laboratory space at 99 Hayden Avenue, Lexington, Massachusetts under a non-cancelable operating lease agreement, or the 2008 Lease Agreement, as amended. The term of the 2008 Lease Agreement expired September 30, 2018. The future minimum lease payments under the Lease is as follows (in thousands): Base rent obligations At December 31, 2018 2019 $ 2,776 2020 2,383 2021 2,945 2022 3,034 2023 3,125 Greater than 5 years 17,085 Total minimum lease payments $ 31,348

Revenue

Revenue	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Revenue	Revenue The Company's revenue is currently generated through collaborative licensing agreements, patent assignments, and sales of intellectual property. The Company generates its revenue through one segment and the revenue recognized under each of the Company's arrangements during the current and prior periods is described below. The terms of these agreements may contain multiple promised goods or services or optional goods and services, including 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. Revenue recognition Revenue is recognized when control of the promised goods or services are transferred to customers, in an amount that reflects the consideration the Company expects to be entitled to in exchange for transferring those goods or providing services. The Company accounts for a contract when it has approval and commitment from both parties, the rights of the parties are identified, payment terms are identified, the contract has commercial substance and collectability of consideration is probable. When determining whether the customer has obtained control of the goods or services, the Company considers the point at which the customer may benefit from the goods or services. For licenses to product candidates, revenue is recognized upon grant or transfer of the exclusive license, as the Company's licenses are considered functional in nature. For research, development, and manufacturing activities, revenue is recognized as the work is performed using either the output or input method. Performance obligations A performance obligation is a promise in a contract to transfer a distinct good or service to the customer, and is the unit of account in ASC 606. A contract’s transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. The Company's contracts may contain multiple performance obligations if a promise to transfer goods or services is separately identifiable from other promises in a contract and, therefore, is considered distinct. For contracts with multiple performance obligations, the Company determines the standalone selling price of each performance obligation and allocates the total transaction price using the relative selling price basis. The Company recognizes performance obligations based on their nature. Options to exclusive licenses The collaborative arrangement with Celgene provides the customer the option to purchase additional licenses in addition to preclinical and clinical development services at a discount. These options are considered performance obligations as they provide the customer with material rights that the customer would not receive without entering into the contract. The portion of the transaction price attributed to a material right is recognized when the underlying option is exercised or when the option expires. To date, Celgene has not exercised any of its options that were determined to represent material rights. Significant Payment Terms The Company’s revenue arrangements 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. Under ASC 606, the Company estimates the amount of consideration to which it will be entitled in exchange for satisfying performance obligations. Based on the Company’s current contracts, variable consideration primarily exists in the following forms: development and regulatory milestones, royalties and sales-based milestones, and consideration held in escrow for indemnification purposes. The Company utilizes the "most likely amount" variable consideration method for estimating development and regulatory milestone consideration to include in the transaction price and the “expected value” variable consideration method for the consideration held in escrow for indemnification purposes. The Company only includes an amount of variable consideration in the transaction price to the extent it is probable that a significant reversal in the cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. The Company refers to this as the variable consideration constraint. Due to the uncertainty associated with the occurrence of the underlying events which would trigger development and regulatory milestone consideration under its revenue arrangements, with the exception of those development and regulatory milestones received to date, the Company has concluded the variable consideration associated with all development and regulatory milestones to be fully constrained as of the ASC 606 transition date and as of December 31, 2018 and therefore has not included such consideration in the transaction price for any of its revenue arrangements. The Company will re-assess this conclusion at each subsequent reporting period and will only include amounts associated with regulatory or development milestones in the transaction price when, or if, the variable consideration is determined to be released from the constraint. To date, the Company has not recognized any royalties or sales-based milestones under its licensing and collaboration arrangements. Royalties and sales-based milestones qualify for the sales-and-usage exemption under ASC 606 as (i) royalties are based strictly on the sales-and-usage by the licensee and (ii) a license of IP is the sole or predominant item to which such royalties relate. Based on this exemption, these royalties are earned under the terms of a license agreement in the period the products are sold by the Company's collaborator and the Company has a present right to payment. In accordance with ASC 606, the Company is required to adjust the transaction price for the effects of the time value of money if the timing of payments agreed to by the parties to the contract, explicitly or implicitly, provides the Company or its customer with a significant benefit of financing the transfer of goods or services. The Company concluded that its licensing and collaboration arrangements do not contain a significant financing component because the payment structure of its agreements arise from reasons other than providing a significant benefit of financing. Application of Practical Expedients The collaborative arrangements with Glaxo Group Limited, or GSK, and Jazz Pharmaceuticals contained contract modifications. The Company elected to apply the transition practical expedient under ASC 606-10-65-1(f)(4) that allows an entity to reflect the aggregate effect of all contract modifications on contracts that were modified before the beginning of the earliest period presented under the new standard (that is, January 1, 2018) when (i) identifying the satisfied and unsatisfied performance obligations, (ii) determining the transaction price, and (iii) allocating the transaction price to the satisfied and unsatisfied performance obligations. The application of the practical expedient did not have a material effect on the Company’s revenue recognition. Contract Assets As of January 1, 2018, the Company identified a contract asset of $16.0 million associated to the Vertex indemnification payment held in escrow. As the receipt of the Vertex indemnification consideration involves more than the passage of time, the consideration was concluded to be conditional and therefore classified as a contract asset. As of December 31, 2018, there have been no changes to the balance of the Company's contract asset from the date of adoption of ASC 606. In February 2019, the escrow was released to the Company. Contract Liabilities As of January 1, 2018, the Company identified contract liabilities of $10.5 million related to unsatisfied performance obligations as well as variable consideration paid in advance but currently constrained from recognition. Contract liabilities are presented as deferred revenue and classified as current or noncurrent based on the timing of when the Company expects to recognize revenue. During the twelve months ended December 31, 2018, $16 thousand of deferred revenue was recognized into revenue. As of December 31, 2018, the Company recorded $10.5 million of contract liabilities in the condensed consolidated statement of financial position. Collaboration Arrangements 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 agreement is primarily focused on the research, development and commercialization of specified deuterated compounds targeting inflammation or cancer. The initial program in the collaboration is CTP-730, a deuterium-modified analog of apremilast. Celgene has an exclusive worldwide license to develop, manufacture and commercialize deuterated analogs of apremilast 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. 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. As a result of the restrictions placed on the two additional license programs that preclude Celgene from exercising its rights under the respective licenses without the payment of a significant license exercise fee, for accounting purposes the Company concluded that it had effectively provided Celgene an option to obtain licenses to those programs. The Company was responsible for conducting and funding research and early development activities for the CTP-730 program at its own expense pursuant to mutually agreed upon development plans. This included the completion of single and multiple ascending dose Phase 1 clinical trials in 2015. The Company does not have any obligation to conduct any research or development activities for any of the additional programs unless and until Celgene exercises its rights with respect to such program and pays the applicable exercise fee. If Celgene exercises its rights with respect to any additional program and pays the Company the applicable exercise fee, the Company is responsible, at its own expense, for conducting research and development activities for such program pursuant to agreed-upon development plans until the completion of Phase 1 clinical trial, which will be defined in each development plan on a program-by-program basis. In addition, if Celgene exercises its rights with respect to the option program and pays the Company the applicable option exercise fee, the Company is responsible for seeking to generate a deuterated compound for clinical development in the selected option program. Oversight of the development program for each program under the Celgene Agreement is guided by separate JSCs. Celgene is solely responsible for all research, development and commercialization costs with respect to the initial program beyond the Phase 1 clinical trials that the Company conducts. If Celgene exercises its rights with respect to any additional program, Celgene will be solely responsible for all research, development and commercialization costs for such program following the completion of the first Phase 1 clinical trial for such program. Under the terms of the agreement, the Company received a non-refundable upfront payment of $35.0 million . In October 2015, the Company received an $8.0 million development milestone payment based on the completion of Phase 1 clinical evaluation of CTP-730. In addition, the Company is eligible to earn an additional $15.0 million development milestone payment, 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 CTP-730 program. The next milestone payment the Company may be entitled to achieve under the CTP-730 program is $15.0 million related to the first actual dosing in a Phase 3 clinical trial or, if earlier, acceptance for filing of a new drug application, or NDA. 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 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 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 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. Under ASC 606, the Company's collaborative arrangement with Celgene contains the following performance obligations: (i) an exclusive worldwide license to develop, manufacture and commercialize deuterated analogs of apremilast related to the CTP-730 program, or the License Performance Obligation, (ii) obligations to perform research and development services associated with the CTP-730 program, or the R&D Services Performance Obligation, (iii) obligation to supply nonclinical and clinical trial material related to the CTP-730 program, or the Supply Performance Obligation, (iv) material right related to the first additional license program for which the non-deuterated compound has been selected, or the First Discount Performance Obligation and (v) material right related to the second additional license program for which the non-deuterated compound has been selected, or the Second Discount Performance Obligation. The transaction price, exclusive of amounts subject to the variable consideration constraint, as of the transition date consisted of the $35.0 million non-refundable upfront payment and the $8.0 million milestone payment received upon successful completion of the Phase 1 clinical program totaling to $43.0 million . The Company allocated the upfront arrangement consideration of $35.0 million among the performance obligations using the relative selling price method based on the standalone selling prices of each performance obligation, which is generally the price at which it would sell such deliverable if it were to be sold regularly on a standalone basis. The standalone selling price of License Performance Obligation was based on historical valuations for other licensing arrangements entered into by the Company. The standalone selling prices of the R&D Services Performance Obligation and the Supply Performance Obligation were based on the expected cost plus margin approach. The standalone selling prices of the First and Second Discount Performance