Concert Pharmaceuticals (CNCE) 10-Q 30 Apr 20 2020 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	Apr. 24, 2020
Document And Entity Information [Abstract]
Entity Current Reporting Status	Yes
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Entity Registrant Name	CONCERT PHARMACEUTICALS, INC.
Entity Central Index Key	0001367920
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		29,653,295

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 46,079	$ 53,043
Investments, available for sale	113,515	53,395
Marketable equity securities	2,986	5,375
Interest receivable	428	260
Deferred offering costs	0	143
Accounts receivable	1	72
Income taxes receivable, current	2,358	0
Prepaid expenses and other current assets	4,028	4,567
Total current assets	169,395	116,855
Property and equipment, net	7,457	7,753
Restricted cash	1,157	1,157
Other assets	82	96
Income taxes receivable	0	2,358
Operating lease right-of-use assets, long-term	9,184	9,252
Total assets	187,275	137,471
Current liabilities:
Accounts payable	1,444	881
Accrued expenses and other liabilities	4,261	8,336
Income taxes payable	0	0
Deferred revenue, current portion	7,783	7,783
Lease liability, current portion	783	268
Total current liabilities	14,271	17,268
Deferred revenue, net of current portion	2,750	2,750
Lease liability, net of current portion	15,775	15,996
Total liabilities	32,796	36,014
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 March 31, 2020 and December 31, 2019	0	0
Common stock, $0.001 par value per share; 100,000,000 shares authorized; 29,852,196 and 24,065,676 shares issued and 29,651,595 and 23,865,075 shares outstanding as of March 31, 2020 and December 31, 2019, respectively	29	24
Additional paid-in capital	369,116	296,145
Accumulated other comprehensive gain (loss)	492	(31)
Accumulated deficit	(215,158)	(194,681)
Total stockholders’ equity	154,479	101,457
Total liabilities and stockholders’ equity	$ 187,275	$ 137,471

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
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)	29,852,196	24,065,676
Common stock, shares outstanding (in shares)	29,651,595	23,865,075

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue:
License and research and development revenue	$ 7	$ 1,005
Operating expenses:
Research and development	13,986	15,790
General and administrative	4,672	5,609
Total operating expenses	18,658	21,399
Loss from operations	(18,651)	(20,394)
Investment income	563	867
Unrealized loss on marketable equity securities	(2,389)	(2,299)
Net loss	(20,477)	(21,826)
Other comprehensive income:
Unrealized gain on investments, available for sale	523	97
Comprehensive loss	$ (19,954)	$ (21,729)
Net loss per share applicable to common stockholders - basic and diluted (in dollars per share)	$ (0.70)	$ (0.93)
Weighted-average number of common shares used in net loss per share applicable to common stockholders - basic and diluted (in shares)	29,110	23,508

