Concert Pharmaceuticals (CNCE) 10-K 27 Feb 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Feb. 21, 2020	Jun. 30, 2019
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Registrant Name	CONCERT PHARMACEUTICALS, INC.
Entity Central Index Key	0001367920
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	false
Entity Shell Company	false
Entity Interactive Data Current	Yes
Entity Small Business	true
Entity Common Stock, Shares Outstanding		29,636,994
Entity Public Float			$ 172,718

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 53,043,000	$ 17,770,000
Investments, available for sale	53,395,000	135,544,000
Marketable equity securities	5,375,000	7,525,000
Interest receivable	260,000	556,000
Deferred offering costs	143,000	0
Accounts receivable	72,000	15,000
Contract asset (Note 12)	0	16,000,000
Prepaid expenses and other current assets	4,567,000	2,739,000
Total current assets	116,855,000	180,149,000
Property and equipment, net	7,753,000	8,919,000
Restricted cash	1,157,000	1,157,000
Other assets	96,000	0
Income taxes receivable	2,358,000	2,322,000
Operating lease right-of-use assets, long-term (Note 11)	9,252,000
Total assets	137,471,000	192,547,000
Current liabilities:
Accounts payable	881,000	1,277,000
Accrued expenses and other liabilities	8,336,000	5,669,000
Income taxes payable	0	390,000
Deferred revenue, current portion	7,783,000	1,413,000
Lease liability, current portion (Note 11)	268,000
Total current liabilities	17,268,000	8,749,000
Deferred revenue, net of current portion	2,750,000	9,120,000
Deferred lease incentive, net of current portion	0	4,088,000
Deferred rent, net of current portion		2,850,000
Lease liability, net of current portion (Note 11)	15,996,000
Total liabilities	36,014,000	24,807,000
Commitments (Note 11)
Stockholders’ equity:
Preferred stock, $0.001 par value per share; 5,000,000 shares authorized; no shares issued and outstanding as of December 31, 2019 and 2018, respectively	0	0
Common stock, $0.001 par value per share; 100,000,000 shares authorized; 24,065,676 and 23,518,690 shares issued and 23,865,075 and 23,437,587 outstanding as of December 31, 2019 and 2018, respectively	24,000	23,000
Additional paid-in capital	296,145,000	284,369,000
Accumulated other comprehensive loss	(31,000)	(137,000)
Accumulated deficit	(194,681,000)	(116,515,000)
Total stockholders’ equity	101,457,000	167,740,000
Total liabilities and stockholders’ equity	$ 137,471,000	$ 192,547,000

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
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)	24,065,676	23,518,690
Common stock, shares outstanding (in shares)	23,865,075	23,437,587

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenue:
Total revenue	$ 1,077,000	$ 10,505,000
Operating expenses:
Research and development	59,816,000	43,149,000
General and administrative	20,276,000	22,940,000
Total operating expenses	80,092,000	66,089,000
Loss from operations	(79,015,000)	(55,584,000)
Investment income	2,987,000	2,787,000
Other income	12,000	12,000
Unrealized loss on marketable equity securities	(2,150,000)	(2,926,000)
Loss before income taxes	(78,166,000)	(55,711,000)
Provision for income taxes	0	313,000
Net loss	(78,166,000)	(56,024,000)
Other comprehensive income:
Unrealized gain on investments, net of tax of $76 in 2018	106,000	270,000
Comprehensive loss	$ (78,060,000)	$ (55,754,000)
Net loss per share attributable to common stockholders - basic and diluted (in dollars per share)	$ (3.29)	$ (2.40)
Weighted-average number of common shares used in net loss per share attributable to common stockholders - basic and diluted (in shares)	23,740	23,370
License and research and development revenue
Revenue:
Total revenue	$ 1,077,000	$ 10,505,000

CONSOLIDATED STATEMENTS OF OP_2

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Income Statement [Abstract]
Unrealized gain 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, 2017		23,148	8
Beginning 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			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 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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	237,473	237	58
Exercise of stock options	$ 1,076			1,076
Release of restricted stock units (in shares)		203	61
Release of restricted stock units	(740)	$ 1		(741)
Unrealized gain on short-term investments	106				106
Stock-based compensation expense	10,326			10,326
Exercise of stock warrants (in shares)		71
Exercise of stock warrants	1,000			1,000
Proceeds from at-the-market offering, net of issuance costs (in shares)		36
Proceeds from at-the-market offering, net of issuance costs	115			115
Net loss	(78,166)					(78,166)
Ending balance (in shares) at Dec. 31, 2019		24,066	200
Ending balance at Dec. 31, 2019	$ 101,457	$ 24		$ 296,145	$ (31)	$ (194,681)

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, 2019	Dec. 31, 2018
Operating activities
Net loss	$ (78,166)	$ (56,024)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,664	1,247
Stock-based compensation expense	10,326	11,500
Accretion of premiums and discounts on investments	(1,013)	(469)
Amortization of deferred lease incentive	0	(703)
Non-cash license consideration (Note 12)	0	(10,451)
Non-cash lease expense (Note 11)	226
Other non-cash items	0	(77)
Unrealized loss on marketable equity securities	2,150	2,926
Loss on disposal of asset	4	52
Changes in operating assets and liabilities:
Accounts receivable	(57)	119
Contract asset (Note 12)	16,000	0
Interest receivable	296	72
Prepaid expenses and other current assets	(1,828)	(953)
Other assets	(96)	34
Accounts payable	(217)	435
Accrued expenses and other liabilities	2,984	1,265
Income taxes receivable	(36)	(76)
Income taxes payable	(392)	344
Deferred rent	0	2,746
Operating lease liabilities (Note 11)	(606)
Deferred revenue	0	(16)
Net cash used in operating activities	(48,761)	(48,029)
Investing activities
Purchases of property and equipment	(685)	(2,869)
Purchases of investments	(97,837)	(99,435)
Maturities of investments	181,105	140,207
Net cash provided by investing activities	82,583	37,903
Financing activities
Proceeds from at-the-market offering, net of issuance costs (Note 13)	115	0
Proceeds from warrants exercised	1,000	0
Repurchase of common stock pursuant to share surrender	(740)	(1,206)
Proceeds from exercise of stock options	1,076	1,037
Net cash provided by (used in) financing activities	1,451	(169)
Net increase (decrease) in cash, cash equivalents and restricted cash	35,273	(10,295)
Cash, cash equivalents and restricted cash at beginning of period	18,927	29,222
Cash, cash equivalents and restricted cash at end of period	54,200	18,927
Supplemental cash flow information:
Cash paid for income taxes	459	123
Purchases of property and equipment unpaid at period end	4	188
Tenant improvements paid by landlord (Note 11)	0	4,996
Public offering costs unpaid at period end	143	$ 0
Cash paid included in measurement of lease liabilities (Note 11)	$ 2,778