Obligations were based the expected value of the options. The Company allocated the $8.0 million milestone payment to only the License Performance Obligation, R&D Services Performance Obligation and the Supply Performance Obligation using the relative selling price method based on the standalone selling prices of each of these three performance obligations. The Company concluded that the achievement of the performance-based milestone for the CTP-730 program should only be allocated to the performance obligations associated to the CTP-730 program as the achievement of the milestone related specifically to the Company’s efforts with respect to the satisfaction of the performance obligations related to that program. The transaction price was allocated as follows: (i) $21.7 million to the License Performance Obligation, (ii) $11.0 million to the R&D Services Performance Obligation, (iii) $4.0 million to the Supply Performance Obligation, (iv) $3.2 million to the First Discount Performance Obligation and (v) $3.2 million to the Second Discount Performance Obligation. Revenue is recognized when the performance obligation is considered satisfied. The License Performance Obligation was considered satisfied at contract inception as the exclusive license transferred control to the customer at this point in time. The R&D Services Performance Obligation and the Supply Performance Obligation are satisfied over time using the input method based on costs incurred determined by estimates of associated effort and cost of services adjusted for a reasonable profit margin such that they represent estimated market rates for similar services on a standalone basis. The First Discount Performance Obligation and the Second Discount Performance Obligation shall be considered satisfied upon the option's exercise or expiration. Unsatisfied performance obligations represent contract liabilities that are presented as deferred revenue within the accompanying consolidated balance sheet. The collaborative arrangement with Celgene contains consideration that is variable based on the customer's achievement of certain development, regulatory, and sales-based milestones in addition to royalties upon the customer's commercial success with licensed programs. The next milestone payment of $15.0 million upon first actual dosing in a Phase 3 clinical trial, or if earlier, acceptance for filing of a new drug application, or NDA, for the CTP-730 program is considered variable consideration that is fully constrained due to the uncertainty associated to the achievement of the milestone. As a result, the variable consideration that is considered fully constrained related to this and the remaining development and regulatory milestones will not be recognized until the time at which the constraint is released. The consideration related to royalty and sales-based milestones are recognized pursuant to the sales- and usage-based exemption under ASC 606. The variable consideration related to sales-based milestones and royalties will be recognized in the period the products are sold by Celgene and the Company has a present right to payment. During the year ended December 31, 2018, the Company recognized no revenue for the R&D Services and Supply Performance Obligation as no services were performed. During the years ended December 31, 2017 and 2016 the Company recognized revenue of $20 thousand , and $62 thousand for the R&D Services and Supply Performance Obligations, respectively. The revenue in the prior year period was recognized in accordance with legacy authoritative guidance. The revenue was classified as license and research and development revenue in the accompanying consolidated statements of operations and comprehensive income (loss). As of December 31, 2018, there was $7.8 million of deferred revenue related to the Company’s collaboration with Celgene, consisting of $1.3 million related to the R&D Services Performance Obligation, $0.1 million related to the Supply Performance Obligation and $6.4 million related to the First and Second Discount Performance Obligations. The Company classified the $1.4 million related to the R&D Services Performance Obligation and the Supply Performance Obligation as a current liability and the $6.4 million related to the First and Second Discount Performance Obligations as a noncurrent liability in the accompanying consolidated balance sheet. 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 deudextromethorphan-containing products. Avanir is currently focused on developing AVP-786, which is a combination of deudextromethorphan and an ultra-low dose of quinidine. 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. Since June 2012, Avanir has elected to conduct all research and development activities, including manufacturing activities; however, the Company has received intellectual property cost reimbursements. Under the agreement, the Company received a non-refundable upfront payment of $2.0 million and has received milestone payments of $6.0 million . The Company is also eligible to earn, with respect to licensed products comprising a combination of deudextromethorphan and quinidine, up to $37.0 million in regulatory and commercial launch milestone payments, of which $21.5 million in development and regulatory milestone payments are associated with the first indication, and up to $125.0 million in sales-based milestone payments. The next milestone payments that the Company may be entitled to receive are $5.0 million upon acceptance for filing of a NDA, $3.0 million upon acceptance for filing of a Marketing Authorization Application, or MAA, and $1.5 million upon acceptance for filing of a NDA by the Ministry of Health, Labour and Welfare, or MHLW, related to 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 deudextromethorphan 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 net sales of licensed products on a country-by-country basis. 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 all promised goods and services related to the arrangement with Avanir were considered satisfied as of the ASC 606 adoption date of January 1, 2018. The transaction price, exclusive of amounts subject to the variable consideration constraint, consists of the $2.0 million non-refundable upfront payment and $6.0 million in development milestone payments received totaling to $8.0 million . As all promised goods and services were considered satisfied as of the ASC 606 adoption date, the arrangement consideration need not be allocated among the performance obligations because the arrangement consideration was fully recognized as of January 1, 2018. The arrangement with Avanir contains consideration that is variable based on the customer's achievement of certain development, regulatory, and sales-based milestones in addition to royalties upon the customer's commercial success with the licensed product. The $6.0 million resulting from the achievement of development milestones to date represents variable consideration that has been earned and therefore is not subject to constraint. The next milestones that the Company may be entitled to are regulatory milestones that represent variable consideration that is fully constrained due to the uncertainty associated to the achievement of milestones of this nature. As a result, the variable consideration that is considered fully constrained will not be recognized until the time at which the constraint is released. The consideration related to royalty and sales-based milestones are recognized pursuant to the sales- and usage-based exemption under ASC 606. The variable consideration related to sales-based milestones and royalties will be recognized in the period the products are sold by Avanir and the Company has a present right to payment. 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 a deuterated sodium oxybate analog, or D-SXB. Under the agreement, Jazz Pharmaceuticals initially focused on one analog, designated as JZP-386, a once-nightly oxybate product. Under the terms of the agreement, the Company granted Jazz Pharmaceuticals an exclusive, worldwide, royalty-bearing license under intellectual property controlled by the Company to develop, manufacture and commercialize D-SXB products including, but not limited to, JZP-386. 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-based 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 initiation of the first Phase 2 clinical trial of a D-SXB compound. 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 worldwide net sales of licensed products. The royalty rate is lowered, on a country-by-country basis, under certain circumstances as specified in the agreement. The Company determined that all promised goods and services related to the collaborative arrangement with Jazz Pharmaceuticals were considered satisfied as of the ASC 606 adoption date of January 1, 2018. The transaction price, exclusive of amounts subject to the variable consideration constraint, consists of the $4.0 million non-refundable upfront payment. As all promised goods and services were considered satisfied as of the ASC 606 adoption date, the arrangement consideration need not be allocated among the performance obligations. Furthermore, as all promised goods and services are considered satisfied, the consideration was fully recognized as of January 1, 2018. The collaborative arrangement with Jazz Pharmaceuticals contains consideration that is variable based on the customer's achievement of certain development, regulatory, and sales-based milestones in addition to royalties upon the customer's commercial success with the licensed product. The next milestone payment the Company may be entitled to receive of $4.0 million related to initiation of the first Phase 2 clinical trial of JZP-386 or D-SXB is considered variable consideration that is fully constrained due to the uncertainty associated to the achievement of the development milestone. As a result, the variable consideration that is considered fully constrained will not be recognized until the time at which the constraint is released. The consideration related to royalty and sales-based milestones are recognized pursuant to the sales- and usage-based exemption under ASC 606. The variable consideration related to royalties will be recognized in the period the products are sold by Jazz and the Company has a present right to payment. Other Revenue Arrangements Vertex On March 3, 2017, the Company and Vertex entered into an Asset Purchase Agreement pursuant to which, subject to the satisfaction or waiver of the conditions therein, the Company sold and assigned to Vertex, CTP-656, a deuterated analog of ivacaftor now known as VX-561, and other cystic fibrosis assets of the Company. On July 25, 2017, the Closing Date, the transaction contemplated by the Asset Purchase Agreement closed and Vertex paid the Company $160 million in cash consideration, with $16 million initially held in escrow for a period of eighteen months . In February 2019, the $16.0 million held in escrow was released to the Company. Additionally, upon the achievement of certain milestone events, Vertex has agreed to pay the Company an aggregate of up to $90 million . Of this amount, $50 million will become payable to the Company upon receipt of FDA marketing approval for a combination treatment regimen containing VX-561, for patients with cystic fibrosis, and $40 million will become payable to the Company upon completion of a pricing and reimbursement agreement in the first of the United Kingdom, Germany or France with respect to a combination treatment regimen containing VX-561 for patients with cystic fibrosis. The Asset Purchase Agreement with Vertex contains a single performance obligation: all rights to develop, manufacture, and commercialize deuterated analogs of ivacaftor related to the CTP-656 program, including all intellectual property, permits and registrations, and records, documentation, and regulatory filings, in addition to an obligation to perform research and testing consulting services to facilitate the transfer of materials, documents, and knowledge up to the close of the Asset Purchase Agreement, referred to as the Transfer of IP Performance Obligation. The Asset Purchase Agreement with Vertex contains consideration that is variable based on Vertex's achievement of certain regulatory milestones in addition to the $16.0 million held in escrow to indemnify Vertex, which was released to us February 2019. The regulatory milestone payments are fully constrained due to the uncertainty associated to the achievement of the respective milestones. The Company concluded that an indemnification claim was remote and as a result was not subject to the variable consideration constraint at the ASC 606 transition date. Accordingly, the variable consideration of $16.0 million was included in the transaction price. The transaction price was $160.0 million , as the variable consideration associated with the escrow amount was not subject to the constraint. As the arrangement contained a single performance obligation, the Company attributed the full transaction price (exclusive of amounts subject to the variable consideration constraint) of $160.0 million to the Transfer of IP Performance Obligation. The Transfer of IP Performance Obligation was satisfied as of the Closing Date as the control of CTP-656 transferred to Vertex, the customer. As a result, the full transaction price was recognized as revenue as of the ASC 606 adoption date. As of December 31, 2018, the Vertex indemnification variable consideration represented a contract asset to be released from escrow 18 months following the Closing Date and was classified as a current asset in the accompanying consolidated balance sheet. In February 2019, the $16.0 million initially held in escrow was released to the Company. GSK In May 2009, the Company entered into a research and development collaboration and license agreement with 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 $2.8 million payment to the Company. The Company has an obligat