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock	In Treasury	Additional paid-in capital	Accumulated other comprehensive income	Accumulated deficit
Beginning balance (in shares) at Dec. 31, 2018		23,519,000	81,000
Beginning 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)		154,000	47,000
Exercise of stock options	805			805
Release of restricted stock units (in shares)		202,000	61,000
Release of restricted stock units	(741)			(741)
Unrealized gain (loss) on short-term investments	97				97
Stock-based compensation expense	2,929			2,929
Exercise of stock warrants	$ 1,000			1,000	0	0
Proceeds from at-the-market offering (in shares)	71,000
Sale of common stock and pre-funded warrants, net of underwriters' discount and costs	$ (206)			(206)	0	0
Net loss	(21,826)					(21,826)
Ending balance (in shares) at Mar. 31, 2019		23,946,000	189,000
Ending balance at Mar. 31, 2019	149,798	$ 23		288,156	(40)	(138,341)
Beginning balance (in shares) at Dec. 31, 2019		24,066,000	200,000
Beginning balance at Dec. 31, 2019	$ 101,457	$ 24		296,145	(31)	(194,681)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	51,237	51,000	0
Exercise of stock options	$ 435			435
Unrealized gain (loss) on short-term investments	523				523
Stock-based compensation expense	2,477			2,477
Proceeds from at-the-market offering (in shares)		5,735,000
Sale of common stock and pre-funded warrants, net of underwriters' discount and costs	70,064	$ 5		70,059	0	0
Net loss	(20,477)					(20,477)
Ending balance (in shares) at Mar. 31, 2020		29,852,000	200,000
Ending balance at Mar. 31, 2020	$ 154,479	$ 29		$ 369,116	$ 492	$ (215,158)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities
Net loss	$ (20,477)	$ (21,826)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	408	444
Stock-based compensation expense	2,477	2,929
Accretion of premiums and discounts on investments	(80)	(294)
Unrealized loss on marketable equity securities	2,389	2,299
Loss on disposal of asset	0	4
Non-cash lease expense	68	49
Changes in operating assets and liabilities:
Accounts receivable	71	4
Interest receivable	(168)	174
Prepaid expenses and other current assets	539	381
Contract asset	0	16,000
Other assets	14	(23)
Accounts payable	563	479
Accrued expenses and other liabilities	(3,932)	(1,388)
Income taxes receivable	0	(36)
Income taxes payable	0	(390)
Operating lease liability	294	(144)
Net cash used in operating activities	(17,834)	(1,338)
Investing activities
Purchases of property and equipment	(112)	(315)
Purchases of investments	(93,417)	(13,331)
Maturities of investments	33,900	55,721
Net cash (used in) provided by investing activities	(59,629)	42,075
Financing activities
Proceeds from exercises of stock options	435	805
Proceeds from exercise of warrants	0	1,000
Proceeds from common stock and pre-funded warrants sold, net of underwriters' discount and costs	70,064	(50)
Net cash provided by financing activities	70,499	1,755
Net increase in cash and cash equivalents and restricted cash	(6,964)	42,492
Cash, cash equivalents and restricted cash at beginning of period	54,200	18,927
Cash, cash equivalents and restricted cash at end of period	47,236	61,419
Supplemental cash flow information:
Cash paid for income taxes	0	425
Purchases of property and equipment unpaid at period end	0	16
Public offering costs unpaid at period end	0	156
Cash paid included in measurement of lease liabilities	244	694
Pre-funded stock warrants issued	$ 16,736	$ 0

Nature of Business

Nature of Business	3 Months Ended
	Mar. 31, 2020
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 central nervous system, or CNS, disorders, and a number of preclinical compounds that it is currently assessing. The Company had cash and cash equivalents and investments of $159.6 million as of March 31, 2020 . The Company believes that its cash and cash equivalents and investments as of March 31, 2020 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 $215.2 million through March 31, 2020 . 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	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	Basis of Presentation and Significant Accounting Policies Basis of Presentation The condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments, consisting of normal recurring accruals and revisions of estimates, considered necessary for a fair presentation of the condensed consolidated financial statements have been included. Interim results for the three months ended March 31, 2020 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2020 or any other future period. The accompanying condensed consolidated financial statements reflect the accounts of the Company and its subsidiaries. All intercompany transactions between the Company and its subsidiaries have been eliminated. Management has determined that the Company operates in one segment: the development of pharmaceutical products on its own behalf or in collaboration with others. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the Company’s consolidated financial statements and the accompanying notes included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2019 filed with the Securities and Exchange Commission, or SEC, on February 27, 2020. Use of Estimates and Summary of Significant Accounting Policies The preparation of the consolidated financial statements in conformity with U.S. generally accepted accounting principles, or 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. During the three months ended March 31, 2020 , there have been no material changes to the significant accounting policies previously disclosed in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2019. Recently Adopted Accounting Pronouncements In August 2018, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or 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 . This 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 adopted this new standard effective January 1, 2020, on a prospective basis, and it did not have a material effect on the consolidated financial statements and related disclosures. In December 2019, the FASB issued ASU 2019-12 , Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes . This standard includes removal of certain exceptions to the general principles of Accounting Standards Codification, or 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 adopted this new standard effective January 1, 2020, and it did not have a material effect on the consolidated financial statements and related disclosures. For a detailed discussion of the adoption of ASU 2019-12, refer to Note 7. Pending Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses . This 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.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value 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. The tables below present information about the Company’s financial assets and liabilities that are measured and carried at fair value as of March 31, 2020 and December 31, 2019 and indicate the level within the fair value hierarchy where each measurement is classified. The carrying amounts reflected in the condensed consolidated balance sheets for cash, prepaid expenses and other current assets, restricted cash, accounts payable and accrued expenses approximate their fair value due to their short-term nature. Level 1 Level 2 Level 3 Total March 31, 2020 Cash equivalents: Money market funds $ 31,821 $ — $ — $ 31,821 U.S. Treasury obligations 7,998 — — 7,998 Investments, available for sale: U.S. Treasury obligations 36,868 — — 36,868 Government agency securities 22,530 54,117 — 76,647 Marketable equity securities: Corporate equity securities (Note 8) 2,986 — — 2,986 Total $ 102,203 $ 54,117 $ — $ 156,320 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 (Note 8) 5,375 — — 5,375 Total $ 91,653 $ 9,899 $ — $ 101,552