Nature of Business

Nature of Business	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	Nature of Business Concert Pharmaceuticals, Inc., or the Company, was incorporated on April 12, 2006 as a Delaware corporation and has its operations based in Lexington, Massachusetts. The Company is a clinical stage biopharmaceutical company that is applying its extensive knowledge of deuterium chemistry to discover and develop novel small molecule drugs. The Company’s approach typically starts with previously studied compounds, including approved drugs, that the Company believes may be improved with deuterium substitution. The Company’s pipeline includes multiple clinical stage candidates targeting autoimmune and CNS disorders, and a number of preclinical compounds that it is currently assessing. During February 2014, the Company completed its IPO, whereby the Company sold 6,649,690 shares of common stock at a price to the public of $14.00 per share, raising aggregate net proceeds of $83.1 million . 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. During January 2020, the Company completed an underwriting public offering pursuant to which it sold 5,735,283 shares of common stock at the public offering price of $9.92 per share. In addition, the Company sold to a certain existing investor pre-funded warrants to purchase up to an aggregate of 1,800,000 shares of common stock at a purchase price of $9.919 per pre-funded warrant, which represents the per share public offering price for the common stock less the $0.001 per share exercise price for each pre-funded warrant. The aggregate gross proceeds the Company received from the public offering was $74.7 million , before deducting underwriting discounts and commissions and other offering related expenses of $4.8 million . In June 2015, the Company received a one-time payment of $50.2 million from Auspex pursuant to a patent assignment agreement between the Company and Auspex. The Company became eligible to receive the payment due to a change of control of Auspex, which was acquired by Teva in May 2015. In March 2017, the Company entered into the Vertex Agreement with Vertex, pursuant to which the Company agreed to sell and assign to Vertex CTP-656, now known as VX-561, and other cystic fibrosis assets of the Company for up to $250.0 million , subject to the satisfaction of certain closing conditions. In July 2017, the transaction contemplated by the Vertex Agreement closed, and Vertex paid the Company $160.0 million in cash consideration, with $16.0 million initially held in escrow. In February 2019, the $16.0 million held in escrow was released to the Company. Additional information concerning the sale of CTP-656 is discussed in Note 12. The Company had cash and cash equivalents and investments of $106.4 million as of December 31, 2019. The Company believes that its cash and cash equivalents and investments as of December 31, 2019 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, 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 $194.7 million through December 31, 2019. 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 of 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 in the following tables 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, 2019
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. Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision making group, in making decisions on how to allocate resources and assess performance. The Company's chief operating decision maker is the Chief Executive Officer. The Company and the Chief Executive Officer view the Company's operations and manage its business as one operating segment: the development of pharmaceutical products on its own behalf or in collaboration with others. All material long-lived assets of the Company reside in the United States. The Company does use contract research organizations and research institutions located outside the United States. Some of these expenses are subject to collaboration reimbursement, which is presented as a component of license and research and development revenue in the consolidated statements of operations and comprehensive loss. 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. Use of Estimates and Summary of Significant Accounting Policies 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; prepaid and accrued research and development expenses; stock-based compensation expense; 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 2019 and 2018, 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. Deferred Offering Costs Costs incurred such as legal, accounting and other professional fees incurred in the course of preparing for a capital raise are deferred on the balance sheet as deferred offering costs. At the time of the completion of the offering, the costs are reclassified as a reduction of the proceeds of the capital raise as part of additional paid-in capital. Should the offering be terminated, deferred offering costs are charged to operations during the period in which the offering is terminated. Marketable Equity Securities Marketable equity securities consist of the fair value of shares of common stock of Processa held by the Company, as discussed further in Note 12. The Company recognizes 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, see Note 3. 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. The Company's 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. The Company's 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. As of December 31, 2019 and 2018, 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, 2019. Rent Expense Rent expense for the year ended December 31, 2019 consists of the Company's facility at 65 Hayden Avenue, Lexington, Massachusetts. The Company ceased recognizing rent expense for its previous facility at 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 facility at 65 Hayden Avenue in Lexington, Massachusetts provides for scheduled annual rent increases throughout the lease term, which expires on January 1, 2029. Additionally, the Company has received certain lease incentives, 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 lease. Contingencies The Company records liabilities for legal and other contingencies when information available to the Company indicates that it is probable that a liability has been incurred and the amount of loss can be reasonably estimated. Legal costs in connection with legal and other contingencies are expensed as costs are incurred. No liabilities for legal and other contingencies were accrued as of December 31, 2019 and 2018. 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 FASB ASU 2014-09, Revenue from Contracts with Customers , and all related amendments, which is also referred to as ASC 606. 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. ASC 606 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. ASC 606 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 ASC 606 was as follows: 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 ASC 606 primarily relates to the treatment of the consideration held in escrow under the Vertex 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, as 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. Non-refundable 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 Income taxes are recorded in accordance with ASC Topic 740, Income Taxes , or ASC 740, which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. 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 accounts for uncertain tax positions in accordance with the provisions of ASC 740. 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. As of December 31, 2019 or 2018, the Company did not have any significant uncertain tax positions. 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 a non-cancelable operating lease, which is further described in Note 11. The Company has standard indemnification arrangements under the lease that require it to indemnify the landlord against all costs, expenses, fines, suits, claims, demands, liabilities and actions directly resulting from any breach, violation or non-performance of any covenant or condition of the Company’s lease. Pursuant to the Vertex Agreement, as 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 Vertex 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 $16.0 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, 2019 and 2018, the Company had not experienced any material losses related to these indemnification obligations, and no material claims with respect thereto were outstanding. The Company does not expect significant claims related to these indemnification obligations and, consequently, concluded that the fair value of these obligations is negligible, and no related reserves were established. Comprehensive Loss Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions, other events and circumstances from non-owner sources. Comprehensive loss consists of net loss and other comprehensive loss, which includes certain changes in equity that are excluded from net loss. Comprehensive loss has been disclosed in the accompanying consolidated statements of operations and comprehensive loss. Accumulated other comprehensive loss is presented separately on the consolidated balance sheets and consists entirely of unrealized holdings losses on investments as of December 31, 2019 and 2018. Recently Adopted 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. On January 1, 2019, the Company adopted ASU 2016-02 and all related amendments. For discussion regarding the impact of this accounting pronouncement, refer to Note 11. In June 2018, the FASB issued ASU 2018-07, Improvements to Nonemployee Share-Based Payment Accounting , that expands the scope of Topic 718, Compensation - Stock Compensation , to include share-based payment transactions for acquiring goods and services from non-employees. ASU 2018-07 provides that an entity should apply the requirements of Topic 718 to non-employee awards except for certain exemptions specified in the amendment. The Company adopted this new standard effective January 1, 2019, and it did not have a material effect on the consolidated financial statements and related disclosures. In August 2018, the SEC issued Release No. 33-10532 that amends and clarifies certain financial reporting requirements. The principal change to the Company’s financial reporting is the inclusion of the annual disclosure requirement of changes in stockholders’ equity in Rule 3-04 of Regulation S-X to interim periods. The Company adopted this new rule beginning with its Quarterly Report on Form 10-Q for the quarter ended March 31, 2019. Pending Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses . 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. As a smaller reporting company, ASU 2016-13 will become effective for the Company for fiscal years beginning after December 15, 2022, and early adoption is permitted. The Company is currently evaluating the impact that ASU 2016-13 will have on its financial statements and related disclosures. In August 2018, the FASB issued ASU 2018-15, Intangible-Goodwill and Other Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract . The standard aligns the requirements for capitalizing implementation costs in a cloud computing arrangement service contract with the requirements for capitalizing implementation costs incurred for internal-use software. The new guidance also prescribes the balance sheet, income statement and cash flow classification of the capitalized implementation costs and related amortization expense, and requires additional quantitative and qualitative disclosures. ASU 2018-15 is effective for fiscal years beginning after December 15, 2019, and early adoption is permitted. The Company is currently evaluating the impact that ASU 2018-15 will have on its financial statements and related disclosures. On December 18, 2019, the FASB issued ASU 2019-12 , Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes . The standard includes removal of certain exceptions to the general principles of ASC 740, Income Taxes , and simplification in several other areas. ASU 2019-12 is effective for public business entities for annual reporting periods beginning after December 15, 2020, and interim periods within those reporting periods, and early adoption is permitted. The Company is currently evaluating the impact that ASU 2019-12 will have on its financial statements and related disclosures.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
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, 2019 and 2018 and indicate the level within the fair value hierarchy where each measurement is classified. The carrying amounts reflected in the consolidated balance sheets for cash, prepaid expenses and other current assets, restricted cash, accounts payable and accrued expenses approximate their fair values due to their short-term nature. Level 1 Level 2 Level 3 Total December 31, 2019 Cash equivalents: Money market funds $ 40,782 $ — $ — $ 40,782 Government agency securities — 2,000 — 2,000 Investments, available for sale: U.S. Treasury obligations 34,499 — — 34,499 Government agency securities 10,997 7,899 — 18,896 Marketable equity securities: Corporate equity securities 5,375 — — 5,375 Total $ 91,653 $ 9,899 $ — $ 101,552 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 7,525 — — 7,525 Total $ 115,752 $ 36,708 $ — $ 152,460

Cash, Cash Equivalents, Investm

Cash, Cash Equivalents, Investments and Marketable Equity Securities	12 Months Ended
	Dec. 31, 2019
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 as of December 31, 2019 and 2018: Average maturity Amortized cost Unrealized gains Unrealized losses Fair value December 31, 2019 Cash $ 10,261 $ — $ — $ 10,261 Money market funds 40,782 — — 40,782 Government agency securities 8 days 2,000 — — 2,000 Cash and cash equivalents $ 53,043 $ — $ — $ 53,043 U.S. Treasury obligations 108 days $ 34,475 $ 24 $ — $ 34,499 Government agency securities 74 days 18,874 22 — 18,896 Investments, available for sale $ 53,349 $ 46 $ — $ 53,395 December 31, 2019 Acquisition value Unrealized gains Unrealized losses Fair value Marketable equity securities $ 10,451 $ — $ (5,076 ) $ 5,375 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 $ 10,451 $ — $ (2,926 ) $ 7,525

Restricted Cash

Restricted Cash	12 Months Ended
	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Restricted Cash	Restricted Cash Restricted cash as of December 31, 2019 and 2018 was held as collateral for stand-by letters of credit issued by the Company to its landlords in connection with the current lease for its principal facilities located at 65 Hayden Avenue, Lexington, Massachusetts. For additional information regarding the Company's lease, see Note 11. Cash, cash equivalents and restricted cash consisted of the following as of December 31, 2019 and 2018: December 31, December 31, 2018 Cash and cash equivalents $ 53,043 $ 17,770 Restricted cash 1,157 1,157 Total cash, cash equivalents and restricted cash shown in the statement of cash flows $ 54,200 $ 18,927

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment Property and equipment consist of the following as of December 31, 2019 and 2018: Estimated useful life (in years) December 31, 2019 December 31, Laboratory equipment 5 $ 3,736 $ 3,484 Computer, telephone and office equipment 3 891 875 Software 3 122 206 Leasehold improvements Lesser of useful life or remaining lease term 5,929 5,866 10,678 10,431 Less accumulated depreciation and amortization (2,925 ) (1,512 ) $ 7,753 $ 8,919 Depreciation and amortization expense was charged to operations in the amounts of $1.7 million and $1.2 million for the years ended December 31, 2019 and 2018, respectively.

Accrued Expenses and Other Liab

Accrued Expenses and Other Liabilities	12 Months Ended
	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued Expenses and Other Liabilities	Accrued Expenses and Other Liabilities Accrued expenses and other liabilities consist of the following as of December 31, 2019 and 2018: December 31, 2019 December 31, Accrued professional fees and other $ 862 $ 672 Employee compensation and benefits 3,222 3,067 Research and development expenses 4,252 1,476 Deferred lease incentive, current portion — 454 $ 8,336 $ 5,669

Stock Compensation

Stock Compensation	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [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, 2020, 954,603 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, 2019, 1,265,774 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 as of December 31, 2019 and 2018: Year ended December 31, 2019 2018 Weighted-average fair value of options granted, per option $ 8.94 $ 17.74 Aggregate grant date fair value of options vested during the year $ 9,354 $ 7,755 Total cash received from exercises of stock options $ 1,076 $ 1,037 Total intrinsic market value of stock options exercised $ 1,277 $ 2,599 The weighted-average fair value of options granted in the years ended December 31, 2019 and 2018 reflect the following weighted-average assumptions: Year ended December 31, 2019 2018 Expected volatility 76.83 % 77.22 % Expected term 6.0 years 6.0 years Risk-free interest rate 2.16 % 2.64 % Expected dividend yield — % — % Expected volatility. For the years ended December 31, 2019 and 2018, 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. 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. 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 SAB 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, 2019 and 2018, 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, 2019 and 2018, the Company assumed forfeiture rates of approximately 7% . The following is a summary of stock option activity for the year ended December 31, 2019: Number of Option Shares Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Market Value (In years) Outstanding at December 31, 2018 3,557,406 $ 15.26 Granted 1,037,750 $ 13.22 Exercised (237,473 ) $ 7.75 Forfeited or expired (245,074 ) $ 18.02 Outstanding at December 31, 2019 4,112,609 $ 15.01 6.86 $ 1,183 Exercisable at December 31, 2019 2,599,751 $ 14.04 5.98 $ 1,179 Vested and expected to vest at December 31, 2019 (1) 3,989,373 $ 14.98 6.79 $ 1,182 (1) Represents the number of vested stock option shares as of December 31, 2019, plus the number of unvested stock option shares that the Company estimated as of December 31, 2019 would vest, based on the unvested stock option shares as of December 31, 2019 and an estimated forfeiture rate of 7% . As of December 31, 2019, there was $15.0 million of unrecognized compensation cost related to stock options that are expected to vest. The stock option costs are expected to be recognized over a weighted-average remaining vesting period of 2.4 years. Restricted stock units On July 6, 2017, the Company granted 0.5 million RSUs, or the 2017 RSU grant, to executives and employees. The awards granted to non-executive employees were service-based, whereas the awards granted to executives were 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 transaction contemplated by the Vertex Agreement and the institution by the PTAB of the PGR petition filed by the Company against Incyte. In January 2018, the PTAB did not grant the Company's petition to institute the PGR and, as a result, the corresponding performance-based awards did not vest on March 31, 2018. The Company used the accelerated attribution method to recognize expense over the required service period based on its estimate of the number of performance-based awards vested. For any change in the estimate of the number of performance-based awards that were probable of vesting, the Company cumulatively adjusted compensation expense in the period that the change in estimate was made. On August 15, 2019, the 2019 RSU grant date, the Company granted 0.4 million RSUs, or the 2019 RSU grant, to certain executives and employees. All awards are service-based and vest annually over two years . On the first anniversary of the 2019 RSU grant date, thirty-five percent of the RSUs will vest. The remainder of the RSUs will vest on the second anniversary of the 2019 RSU grant date. RSUs are not included in issued and outstanding common stock until the shares are vested and settled. As of December 31, 2019, all achieved RSUs from the 2017 RSU grant had vested, and no RSUs from the 2019 RSU grant 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 service-based and performance-based RSUs for the year ended December 31, 2019: Number of RSU Shares Weighted Average Grant Date Fair Value Outstanding at December 31, 2018 228,150 $ 13.87 Granted 412,220 $ 10.27 Released (202,550 ) $ 13.87 Forfeited (44,191 ) $ 12.36 Outstanding at December 31, 2019 393,629 $ 10.27 As of December 31, 2019, there was $3.5 million of unrecognized compensation cost related to RSUs that are expected to vest. The RSU costs are expected to be recognized over a weighted-average remaining vesting period of 1.6 years. Stock-based compensation expense Total compensation cost recognized for all stock-based compensation awards in the consolidated statements of operations and comprehensive loss is as follows for the years ended December 31, 2019 and 2018: For the Year Ended December 31, 2019 2018 Research and development $ 5,049 $ 5,221 General and administrative 5,277 6,279 Total stock-based compensation expense $ 10,326 $ 11,500