Loan Payable and Warrant to Pur

Loan Payable and Warrant to Purchase Redeemable Securities	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Loan Payable and Warrant to Purchase Redeemable Securities	Loan Payable and Warrant to Purchase Redeemable Securities On June 8, 2017, the Company entered into a Loan Agreement with Hercules, pursuant to which Hercules agreed to make available to the Company a Term Loan Facility in the amount of $30.0 million , subject to certain terms and conditions. The Company borrowed $30.0 million under the Loan Agreement in one advance. The Company incurred $0.3 million in loan issuance costs paid directly to the lenders, which was offset against the loan proceeds as a loan discount. The advance under the Loan and Security Agreement bore interest at a variable rate of the greater of 8.55% and an amount equal to 8.55% plus the prime rate of interest minus 4.50% . Through September 7, 2017, the Term Loan Facility had an interest rate of 8.55% . Pursuant to the Loan Agreement, the Company had the option to prepay the principal of the Loan Agreement at any time subject to a prepayment charge; however the prepayment charge was waived upon the completion of the sale of CTP-656 to Vertex, discussed further in Note 12, and the prepayment of the Term Loan Facility after the 90 th day following the closing date of the Loan Agreement but prior to the six month anniversary of the closing date of the Loan Agreement. On September 7, 2017, the Company paid a total of $30.8 million to Hercules, representing the principal, accrued and unpaid interest, fees, costs and expenses outstanding under the Loan Agreement. The payoff amount included a final end of term charge to Hercules in the amount of $0.7 million , reduced from the $1.5 million end of term charge required had the debt been outstanding to maturity. Upon the payment of the $30.8 million pursuant to a payoff letter between the Company and Hercules, all outstanding indebtedness and obligations of the Company owed to Hercules under the Loan Agreement were paid in full, and the Loan Agreement was terminated. As a result of the debt extinguishment, the Company recognized a loss of $1.4 million during the year ended December 31, 2017. In connection with the entry into the Loan Agreement, the Company issued warrants (the "Warrants") to certain entities affiliated with Hercules, exercisable for an aggregate of 61,273 shares of the Company’s common stock at an exercise price of $12.24 per share. The Warrants have a five year term, expiring June 8, 2022, and may be exercised on a cashless basis. The Hercules Warrants had a total relative fair value of $0.5 million upon issuance and were recorded as a debt discount. Pursuant to ASC 480, Distinguishing Liabilities from Equity and ASC 815, Derivatives and Hedging, the Warrants were classified as equity and were initially measured at relative fair value. Subsequent changes to fair value will not be recognized so long as the instrument continues to be equity classified. To determine the relative fair value, the Company measured the fair value of the Warrants as of June 8, 2017 using the Black-Scholes-Merton option pricing model. The significant assumptions used in estimating the fair value of the Warrants include the volatility of the stock underlying the warrants, risk-free interest rate, and estimated life of the warrant. The Company used the following weighted-average assumptions: Expected volatility 73.71 % Expected term (in years) 5 Risk-free interest rate 1.75 % Expected dividend yield — % Consistent with the Company’s weighted-average assumptions used in determining the fair value of options, expected volatility was estimated using a weighted-average of the Company's historical volatility of its common stock and the historical volatility of the common stock of a group of similar companies that were publicly traded.

Disgorgement of Profits

Disgorgement of Profits	12 Months Ended
	Dec. 31, 2018
Other Income and Expenses [Abstract]
Disgorgement of Profits	Disgorgement of Profits On December 28, 2017, the Company received $3.6 million due to a disgorgement of short-swing profits arising from the sales of the Company's stock by a greater than 10% stockholder pursuant to Section 16(b) of the Securities and Exchange Act of 1934. The funds disgorged to the Company were based on a formulaic computation as proscribed by the 1934 Act as a result of security activities that generally fall under the Section 16(b) rules. The sales of the Company's stock was conducted without the knowledge of the Company, and the disgorgement profits were unrelated to the Company's primary business operations. Furthermore, under Section 16(b) of the Securities and Exchange Act of 1934, the Company was legally entitled to receive the disgorged profits without any corresponding obligations owed by the Company and no shares or other benefits were given to BVF by the Company in exchange for the disgorgement proceeds. As a result, the disgorgement receipt was recognized in other income for the fiscal year ended December 31, 2017.

401(k) Retirement Plan

401(k) Retirement Plan	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
401(k) Retirement Plan	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 $0.3 million , $0.3 million and $0.3 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Quarterly Financial Information

Quarterly Financial Information (unaudited)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (unaudited)	Quarterly Financial Information (unaudited) Three Months Ended March 31, June 30, September 30, December 31, (in thousands, except per share data) (unaudited) Revenue $ 10,479 $ 2 $ 11 $ 13 Operating expenses 14,286 14,376 17,351 20,076 Loss from operations (3,807 ) (14,374 ) (17,340 ) (20,063 ) Other (expense) income, net (656 ) 1,329 (29 ) (771 ) Provision for income taxes — (280 ) (18 ) (15 ) Net loss $ (4,463 ) $ (13,325 ) $ (17,387 ) $ (20,849 ) Net loss per share - basic and diluted $ (0.19 ) $ (0.57 ) $ (0.74 ) $ (0.89 ) Three Months Ended March 31, 2017 June 30, 2017 September 30, 2017 December 31, 2017 (in thousands, except per share data) (unaudited) Revenue $ 20 $ 15 $ 143,844 $ 12 Operating expenses 13,490 12,992 12,011 12,749 Income (Loss) from operations (13,470 ) (12,977 ) 131,833 (12,737 ) Other income (expense), net 137 (50 ) (1,591 ) 4,194 (Provision) Benefit for income taxes — — (2,177 ) 2,477 Net income (loss) $ (13,333 ) $ (13,027 ) $ 128,065 $ (6,066 ) Net income (loss) per share—basic $ (0.60 ) $ (0.58 ) $ 5.61 $ (0.26 ) Net income (loss) per share—diluted $ (0.60 ) $ (0.58 ) $ 5.44 $ (0.26 )