Cash, Cash Equivalents, Investm

Cash, Cash Equivalents, Investments and Marketable Equity Securities	3 Months Ended
	Mar. 31, 2020
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents, Investments and Marketable Equity Securities	Cash, Cash Equivalents, Investments and Marketable Equity Securities 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 from equity securities are included in net income. Unrealized gains or losses from other investments, including debt securities, 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. Cash, cash equivalents, available for sale investments and marketable equity securities included the following as of March 31, 2020 and December 31, 2019: Average Maturity Amortized Cost Unrealized Gains Unrealized Losses Fair Value March 31, 2020 Cash $ 6,260 $ — $ — $ 6,260 Money market funds 31,821 — — 31,821 U.S. Treasury obligations 30 days 7,998 — — 7,998 Cash and cash equivalents $ 46,079 $ — $ — $ 46,079 U.S. Treasury obligations 173 days 36,586 282 — 36,868 Government agency securities 130 days 76,360 287 — 76,647 Investments, available for sale $ 112,946 $ 569 $ — $ 113,515 March 31, 2020 Acquisition Value Unrealized Gains Unrealized Losses Fair Value Marketable equity securities (Note 8) $ 10,451 $ — $ (7,465 ) $ 2,986 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 (Note 8) $ 10,451 $ — $ (5,076 ) $ 5,375 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 2020 and 2019, there were no realized gains or losses on sales of investments, and no investments were adjusted other than for temporary declines in fair value.

Restricted Cash

Restricted Cash	3 Months Ended
	Mar. 31, 2020
Cash and Cash Equivalents [Abstract]
Restricted Cash	Restricted Cash Restricted cash as of March 31, 2020 and 2019 was held as collateral for stand-by letters of credit issued by the Company to its landlord 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, refer to Note 11. Cash, cash equivalents and restricted cash consisted of the following as of March 31, 2020 and 2019: March 31, March 31, Cash and cash equivalents $ 46,079 $ 60,262 Restricted cash 1,157 1,157 Total cash, cash equivalents and restricted cash shown in the statements of cash flows $ 47,236 $ 61,419

Accrued Expenses and Other Liab

Accrued Expenses and Other Liabilities	3 Months Ended
	Mar. 31, 2020
Payables and Accruals [Abstract]
Accrued Expenses and Other Liabilities	Accrued Expenses and Other Liabilities Accrued expenses and other liabilities consisted of the following as of March 31, 2020 and December 31, 2019: March 31, December 31, Accrued professional fees and other $ 342 $ 862 Employee compensation and benefits 812 3,222 Research and development expenses 3,107 4,252 $ 4,261 $ 8,336

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Deferred tax assets and deferred tax liabilities are recognized based on temporary differences between the financial reporting and tax basis of assets and liabilities using statutory rates. A valuation allowance is recorded against deferred tax assets if it is more likely than not that some or all of the deferred tax assets will not be realized. The Company’s ability to use its operating loss carryforwards and tax credits to offset future taxable income is subject to restrictions under Sections 382 and 383 of the U.S. Internal Revenue Code. Net operating loss and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three-year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code. Such changes would limit the Company’s use of its operating loss carryforwards and tax credits. In such a situation, the Company may be required to pay income taxes, even though significant operating loss carryforwards and tax credits exist. The Company records a provision or benefit for income taxes on ordinary pre-tax income or loss based on its estimated effective tax rate for the year. As of March 31, 2020 , the Company forecasts an ordinary pre-tax loss for the year ended December 31, 2020 and, since it maintains a full valuation allowance on its deferred tax assets, the Company did not record an income tax benefit for the three months ended March 31, 2020 . The Company adopted ASU 2019-12 , Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes , effective January 1, 2020. Under ASU 2019-12, the Company, having a full valuation and a loss in continuing operations, will no longer include the impacts of items in other comprehensive income in determining intra-period allocation of tax expense for continuing operations. Under ASU 2019-12, the Company can apply this change to intra-period tax allocation on a prospective basis. For the three months ended March 31, 2020, the Company applied the tax allocation rules of ASU 2019-12 to the $523 thousand of unrealized gains on available for sale investments recognized in other comprehensive income, which did not have a material impact on the consolidated financial statements or related disclosures.