Loss Per Share

Loss Per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Loss Per Share	Loss Per Share Basic net loss per common share is calculated by dividing net loss allocable to common stockholders by the weighted-average common shares outstanding during the period, without consideration of common stock equivalents. 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 following table illustrates the determination of loss per share for the years ended December 31, 2019 and 2018: For the Year Ended December 31, 2019 2018 Numerator: Net loss applicable to common stockholders - basic and diluted $ (78,166 ) $ (56,024 ) Denominator: Weighted-average shares outstanding - basic and diluted 23,740 23,370 Net loss per share applicable to common stockholders - basic and diluted $ (3.29 ) $ (2.40 ) Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share: Stock options 232 666 Restricted stock units 61 185 Warrants 70 132

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes During the year ended December 31, 2019, the Company recorded net loss before taxes of $78.2 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, 2019. On July 25, 2017, the transaction contemplated by the Vertex Agreement closed, as discussed in Note 12, and Vertex paid the Company $160.0 million in cash consideration, with $16.0 million initially held in escrow. For income tax purposes, the $16.0 million held in escrow was recognized under the installment method and therefore deferred until the cash was received by the Company in February 2019. Under Section 453A of the U.S. Internal Revenue Code, or 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 $5.0 million . As a result, the Company accrued interest of $0.2 million for 2018. The $16.0 million initially held in escrow was released to the Company in February 2019, and the Company recognized no interest for 2019. Additionally, during 2019, 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. There was no impact to the Company for 2019 as a result of these rules. The Tax Cuts and Jobs Act, or TCJA, repealed the corporate alternative minimum tax, or 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, 2019, the Company had a $2.3 million income tax receivable related to AMT taxes in prior years. 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 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 stockholders over a three-year period in excess of 50 percent, as defined under Sections 382 and 383 of the 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 of the Code, which could further limit the Company's use of its operating loss and tax credit carryforwards. In determining the tax provisions for 2018, the Company assessed its ability to use its net operating loss carryforwards in accordance with Sections 382 and 383 of the Code. A reconciliation of the federal statutory income tax rate and the Company’s effective income tax rate is as follows for the years ended December 31, 2019 and 2018: Year ended December 31, 2019 2018 Federal statutory income tax rate 21.0 % 21.0 % State income taxes 6.8 % 6.2 % Change in valuation allowance (29.8 )% (30.9 )% Research and development and other credits 3.2 % 4.0 % Permanent items (1.1 )% (0.3 )% Other (0.1 )% (0.6 )% Federal rate change — % — % Effective income tax rate — % (0.6 )% The significant components of the Company’s net deferred tax assets consist of the following as of December 31, 2019 and 2018: December 31, 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 38,544 $ 23,841 Deferred revenue 2,878 2,878 Research and development and other credit carryforwards 18,573 15,597 Lease liability 4,443 — Other 7,508 7,985 71,946 50,301 Valuation allowance (67,737 ) (44,453 ) Total deferred tax assets, net of valuation allowance $ 4,209 $ 5,848 Deferred tax liabilities: Fixed assets $ 1,681 $ 1,477 Right of use asset 2,528 — Gain deferred under installment method — 4,371 Total deferred tax liabilities $ 4,209 $ 5,848 Net deferred tax assets $ — $ — Subject to the limitations described above and the impacts of the TCJA, as of December 31, 2019, the Company had gross federal net operating loss carryforwards of $153.0 million and state net operating loss carryforwards of $101.6 million available to reduce future taxable income, of which $54.8 million of the gross federal net operating loss carryforwards and $101.6 million of the state net operating loss carryforwards will expire at various dates beginning in 2034. Approximately $98.2 million of the federal net operating loss carryforwards will be carried forward indefinitely. The Company also had federal and state tax credit carryforwards of $14.2 million and $5.5 million , respectively, available to reduce future tax liabilities, which expire at various dates through 2039. 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 as of December 31, 2019 and 2018. As of December 31, 2019, 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 statement of operations. As of December 31, 2019, 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 IRS and state jurisdictions for the tax years ended 2016 through 2018. Carryforward tax attributes generated in years prior to 2016 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 IRS 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, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments	Commitments Lease In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which is also referred to as ASC 842. ASC 842 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. ASC 842 also requires certain qualitative and quantitative disclosures designed to give financial statement users information on the amount, timing and uncertainty of cash flows arising from leases. The Company adopted ASC 842 effective January 1, 2019. The Company has elected to employ the transitionary relief offered by the FASB under ASU 2018-11, and implement the new standard without the restatement of comparative periods' financial information. ASU 2018-11 also provides for recognizing the effects of applying ASC 842 as a cumulative-effect adjustment to retained earnings as of January 1, 2019; however, no such adjustment was required by the Company. The Company has elected to employ the package of practical expedients offered under ASC 842, which allow the Company to not reassess the following: • the presence of a lease in any expired or existing contracts; • the lease classification for any expired or existing leases; and • the initial direct costs for any existing leases. The Company currently has a lease, or the Lease, for approximately 56,000 square feet of office and laboratory space located at 65 Hayden Avenue, Lexington, Massachusetts, or the Premises, which was classified as an operating lease under the previous leasing standard, ASC 840. The Lease is also classified as an operating lease under ASC 842 in accordance with the Company's election of the practical expedient under ASC 842. Pursuant to the package of practical expedients, the Company did not reassess initial direct costs for the Premises. Additionally, the Company made the policy election to adopt the practical expedient to not separate lease components from non-lease components for the right-to-use asset class of office and laboratory space. This policy election results in the Company accounting for the lease component, the use of the Premises and the non-lease components, which include the use of the parking garage, building elevators and HVAC, as a single lease component. 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, the lease commencement date was determined to be January 1, 2018 under the prior guidance of ASC 840, and therefore the Company began recognizing lease expense as of that date. The Lease term extends ten years following January 1, 2019. The Company is entitled to two five -year options to extend the Lease; however, these options were not included in the calculation of the Lease asset or liability. The Company elected to employ the provision under ASC 842 to use hindsight with respect to determining the lease term (i.e., consideration of the actual outcome of lease renewals, termination options and purchase options) and in assessing any impairment of right-of-use assets for existing leases. The Company notes that no events such as renewals or termination options have occurred with respect to the Lease for the Premises. Therefore, the hindsight practical expedient under ASC 842 had no impact on the accounting term as previously determined under ASC 840. As of December 31, 2019, the remaining lease term for the Premises is 9 years . 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). There are no variable payments, exercise purchase options, penalties, fees or residual value guarantees 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; however, the Company concluded that these payments are not in-substance fixed payments and therefore are not included in the calculation of the related lease liability and asset under ASC 842. The Company recorded the liability associated with the Lease for the Premises at the present value of the lease payments not yet paid, discounted using the discount rate for the Lease established at the commencement date. Since the Lease does not provide an implicit rate, the Company had to estimate the incremental borrowing rate, or IBR, as of the commencement date. The IBR is defined under ASC 842 as the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term for an amount equal to the lease payments in a similar economic environment. The IBR for the Lease was determined by establishing a credit rating of the Company using the Rank Order Model. Based on the established credit rating, the Company determined a borrowing rate using the Recovery Rate method, adjusted for the risk-free rate, which resulted in an IBR of approximately 13% . The Company used this IBR of 13% to discount the remaining lease payments over the remaining lease term and recorded a lease liability of $16.9 million on January 1, 2019. This lease liability will be amortized over the remaining lease term in an amount equal to the difference between the cash rent paid and the monthly interest calculated on the remaining lease liability. As of December 31, 2019, the Company had a current lease liability of $0.3 million and a non-current lease liability of $16.0 million recorded in its consolidated balance sheets. The Company received an improvement allowance from the landlord of approximately $5.0 million for certain permitted costs related to the design of the Company's 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. These $5.0 million of improvements are included in the Company’s property, plant and equipment balances in its consolidated balance sheets as of December 31, 2019 and are depreciated over the shorter of their useful life or the related lease term. On January 1, 2019, the Company recorded a right-of-use asset in the amount of $9.5 million , which represented the lease liability of $16.9 million , adjusted for previously accrued rent of $2.9 million and previously recorded unamortized lease incentives (the improvement allowance) in the amount of $4.5 million . The right-of-use asset will be amortized over the remaining Lease term in an amount equal to the difference between the calculated straight-line expense of the total Lease payments less the monthly interest calculated on the remaining lease liability. As of December 31, 2019, the Company had a long-term lease asset of $9.3 million recorded in its consolidated balance sheets. The following table presents a summary of the amount by which each financial statement line item was affected by the adoption of ASC 842: January 1, 2019 Prior to Adoption of ASC 842 Effect of Adoption Subsequent to Adoption of ASC 842 Operating lease right-of-use assets, long-term $ — $ 9,478 $ 9,478 Accrued expenses and other liabilities 5,669 (454 ) 5,215 Lease liability, current portion — 607 607 Deferred lease incentive, net of current portion 4,088 (4,088 ) — Deferred rent, net of current portion 2,850 (2,850 ) — Lease liability, net of current portion — 16,264 16,264 Accumulated deficit (116,515 ) — (116,515 ) The adoption of ASC 842 did not have a material impact on the consolidated statement of operations and comprehensive loss for the year ended December 31, 2019, or the consolidated statement of cash flows for the year ended December 31, 2019. The Company will recognize rent expense, calculated as the remaining cost of the Lease allocated over the remaining Lease term, on a straight-line basis. Rent expense will be presented as part of continuing operations in the condensed consolidated statement of operations and comprehensive loss. For the year ended December 31, 2019, the Company recognized $2.4 million in rent expense. For the year ended December 31, 2019, the Company paid $2.8 million in rent relating to the Lease. As a payment arising from an operating lease, the $2.8 million will be classified within operating activities in the consolidated statements of cash flows. As of December 31, 2019, the discount rate for the Lease was 13.08% , and the remaining Lease term for the Premises was 9 years. Future minimum lease payments under the Company's non-cancelable operating leases as of December 31, 2019 were as follows : Maturities of lease liabilities: For the year ended December 31, 2020 $ 2,406 2021 2,969 2022 3,058 2023 3,150 2024 3,244 Thereafter 13,979 Total lease payments $ 28,806 Less imputed interest $ (12,542 ) Total $ 16,264 Prior to the adoption of ASC 842, and pursuant to the legacy guidance within ASC 840, the Company recorded rent expense on a straight-line basis through the end of the lease term and also recorded deferred rent on the consolidated balance sheets. The Company recorded the tenant improvement allowance as a deferred lease incentive and was amortizing the deferred lease incentive through a reduction of rent expense ratably over the lease term. As of December 31, 2018, the future minimum lease payments due under the Lease were as follows: For the year ended December 31, 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 The Company recorded total rent expense of $3.3 million for the year ended December 31, 2018 pursuant to ASC 840.