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation 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 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 subsidiaries. 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.
Estimates and Uncertainties	Estimates and Uncertainties The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, equity, revenue, expenses and the disclosure of contingent assets and liabilities and the Company's ability to continue as a going concern. In preparing the consolidated financial statements, management used estimates in the following areas, among others: revenue recognition; income tax expense; stock-based compensation expense; accrued expenses; and the evaluation of the existence of conditions and events that raise substantial doubt regarding the Company’s ability to continue as a going concern. Actual results could differ from those estimates.
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 (loss). Premiums or discounts from par value are amortized to investment income over the life of the underlying investment. Although available to be sold to meet operating needs or otherwise, securities are generally held through maturity. The Company classifies all investments as current assets as these assets are readily available for use in current operations. The cost of securities sold is determined based on the specific identification method for purposes of recording realized gains and losses. During 2018 and 2017, there were no realized gains or losses on sales of investments, and no investments were adjusted for other than temporary declines in fair value. The Company reviews available-for-sale securities for other-than-temporary impairment whenever the fair value of an available-for-sale security is less than the amortized cost and evidence indicates that an available-for-sale security’s carrying amount is not recoverable within a reasonable period of time. Other-than-temporary impairments of investments are recognized in the consolidated statements of operations if the Company has experienced a credit loss, has the intent to sell the security, or if it is more likely than not that the Company will be required to sell the security before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with the Company’s investment policy, the severity and the duration of the impairment and changes in value subsequent to the end of the period.
Marketable Equity Securities	Marketable Equity Securities Marketable equity securities consist of the fair value of common shares of Processa held by the Company, as discussed further in Note 12. As discussed below in this Note 2, effective January 1, 2018 the Company prospectively adopted ASU 2016-01, resulting in the recognition of the effects of changes in fair value of equity securities within net income. The Company reviews investments in marketable securities for other-than-temporary impairment whenever the fair value of the investment is less than the cost and evidence indicates that an investment’s carrying amount is not recoverable within a reasonable period of time. To determine whether an impairment is other-than-temporary, the Company considers whether it has an intent to sell, or whether it is more likely than not that the Company will be required to sell, the investment before recovery of the investment’s cost basis. Evidence considered in this assessment includes reasons for the impairment, the severity and the duration of the impairment and changes in value subsequent to year-end.
Fair Value of Financial Measurements	Fair Value of Financial Measurements The Company has certain financial assets and liabilities that are recorded at fair value which have been classified as Level 1, 2 or 3 within the fair value hierarchy as described in the accounting standards for fair value measurements: • Level 1—quoted prices for identical instruments in active markets; • Level 2—quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all significant inputs and significant value drivers are observable in active markets; and • Level 3—valuations derived from valuation techniques in which one or more significant value drivers are unobservable. For additional information related to fair value measurements, please read Note 3 to the consolidated financial statements.
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, investments (including interest receivable), and accounts receivable. Our current investment policy is to maintain a diversified investment portfolio in U.S. government-backed securities and money market mutual funds consisting of U.S. government-backed securities. Our cash is deposited in and invested through highly rated financial institutions in North America. 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, 2018 and 2017, substantially all of the Company’s cash was deposited in accounts at two 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 generally 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. Leasehold improvements are amortized over the shorter of their useful life or the related lease term. 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, 2018.
Rent Expense	Rent Expense Rent expense for the year ended December 31, 2018 consists of the Company's previous facility at 99 Hayden Avenue, Lexington, Massachusetts, and the Company's new facility at 65 Hayden Avenue, Lexington, Massachusetts. The Company ceased recognizing rent expense for 99 Hayden Avenue when the lease expired on September 30, 2018. The Company began recognizing rent expense for 65 Hayden Avenue on January 1, 2018 when it obtained access to the premises. The Company's operating lease for its new facility at 65 Hayden Avenue in Lexington, Massachusetts 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 on January 1, 2029. Additionally, the Company has received certain lease incentives in connection with its existing Lexington, Massachusetts facility lease, which are recognized as a reduction to rent expense over the remaining lease term. Refer to Note 11 for additional details regarding the Company’s operating leases.
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 generated revenue through arrangements with collaborators and nonprofit organizations for the development and commercialization of product candidates, a patent assignment agreement and an asset sale. On January 1, 2018, the Company adopted Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers and all related amendments ("ASC 606" or "the new revenue standard"). ASC 606 is a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most legacy revenue recognition guidance, including industry-s pecific guidance. The new revenue standard is based on the principle that an entity should recognize revenue to depict the transfer of 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, ASC 606 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. The new revenue standard also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts and costs to obtain or fulfill contracts. The Company applied ASC 606 on January 1, 2018 to all contracts using the modified retrospective approach. As a result of the adoption, the cumulative effect to retained earnings at January 1, 2018 was $15.8 million . The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The adoption of the new standard had an immaterial impact on the Company’s reported revenues, operating income and changes in operating cash flows for the twelve months ended December 31, 2018 as compared to what reported amounts would have been under legacy guidance. The cumulative effect of the changes made to the consolidated January 1, 2018 balance sheet for the adoption of the new revenue standard was as follows: (Amounts in thousands) Balance at December 31, 2017 ASC 606 Adjustments Opening Balance at January 1, 2018 Assets Contract Asset $ — $ 16,000 $ 16,000 Liabilities and Equity Deferred revenue, current portion $ 1,442 $ (14 ) $ 1,428 Deferred revenue, net of current portion 8,859 261 9,120 Retained earnings 76,243 15,753 60,490 The impact of adopting the new revenue standard primarily relates to the treatment of the consideration held in escrow under the Vertex Asset Purchase Agreement. Under previous authoritative guidance, the Company concluded that it would not recognize the Vertex escrow consideration until it was received. However, under ASC 606, the Vertex escrow consideration represents variable consideration and was included in the transaction price at contract inception, discussed further in Note 12. There was no material effect on the accounting for income taxes resulting from the adoption of ASC 606.
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. External research and development expenses associated with the Company’s programs include clinical trial site costs, research compounds and 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 and nonclinical programs. Internal costs of the Company’s clinical program include salaries, benefits, 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 and restricted-stock-units, or RSUs, 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 8 for additional information.
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. On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act (“TCJA”). This legislation made broad and complex changes to the U.S. tax code, including, but not limited to, (i) reducing the U.S. federal statutory tax rate from 35% to 21%; (ii) eliminating the corporate alternative minimum tax (AMT) and changing how existing AMT credits can be realized; (iii) changing rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017, and (iv) modifying the officer’s compensation limitation. The Company recognized the effects of changes in tax law, including the TCJA, in the period the law is enacted. Accordingly, the effects of the TCJA were recognized in the financial statements for the year ended December 31, 2017. For additional details regarding the accounting for income taxes, see Note 10.
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 non-cancelable operating leases which are further described in Note 11. The Company has standard indemnification arrangements under the leases that requires it to indemnify the landlords 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 leases. Pursuant to the Asset Purchase Agreement, discussed further in Note 12, the Company agreed to indemnify Vertex for certain matters, including breaches of specified representations and warranties, covenants included in the Asset Purchase Agreement and specified tax claims. Representations and warranties, other than certain fundamental representations and warranties, survived for a period of eighteen months following the Closing and the maximum liability of the Company for claims by Vertex related to the breaches of such representations and warranties, with limited exceptions, was limited to the escrow amount, or $16 million . In January 2019, the escrow period expired and the escrow of $16.0 million was released to the Company in February 2019. As of December 31, 2018 and 2017, 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) Income	Comprehensive (Loss) Income Comprehensive (loss) income is comprised of net (loss) income and other comprehensive income or loss. Other comprehensive income or loss consists of unrealized gains and losses on investments.
Recently Adopted Accounting Pronouncements and Pending Accounting Pronouncements	Recently Adopted Accounting Pronouncements On January 1, 2018, the Company adopted ASU 2014-09, Revenue from Contracts with Customers and all related amendments. For further discussion, see the Revenue Recognition discussion appearing elsewhere in this Note 2. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows - Restricted Cash (Topic 230). This standard requires companies to include amounts generally described as restricted cash and restricted cash equivalents in cash and cash equivalents when reconciling beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The Company adopted this standard on January 1, 2018. The adoption of ASU 2016-18 resulted in the Company's cash, cash equivalents and restricted cash being included in the beginning and ending amounts for the periods shown on the statement of cash flows and was applied retroactively and reflected in the balances presented for any prior periods. The Company believes that the adoption of this guidance did not have a significant impact on its consolidated financial statements and related disclosures. Restricted cash as of December 31, 2018 and 2017 is held as collateral for stand-by letters of credit issued by the Company to its landlords in connection with the leases of both the Company's current facility at 65 Hayden Avenue, Lexington, Massachusetts, as well as its previous facility at 99 Hayden Avenue, Lexington, Massachusetts. Cash, cash equivalents and restricted cash consisted of the following: December 31, December 31, Cash and cash equivalents $ 17,770 $ 27,665 Restricted cash 1,157 1,557 $ 18,927 $ 29,222 In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities, which revises the classification and measurement of investments in equity securities. ASU 2016-01 generally requires that equity investments, except for those accounted for under the equity method of accounting, be measured at fair value and changes in fair value are recognized in net income. Unrealized gains or losses from other investments, including debt securities, continue to be included in accumulated other comprehensive income (loss). Effective January 1, 2018, the Company prospectively adopted this new standard resulting in the recognition of the effects of changes in fair value of equity securities within net income (loss) in the consolidated statement of operations and comprehensive loss. Refer to Note 12 for discussion of the Company's marketable equity securities holdings. Pending Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). ASU 2016-02 requires lessees to recognize assets and liabilities on the balance sheet for the rights and obligations created by all leases with terms of more than 12 months. ASU 2016-02 will also require certain qualitative and quantitative disclosures designed to give financial statement users information on the amount, timing, and uncertainty of cash flows arising from leases. ASU 2016-02 will be effective for the Company on January 1, 2019. The Company plans to adopt the new standard with a cumulative-effect adjustment to the opening balance of retained earnings at that date and no restatement of comparative periods’ financial information, as recently allowed by the FASB. The Company is currently evaluating the effect of adopting the requirements of ASU 2016-02 as it relates to the accounting for its facility lease at 65 Hayden Avenue, Lexington, Massachusetts, which was executed in December 2017 and is discussed further in Note 11. The Company has performed a preliminary evaluation of other material contracts to determine if any contain embedded leases, and has not identified any to date. The Company's lease for its 99 Hayden Avenue, Lexington, Massachusetts facility expired in September 2018 and as a result will not be evaluated under the scope of ASU 2016-02. The Company expects to elect certain relief options offered in ASU 2016-02 including the package of practical expedients, the option not to separate lease and non-lease components and instead to account for them as a single lease component, and the option not to recognize right-of-use assets and lease liabilities that arise from short-term leases (i.e., leases with terms of twelve months or less). In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326)-Measurement of Credit Losses on Financial Instruments, or ASU 2016-13. The new standard requires entities to measure all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions and reasonable and supportable forecasts. ASU 2016-13 will become effective for the Company for fiscal years beginning after December 15, 2019, with early adoption permitted. The Company is currently evaluating the impact ASU 2016-13 will have on its financial statements and related disclosures. In June 2018, the FASB issued ASU 2018-07 (Topic 718) - Improvements to Nonemployee Share-Based Payment Accounting that expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. ASU 2018-07 provides that an entity should apply the requirements of Topic 718 to nonemployee awards except for certain exemptions specified in the amendment. The guidance is effective for fiscal years beginning after December 15, 2018, including interim reporting periods within that fiscal year. Early adoption is permitted, but no earlier than an entity’s adoption date of ASC 606. The Company believes that this guidance will not have a significant impact on its consolidated financial statements and related disclosures.

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The cumulative effect of the changes made to the consolidated January 1, 2018 balance sheet for the adoption of the new revenue standard was as follows: (Amounts in thousands) Balance at December 31, 2017 ASC 606 Adjustments Opening Balance at January 1, 2018 Assets Contract Asset $ — $ 16,000 $ 16,000 Liabilities and Equity Deferred revenue, current portion $ 1,442 $ (14 ) $ 1,428 Deferred revenue, net of current portion 8,859 261 9,120 Retained earnings 76,243 15,753 60,490
Schedule of Cash and Cash Equivalents	Cash, cash equivalents and restricted cash consisted of the following: December 31, December 31, Cash and cash equivalents $ 17,770 $ 27,665 Restricted cash 1,157 1,557 $ 18,927 $ 29,222

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities	The tables below present information about the Company’s financial assets and liabilities that are measured and carried at fair value as of December 31, 2018 and 2017 (in thousands) and indicate the level within the fair value hierarchy where each measurement is classified. Level 1 Level 2 Level 3 Total December 31, 2018 Cash equivalents: Money market funds $ 7,643 $ — $ — $ 7,643 U.S. Treasury obligations 1,748 — — 1,748 Investments, available for sale: U.S. Treasury obligations 34,103 746 — 34,849 Government agency securities 64,733 35,962 — 100,695 Marketable equity securities: Corporate equity securities (Note 12) 7,525 — — 7,525 Total $ 115,752 $ 36,708 $ — $ 152,460 Level 1 Level 2 Level 3 Total December 31, 2017 Cash equivalents: Money market funds $ 8,108 $ — $ — $ 8,108 Investments, available for sale: U.S. Treasury obligations 53,910 — — 53,910 Government agency securities 88,651 32,939 — 121,590 Total $ 150,669 $ 32,939 $ — $ 183,608

Cash, Cash Equivalents, Inves_2

Cash, Cash Equivalents, Investments and Marketable Equity Securities (Tables)	12 Months Ended
	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents and Investments, Available for Sale	Average maturity Amortized cost Unrealized gains Unrealized losses Fair value December 31, 2018 Cash $ 8,379 $ — $ — $ 8,379 Money market funds 7,643 — — 7,643 U.S. Treasury obligations 31 days 1,748 — — 1,748 Cash and cash equivalents $ 17,770 $ — $ — $ 17,770 U.S. Treasury obligations 151 days $ 34,856 $ 2 $ (9 ) $ 34,849 Government agency securities 153 days 100,748 7 (60 ) 100,695 Investments, available for sale $ 135,604 $ 9 $ (69 ) $ 135,544 December 31, 2018 Acquisition value Unrealized gains Unrealized losses Fair value Marketable equity securities (Note 12) $ 10,451 $ — $ (2,926 ) $ 7,525 Average maturity Amortized cost Unrealized gains Unrealized losses Fair value December 31, 2017 Cash $ 19,557 $ — $ — $ 19,557 Money market funds 8,108 — — 8,108 Cash and cash equivalents $ 27,665 $ — $ — $ 27,665 U.S. Treasury obligations 184 days $ 54,004 $ — $ (94 ) $ 53,910 Government agency securities 229 days 121,903 — (313 ) 121,590 Investments, available for sale $ 175,907 $ — $ (407 ) $ 175,500

Restricted Cash Restricted Cash

Restricted Cash Restricted Cash (Tables)	12 Months Ended
	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Restricted Cash and Cash Equivalents	December 31, December 31, 2017 Letter of Credit: 99 Hayden Avenue, Lexington, Massachusetts $ — $ 400 Letter of Credit: 65 Hayden Avenue, Lexington, Massachusetts 1,157 1,157 $ 1,157 $ 1,557

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consists of the following at December 31, 2018 and 2017 (in thousands): Estimated useful life (in years) December 31, 2018 December 31, Laboratory equipment 5 $ 3,484 $ 2,674 Computer, telephone and office equipment 3 875 147 Software 3 206 160 Leasehold improvements Lesser of useful life or remaining lease term 5,866 6,551 10,431 9,532 Less accumulated depreciation and amortization (1,512 ) (7,367 ) $ 8,919 $ 2,165