Revenue

Revenue	3 Months Ended
	Mar. 31, 2020
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. The revenue recognized under each of the Company's arrangements during the current and prior periods is described below. On January 1, 2018, the Company adopted ASU 2014-09, Revenue from Contracts with Customers , which is also referred to as ASC 606, using the modified retrospective approach. For detailed information regarding the adoption of ASC 606, the impact on its consolidated financial statements and its collaboration arrangements, see Note 2 and Note 12 to the consolidated financial statements appearing in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2018 filed with the SEC on February 28, 2019. Contract Assets In February 2019, the Company received $16.0 million that had previously been held in escrow for indemnification purposes related to the asset purchase by Vertex Pharmaceuticals, Inc., or Vertex. The Company did no t have a contract asset as of March 31, 2020 or December 31, 2019. Contract Liabilities As of March 31, 2020 and December 31, 2019, the Company had $10.6 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 Corporation, $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 the rights to those programs are exercised, or in the second quarter of 2020 at such time that the rights lapse; and • $2.8 million related to a payment received from GlaxoSmithKline that the Company will not recognize as revenue until all repayment obligations lapse. Revenue Arrangements Vertex On March 3, 2017, the Company and Vertex entered into an Asset Purchase Agreement, or the Vertex Agreement, pursuant to which, subject to the satisfaction or waiver of the conditions therein, the Company sold and assigned to Vertex CTP-656, a deuterated analog of ivacaftor, now known as VX-561, and other cystic fibrosis assets of the Company. On July 25, 2017, or the Vertex Closing Date, the transaction contemplated by the Vertex Agreement closed and Vertex paid the Company $160 million in cash consideration. In addition, Vertex has agreed to pay the Company an aggregate of up to $90 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. In February 2019, the $16.0 million that had previously been held in escrow was released to the Company. 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 March 31, 2020 or December 31, 2019. Processa On October 4, 2017, the Company entered into an Option and License Agreement, or the Option, 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 Pharmaceuticals, Inc., or Processa. On March 21, 2018, the Company entered into an Amendment to the Option, or the Amendment, and a Securities Purchase Agreement, with both 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 condensed consolidated statements 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 both the three months ended March 31, 2020 and 2019, the Company recognized $1 thousand related to intellectual property cost reimbursements. Cipla The Company entered into a License Agreement, or the Cipla Agreement, with Cipla Technologies LLC, or 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 Cipla Closing Date, valued in the 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 investigational new drug application, or 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 did not recognize revenue related to the Cipla Agreement for the three months ended March 31, 2020 . The Company recognized $1.0 million in revenue associated with the Transfer of License Performance Obligation for the three months ended March 31, 2019 .