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Revenue	Revenue The Company's revenue is 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 period is described below. The terms of these agreements may contain multiple promised goods or services or optional goods and services, including 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. Significant payment terms The Company’s revenue arrangements include payments to the Company of one or more of the following: a non-refundable, 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. The Company utilizes the "most likely amount" variable consideration method for estimating development and regulatory milestone consideration to include in the transaction price. 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, 2019, and therefore has not included such consideration in the transaction price for any of its revenue arrangements. The Company will reassess 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 intellectual property 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. Contract assets The Company did no t have a contract asset as of December 31, 2019 as compared to $16.0 million as of December 31, 2018. The decrease in the contract asset balance is the result of the receipt of the $16.0 million that had initially been held in escrow for indemnification purposes related to the asset purchase by Vertex, and was released to the Company in February 2019. Contract liabilities As of December 31, 2019 and 2018, the Company had $10.5 million in contract liabilities related to unsatisfied performance obligations as well as variable consideration paid in advance, but currently constrained from recognition. The contract liabilities consist of the following deferred revenue: • $7.8 million related to the Company's collaboration with Celgene, $1.4 million of which is attributable to the CTP-730 program and is currently expected to be recognized as revenue in the next twelve months as the Company satisfies its remaining research and development activities pursuant to mutually agreed upon development plans, and $6.4 million of which is attributable to two additional license programs that the Company will not recognize as revenue unless Celgene exercises its rights with respect to those programs, or in the second quarter of 2020 at such time that Celgene's rights lapse; and • $2.8 million related to a payment received from GSK that the Company will not recognize as revenue until all repayment obligations lapse. Contract liabilities are presented as deferred revenue and classified as current or non-current based on the timing of when the Company expects to recognize revenue. During the twelve months ended December 31, 2019, no deferred revenue was recognized into revenue. During the twelve months ended December 31, 2018, $16 thousand of deferred revenue was recognized into revenue. Revenue arrangements Vertex On March 3, 2017, the Company entered into the Vertex Agreement with Vertex pursuant to which the Company agreed to sell and assign to Vertex CTP-656, now known as VX-561, and other cystic fibrosis assets of the Company. On July 25, 2017, or the Vertex Closing Date, the transaction contemplated by the Vertex Agreement closed, and Vertex paid the Company $160.0 million in cash consideration, with $16.0 million initially held in escrow, which was released to the Company in February 2019. In addition, Vertex has agreed to pay the Company an aggregate of up to $90.0 million upon the achievement of certain milestone events. As of December 31, 2018, the Vertex indemnification variable consideration represented a contract asset to be released from escrow 18 months following the Vertex Closing Date and was classified as a current asset in the accompanying consolidated balance sheet. Additionally, the variable consideration related to the regulatory milestone payments are fully constrained due to the uncertainty associated with the achievement of the respective milestones. Accordingly, no contract asset was recorded as of December 31, 2019. Processa On October 4, 2017, the Company entered into an Option and License Agreement, or the Option Agreement, with Promet Therapeutics, LLC, or Promet, pursuant to which the Company granted Promet an option to obtain an exclusive license to CTP-499, a deuterated analog of 1-(S)-5-hydroxyhexyl-3,7-dimethylxanthine, or HDX, an active metabolite of pentoxifylline, provided certain conditions were met. On October 5, 2017, Promet closed an asset purchase agreement with Heatwurx, Inc., a public company, creating Processa. On March 19, 2018, the Company entered into an Amendment to the Option Agreement, or the Amendment, and a Securities Purchase Agreement, or the Securities Agreement, both with Promet and Processa. Pursuant to the Amendment, the Company granted Promet, who then assigned to Processa, an exclusive, worldwide, royalty-bearing license to develop, manufacture and commercialize CTP-499, now known as PCS-499. Upon transfer of the license and as consideration for the license, the Company received 2,090,301 shares of common stock of Processa. In December 2019, Processa implemented a reverse stock split, and the Company now owns 298,615 shares of common stock of Processa. The Company is also eligible to receive royalties on worldwide net sales. The Amendment contained one performance obligation: an exclusive, worldwide, royalty-bearing license to develop, manufacture and commercialize CTP-499. The Company determined that the transaction price was $10.5 million , which was based on the fair value of the non-cash consideration received on March 19, 2018, which consisted of 2,090,301 shares of publicly traded common stock of Processa. The transaction price of $10.5 million was allocated to the single performance obligation. The performance obligation was considered satisfied at contract inception, as the exclusive license transferred control to the customer at this point in time. Accordingly, revenue of $10.5 million was recognized during the first quarter of 2018. Subsequent changes to the fair value of the underlying securities are recognized as unrealized gains or losses on marketable equity securities within the consolidated statement of operations and comprehensive loss. The Amendment contains consideration that is variable based on royalties upon the customer's commercial success with the licensed product. The consideration related to royalty payments is considered variable consideration that is fully constrained in accordance with the royalty recognition constraint. The variable consideration related to royalties will be recognized in the period the products are sold by Processa and the Company has a present right to payment. For the year ended December 31, 2019, the Company recognized $34 thousand in revenue related to intellectual property cost reimbursements. For the year ended December 31, 2018, the Company recognized $10.5 million in revenue related to the transfer of the license. Cipla The Company entered into the Cipla Agreement with Cipla on January 16, 2019, or the Cipla Closing Date, pursuant to which the Company granted Cipla an exclusive, worldwide, royalty-bearing license to develop, manufacture and commercialize CTP-354, a novel GABA A receptor subtype-selective modulator. As consideration for the license, the Company received an upfront payment of $1.0 million . The Cipla Agreement also provides Cipla the option to purchase the Company’s existing inventory of CTP-354 held as of the effective date, valued in aggregate at $0.3 million . Additionally, upon the achievement of certain milestone events, Cipla has agreed to pay the Company an aggregate of up to $57.0 million . The first milestone payment the Company may be entitled to receive is $3.0 million when the first IND for the first CTP-354 product goes into effect. Furthermore, the Company is eligible to receive royalties on worldwide net sales of future product sales at defined percentages ranging from the mid-single to high-single digits. The Cipla Agreement contained one performance obligation: an exclusive, worldwide, royalty-bearing license to develop, manufacture and commercialize CTP-354, referred to as the Transfer of License Performance Obligation. The Company concluded that the option to purchase existing inventory did not provide Cipla a material right, and as such, was treated as a separate contract. The transaction price was determined to be $1.0 million based on the upfront consideration received as of the Cipla Closing Date. As of the Cipla Closing Date, the Transfer of License Performance Obligation was satisfied, as the control of CTP-354 transferred to Cipla, the customer. As a result, the full transaction price was recognized as revenue on the Cipla Closing Date. The sale of existing inventory is recognized as goods are transferred to the customer. The arrangement with Cipla contains consideration that is variable based on the customer’s achievement of certain development and regulatory 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 $3.0 million related to the first IND for the first CTP-354 product going into effect is considered variable consideration that is fully constrained due to the uncertainty associated with the achievement of the development milestone. The consideration related to royalties is also variable consideration that is fully constrained in accordance with the royalty recognition constraint. The variable consideration related to royalties will be recognized in the period the products are sold by Cipla and the Company has a present right to payment. The Company recognized $1.0 million in revenue associated with the sale of existing inventory and the Transfer of License Performance Obligation for the year ended December 31, 2019.

Open Market Sale Agreement

Open Market Sale Agreement	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Open Market Sale Agreement	Open Market Sale Agreement On March 1, 2019, the Company entered into an Open Market Sale Agreement, or the ATM Agreement, with Jefferies LLC, or Jefferies, with respect to an at-the-market offering program under which the Company may offer and sell, from time to time at its sole discretion, shares of its common stock, par value $0.001 per share, having an aggregate offering price of up to $50 million , referred to as Placement Shares, through Jefferies as its sales agent. The Company will pay Jefferies a commission equal to 3.0% of the gross sales proceeds of any Placement Shares sold through Jefferies under the ATM Agreement, and also has provided Jefferies with customary indemnification and contribution rights. In addition, the Company has agreed to reimburse certain legal expenses and fees by Jefferies in connection with the offering up to a maximum of $50 thousand , in addition to certain ongoing disbursements of Jefferies' counsel. As of February 24, 2020, the Company has sold 36,167 shares of its common stock in accordance with the ATM Agreement for net proceeds of $0.4 million , after payment of cash commissions of 3.0 percent of the gross proceeds to its sales agent. Additionally, the Company incurred approximately $0.3 million related to legal, accounting and other fees in connection with the ATM Agreement as of December 31, 2019.

401(k) Retirement Plan

401(k) Retirement Plan	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
401(k) Retirement Plan	401(k) Retirement Plan In January 2008, the Company established the Concert Pharmaceuticals 401(k) Retirement Plan, or 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 $0.4 million and $0.3 million for the years ended December 31, 2019 and 2018, respectively.