Accrued Expenses and Other Li_2

Accrued Expenses and Other Liabilities (Tables)	12 Months Ended
	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued Expenses and Other Liabilities	Accrued expenses and other liabilities consist of the following (in thousands): December 31, 2018 December 31, Accrued professional fees and other $ 672 $ 628 Employee compensation and benefits 3,067 2,797 Research and development expenses 1,476 521 Deferred lease incentive, current portion 454 249 Deferred rent, current portion — 104 $ 5,669 $ 4,299

Stock Compensation (Tables)

Stock Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Stock Option Granted Fair Value	The following table provides certain information related to the Company's outstanding stock options: Year ended December 31, 2018 2017 2016 (in thousands, except per share data) Weighted average fair value of options granted, per option $ 17.74 $ 7.67 $ 10.42 Aggregate grant date fair value of options vested during the year $ 7,755 $ 6,212 $ 4,614 Total cash received from exercises of stock options $ 1,037 $ 6,576 $ 601 Total intrinsic value of stock options exercised $ 2,599 $ 8,692 $ 1,160
Estimated Weighted-Average Assumptions of Options Granted	The weighted average fair value of options granted in the years ended December 31, 2018, 2017 and 2016, reflect the following weighted-average assumptions: Year ended December 31, 2018 2017 2016 Expected volatility 77.22 % 78.15 % 78.29 % Expected term 6.0 years 6.0 years 6.0 years Risk-free interest rate 2.64 % 2.07 % 1.36 % Expected dividend yield — % — % — %
Summary of Stock Option Activity	The following is a summary of option activity under the 2006 Plan and 2014 Plan: Number of Option Shares Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (In years) (In thousands) Outstanding at December 31, 2017 2,889,722 $ 11.25 Granted 968,043 $ 26.01 Exercised (196,861 ) $ 7.27 Forfeited or expired (103,498 ) $ 19.20 Outstanding at December 31, 2018 3,557,406 $ 15.26 6.97 5,834 Exercisable at December 31, 2018 2,134,434 $ 12.27 6.05 5,052 Vested and expected to vest at December 31, 2018 (1) 3,444,612 $ 15.06 6.92 5,780 (1) This represents the number of vested stock option shares as of December 31, 2018, plus the number of unvested stock option shares that the Company estimated as of December 31, 2018 would vest, based on the unvested stock option shares at December 31, 2018 and an estimated forfeiture rate of 7% .
Schedule of Restricted Stock Units Award Activity	The following is a summary of RSU activity, including both time-based and performance-based restricted stock units for the year ended December 31, 2018: Number of RSU Shares Weighted Average Grant Date Fair Value Outstanding at December 31, 2017 517,300 $ 13.87 Granted — $ — Released (174,050 ) $ 13.87 Forfeited (115,100 ) $ 13.87 Outstanding at December 31, 2018 228,150 $ 13.87
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 income (loss) is as follows (in thousands): For the Year Ended December 31, 2018 2017 2016 Research and development $ 5,221 $ 3,708 $ 2,147 General and administrative 6,279 4,792 2,920 Total stock-based compensation expense $ 11,500 $ 8,500 $ 5,067

Earnings (Loss) Per Share (Tabl

Earnings (Loss) Per Share (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table illustrates the determination of earnings (loss) per share for each period presented. For the Year Ended December 31, 2018 2017 2016 Basic Earnings per Share (in thousands, except per share amounts) Numerator: Net (loss) income $ (56,024 ) $ 95,639 $ (50,720 ) Income attributable to participating securities - basic — 444 — (Loss) income attributable to common stockholders - basic (56,024 ) 95,195 (50,720 ) Denominator: Weighted average shares outstanding 23,370 22,641 22,233 Net (loss) income per share applicable to common stockholders - basic $ (2.40 ) $ 4.20 $ (2.28 ) Diluted Earnings per Share Numerator: Net (loss) income (56,024 ) 95,639 (50,720 ) Income attributable to participating securities - diluted — 429 — (Loss) income attributable to common stockholders - diluted (56,024 ) 95,210 (50,720 ) Denominator: Weighted average shares outstanding 23,370 22,641 22,233 Dilutive impact from: Stock options — 688 — Restricted stock units — 113 — Weighted average shares outstanding - diluted 23,370 23,442 22,233 Net (loss) income per share applicable to common stockholders - diluted $ (2.40 ) $ 4.06 $ (2.28 ) Anti-dilutive potential common stock equivalents excluded from the calculation of net (loss) income per share: Stock options 666 1,833 620 Restricted stock units 185 408 — Warrants 132 — 71

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
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, 2018 2017 2016 Federal statutory income tax rate 21.0 % (35.0 )% 34.0 % State income taxes 6.2 % (5.1 )% 4.5 % Change in valuation allowance (30.9 )% 46.2 % (40.3 )% Research and development and other credits 4.0 % 2.5 % 3.1 % Permanent items (0.3 )% 0.8 % (1.0 )% Alternative minimum tax — % — % — % Other (0.6 )% — % (0.3 )% Federal rate change — % (9.1 )% — % Effective income tax rate (0.6 )% 0.3 % — %
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, 2018 2017 Deferred tax assets: Net operating loss carryforwards $ 23,841 $ 11,670 Deferred revenue 2,878 2,733 Research and development and other credit carryforwards 15,597 13,399 Fixed assets — 236 Other 7,985 3,575 50,301 31,613 Valuation allowance (44,453 ) (31,613 ) Total deferred tax assets, net of valuation allowance $ 5,848 $ — Deferred tax liabilities: Fixed assets $ 1,477 $ — Gain deferred under installment method 4,371 — Total deferred tax liabilities $ 5,848 $ — Net deferred tax assets $ — $ —

Commitments (Tables)

Commitments (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Lease Payments	The future minimum lease payments under the Lease is as follows (in thousands): Base rent obligations At December 31, 2018 2019 $ 2,776 2020 2,383 2021 2,945 2022 3,034 2023 3,125 Greater than 5 years 17,085 Total minimum lease payments $ 31,348

Loan Payable and Warrant to P_2

Loan Payable and Warrant to Purchase Redeemable Securities (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Summary of Significant Assumptions Used in Warrant Fair Value Measurements	The Company used the following weighted-average assumptions: Expected volatility 73.71 % Expected term (in years) 5 Risk-free interest rate 1.75 % Expected dividend yield — %

Quarterly Financial Informati_2

Quarterly Financial Information (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (unaudited)	Three Months Ended March 31, June 30, September 30, December 31, (in thousands, except per share data) (unaudited) Revenue $ 10,479 $ 2 $ 11 $ 13 Operating expenses 14,286 14,376 17,351 20,076 Loss from operations (3,807 ) (14,374 ) (17,340 ) (20,063 ) Other (expense) income, net (656 ) 1,329 (29 ) (771 ) Provision for income taxes — (280 ) (18 ) (15 ) Net loss $ (4,463 ) $ (13,325 ) $ (17,387 ) $ (20,849 ) Net loss per share - basic and diluted $ (0.19 ) $ (0.57 ) $ (0.74 ) $ (0.89 ) Three Months Ended March 31, 2017 June 30, 2017 September 30, 2017 December 31, 2017 (in thousands, except per share data) (unaudited) Revenue $ 20 $ 15 $ 143,844 $ 12 Operating expenses 13,490 12,992 12,011 12,749 Income (Loss) from operations (13,470 ) (12,977 ) 131,833 (12,737 ) Other income (expense), net 137 (50 ) (1,591 ) 4,194 (Provision) Benefit for income taxes — — (2,177 ) 2,477 Net income (loss) $ (13,333 ) $ (13,027 ) $ 128,065 $ (6,066 ) Net income (loss) per share—basic $ (0.60 ) $ (0.58 ) $ 5.61 $ (0.26 ) Net income (loss) per share—diluted $ (0.60 ) $ (0.58 ) $ 5.44 $ (0.26 )

Nature of Business - Additional

Nature of Business - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 21, 2018	Mar. 03, 2017	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018	Jul. 25, 2017
Subsidiary, Sale of Stock [Line Items]
Patent assignment agreement payment	$ 10,500				$ 13	$ 11	$ 2	$ 10,479	$ 12	$ 143,844	$ 15	$ 20	$ 10,505	$ 143,891	$ 174
Cash and cash equivalents and investments					153,300								153,300
Sufficiency of cash time period														12 months
Accumulated deficit					116,500								116,500
IPO
Subsidiary, Sale of Stock [Line Items]
Common stock, issued (in shares)				3,300,000
Common stock price per share (in dollars per share)				$ 15.15
Net proceeds of IPO				$ 46,700
Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Subsidiary, Sale of Stock [Line Items]
Consideration (up to)		$ 250,000
Cash consideration		160,000															$ 160,000
Indemnification Agreement | Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Subsidiary, Sale of Stock [Line Items]
Patent assignment agreement payment		160,000
Cash consideration		160,000
Guarantor maximum liability		$ 16,000			$ 16,000								16,000			$ 16,000	$ 16,000
Product and Service, Other
Subsidiary, Sale of Stock [Line Items]
Patent assignment agreement payment			$ 50,200										$ 0	$ 143,829	$ 0

Basis of Presentation and Sig_4

Basis of Presentation and Significant Accounting Policies - Additional Information (Details)	Dec. 28, 2017USD ($)	Mar. 03, 2017USD ($)	Feb. 28, 2019USD ($)	Dec. 31, 2018USD ($)institutionsegment	Dec. 31, 2017USD ($)institution	Dec. 31, 2016USD ($)	Jan. 01, 2018USD ($)	Jul. 25, 2017USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of segments | segment				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
Number of financial institutions | institution				2	2
Impairment losses				$ 0
Rent expense				3,300,000	$ 1,100,000	$ 1,200,000
Retained earnings				$ (116,515,000)	(76,243,000)		$ 60,490,000
Other income from disgorgement of short-swing profits	$ 3,600,000				$ 3,600,000
Subsequent event
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Escrow amount released			$ 16,000,000
Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Indemnification Agreement | Disposal Group, Disposed of by Sale, Not Discontinued Operations
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Guarantor obligations term		18 months		18 months
Guarantor maximum liability		$ 16,000,000		$ 16,000,000			16,000,000	$ 16,000,000
Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Indemnification Agreement | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Subsequent event
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Escrow amount released			$ 16,000,000
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings							$ 15,753,000

Basis of Presentation and Sig_5

Basis of Presentation and Significant Accounting Policies - Cumulative Effect of Changes from New Revenue Guidance (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract Asset	$ 16,000	$ 16,000	$ 0
Deferred revenue, current portion	1,413	1,428	1,442
Deferred revenue, net of current portion	9,120	9,120	8,859
Retained earnings	$ (116,515)	60,490	(76,243)
Calculated under Revenue Guidance in Effect before Topic 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract Asset			0
Deferred revenue, current portion			1,442
Retained earnings			$ 76,243
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract Asset		16,000
Deferred revenue, current portion		(14)
Deferred revenue, net of current portion		261
Retained earnings		$ 15,753