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation The Company’s equity incentive plans provide for the issuance of a variety of stock-based awards, including incentive stock options, nonstatutory stock options and awards of stock, to directors, officers and employees of the Company, as well as consultants and advisors to the Company. As of March 31, 2020 , the Company has granted awards in the form of stock options and restricted stock units, or RSUs. The stock options generally have been granted with an exercise price equal to the closing market price of the Company's common stock on the date of grant, a vesting period of one, three or four years , and an expiration date no later than ten years from the date of grant. Effective January 1, 2020, an additional 954,603 shares were added to the Company’s 2014 Stock Incentive Plan, or the 2014 Plan, for future issuance pursuant to the terms of the 2014 Plan. As of March 31, 2020 , there were 1,243,137 shares of common stock available for future awards under the 2014 Plan. Total stock-based compensation expense related to all stock-based options and awards recognized in the condensed consolidated statements of operations and comprehensive loss consisted of: Three Months Ended March 31, 2020 2019 Research and development $ 1,255 $ 1,475 General and administrative 1,222 1,454 Total stock-based compensation expense $ 2,477 $ 2,929 Stock Options 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 weighted-average fair value of options granted in the three months ended March 31, 2020 and 2019 reflect the following weighted-average assumptions: Three Months Ended March 31, 2020 2019 Expected volatility 68.19 % 77.16 % Expected term 6.0 years 6.0 years Risk-free interest rate 1.47 % 2.27 % Expected dividend yield — % — % For the three months ended March 31, 2019, 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. For the three months ended March 31, 2020 , expected volatility was estimated using solely the historical volatility of the Company's common stock because the Company had accumulated sufficient historical pricing data. The following table provides certain information related to the Company's outstanding stock options: Three Months Ended March 31, 2020 2019 (in thousands, except per share data) Weighted-average fair value of options granted, per option $ 6.67 $ 9.45 Aggregate grant date fair value of options vested during the period $ 2,184 $ 2,442 Total cash received from exercises of stock options $ 435 $ 805 Total intrinsic value of stock options exercised $ 93 $ 879 The following is a summary of stock option activity for the three months ended March 31, 2020 : Number of Option Shares Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (in years) (in thousands) Outstanding at December 31, 2019 4,112,609 $ 15.01 Granted 615,050 $ 10.87 Exercised (51,237 ) $ 8.48 Forfeited or expired (42,937 ) $ 19.57 Outstanding at March 31, 2020 4,633,485 $ 14.49 7.14 $ 886 Exercisable at March 31, 2020 2,718,386 $ 14.26 5.98 $ 886 Vested and expected to vest at March 31, 2020 (1) 4,452,847 $ 14.52 7.06 $ 886 (1) Represents the number of vested stock option shares as of March 31, 2020 , plus the number of unvested stock option shares that the Company estimated as of March 31, 2020 would vest, based on the unvested stock option shares as of March 31, 2020 and an estimated forfeiture rate of 7% . As of March 31, 2020 , there was $17.0 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 2.7 years . Restricted Stock Units On August 15, 2019, or the 2019 RSU grant date, the Company granted 0.4 million RSUs, or the 2019 RSUs, to certain executives and employees. All of the 2019 RSUs are service-based and vest ratably over two years . On the first anniversary of the 2019 RSU grant date, 35 % of the 2019 RSUs will vest. The remainder of the 2019 RSUs will vest on the second anniversary of the 2019 RSU grant date. On February 14, 2020, or the 2020 RSU grant date, the Company granted 0.4 million RSUs, or the 2020 RSUs, to certain executives and employees. All of the 2020 RSUs are service-based and vest ratably over three years, with one third of the 2020 RSUs vesting on each anniversary of the 2020 RSU grant date through February 14, 2023. RSUs are not included in issued and outstanding common stock until the shares have vested and settled. As of March 31, 2020 , none of the 2019 RSUs or 2020 RSUs had vested. The fair value of an RSU is measured based on the market price of the underlying common stock as of the date of grant. The following is a summary of RSU activity for the three months ended March 31, 2020 : Number of RSUs Weighted- Average Grant Date Fair Value Outstanding at December 31, 2019 393,629 $ 10.27 Granted 409,295 $ 10.87 Released — $ — Forfeited (4,168 ) $ 10.27 Outstanding at March 31, 2020 798,756 $ 10.58 As of March 31, 2020 , there was $7.4 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 2.2 years .

Loss Per Share

Loss Per Share	3 Months Ended
	Mar. 31, 2020
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 stock options and RSUs as common stock equivalents. The weighted-average common shares outstanding as of March 31, 2020 includes pre-funded warrants to purchase up to an aggregate of 1.8 million shares of common stock that were issued in connection with the January 2020 public offering, as discussed in Note 13. 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 each period presented. Three Months Ended March 31, 2020 2019 (in thousands, except per share amounts) Numerator: Net loss applicable to common stockholders - basic and diluted $ (20,477 ) $ (21,826 ) Denominator: Weighted-average shares outstanding - basic and diluted 29,110 23,508 Net loss per share applicable to common stockholders - basic and diluted $ (0.70 ) $ (0.93 ) Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share: Stock options 156 448 Restricted stock units 55 187 Warrants 61 95

Lease

Lease	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Lease	Lease 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. The Lease is classified as an operating lease. The lease term extends ten years following January 1, 2019. The Company is entitled to two five -year options to extend the Lease. The Lease provides for annual base rent of approximately $2.8 million in the first year following 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). 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. The Company recorded a liability for the Lease of $16.9 million on January 1, 2019. This lease liability is 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 March 31, 2020 , the Company had a current lease liability of $0.8 million and a non-current lease liability of $15.8 million recorded in its condensed consolidated balance sheets. On January 1, 2019, the Company recorded a right-of-use asset in the amount of $9.5 million , which represents the lease liability of $16.9 million , adjusted for previously accrued rent of $2.9 million and previously recorded unamortized lease incentives in the amount of $4.5 million . The right-of-use asset is 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 March 31, 2020 , the Company had a long-term lease asset of $9.2 million recorded in its condensed consolidated balance sheets. The Company recognizes lease expense, calculated as the remaining cost of the Lease allocated over the remaining lease term, on a straight-line basis. Lease expense is presented as part of continuing operations in the condensed consolidated statements of operations and comprehensive loss. For the three months ended March 31, 2020 , the Company recognized $0.6 million in lease expense. The three months ended March 31, 2020 included two months of rent abatement according to the terms of the Lease, and the Company paid $0.2 million in rent. As a payment arising from an operating lease, the $0.2 million is classified within operating activities in the condensed consolidated statements of cash flows. For the three months ended March 31, 2020 and 2019, the weighted-average remaining lease term was 8.75 years and 9.75 years, respectively, and the weighted-average discount rate was 13.08% .