Warrant to Purchase Redeemable

Warrant to Purchase Redeemable Securities	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Warrant to Purchase Redeemable Securities	Warrant to Purchase Redeemable Securities On June 8, 2017, the Company entered into a Loan Agreement with Hercules Technology Growth Capital, Inc., or Hercules. In connection with the entry into the Loan Agreement, the Company issued warrants, or 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 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.

Quarterly Financial Information

Quarterly Financial Information (unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (unaudited)	Quarterly Financial Information (unaudited) Three Months Ended March 31, June 30, September 30, December 31, Revenue $ 1,005 $ 49 $ 10 $ 13 Operating expenses 21,399 19,474 18,253 20,966 Loss from operations (20,394 ) (19,425 ) (18,243 ) (20,953 ) Other (expense) income, net (1,432 ) 757 1,058 466 Net loss $ (21,826 ) $ (18,668 ) $ (17,185 ) $ (20,487 ) Net loss per share - basic and diluted $ (0.93 ) $ (0.78 ) $ (0.72 ) $ (0.86 ) Three Months Ended March 31, 2018 June 30, 2018 September 30, 2018 December 31, 2018 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 )

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events During January 2020, the Company completed an underwriting public offering pursuant to which it sold 5,735,283 shares of its common stock at the public offering price of $9.92 per share. In addition, the Company sold to a certain existing investor pre-funded warrants to purchase up to an aggregate of 1,800,000 shares of common stock at a purchase price of $9.919 per pre-funded warrant, which represents the per share public offering price for the common stock less the $0.001 per share exercise price for each pre-funded warrant. The aggregate gross proceeds the Company received from the public offering was $74.7 million , before deducting underwriting discounts and commissions and other offering related expenses of $4.8 million .

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
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. Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision making group, in making decisions on how to allocate resources and assess performance. The Company's chief operating decision maker is the Chief Executive Officer. The Company and the Chief Executive Officer view the Company's operations and manage its business as one operating segment: the development of pharmaceutical products on its own behalf or in collaboration with others. All material long-lived assets of the Company reside in the United States. The Company does use contract research organizations and research institutions located outside the United States. Some of these expenses are subject to collaboration reimbursement, which is presented as a component of license and research and development revenue in the consolidated statements of operations and comprehensive loss. 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.
Use of Estimates and Summary of Significant Accounting Policies	Use of Estimates and Summary of Significant Accounting Policies 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; prepaid and accrued research and development expenses; stock-based compensation expense; 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 investme
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 2019 and 2018, 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.
Deferred Offering Costs	Deferred Offering Costs Costs incurred such as legal, accounting and other professional fees incurred in the course of preparing for a capital raise are deferred on the balance sheet as deferred offering costs. At the time of the completion of the offering, the costs are reclassified as a reduction of the proceeds of the capital raise as part of additional paid-in capital. Should the offering be terminated, deferred offering costs are charged to operations during the period in which the offering is terminated.
Marketable Equity Securities	Marketable Equity Securities Marketable equity securities consist of the fair value of shares of common stock of Processa held by the Company, as discussed further in Note 12. The Company recognizes 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.
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. The Company's 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. The Company's 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. As of December 31, 2019 and 2018, 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.
Rent Expense	Rent Expense Rent expense for the year ended December 31, 2019 consists of the Company's facility at 65 Hayden Avenue, Lexington, Massachusetts. The Company ceased recognizing rent expense for its previous facility at 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 facility at 65 Hayden Avenue in Lexington, Massachusetts provides for scheduled annual rent increases throughout the lease term, which expires on January 1, 2029. Additionally, the Company has received certain lease incentives, 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 lease.
Contingencies	Contingencies The Company records liabilities for legal and other contingencies when information available to the Company indicates that it is probable that a liability has been incurred and the amount of loss can be reasonably estimated. Legal costs in connection with legal and other contingencies are expensed as costs are incurred.
Revenue Recognition	Revenue Recognition The Company has 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 FASB ASU 2014-09, Revenue from Contracts with Customers , and all related amendments, which is also referred to as ASC 606. 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. ASC 606 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. ASC 606 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 ASC 606 was as follows: 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 ASC 606 primarily relates to the treatment of the consideration held in escrow under the Vertex 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, as 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. Non-refundable 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.
Income Taxes	Income Taxes Income taxes are recorded in accordance with ASC Topic 740, Income Taxes , or ASC 740, which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. 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 accounts for uncertain tax positions in accordance with the provisions of ASC 740. The Company evaluates tax positions taken, or expected to be taken, in the course of preparing its tax returns to determine whether the tax positions are “more likely than not” of being sustained by the applicable tax authority. Tax positions not deemed to meet the more-likely-than-not threshold would be recognized as a tax expense.
Guarantees	Guarantees As permitted under Delaware law, the Company indemnifies its officers and directors for certain events or occurrences while the officer or director is, or was, serving at the Company’s request in such capacity. The term of the indemnification is for the officer’s or director’s lifetime. The maximum potential amount of future payments the Company could be required to make is unlimited; however, the Company has directors’ and officers’ insurance coverage that limits its exposure and enables it to recover a portion of any future amounts paid. The Company leases office space under a non-cancelable operating lease, which is further described in Note 11. The Company has standard indemnification arrangements under the lease that require it to indemnify the landlord against all costs, expenses, fines, suits, claims, demands, liabilities and actions directly resulting from any breach, violation or non-performance of any covenant or condition of the Company’s lease. Pursuant to the Vertex Agreement, as 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 Vertex 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 $16.0 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, 2019 and 2018, the Company had not experienced any material losses related to these indemnification obligations, and no material claims with respect thereto were outstanding. The Company does not expect significant claims related to these indemnification obligations and, consequently, concluded that the fair value of these obligations is negligible, and no related reserves were established.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions, other events and circumstances from non-owner sources. Comprehensive loss consists of net loss and other comprehensive loss, which includes certain changes in equity that are excluded from net loss. Comprehensive loss has been disclosed in the accompanying consolidated statements of operations and comprehensive loss.
Recently Adopted Accounting Pronouncements and Pending Accounting Pronouncements	Recently Adopted 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. On January 1, 2019, the Company adopted ASU 2016-02 and all related amendments. For discussion regarding the impact of this accounting pronouncement, refer to Note 11. In June 2018, the FASB issued ASU 2018-07, Improvements to Nonemployee Share-Based Payment Accounting , that expands the scope of Topic 718, Compensation - Stock Compensation , to include share-based payment transactions for acquiring goods and services from non-employees. ASU 2018-07 provides that an entity should apply the requirements of Topic 718 to non-employee awards except for certain exemptions specified in the amendment. The Company adopted this new standard effective January 1, 2019, and it did not have a material effect on the consolidated financial statements and related disclosures. In August 2018, the SEC issued Release No. 33-10532 that amends and clarifies certain financial reporting requirements. The principal change to the Company’s financial reporting is the inclusion of the annual disclosure requirement of changes in stockholders’ equity in Rule 3-04 of Regulation S-X to interim periods. The Company adopted this new rule beginning with its Quarterly Report on Form 10-Q for the quarter ended March 31, 2019. Pending Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses . 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. As a smaller reporting company, ASU 2016-13 will become effective for the Company for fiscal years beginning after December 15, 2022, and early adoption is permitted. The Company is currently evaluating the impact that ASU 2016-13 will have on its financial statements and related disclosures. In August 2018, the FASB issued ASU 2018-15, Intangible-Goodwill and Other Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract . The standard aligns the requirements for capitalizing implementation costs in a cloud computing arrangement service contract with the requirements for capitalizing implementation costs incurred for internal-use software. The new guidance also prescribes the balance sheet, income statement and cash flow classification of the capitalized implementation costs and related amortization expense, and requires additional quantitative and qualitative disclosures. ASU 2018-15 is effective for fiscal years beginning after December 15, 2019, and early adoption is permitted. The Company is currently evaluating the impact that ASU 2018-15 will have on its financial statements and related disclosures. On December 18, 2019, the FASB issued ASU 2019-12 , Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes . The standard includes removal of certain exceptions to the general principles of ASC 740, Income Taxes , and simplification in several other areas. ASU 2019-12 is effective for public business entities for annual reporting periods beginning after December 15, 2020, and interim periods within those reporting periods, and early adoption is permitted. The Company is currently evaluating the impact that ASU 2019-12 will have on its financial statements and related disclosures.

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Schedule of New Accounting Pronouncements - Adoption of ASC 606	The cumulative effect of the changes made to the consolidated January 1, 2018 balance sheet for the adoption of ASC 606 was as follows: 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 following table presents a summary of the amount by which each financial statement line item was affected by the adoption of ASC 842: January 1, 2019 Prior to Adoption of ASC 842 Effect of Adoption Subsequent to Adoption of ASC 842 Operating lease right-of-use assets, long-term $ — $ 9,478 $ 9,478 Accrued expenses and other liabilities 5,669 (454 ) 5,215 Lease liability, current portion — 607 607 Deferred lease incentive, net of current portion 4,088 (4,088 ) — Deferred rent, net of current portion 2,850 (2,850 ) — Lease liability, net of current portion — 16,264 16,264 Accumulated deficit (116,515 ) — (116,515 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Recognized at Fair Value	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, 2019 and 2018 and indicate the level within the fair value hierarchy where each measurement is classified. The carrying amounts reflected in the consolidated balance sheets for cash, prepaid expenses and other current assets, restricted cash, accounts payable and accrued expenses approximate their fair values due to their short-term nature. Level 1 Level 2 Level 3 Total December 31, 2019 Cash equivalents: Money market funds $ 40,782 $ — $ — $ 40,782 Government agency securities — 2,000 — 2,000 Investments, available for sale: U.S. Treasury obligations 34,499 — — 34,499 Government agency securities 10,997 7,899 — 18,896 Marketable equity securities: Corporate equity securities 5,375 — — 5,375 Total $ 91,653 $ 9,899 $ — $ 101,552 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 7,525 — — 7,525 Total $ 115,752 $ 36,708 $ — $ 152,460

Cash, Cash Equivalents, Inves_2

Cash, Cash Equivalents, Investments and Marketable Equity Securities (Tables)	12 Months Ended
	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents and Investments, Available for Sale	Cash, cash equivalents, available for sale investments and marketable equity securities included the following as of December 31, 2019 and 2018: Average maturity Amortized cost Unrealized gains Unrealized losses Fair value December 31, 2019 Cash $ 10,261 $ — $ — $ 10,261 Money market funds 40,782 — — 40,782 Government agency securities 8 days 2,000 — — 2,000 Cash and cash equivalents $ 53,043 $ — $ — $ 53,043 U.S. Treasury obligations 108 days $ 34,475 $ 24 $ — $ 34,499 Government agency securities 74 days 18,874 22 — 18,896 Investments, available for sale $ 53,349 $ 46 $ — $ 53,395 December 31, 2019 Acquisition value Unrealized gains Unrealized losses Fair value Marketable equity securities $ 10,451 $ — $ (5,076 ) $ 5,375 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 $ 10,451 $ — $ (2,926 ) $ 7,525