Basis of Presentation and Sig_6

Basis of Presentation and Significant Accounting Policies - Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Cash and cash equivalents	$ 17,770	$ 27,665
Restricted cash	1,157	1,557
Cash, cash equivalents, restricted cash and restricted cash equivalents	$ 18,927	$ 29,222	$ 40,955	$ 92,910

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Liabilities Recognized at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value	$ 17,770	$ 27,665
Fair value, measurements, recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	7,525
Total assets, fair value	152,460	183,608
Fair value, measurements, recurring | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	34,849	53,910
Fair value, measurements, recurring | Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	100,695	121,590
Fair value, measurements, recurring | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value	7,643	8,108
Fair value, measurements, recurring | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value	1,748
Fair value, measurements, recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	7,525
Total assets, fair value	115,752	150,669
Fair value, measurements, recurring | Level 1 | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	34,103	53,910
Fair value, measurements, recurring | Level 1 | Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	64,733	88,651
Fair value, measurements, recurring | Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value	7,643	8,108
Fair value, measurements, recurring | Level 1 | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value	1,748
Fair value, measurements, recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0
Total assets, fair value	36,708	32,939
Fair value, measurements, recurring | Level 2 | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	746	0
Fair value, measurements, recurring | Level 2 | Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	35,962	32,939
Fair value, measurements, recurring | Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value	0	0
Fair value, measurements, recurring | Level 2 | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value	0
Fair value, measurements, recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0
Total assets, fair value	0	0
Fair value, measurements, recurring | Level 3 | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	0	0
Fair value, measurements, recurring | Level 3 | Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	0	0
Fair value, measurements, recurring | Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value	0	$ 0
Fair value, measurements, recurring | Level 3 | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value	$ 0

Cash, Cash Equivalents, Inves_3

Cash, Cash Equivalents, Investments and Marketable Equity Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents
Amortized cost	$ 17,770	$ 27,665
Fair value	17,770	27,665
U.S. Treasury obligations
Debt Securities
Amortized cost	34,856	54,004
Unrealized gains	2	0
Unrealized losses	(9)	(94)
Fair value	34,849	53,910
Government agency securities
Debt Securities
Amortized cost	100,748	121,903
Unrealized gains	7	0
Unrealized losses	(60)	(313)
Fair value	100,695	121,590
Investments, available-for-sale
Debt Securities
Amortized cost	135,604	175,907
Unrealized gains	9	0
Unrealized losses	(69)	(407)
Fair value	135,544	175,500
Marketable Equity Securities, Corporate Equity Securities
Debt Securities
Equity Securities, FV-NI, Cost	10,451
Equity Securities, FV-NI, Accumulated Gross Unrealized Gain, before Tax	0
Equity Securities, FV-NI, Accumulated Gross Unrealized Loss, before Tax	(2,926)
Equity Securities, FV-NI	7,525
Cash
Cash and Cash Equivalents
Amortized cost	8,379	19,557
Fair value	8,379	19,557
Money market funds
Cash and Cash Equivalents
Amortized cost	7,643	8,108
Fair value	7,643	$ 8,108
U.S. Treasury obligations
Cash and Cash Equivalents
Amortized cost	1,748
Fair value	$ 1,748
Expected term (in years) | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Average maturity	151 days	184 days
Expected term (in years) | Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Average maturity	153 days	229 days
Expected term (in years) | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Average maturity	31 days

Restricted Cash - Additional In

Restricted Cash - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Restricted cash	$ 1,157	$ 1,557

Restricted Cash - Schedule of R

Restricted Cash - Schedule of Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash, noncurrent	$ 1,157	$ 1,557
Collateral, 99 Hayden Street
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash, noncurrent	0	400
Collateral, 65 Hayden Street
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash, noncurrent	$ 1,157	$ 1,157

Property and Equipment - Schedu

Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 10,431	$ 9,532
Less accumulated depreciation and amortization	(1,512)	(7,367)
Total property, plant and equipment, net	$ 8,919	2,165
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	5 years
Property, plant and equipment, gross	$ 3,484	2,674
Computer, telephone and office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	3 years
Property, plant and equipment, gross	$ 875	147
Software
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	3 years
Property, plant and equipment, gross	$ 206	160
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 5,866	$ 6,551

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 1,247	$ 1,008	$ 893

Accrued Expenses and Other Li_3

Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued professional fees and other	$ 672	$ 628
Employee compensation and benefits	3,067	2,797
Research and development expenses	1,476	521
Deferred lease incentive, current portion	454	249
Deferred rent, current portion	0	104
Accrued expenses and other liabilities	$ 5,669	$ 4,299

Stock Compensation - Additional

Stock Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 01, 2019	Jul. 06, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield			0.00%	0.00%	0.00%
Estimated forfeiture rate			7.00%	7.00%	6.00%
2006 stock incentive plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant (in shares)			0
2014 Stock incentive plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant (in shares)			1,488,976
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period			10 years
Total unrecognized compensation cost			$ 16.9
Total unrecognized compensation cost, weighted-average recognition period			2 years 3 months 18 days
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost, weighted-average recognition period				3 months
Restricted stock units granted to executives and employees (in shares)		500,000	0
Restricted stock units, vested (in shares)			174,050
Weighted average grant date fair value of restricted stock units (in dollars per share)			$ 0
Unrecognized compensation cost related to RSUs			$ 0.6
Minimum | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Maximum | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
Subsequent event | 2014 Stock incentive plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares added to plan (in shares)	937,503
Vesting on March 31, 2018 | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage		50.00%
Vesting on March 31, 2019 | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage		50.00%

Stock Compensation - Outstandin

Stock Compensation - Outstanding Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total cash received from exercises of stock options	$ 1,037	$ 6,576	$ 601
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of options granted, per option (in dollars per share)	$ 17.74	$ 7.67	$ 10.42
Aggregate grant date fair value of options vested during the year	$ 7,755	$ 6,212	$ 4,614
Total cash received from exercises of stock options	1,037	6,576	601
Total intrinsic value of stock options exercised	$ 2,599	$ 8,692	$ 1,160

Stock Compensation - Weighted-A

Stock Compensation - Weighted-Average Assumptions of Options Granted (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Expected volatility	77.22%	78.15%	78.29%
Expected term	6 years	6 years	6 years
Risk-free interest rate	2.64%	2.07%	1.36%
Expected dividend yield	0.00%	0.00%	0.00%

Stock Compensation - Summary of

Stock Compensation - Summary of Stock Option Activity (Details) - 2006 And 2014 Stock incentive plan $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)$ / sharesshares
Number of Option Shares
Number of options, outstanding beginning balance (in shares) | shares	2,889,722
Number of options, granted (in shares) | shares	968,043
Number of options, exercised (in shares) | shares	(196,861)
Number of options, forfeited or expired (in shares) | shares	(103,498)
Number of options, outstanding end balance (in shares) | shares	3,557,406
Number of options, exercisable (in shares) | shares	2,134,434
Number of options, vested and expected to vest (in shares) to vest | shares	3,444,612
Weighted Average Exercise Price per Share
Weighted average exercise price per share, outstanding at beginning of year (in dollars per share) | $ / shares	$ 11.25
Weighted average exercise price per share, granted (in dollars per share) | $ / shares	26.01
Weighted average exercise price per share, exercised (in dollars per share) | $ / shares	7.27
Weighted average exercise price per share, forfeited or expired (in dollars per share) | $ / shares	19.20
Weighted average exercise price per share, outstanding ending balance (in dollars per share) | $ / shares	15.26
Weighted average exercise price per share, exercisable (in dollars per share) | $ / shares	12.27
Weighted average exercise price per share, vested and expected to vest (in dollars per share) | $ / shares	$ 15.06
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term, outstanding	6 years 11 months 19 days
Weighted average remaining contractual term, exercisable	6 years 18 days
Weighted average remaining contractual term, vested and expected to vest	6 years 11 months 1 day
Aggregate Intrinsic Value
Aggregate intrinsic value, outstanding | $	$ 5,834
Aggregate intrinsic value, exercisable | $	5,052
Aggregate intrinsic value, vested and expected to vest | $	$ 5,780

Stock Compensation - Summary _2

Stock Compensation - Summary of Restricted Stock Units (Details) - Restricted stock units - $ / shares	Jul. 06, 2017	Dec. 31, 2018
Number of RSU Shares
Number of RSU shares, outstanding beginning balance (in shares)		517,300
Number of RSU shares, granted (in shares)	500,000	0
Number of RSU shares, released (in shares)		(174,050)
Number of RSU shares, forfeited (in shares)		(115,100)
Number of RSU shares, outstanding ending balance (in shares)		228,150
Weighted Average Grant Date Fair Value
Weighted average grant date fair value, outstanding beginning balance (in dollars per share)		$ 13.87
Weighted average grant date fair value, granted (in dollars per share)		0
Weighted average grant date fair value, released (in dollars per share)		13.87
Weighted average grant date fair value, forfeited (in dollars per share)		13.87
Weighted average grant date fair value, outstanding ending balance (in dollars per share)		$ 13.87

Stock Compensation - Stock-Base

Stock Compensation - Stock-Based Compensation Expense Related to All Stock-Based Awards Recognized in Statements of Operations and Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 11,500	$ 8,500	$ 5,067
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	5,221	3,708	2,147
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 6,279	$ 4,792	$ 2,920