Open Market Sale Agreement

Open Market Sale Agreement	3 Months Ended
	Mar. 31, 2020
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 $50.0 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. In 2019, the Company 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% of the gross proceeds to Jefferies. Additionally, in 2019, the Company incurred approximately $0.3 million related to legal, accounting and other fees in connection with the ATM Agreement. The Company has not sold any shares of common stock under the ATM Agreement in 2020. Sale of Common Stock and Pre-Funded Warrants In January 2020, the Company closed an underwritten public offering of 5,735,283 shares of its common stock to the public at $9.92 per share, which included the full exercise of the underwriters' option to purchase 982,863 additional shares of common stock. In addition, and in lieu of common stock, 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 net proceeds to the Company from this offering were approximately $70.1 million , after deducting underwriting discounts and commissions and other offering expenses payable by the Company. The pre-funded warrants are exercisable at any time by either (i) payment in full in immediately available funds for the number of shares of common stock purchased upon such exercise or (ii) a cashless exercise, in which case the holder would receive upon such exercise the net number of shares of common stock determined according to the formula set forth in the pre-funded warrant. A holder will not be entitled to exercise any portion of any pre-funded warrant if the holder’s ownership of the Company’s common stock would exceed 19.99% following such exercise. In the event of certain fundamental transactions, the holders of the pre-funded warrants will be entitled to receive upon exercise of the pre-funded warrants the kind and amount of securities, cash or other property that the holders would have received had they exercised the pre-funded warrants immediately prior to such fundamental transaction without regard to any limitations on exercise contained in the pre-funded warrants. The pre-funded warrants were classified as a component of permanent stockholders’ equity within additional paid-in capital and were recorded at the issuance date using a relative fair value allocation method. The pre-funded warrants are equity classified because they are freestanding financial instruments that are legally detachable and separately exercisable from the equity instruments, are immediately exercisable, do not embody an obligation for the Company to repurchase its shares, permit the holders to receive a fixed number of shares of common stock upon exercise, are indexed to the Company’s common stock and meet the equity classification criteria. In addition, such pre-funded warrants do not provide any guarantee of value or return. The Company valued the pre-funded warrants at issuance, concluding that their sales price approximated their fair value, and allocated net proceeds from the sale proportionately to the common stock and pre-funded warrants, of which $16.7 million was allocated to the pre-funded warrants and recorded as a component of additional paid-in capital.

Sale of Common Stock and Pre-Fu

Sale of Common Stock and Pre-Funded Warrants	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Sale of Common Stock and Pre-Funded Warrants	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 $50.0 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. In 2019, the Company 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% of the gross proceeds to Jefferies. Additionally, in 2019, the Company incurred approximately $0.3 million related to legal, accounting and other fees in connection with the ATM Agreement. The Company has not sold any shares of common stock under the ATM Agreement in 2020. Sale of Common Stock and Pre-Funded Warrants In January 2020, the Company closed an underwritten public offering of 5,735,283 shares of its common stock to the public at $9.92 per share, which included the full exercise of the underwriters' option to purchase 982,863 additional shares of common stock. In addition, and in lieu of common stock, 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 net proceeds to the Company from this offering were approximately $70.1 million , after deducting underwriting discounts and commissions and other offering expenses payable by the Company. The pre-funded warrants are exercisable at any time by either (i) payment in full in immediately available funds for the number of shares of common stock purchased upon such exercise or (ii) a cashless exercise, in which case the holder would receive upon such exercise the net number of shares of common stock determined according to the formula set forth in the pre-funded warrant. A holder will not be entitled to exercise any portion of any pre-funded warrant if the holder’s ownership of the Company’s common stock would exceed 19.99% following such exercise. In the event of certain fundamental transactions, the holders of the pre-funded warrants will be entitled to receive upon exercise of the pre-funded warrants the kind and amount of securities, cash or other property that the holders would have received had they exercised the pre-funded warrants immediately prior to such fundamental transaction without regard to any limitations on exercise contained in the pre-funded warrants. The pre-funded warrants were classified as a component of permanent stockholders’ equity within additional paid-in capital and were recorded at the issuance date using a relative fair value allocation method. The pre-funded warrants are equity classified because they are freestanding financial instruments that are legally detachable and separately exercisable from the equity instruments, are immediately exercisable, do not embody an obligation for the Company to repurchase its shares, permit the holders to receive a fixed number of shares of common stock upon exercise, are indexed to the Company’s common stock and meet the equity classification criteria. In addition, such pre-funded warrants do not provide any guarantee of value or return. The Company valued the pre-funded warrants at issuance, concluding that their sales price approximated their fair value, and allocated net proceeds from the sale proportionately to the common stock and pre-funded warrants, of which $16.7 million was allocated to the pre-funded warrants and recorded as a component of additional paid-in capital.