Restricted Cash Restricted Cash

Restricted Cash Restricted Cash (Tables)	12 Months Ended
	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents and Restricted Cash	Cash, cash equivalents and restricted cash consisted of the following as of December 31, 2019 and 2018: December 31, December 31, 2018 Cash and cash equivalents $ 53,043 $ 17,770 Restricted cash 1,157 1,157 Total cash, cash equivalents and restricted cash shown in the statement of cash flows $ 54,200 $ 18,927

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consist of the following as of December 31, 2019 and 2018: Estimated useful life (in years) December 31, 2019 December 31, Laboratory equipment 5 $ 3,736 $ 3,484 Computer, telephone and office equipment 3 891 875 Software 3 122 206 Leasehold improvements Lesser of useful life or remaining lease term 5,929 5,866 10,678 10,431 Less accumulated depreciation and amortization (2,925 ) (1,512 ) $ 7,753 $ 8,919

Accrued Expenses and Other Li_2

Accrued Expenses and Other Liabilities (Tables)	12 Months Ended
	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued Expenses and Other Liabilities	Accrued expenses and other liabilities consist of the following as of December 31, 2019 and 2018: December 31, 2019 December 31, Accrued professional fees and other $ 862 $ 672 Employee compensation and benefits 3,222 3,067 Research and development expenses 4,252 1,476 Deferred lease incentive, current portion — 454 $ 8,336 $ 5,669

Stock Compensation (Tables)

Stock Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Certain Information Related to Outstanding Stock Options	The following table provides certain information related to the Company's outstanding stock options as of December 31, 2019 and 2018: Year ended December 31, 2019 2018 Weighted-average fair value of options granted, per option $ 8.94 $ 17.74 Aggregate grant date fair value of options vested during the year $ 9,354 $ 7,755 Total cash received from exercises of stock options $ 1,076 $ 1,037 Total intrinsic market value of stock options exercised $ 1,277 $ 2,599
Estimated Weighted-Average Assumptions of Options Granted	The weighted-average fair value of options granted in the years ended December 31, 2019 and 2018 reflect the following weighted-average assumptions: Year ended December 31, 2019 2018 Expected volatility 76.83 % 77.22 % Expected term 6.0 years 6.0 years Risk-free interest rate 2.16 % 2.64 % Expected dividend yield — % — %
Summary of Stock Option Activity	The following is a summary of stock option activity for the year ended December 31, 2019: Number of Option Shares Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Market Value (In years) Outstanding at December 31, 2018 3,557,406 $ 15.26 Granted 1,037,750 $ 13.22 Exercised (237,473 ) $ 7.75 Forfeited or expired (245,074 ) $ 18.02 Outstanding at December 31, 2019 4,112,609 $ 15.01 6.86 $ 1,183 Exercisable at December 31, 2019 2,599,751 $ 14.04 5.98 $ 1,179 Vested and expected to vest at December 31, 2019 (1) 3,989,373 $ 14.98 6.79 $ 1,182 (1) Represents the number of vested stock option shares as of December 31, 2019, plus the number of unvested stock option shares that the Company estimated as of December 31, 2019 would vest, based on the unvested stock option shares as of December 31, 2019 and an estimated forfeiture rate of 7% .
Summary of RSU Activity	The following is a summary of RSU activity, including both service-based and performance-based RSUs for the year ended December 31, 2019: Number of RSU Shares Weighted Average Grant Date Fair Value Outstanding at December 31, 2018 228,150 $ 13.87 Granted 412,220 $ 10.27 Released (202,550 ) $ 13.87 Forfeited (44,191 ) $ 12.36 Outstanding at December 31, 2019 393,629 $ 10.27
Stock-Based Compensation Expense Related to All Stock-Based Awards Recognized in Statements of Operations and Comprehensive Loss	Total compensation cost recognized for all stock-based compensation awards in the consolidated statements of operations and comprehensive loss is as follows for the years ended December 31, 2019 and 2018: For the Year Ended December 31, 2019 2018 Research and development $ 5,049 $ 5,221 General and administrative 5,277 6,279 Total stock-based compensation expense $ 10,326 $ 11,500

Loss Per Share (Tables)

Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Schedule of Loss Per Share, Basic and Diluted	The following table illustrates the determination of loss per share for the years ended December 31, 2019 and 2018: For the Year Ended December 31, 2019 2018 Numerator: Net loss applicable to common stockholders - basic and diluted $ (78,166 ) $ (56,024 ) Denominator: Weighted-average shares outstanding - basic and diluted 23,740 23,370 Net loss per share applicable to common stockholders - basic and diluted $ (3.29 ) $ (2.40 ) Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share: Stock options 232 666 Restricted stock units 61 185 Warrants 70 132

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
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 for the years ended December 31, 2019 and 2018: Year ended December 31, 2019 2018 Federal statutory income tax rate 21.0 % 21.0 % State income taxes 6.8 % 6.2 % Change in valuation allowance (29.8 )% (30.9 )% Research and development and other credits 3.2 % 4.0 % Permanent items (1.1 )% (0.3 )% Other (0.1 )% (0.6 )% Federal rate change — % — % Effective income tax rate — % (0.6 )%
Significant Components of Net Deferred Tax Assets	The significant components of the Company’s net deferred tax assets consist of the following as of December 31, 2019 and 2018: December 31, 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 38,544 $ 23,841 Deferred revenue 2,878 2,878 Research and development and other credit carryforwards 18,573 15,597 Lease liability 4,443 — Other 7,508 7,985 71,946 50,301 Valuation allowance (67,737 ) (44,453 ) Total deferred tax assets, net of valuation allowance $ 4,209 $ 5,848 Deferred tax liabilities: Fixed assets $ 1,681 $ 1,477 Right of use asset 2,528 — Gain deferred under installment method — 4,371 Total deferred tax liabilities $ 4,209 $ 5,848 Net deferred tax assets $ — $ —

Commitments (Tables)

Commitments (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Schedule of New Accounting Pronouncements - Adoption of ASC 842	The cumulative effect of the changes made to the consolidated January 1, 2018 balance sheet for the adoption of ASC 606 was as follows: 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 following table presents a summary of the amount by which each financial statement line item was affected by the adoption of ASC 842: January 1, 2019 Prior to Adoption of ASC 842 Effect of Adoption Subsequent to Adoption of ASC 842 Operating lease right-of-use assets, long-term $ — $ 9,478 $ 9,478 Accrued expenses and other liabilities 5,669 (454 ) 5,215 Lease liability, current portion — 607 607 Deferred lease incentive, net of current portion 4,088 (4,088 ) — Deferred rent, net of current portion 2,850 (2,850 ) — Lease liability, net of current portion — 16,264 16,264 Accumulated deficit (116,515 ) — (116,515 )
Maturities of Lease Liabilities, ASC 842	Maturities of lease liabilities: For the year ended December 31, 2020 $ 2,406 2021 2,969 2022 3,058 2023 3,150 2024 3,244 Thereafter 13,979 Total lease payments $ 28,806 Less imputed interest $ (12,542 ) Total $ 16,264
Future Minimum Lease Payments, ASC 840	As of December 31, 2018, the future minimum lease payments due under the Lease were as follows: For the year ended December 31, 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

Warrant to Purchase Redeemabl_2

Warrant to Purchase Redeemable Securities (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (unaudited)	Three Months Ended March 31, June 30, September 30, December 31, Revenue $ 1,005 $ 49 $ 10 $ 13 Operating expenses 21,399 19,474 18,253 20,966 Loss from operations (20,394 ) (19,425 ) (18,243 ) (20,953 ) Other (expense) income, net (1,432 ) 757 1,058 466 Net loss $ (21,826 ) $ (18,668 ) $ (17,185 ) $ (20,487 ) Net loss per share - basic and diluted $ (0.93 ) $ (0.78 ) $ (0.72 ) $ (0.86 ) Three Months Ended March 31, 2018 June 30, 2018 September 30, 2018 December 31, 2018 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 )

Nature of Business (Details)

Nature of Business (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 24, 2020	Mar. 21, 2018	Jan. 31, 2020	Feb. 28, 2019	Jun. 30, 2015	Mar. 31, 2015	Feb. 28, 2014	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Jul. 31, 2017	Jul. 25, 2017	Mar. 31, 2017
Subsidiary, Sale of Stock [Line Items]
Patent assignment agreement payment		$ 10,500						$ 13	$ 10	$ 49	$ 1,005	$ 13	$ 11	$ 2	$ 10,479	$ 1,077	$ 10,505
Escrow amount released				$ 16,000
Cash and cash equivalents and investments								106,400								$ 106,400
Period of sufficiency of cash resources to fund operating plan																12 months
Accumulated deficit								194,700								$ 194,700
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
Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Indemnification Agreement
Subsidiary, Sale of Stock [Line Items]
Guarantor maximum liability								$ 16,000								$ 16,000		$ 16,000	$ 16,000
Escrow amount released				$ 16,000
Product and Service, Other
Subsidiary, Sale of Stock [Line Items]
Patent assignment agreement payment					$ 50,200
Subsequent Event
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in transaction (in shares)	36,167
Proceeds from issuance of common stock	$ 400
IPO
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in transaction (in shares)						3,300,000	6,649,690
Common stock price per share (in dollars per share)						$ 15.15	$ 14
Proceeds from issuance of common stock						$ 46,700	$ 83,100
Warrants | Subsequent Event
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in transaction (in shares)			1,800,000
Common stock price per share (in dollars per share)			$ 9.919
Warrant exercise price (in dollars per share)			$ 0.001
Underwriting Public Offering | Subsequent Event
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in transaction (in shares)			5,735,283
Common stock price per share (in dollars per share)			$ 9.92
Proceeds from issuance of common stock			$ 74,700
Underwriting discounts and commissions and other offering expenses			$ 4,800