Earnings (Loss) Per Share (Deta

Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Basic Earnings per Share
Net income (loss)	$ (20,849)	$ (17,387)	$ (13,325)	$ (4,463)	$ (6,066)	$ 128,065	$ (13,027)	$ (13,333)	$ (56,024)	$ 95,639	$ (50,720)
Income attributable to participating securities - basic									0	444	0
(Loss) income attributable to common stockholders - basic									$ (56,024)	$ 95,195	$ (50,720)
Weighted average shares outstanding (in shares)									23,370	22,641	22,233
Net income (loss) per share applicable to common stockholders—basic (in dollars per share)					$ (0.26)	$ 5.61	$ (0.58)	$ (0.60)	$ (2.40)	$ 4.20	$ (2.28)
Diluted Earnings per Share
Net income (loss)	$ (20,849)	$ (17,387)	$ (13,325)	$ (4,463)	$ (6,066)	$ 128,065	$ (13,027)	$ (13,333)	$ (56,024)	$ 95,639	$ (50,720)
Income attributable to participating securities - diluted									0	429	0
(Loss) income attributable to common stockholders - diluted									$ (56,024)	$ 95,210	$ (50,720)
Weighted average shares outstanding (in shares)									23,370	22,641	22,233
Dilutive impact from:
Weighted average shares outstanding - diluted (in shares)									23,370	23,442	22,233
Net income (loss) per share applicable to common stockholders—diluted (in dollars per share)					$ (0.26)	$ 5.44	$ (0.58)	$ (0.60)	$ (2.40)	$ 4.06	$ (2.28)
Stock options
Anti-dilutive potential common stock equivalents excluded from the calculation of net (loss) income per share:
Anti-dilutive stock options, restricted stock units, and warrants (in shares)									666	1,833	620
Restricted stock units
Anti-dilutive potential common stock equivalents excluded from the calculation of net (loss) income per share:
Anti-dilutive stock options, restricted stock units, and warrants (in shares)									185	408	0
Warrants
Anti-dilutive potential common stock equivalents excluded from the calculation of net (loss) income per share:
Anti-dilutive stock options, restricted stock units, and warrants (in shares)									132	0	71
Stock options
Dilutive impact from:
Dilutive impact from stock options and restricted stock units (in shares)									0	688	0
Restricted stock units
Dilutive impact from:
Dilutive impact from stock options and restricted stock units (in shares)									0	113	0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018	Jul. 25, 2017	Mar. 03, 2017	Dec. 31, 2015
Schedule Of Income Taxes [Line Items]
Reduction in deferred tax asset										$ 8,600,000
Income taxes receivable, AMT refund current year					$ 1,900,000					1,900,000
Alternative minimum tax credit carryforward					1,900,000					1,900,000					$ 300,000
Income taxes receivable, AMT refund prior year	$ 2,300,000								$ 2,300,000
(Loss) Income before income taxes									(55,711,000)	95,339,000	$ (50,720,000)
Income taxes payable	390,000				46,000				390,000	46,000
Income tax expense (benefit)	15,000	$ 18,000	$ 280,000	$ 0	(2,477,000)	$ 2,177,000	$ 0	$ 0	313,000	(300,000)	0
Income tax benefit, continuing operations									100,000
Unrealized gain (loss) on investments, tax									76,000
Net income (loss) before taxes										95,300,000	$ (50,700,000)
Income taxes receivable, AMT refund					2,200,000					2,200,000
Tax benefit reversal of valuation allowance on 2015 AMT credit carryforward										300,000
Operating loss carryforwards, not subject to expiration	44,700,000								44,700,000
Net operating loss carryforwards	23,841,000				11,670,000				23,841,000	11,670,000
Gain deferred under installment method	4,371,000				0				4,371,000	0
Unrecognized tax benefits	0								0
Accrued interest related to uncertain tax positions	0								0
Accounting Standards Update 2016-09
Schedule Of Income Taxes [Line Items]
Net operating loss carryforwards					$ 3,200,000					$ 3,200,000
Gain deferred under installment method												$ 4,300,000
Federal
Schedule Of Income Taxes [Line Items]
Operating loss carryforwards	99,500,000								99,500,000
Operating loss carryforwards, subject to expiration	54,800,000								54,800,000
Federal | Research and development
Schedule Of Income Taxes [Line Items]
Tax credit carryforwards	11,700,000								11,700,000
State
Schedule Of Income Taxes [Line Items]
Operating loss carryforwards	46,700,000								46,700,000
Operating loss carryforwards, subject to expiration	46,700,000								46,700,000
State | Research and development
Schedule Of Income Taxes [Line Items]
Tax credit carryforwards	4,900,000								4,900,000
Tax Year 2017
Schedule Of Income Taxes [Line Items]
Income tax expense (benefit)									200,000
Tax Year 2018
Schedule Of Income Taxes [Line Items]
Income tax expense (benefit)									200,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Assets for Synthesis and Research and Development for Treating Cystic Fibrosis
Schedule Of Income Taxes [Line Items]
Cash consideration													$ 160,000,000	$ 160,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Indemnification Agreement
Schedule Of Income Taxes [Line Items]
Cash consideration														160,000,000
Guarantor maximum liability	$ 16,000,000								$ 16,000,000			$ 16,000,000	$ 16,000,000	$ 16,000,000

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Federal Statutory Income Tax Rate and Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	35.00%	34.00%
State income taxes	6.20%	5.10%	4.50%
Change in valuation allowance	(30.90%)	(46.20%)	(40.30%)
Research and development and other credits	4.00%	(2.50%)	3.10%
Permanent items	(0.30%)	(0.80%)	(1.00%)
Alternative minimum tax	0.00%	0.00%	0.00%
Other	(0.60%)	0.00%	(0.30%)
Federal rate change	0.00%	9.10%	0.00%
Effective income tax rate	(0.60%)	(0.30%)	0.00%

Income Taxes - Significant Comp

Income Taxes - Significant Components of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 23,841	$ 11,670
Deferred revenue	2,878	2,733
Research and development and other credit carryforwards	15,597	13,399
Fixed assets	0	236
Other	7,985	3,575
Gross deferred tax assets	50,301	31,613
Valuation allowance	(44,453)	(31,613)
Total deferred tax assets, net of valuation allowance	5,848	0
Deferred tax liabilities:
Fixed assets	1,477	0
Gain deferred under installment method	4,371	0
Total deferred tax liabilities	5,848	0
Net deferred tax assets	$ 0	$ 0

Commitments - Additional Inform

Commitments - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)ft²option	Sep. 30, 2018ft²
2017 Lease Agreement
Commitments [Line Items]
Land subject to ground leases | ft²	55,522
Operating lease renewal term	10 years
Options to extend | option	2
Operating lease option to extend term	5 years
Operating lease annual base rent amount	$ 2.8
Operating lease yearly basis increase rate	3.00%
Operating lease abatement of base rent amount	$ 0.5
Operating lease allowance for design and construction improvements	5
Operating lease security deposit	$ 1.2
2008 Lease Agreement
Commitments [Line Items]
Land subject to ground leases | ft²		50,000

Commitments - Future Minimum Le

Commitments - Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,019	$ 2,776
2,020	2,383
2,021	2,945
2,022	3,034
2,023	3,125
Greater than 5 years	17,085
Total minimum lease payments	$ 31,348

Revenue - Revenue Recognition (

Revenue - Revenue Recognition (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018segment	Dec. 31, 2018USD ($)	Jan. 01, 2018USD ($)	Dec. 31, 2017USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments | segment	1
Contract asset		$ 16,000	$ 16,000	$ 0
Deferred revenue		10,500	$ 10,500
Revenue recognized		$ 16

Revenue - Celgene (Details)

Revenue - Celgene (Details)

Mar. 21, 2018USD ($)

Apr. 30, 2013USD ($)licenseoption

Dec. 31, 2018USD ($)

Sep. 30, 2018USD ($)

Jun. 30, 2018USD ($)

Mar. 31, 2018USD ($)

Dec. 31, 2017USD ($)

Sep. 30, 2017USD ($)

Jun. 30, 2017USD ($)

Mar. 31, 2017USD ($)

Oct. 30, 2013USD ($)

Dec. 31, 2018USD ($)

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Oct. 31, 2015USD ($)

Jan. 01, 2018USD ($)

Oct. 30, 2015USD ($)

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Deferred revenue

$ (16,000)

$ 251,000

$ (120,000)

Deferred revenue, current portion

$ 1,413,000

$ 1,442,000

1,413,000

1,442,000

$ 1,428,000

Total revenue

$ 10,500,000

13,000

$ 11,000

$ 2,000

$ 10,479,000

12,000

$ 143,844,000

$ 15,000

$ 20,000

10,505,000

143,891,000

174,000

Deferred revenue

10,500,000

10,500,000

10,500,000

Deferred revenue, net of current portion

9,120,000

$ 8,859,000

9,120,000

8,859,000

$ 9,120,000

Celgene

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Number of additional license program | license

2

Term of contract

7 years

Exercise fee option term

7 years

Deferred revenue, current portion

1,400,000

1,400,000

Percentage of royalty on net sales required to pay under the agreement

20.00%

Deferred revenue

7,800,000

7,800,000

Deferred revenue, net of current portion

$ 6,400,000

6,400,000

Celgene | Milestone Scenario Two

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Deferred revenue, current portion

$ 10,000,000

Celgene | Research and Development Services Deliverable | License and Service

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Total revenue

0

$ 20,000

$ 62,000

Celgene | Development Based Milestones | Milestone Scenario Two | Maximum

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

23,000,000

Celgene | Development Based Milestones | Milestone Scenario One | Maximum

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

23,000,000

Celgene | Regulatory Milestones | Milestone Scenario Two | Maximum

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

247,500,000

Celgene | Regulatory Milestones | Milestone Scenario One | Maximum

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

247,500,000

Celgene | Sales-Based Milestones | Milestone Scenario One | Maximum

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

100,000,000

Celgene | Sales-Based Milestones | Other Additional License Program | Maximum

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

$ 50,000,000

Celgene | License Exercise Fee

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Number of options for providing license program | option

1

Celgene | License Exercise Fee | Milestone Scenario One

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Number of options for providing license program | option

2

Deferred revenue, current portion

$ 30,000,000

Celgene | CTP-730 Program | Up-front Payment Arrangement

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Deferred revenue

35,000,000

Celgene | CTP-730 Program | Development Based Milestones

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

$ 8,000,000

Total revenue

$ 43,000,000

Celgene | CTP-730 Program | Development Based Milestones | License Performance Obligation

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Total revenue

$ 21,700,000

Celgene | CTP-730 Program | Development Based Milestones | R&D Services Performance Obligation

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Total revenue

11,000,000

1,300,000

Celgene | CTP-730 Program | Development Based Milestones | Supply Performance Obligation

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Total revenue

4,000,000

100,000

Celgene | CTP-730 Program | Development Based Milestones | First Discount Performance Obligation

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Total revenue

3,200,000

Celgene | CTP-730 Program | Development Based Milestones | Second Discount Performance Obligation

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Total revenue

$ 3,200,000

Celgene | CTP-730 Program | Development Based Milestones | First and Second Discount Performance Obligations

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Total revenue

$ 6,400,000

Celgene | CTP-730 Program | Development Based Milestones | Maximum | Collaborative Arrangement, Product

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

15,000,000

Celgene | CTP-730 Program | Development Based Milestones | Milestone Scenario Two