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments, consisting of normal recurring accruals and revisions of estimates, considered necessary for a fair presentation of the condensed consolidated financial statements have been included. Interim results for the three months ended March 31, 2020 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2020 or any other future period. The accompanying condensed consolidated financial statements reflect the accounts of the Company and its subsidiaries. All intercompany transactions between the Company and its subsidiaries have been eliminated. Management has determined that the Company operates in one segment: the development of pharmaceutical products on its own behalf or in collaboration with others. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the Company’s consolidated financial statements and the accompanying notes included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2019 filed with the Securities and Exchange Commission, or SEC, on February 27, 2020.
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 U.S. generally accepted accounting principles, or 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. During the three months ended March 31, 2020 , there have been no material changes to the significant accounting policies previously disclosed in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2019.
Recently Adopted Accounting Pronouncements and Pending Accounting Pronouncements	Recently Adopted Accounting Pronouncements In August 2018, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or 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 . This 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 adopted this new standard effective January 1, 2020, on a prospective basis, and it did not have a material effect on the consolidated financial statements and related disclosures. In December 2019, the FASB issued ASU 2019-12 , Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes . This standard includes removal of certain exceptions to the general principles of Accounting Standards Codification, or 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 adopted this new standard effective January 1, 2020, and it did not have a material effect on the consolidated financial statements and related disclosures. For a detailed discussion of the adoption of ASU 2019-12, refer to Note 7. Pending Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses . This 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.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2020
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 March 31, 2020 and December 31, 2019 and indicate the level within the fair value hierarchy where each measurement is classified. The carrying amounts reflected in the condensed consolidated balance sheets for cash, prepaid expenses and other current assets, restricted cash, accounts payable and accrued expenses approximate their fair value due to their short-term nature. Level 1 Level 2 Level 3 Total March 31, 2020 Cash equivalents: Money market funds $ 31,821 $ — $ — $ 31,821 U.S. Treasury obligations 7,998 — — 7,998 Investments, available for sale: U.S. Treasury obligations 36,868 — — 36,868 Government agency securities 22,530 54,117 — 76,647 Marketable equity securities: Corporate equity securities (Note 8) 2,986 — — 2,986 Total $ 102,203 $ 54,117 $ — $ 156,320 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 (Note 8) 5,375 — — 5,375 Total $ 91,653 $ 9,899 $ — $ 101,552

Cash, Cash Equivalents, Inves_2

Cash, Cash Equivalents, Investments and Marketable Equity Securities (Tables)	3 Months Ended
	Mar. 31, 2020
Cash and Cash Equivalents [Abstract]
Cash Equivalents and Short-term and Long-term Investments	Cash, cash equivalents, available for sale investments and marketable equity securities included the following as of March 31, 2020 and December 31, 2019: Average Maturity Amortized Cost Unrealized Gains Unrealized Losses Fair Value March 31, 2020 Cash $ 6,260 $ — $ — $ 6,260 Money market funds 31,821 — — 31,821 U.S. Treasury obligations 30 days 7,998 — — 7,998 Cash and cash equivalents $ 46,079 $ — $ — $ 46,079 U.S. Treasury obligations 173 days 36,586 282 — 36,868 Government agency securities 130 days 76,360 287 — 76,647 Investments, available for sale $ 112,946 $ 569 $ — $ 113,515 March 31, 2020 Acquisition Value Unrealized Gains Unrealized Losses Fair Value Marketable equity securities (Note 8) $ 10,451 $ — $ (7,465 ) $ 2,986 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 (Note 8) $ 10,451 $ — $ (5,076 ) $ 5,375