Basis of Presentation and Sig_4

Basis of Presentation and Significant Accounting Policies - Additional Information (Details)	1 Months Ended	12 Months Ended
	Feb. 28, 2019USD ($)	Dec. 31, 2019USD ($)institutionsegment	Dec. 31, 2018USD ($)institution	Jan. 01, 2019USD ($)	Jan. 01, 2018USD ($)	Jul. 31, 2017USD ($)	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
Retained earnings		$ (194,681,000)	$ (116,515,000)	$ (116,515,000)	$ 60,490,000
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
Guarantor maximum liability		$ 16,000,000				$ 16,000,000	$ 16,000,000
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 ($)	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract asset	$ 0		$ 16,000,000	$ 16,000,000
Deferred revenue, current portion	7,783,000		1,413,000	1,428,000
Deferred revenue, net of current portion	2,750,000		9,120,000	9,120,000	$ 8,859,000
Retained earnings	$ (194,681,000)	$ (116,515,000)	$ (116,515,000)	60,490,000
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					1,442,000
Retained earnings					$ 76,243,000
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				16,000,000
Deferred revenue, current portion				(14,000)
Deferred revenue, net of current portion				261,000
Retained earnings				$ 15,753,000

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	$ 53,043	$ 17,770
Total financial assets at fair value	101,552	152,460
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	40,782	7,643
Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	2,000
Fair value, investments available-for-sale	18,896	100,695
U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents		1,748
Fair value, investments available-for-sale	34,499	34,849
Corporate equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	5,375	7,525
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets at fair value	91,653	115,752
Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	40,782	7,643
Level 1 | Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	0
Fair value, investments available-for-sale	10,997	64,733
Level 1 | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents		1,748
Fair value, investments available-for-sale	34,499	34,103
Level 1 | Corporate equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	5,375	7,525
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets at fair value	9,899	36,708
Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	0	0
Level 2 | Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	2,000
Fair value, investments available-for-sale	7,899	35,962
Level 2 | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents		0
Fair value, investments available-for-sale	0	746
Level 2 | Corporate equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets at fair value	0	0
Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	0	0
Level 3 | Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	0
Fair value, investments available-for-sale	0	0
Level 3 | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents		0
Fair value, investments available-for-sale	0	0
Level 3 | Corporate equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	$ 0	$ 0

Cash, Cash Equivalents, Inves_3

Cash, Cash Equivalents, Investments and Marketable Equity Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents
Amortized cost	$ 53,043	$ 17,770
Fair value	53,043	17,770
U.S. Treasury obligations
Debt Securities
Amortized cost	34,475	34,856
Unrealized gains	24	2
Unrealized losses	0	(9)
Fair value	34,499	34,849
Government agency securities
Debt Securities
Amortized cost	18,874	100,748
Unrealized gains	22	7
Unrealized losses	0	(60)
Fair value	18,896	100,695
Investments, available for sale
Debt Securities
Amortized cost	53,349	135,604
Unrealized gains	46	9
Unrealized losses	0	(69)
Fair value	53,395	135,544
Marketable equity securities
Debt Securities
Acquisition value	10,451	10,451
Unrealized gains	0	0
Unrealized losses	(5,076)	(2,926)
Fair value	5,375	7,525
Cash
Cash and Cash Equivalents
Amortized cost	10,261	8,379
Fair value	10,261	8,379
Money market funds
Cash and Cash Equivalents
Amortized cost	40,782	7,643
Fair value	40,782	7,643
U.S. Treasury obligations
Cash and Cash Equivalents
Amortized cost		1,748
Fair value		$ 1,748
Government agency securities
Cash and Cash Equivalents
Amortized cost	2,000
Fair value	$ 2,000
Expected term (in years) | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Average maturity	108 days	151 days
Expected term (in years) | Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Average maturity	74 days	153 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
Expected term (in years) | Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Average maturity	8 days

Restricted Cash (Details)

Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 53,043	$ 17,770
Restricted cash	1,157	1,157
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 54,200	$ 18,927	$ 29,222

Property and Equipment - Schedu

Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 10,678	$ 10,431
Less accumulated depreciation and amortization	(2,925)	(1,512)
Total property, plant and equipment, net	$ 7,753	8,919
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life (in years)	5 years
Property, plant and equipment, gross	$ 3,736	3,484
Computer, telephone and office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life (in years)	3 years
Property, plant and equipment, gross	$ 891	875
Software
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life (in years)	3 years
Property, plant and equipment, gross	$ 122	206
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 5,929	$ 5,866

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 1,664	$ 1,247

Accrued Expenses and Other Li_3

Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued professional fees and other	$ 862		$ 672
Employee compensation and benefits	3,222		3,067
Research and development expenses	4,252		1,476
Deferred lease incentive, current portion	0		454
Accrued expenses and other liabilities	$ 8,336	$ 5,215	$ 5,669

Stock Compensation - Additional

Stock Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 01, 2020	Aug. 15, 2019	Jul. 06, 2017	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield				0.00%	0.00%
Estimated forfeiture rate				7.00%	7.00%
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period				10 years
Estimated forfeiture rate				7.00%
Total unrecognized compensation cost				$ 15
Total unrecognized compensation cost, weighted-average recognition period				2 years 4 months 10 days
Stock Options | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				3 years
Stock Options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				4 years
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		2 years
Total unrecognized compensation cost, weighted-average recognition period					1 year 7 months 15 days
Restricted stock units granted to executives and employees (in shares)		400,000	500,000	412,220
Award vesting percentage		35.00%
Weighted average grant date fair value of restricted stock units (in dollars per share)				$ 10.27
Unrecognized compensation cost related to RSUs				$ 3.5
Restricted Stock Units | Vesting on March 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage			50.00%
Restricted Stock Units | Vesting on March 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage			50.00%
2014 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant (in shares)				1,265,774
2014 Stock Incentive Plan | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares issued under the plan (in shares)	954,603
2006 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant (in shares)				0

Stock Compensation - Outstandin

Stock Compensation - Outstanding Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total cash received from exercises of stock options	$ 1,076	$ 1,037
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)	$ 8.94	$ 17.74
Aggregate grant date fair value of options vested during the year	$ 9,354	$ 7,755
Total cash received from exercises of stock options	1,076	1,037
Total intrinsic market value of stock options exercised	$ 1,277	$ 2,599

Stock Compensation - Weighted-A

Stock Compensation - Weighted-Average Assumptions of Options Granted (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Payment Arrangement [Abstract]
Expected volatility	76.83%	77.22%
Expected term	6 years	6 years
Risk-free interest rate	2.16%	2.64%
Expected dividend yield	0.00%	0.00%

Stock Compensation - Summary of

Stock Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Number of Option Shares
Number of options, outstanding beginning balance (in shares)	3,557,406
Number of options, granted (in shares)	1,037,750
Number of options, exercised (in shares)	(237,473)
Number of options, forfeited or expired (in shares)	(245,074)
Number of options, outstanding end balance (in shares)	4,112,609	3,557,406
Number of options, exercisable (in shares)	2,599,751
Number of options, vested and expected to vest (in shares) to vest	3,989,373
Weighted Average Exercise Price per Share
Weighted average exercise price per share, outstanding at beginning of year (in dollars per share)	$ 15.26
Weighted average exercise price per share, granted (in dollars per share)	13.22
Weighted average exercise price per share, exercised (in dollars per share)	7.75
Weighted average exercise price per share, forfeited or expired (in dollars per share)	18.02
Weighted average exercise price per share, outstanding ending balance (in dollars per share)	15.01	$ 15.26
Weighted average exercise price per share, exercisable (in dollars per share)	14.04
Weighted average exercise price per share, vested and expected to vest (in dollars per share)	$ 14.98
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term, outstanding	6 years 10 months 10 days
Weighted average remaining contractual term, exercisable	5 years 11 months 23 days
Weighted average remaining contractual term, vested and expected to vest	6 years 9 months 14 days
Aggregate Intrinsic Market Value
Aggregate intrinsic value, outstanding	$ 1,183
Aggregate intrinsic value, exercisable	1,179
Aggregate intrinsic value, vested and expected to vest	$ 1,182
Estimated forfeiture rate	7.00%	7.00%
Stock Options
Aggregate Intrinsic Market Value
Estimated forfeiture rate	7.00%

Stock Compensation - Summary _2

Stock Compensation - Summary of Restricted Stock Units (Details) - Restricted Stock Units - $ / shares	Aug. 15, 2019	Jul. 06, 2017	Dec. 31, 2019
Number of RSU Shares
Number of RSU shares, outstanding beginning balance (in shares)			228,150
Number of RSU shares, granted (in shares)	400,000	500,000	412,220
Number of RSU shares, released (in shares)			(202,550)
Number of RSU shares, forfeited (in shares)			(44,191)
Number of RSU shares, outstanding ending balance (in shares)			393,629
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)			10.27
Weighted average grant date fair value, released (in dollars per share)			13.87
Weighted average grant date fair value, forfeited (in dollars per share)			12.36
Weighted average grant date fair value, outstanding ending balance (in dollars per share)			$ 10.27

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, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 10,326	$ 11,500
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	5,049	5,221
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 5,277	$ 6,279

Loss Per Share (Details)

Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss applicable to common stockholders - basic and diluted	$ (20,487)	$ (17,185)	$ (18,668)	$ (21,826)	$ (20,849)	$ (17,387)	$ (13,325)	$ (4,463)	$ (78,166)	$ (56,024)
Denominator:
Weighted-average shares outstanding - basic and diluted (in shares)									23,740	23,370
Net loss per share applicable to common stockholders - basic and diluted (in dollars per share)	$ (0.86)	$ (0.72)	$ (0.78)	$ (0.93)	$ (0.89)	$ (0.74)	$ (0.57)	$ (0.19)	$ (3.29)	$ (2.40)
Stock options
Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share:
Anti-dilutive stock options, restricted stock units, and warrants (in shares)									232	666
Restricted stock units
Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share:
Anti-dilutive stock options, restricted stock units, and warrants (in shares)									61	185
Warrants
Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share:
Anti-dilutive stock options, restricted stock units, and warrants (in shares)									70	132

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended				12 Months Ended
	Feb. 28, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2015	Dec. 31, 2017	Jul. 31, 2017	Jul. 25, 2017
Schedule Of Income Taxes [Line Items]
Loss before income taxes						$ 78,166,000	$ 55,711,000
Income tax expense (benefit)		$ 15,000	$ 18,000	$ 280,000	$ 0	0	313,000
Escrow amount released	$ 16,000,000
Income tax benefit, continuing operations							100,000
Unrealized gain (loss) on investments, tax							76,000
Income taxes receivable, AMT refund current year									$ 1,900,000
Income taxes receivable, AMT refund									$ 1,900,000
Tax benefit reversal of valuation allowance on 2015 AMT credit carryforward								$ 300,000
Income taxes receivable, AMT refund prior year						2,300,000
Operating loss carryforwards, not subject to expiration						98,200,000
Federal
Schedule Of Income Taxes [Line Items]
Operating loss carryforwards						153,000,000
Operating loss carryforwards, subject to expiration						54,800,000
Federal | Research and Development
Schedule Of Income Taxes [Line Items]
Tax credit carryforwards						14,200,000
State
Schedule Of Income Taxes [Line Items]
Operating loss carryforwards						101,600,000
Operating loss carryforwards, subject to expiration						101,600,000
State | Research and Development
Schedule Of Income Taxes [Line Items]
Tax credit carryforwards						5,500,000
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]
Guarantor maximum liability						$ 16,000,000				$ 16,000,000	$ 16,000,000
Escrow amount released	$ 16,000,000
Tax Year 2018
Schedule Of Income Taxes [Line Items]
Income tax expense (benefit)							$ 200,000