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

15,000,000

Celgene | CTP-730 Program | Regulatory Milestones | Maximum

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

247,500,000

Celgene | CTP-730 Program | Sales-Based Milestones | Maximum

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

$ 50,000,000

Celgene | CTP-730 Program | Milestone Payment, Phase 3 Clinical Trial

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

$ 15,000,000

Revenue - Avanir (Details)

Revenue - Avanir (Details) - USD ($)

Mar. 21, 2018

Jan. 01, 2018

Feb. 29, 2012

Dec. 31, 2018

Sep. 30, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Total revenue

$ 10,500,000

$ 13,000

$ 11,000

$ 2,000

$ 10,479,000

$ 12,000

$ 143,844,000

$ 15,000

$ 20,000

$ 10,505,000

$ 143,891,000

$ 174,000

Avanir pharmaceuticals

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

$ 6,000,000

$ 6,000,000

Total revenue

$ 8,000,000

Avanir pharmaceuticals | Non-Refundable Upfront Payment

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Total revenue

2,000,000

Avanir pharmaceuticals | Development Milestone Payments

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Total revenue

$ 6,000,000

Avanir pharmaceuticals | Collaborative Arrangement, Product

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Percentage of royalty on net sales required to pay under the agreement

20.00%

Avanir pharmaceuticals | Up-front Payment Arrangement

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

$ 2,000,000

Avanir pharmaceuticals | Regulatory And Commercial Launch Milestone | Maximum

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

37,000,000

Avanir pharmaceuticals | Development Based Milestones | Collaborative Arrangement, Product | US Food and Drug Administration | AVP-786 Program

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

5,000,000

Avanir pharmaceuticals | Development Based Milestones | Collaborative Arrangement, Product | Ministry of Health, Labour and Welfare (MHLW) | AVP-786 Program

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

1,500,000

Avanir pharmaceuticals | Development Based Milestones | Collaborative Arrangement, Co-promotion | AVP-786 Program

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

3,000,000

Avanir pharmaceuticals | Development Based Milestones | Maximum

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

21,500,000

Avanir pharmaceuticals | Sales-Based Milestones | Maximum

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

125,000,000

Avanir pharmaceuticals | Licensed | Collaborative Arrangement, Product

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

$ 43,000,000

Revenue - Jazz Pharmaceuticals

Revenue - Jazz Pharmaceuticals (Details) - USD ($)

Mar. 21, 2018

Feb. 28, 2013

Dec. 31, 2018

Sep. 30, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Deferred revenue

$ (16,000)

$ 251,000

$ (120,000)

Total revenue

$ 10,500,000

$ 13,000

$ 11,000

$ 2,000

$ 10,479,000

$ 12,000

$ 143,844,000

$ 15,000

$ 20,000

$ 10,505,000

$ 143,891,000

$ 174,000

Jazz Pharmaceuticals

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Percentage of royalty on net sales required to pay under the agreement

20.00%

Jazz Pharmaceuticals | JZP-386

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

$ 4,000,000

Jazz Pharmaceuticals | Up-front Payment Arrangement

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Deferred revenue

4,000,000

Jazz Pharmaceuticals | Development Based Milestones | Collaborative Arrangement, Co-promotion | Maximum

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

8,000,000

Jazz Pharmaceuticals | Sales-Based Milestones | Maximum

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

70,000,000

Jazz Pharmaceuticals | Regulatory Milestones | Maximum

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Eligible payments receivable

$ 35,000,000

Revenue - Vertex (Details)

Revenue - Vertex (Details) - USD ($)

Mar. 21, 2018

Mar. 03, 2017

Feb. 28, 2019

Dec. 31, 2018

Sep. 30, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Jan. 01, 2018

Jul. 25, 2017

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Total revenue

$ 10,500,000

$ 13,000

$ 11,000

$ 2,000

$ 10,479,000

$ 12,000

$ 143,844,000

$ 15,000

$ 20,000

$ 10,505,000

$ 143,891,000

$ 174,000

Subsequent event

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Escrow amount released

$ 16,000,000

Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Disposal Group, Disposed of by Sale, Not Discontinued Operations

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Cash consideration

$ 160,000,000

$ 160,000,000

Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Contingent Consideration Asset, After Achievement of Milestone Events

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Contingent consideration receivable

90,000,000

Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Contingent Consideration Asset, Upon Receipt of FDA Marketing Approval

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Contingent consideration receivable

50,000,000

Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Contingent Consideration Asset, Upon Completion of Pricing and Reimbursement Agreement

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Contingent consideration receivable

40,000,000

Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Indemnification Agreement

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Cash consideration

160,000,000

Guarantor maximum liability

$ 16,000,000

$ 16,000,000

$ 16,000,000

$ 16,000,000

$ 16,000,000

Guarantor obligations term

18 months

18 months

Total revenue

$ 160,000,000

Escrow release period

18 months

Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Indemnification Agreement | Subsequent event

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Escrow amount released

$ 16,000,000

Revenue - GSK (Details)

Revenue - GSK (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2012	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue		$ (16)	$ 251	$ (120)
Amended Agreement | GSK
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 2,800

Revenue - Auspex (Details)

Revenue - Auspex (Details) - USD ($) $ in Thousands	Mar. 21, 2018	Jun. 30, 2015	Sep. 30, 2011	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Consideration percentage related to change In control			1.44%
Total revenue	$ 10,500			$ 13	$ 11	$ 2	$ 10,479	$ 12	$ 143,844	$ 15	$ 20	$ 10,505	$ 143,891	$ 174
Product and Service, Other
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue		$ 50,200										$ 0	143,829	$ 0
Concert Auspex Patent Agreement | Product and Service, Other
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue		$ 50,200											$ 50,200

Revenue - Processa (Details)

Revenue - Processa (Details) - USD ($) $ in Thousands	Mar. 21, 2018	Mar. 19, 2018	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue	$ 10,500		$ 13	$ 11	$ 2	$ 10,479	$ 12	$ 143,844	$ 15	$ 20	$ 10,505	$ 143,891	$ 174
Processa
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Equity received from sale of license (in shares)		2,090,301
Percent of common stock		5.40%
Receivables from customers			$ 10,500								$ 10,500

Loan Payable and Warrant to P_3

Loan Payable and Warrant to Purchase Redeemable Securities - Additional Information (Details) - USD ($)	Sep. 07, 2017	Jun. 08, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Repayment of loan			$ 0	$ 30,745,000	$ 0
Loss on extinguishment of debt			$ 0	1,432,000	$ 0
Loan Agreement
Debt Instrument [Line Items]
Amount of warrants issued and exercisable (in shares)		61,273
Warrant exercise price (in dollars per share)		$ 12.24
Warrant expiration term		5 years
Warrants total relative fair value		$ 500,000
Secured Term Loan Facility | Loan Agreement | Line of Credit
Debt Instrument [Line Items]
Aggregate advance provided under the agreement		30,000,000
Loan issuance costs incurred		$ 300,000
Secured term loan variable rate		8.55%
Interest rate during period		8.55%
Repayment of loan	$ 30,800,000
End of term charge	$ 700,000
Original end of term charge		$ 1,500,000
Loss on extinguishment of debt				$ 1,400,000
Secured Term Loan Facility | Loan Agreement | Line of Credit | Minimum
Debt Instrument [Line Items]
Prepayment charge waived term		90 days
Secured Term Loan Facility | Loan Agreement | Line of Credit | Maximum
Debt Instrument [Line Items]
Prepayment charge waived term		6 months
Secured Term Loan Facility | Loan Agreement | Line of Credit | Prime rate
Debt Instrument [Line Items]
Basis spread on variable rate		4.50%

Loan Payable and Warrant to P_4

Loan Payable and Warrant to Purchase Redeemable Securities - Summary of Significant Assumptions Used in Warrant Fair Value Measurements (Details)	Jun. 08, 2017
Expected volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.7371
Expected term (in years)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected term (in years)	5 years
Risk-free interest rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0175
Expected dividend yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0

Disgorgement of Profits (Detail

Disgorgement of Profits (Details) - USD ($) $ in Millions	Dec. 28, 2017	Dec. 31, 2017
Other Income and Expenses [Abstract]
Other income from disgorgement of short-swing profits	$ 3.6	$ 3.6

401(k) Retirement Plan - Additi

401(k) Retirement Plan - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2008	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Company matching contribution, percent of match	50.00%
Company matching contribution, percent of employee contribution	6.00%
Matching contributions under 401(k)		$ 0.3	$ 0.3	$ 0.3

Quarterly Financial Informati_3

Quarterly Financial Information (unaudited) (Details) - USD ($)	Mar. 21, 2018	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 10,500,000	$ 13,000	$ 11,000	$ 2,000	$ 10,479,000	$ 12,000	$ 143,844,000	$ 15,000	$ 20,000	$ 10,505,000	$ 143,891,000	$ 174,000
Operating expenses		20,076,000	17,351,000	14,376,000	14,286,000	12,749,000	12,011,000	12,992,000	13,490,000	66,089,000	51,242,000	51,341,000
(Loss) Income from operations		(20,063,000)	(17,340,000)	(14,374,000)	(3,807,000)	(12,737,000)	131,833,000	(12,977,000)	(13,470,000)	(55,584,000)	92,649,000	(51,167,000)
Other (expense) income, net		(771,000)	(29,000)	1,329,000	(656,000)	4,194,000	(1,591,000)	(50,000)	137,000
Provision for income taxes		(15,000)	(18,000)	(280,000)	0	2,477,000	(2,177,000)	0	0	(313,000)	300,000	0
Net loss		$ (20,849,000)	$ (17,387,000)	$ (13,325,000)	$ (4,463,000)	$ (6,066,000)	$ 128,065,000	$ (13,027,000)	$ (13,333,000)	$ (56,024,000)	$ 95,639,000	$ (50,720,000)
Net loss per share - basic and diluted (in dollars per share)		$ (0.89)	$ (0.74)	$ (0.57)	$ (0.19)
Net income (loss) per share—basic (in dollars per share)						$ (0.26)	$ 5.61	$ (0.58)	$ (0.60)	$ (2.40)	$ 4.20	$ (2.28)
Net income (loss) per share—diluted (in dollars per share)						$ (0.26)	$ 5.44	$ (0.58)	$ (0.60)	$ (2.40)	$ 4.06	$ (2.28)

Uncategorized Items - cnce-2018

Label	Element	Value
Accounting Standards Update 2014-09 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 15,752,000
Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 15,752,000