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Federal Statutory Income Tax Rate and Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	21.00%
State income taxes	6.80%	6.20%
Change in valuation allowance	(29.80%)	(30.90%)
Research and development and other credits	3.20%	4.00%
Permanent items	(1.10%)	(0.30%)
Other	(0.10%)	(0.60%)
Federal rate change	0.00%	0.00%
Effective income tax rate	0.00%	(0.60%)

Income Taxes - Significant Comp

Income Taxes - Significant Components of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 38,544	$ 23,841
Deferred revenue	2,878	2,878
Research and development and other credit carryforwards	18,573	15,597
Lease liability	4,443
Other	7,508	7,985
Gross deferred tax assets	71,946	50,301
Valuation allowance	(67,737)	(44,453)
Total deferred tax assets, net of valuation allowance	4,209	5,848
Deferred tax liabilities:
Fixed assets	1,681	1,477
Right of use asset	2,528
Gain deferred under installment method	0	4,371
Total deferred tax liabilities	4,209	5,848
Net deferred tax assets	$ 0	$ 0

Commitments - Additional Inform

Commitments - Additional Information (Details) ft² in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)ft²option	Dec. 31, 2018USD ($)	Jan. 01, 2019USD ($)
Commitments [Line Items]
Area of leased office and laboratory space | ft²	56
Term of contract	10 years
Number of extensions | option	2
Length of extension	5 years
Remaining lease term	9 years
Annual base rent amount	$ 2,800
Annual rent increase, percent	3.00%
Abatement of base rent amount	$ 500
Discount rate	13.00%
Operating lease liability	$ 16,264		$ 16,900
Lease liability, current portion	268		607
Lease liability, non-current	15,996		16,264
Tenant improvement allowance	5,000
Operating lease right-of-use assets	9,252		9,478
Operating lease, expense	2,400
Cash paid included in measurement of lease liabilities (Note 11)	$ 2,778
Rent expense		$ 3,300
Weighted-average discount rate	13.08%
Accounting Standards Update 2016-02
Commitments [Line Items]
Lease liability, current portion			607
Lease liability, non-current			16,264
Operating lease right-of-use assets			9,478
Reduction to accrued rent			2,900
Reduction to incentive to lessee			$ 4,500

Commitments - Summary of the Am

Commitments - Summary of the Amount each Financial Statement Line was Affected by Adoption of ASC 842 (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets, long-term	$ 9,252	$ 9,478
Accrued expenses and other liabilities	8,336	5,215	$ 5,669
Lease liability, current portion	268	607
Deferred lease incentive, net of current portion	0		4,088
Deferred rent, net of current portion			2,850
Lease liability, net of current portion	15,996	16,264
Accumulated deficit	$ (194,681)	(116,515)	$ (116,515)	$ 60,490
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets, long-term		9,478
Accrued expenses and other liabilities		(454)
Lease liability, current portion		607
Deferred lease incentive, net of current portion		(4,088)
Deferred rent, net of current portion		(2,850)
Lease liability, net of current portion		16,264
Accumulated deficit		$ 0

Commitments - Maturities of Lea

Commitments - Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
Commitments and Contingencies Disclosure [Abstract]
2020	$ 2,406
2021	2,969
2022	3,058
2023	3,150
2024	3,244
Thereafter	13,979
Total lease payments	28,806
Less imputed interest	(12,542)
Total	$ 16,264	$ 16,900

Commitments - Future Minimum Le

Commitments - Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
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 - Additional Informatio

Revenue - Additional Information (Details)	1 Months Ended	12 Months Ended
	Feb. 28, 2019USD ($)	Dec. 31, 2019USD ($)segment	Dec. 31, 2018USD ($)	Jan. 01, 2018USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of segments | segment		1
Contract asset		$ 0	$ 16,000,000	$ 16,000,000
Escrow amount released	$ 16,000,000
Contract liability		10,500,000	10,500,000
Revenue recognized		0	$ 16,000
Celgene
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liability		7,800,000
Celgene | CTP-730
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liability		1,400,000
Celgene | One of the Other Additional License Programs
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liability		6,400,000
GSK
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liability		2,800,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Vertex
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract asset		$ 0
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Indemnification Agreement | Assets for Synthesis and Research and Development for Treating Cystic Fibrosis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Escrow amount released	16,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Indemnification Agreement | Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Vertex
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Escrow amount released	$ 16,000,000

Revenue - Vertex (Details)

Revenue - Vertex (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Feb. 28, 2019	Dec. 31, 2019	Jul. 31, 2017	Jul. 25, 2017	Mar. 03, 2017
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Escrow amount released	$ 16
Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cash consideration			$ 160	$ 160
Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Indemnification Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Escrow amount released	16
Vertex | Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cash consideration					$ 160
Vertex | 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 Arrangement and Arrangement Other than Collaborative [Line Items]
Contingent consideration receivable					$ 90
Vertex | Assets for Synthesis and Research and Development for Treating Cystic Fibrosis | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Indemnification Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Escrow amount released	$ 16
Escrow release period		18 months

Revenue - Processa (Details)

Revenue - Processa (Details) - USD ($) $ in Thousands	Mar. 21, 2018	Mar. 19, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock, outstanding (in shares)			23,865,075				23,437,587				23,865,075	23,437,587
Total revenue	$ 10,500		$ 13	$ 10	$ 49	$ 1,005	$ 13	$ 11	$ 2	$ 10,479	$ 1,077	$ 10,505
Processa
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Equity received from sale of license (in shares)		2,090,301
Common stock, outstanding (in shares)			298,615								298,615
Receivables from customers			$ 34				$ 10,500				$ 34	$ 10,500

Revenue - Cipla (Details)

Revenue - Cipla (Details) - USD ($) $ in Thousands	Jan. 16, 2019	Mar. 21, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
License and research and development revenue		$ 10,500	$ 13	$ 10	$ 49	$ 1,005	$ 13	$ 11	$ 2	$ 10,479	$ 1,077	$ 10,505
Deferred revenue											0	$ (16)
Cipla
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
License and research and development revenue	$ 1,000										$ 1,000
Option to purchase inventory, valuation	300
Eligible payments receivable	3,000
Deferred revenue	1,000
Cipla | Achievement of Certain Milestones
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Eligible payments receivable	57,000
Cipla | First Milestone
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Eligible payments receivable	$ 3,000

Open Market Sale Agreement (Det

Open Market Sale Agreement (Details) - USD ($)	Feb. 24, 2020	Dec. 31, 2019	Mar. 01, 2019	Dec. 31, 2018
Subsidiary, Sale of Stock [Line Items]
Common stock, par value (in dollars per share)		$ 0.001	$ 0.001	$ 0.001
Sale of stock, authorized amount			$ 50,000,000
Sale of stock, commission rate			3.00%
Legal expense maximum			$ 50,000
Professional fees		$ 300,000
Subsequent Event
Subsidiary, Sale of Stock [Line Items]
Sale of stock, commission rate	3.00%
Number of shares issued in transaction (in shares)	36,167
Proceeds from issuance of common stock	$ 400,000

401(k) Retirement Plan (Details

401(k) Retirement Plan (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2008	Dec. 31, 2019	Dec. 31, 2018
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) plan		$ 0.4	$ 0.3

Warrant to Purchase Redeemabl_3

Warrant to Purchase Redeemable Securities - Additional Information (Details) - Loan Agreement $ / shares in Units, $ in Millions	Jun. 08, 2017USD ($)$ / sharesshares
Debt Instrument [Line Items]
Warrants issued and exercisable (in shares) | shares	61,273
Warrant exercise price (in dollars per share) | $ / shares	$ 12.24
Warrant expiration term	5 years
Warrants total relative fair value | $	$ 0.5

Warrant to Purchase Redeemabl_4

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

Quarterly Financial Informati_3

Quarterly Financial Information (unaudited) (Details) - USD ($)	Mar. 21, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 10,500,000	$ 13,000	$ 10,000	$ 49,000	$ 1,005,000	$ 13,000	$ 11,000	$ 2,000	$ 10,479,000	$ 1,077,000	$ 10,505,000
Operating expenses		20,966,000	18,253,000	19,474,000	21,399,000	20,076,000	17,351,000	14,376,000	14,286,000	80,092,000	66,089,000
Loss from operations		(20,953,000)	(18,243,000)	(19,425,000)	(20,394,000)	(20,063,000)	(17,340,000)	(14,374,000)	(3,807,000)	(79,015,000)	(55,584,000)
Other (expense) income, net		466,000	1,058,000	757,000	(1,432,000)	(771,000)	(29,000)	1,329,000	(656,000)
Provision for income taxes						(15,000)	(18,000)	(280,000)	0	0	(313,000)
Net loss		$ (20,487,000)	$ (17,185,000)	$ (18,668,000)	$ (21,826,000)	$ (20,849,000)	$ (17,387,000)	$ (13,325,000)	$ (4,463,000)	$ (78,166,000)	$ (56,024,000)
Net loss per share - basic and diluted (in dollars per share)		$ (0.86)	$ (0.72)	$ (0.78)	$ (0.93)	$ (0.89)	$ (0.74)	$ (0.57)	$ (0.19)	$ (3.29)	$ (2.40)

Subsequent Events (Details)

Subsequent Events (Details) - Subsequent Event - USD ($) $ / shares in Units, $ in Millions	Feb. 24, 2020	Jan. 31, 2020
Subsequent Event [Line Items]
Number of shares issued in transaction (in shares)	36,167
Proceeds from issuance of common stock	$ 0.4
Underwriting Public Offering
Subsequent Event [Line Items]
Number of shares issued in transaction (in shares)		5,735,283
Common stock price per share (in dollars per share)		$ 9.92
Proceeds from issuance of common stock		$ 74.7
Underwriting discounts and commissions and other offering expenses		$ 4.8
Pre-funded Warrants
Subsequent Event [Line Items]
Number of shares issued in transaction (in shares)		1,800,000
Common stock price per share (in dollars per share)		$ 9.919
Warrant exercise price (in dollars per share)		$ 0.001

Uncategorized Items - cnce-2019

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