Restricted Cash (Tables)

Restricted Cash (Tables)	3 Months Ended
	Mar. 31, 2020
Cash and Cash Equivalents [Abstract]
Restrictions on Cash and Cash Equivalents	Cash, cash equivalents and restricted cash consisted of the following as of March 31, 2020 and 2019: March 31, March 31, Cash and cash equivalents $ 46,079 $ 60,262 Restricted cash 1,157 1,157 Total cash, cash equivalents and restricted cash shown in the statements of cash flows $ 47,236 $ 61,419

Accrued Expenses and Other Li_2

Accrued Expenses and Other Liabilities (Tables)	3 Months Ended
	Mar. 31, 2020
Payables and Accruals [Abstract]
Accrued Expenses and Other Liabilities	Accrued expenses and other liabilities consisted of the following as of March 31, 2020 and December 31, 2019: March 31, December 31, Accrued professional fees and other $ 342 $ 862 Employee compensation and benefits 812 3,222 Research and development expenses 3,107 4,252 $ 4,261 $ 8,336

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation Expense Related to All Stock Based Awards Recognized in Statements of Operations and Comprehensive Income (Loss)	Total stock-based compensation expense related to all stock-based options and awards recognized in the condensed consolidated statements of operations and comprehensive loss consisted of: Three Months Ended March 31, 2020 2019 Research and development $ 1,255 $ 1,475 General and administrative 1,222 1,454 Total stock-based compensation expense $ 2,477 $ 2,929
Estimated Weighted-Average Assumptions of Options Granted	The weighted-average fair value of options granted in the three months ended March 31, 2020 and 2019 reflect the following weighted-average assumptions: Three Months Ended March 31, 2020 2019 Expected volatility 68.19 % 77.16 % Expected term 6.0 years 6.0 years Risk-free interest rate 1.47 % 2.27 % Expected dividend yield — % — %
Certain Information Related to Outstanding Stock Options	The following table provides certain information related to the Company's outstanding stock options: Three Months Ended March 31, 2020 2019 (in thousands, except per share data) Weighted-average fair value of options granted, per option $ 6.67 $ 9.45 Aggregate grant date fair value of options vested during the period $ 2,184 $ 2,442 Total cash received from exercises of stock options $ 435 $ 805 Total intrinsic value of stock options exercised $ 93 $ 879
Summary of Stock Option Activity	The following is a summary of stock option activity for the three months ended March 31, 2020 : Number of Option Shares Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (in years) (in thousands) Outstanding at December 31, 2019 4,112,609 $ 15.01 Granted 615,050 $ 10.87 Exercised (51,237 ) $ 8.48 Forfeited or expired (42,937 ) $ 19.57 Outstanding at March 31, 2020 4,633,485 $ 14.49 7.14 $ 886 Exercisable at March 31, 2020 2,718,386 $ 14.26 5.98 $ 886 Vested and expected to vest at March 31, 2020 (1) 4,452,847 $ 14.52 7.06 $ 886 (1) Represents the number of vested stock option shares as of March 31, 2020 , plus the number of unvested stock option shares that the Company estimated as of March 31, 2020 would vest, based on the unvested stock option shares as of March 31, 2020 and an estimated forfeiture rate of 7% .
Summary of RSU Activity	The following is a summary of RSU activity for the three months ended March 31, 2020 : Number of RSUs Weighted- Average Grant Date Fair Value Outstanding at December 31, 2019 393,629 $ 10.27 Granted 409,295 $ 10.87 Released — $ — Forfeited (4,168 ) $ 10.27 Outstanding at March 31, 2020 798,756 $ 10.58

Loss Per Share (Tables)

Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings (Loss) Per Share	The following table illustrates the determination of loss per share for each period presented. Three Months Ended March 31, 2020 2019 (in thousands, except per share amounts) Numerator: Net loss applicable to common stockholders - basic and diluted $ (20,477 ) $ (21,826 ) Denominator: Weighted-average shares outstanding - basic and diluted 29,110 23,508 Net loss per share applicable to common stockholders - basic and diluted $ (0.70 ) $ (0.93 ) Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share: Stock options 156 448 Restricted stock units 55 187 Warrants 61 95

Nature of Business - Additional

Nature of Business - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents and investments	$ 159,600
Period of sufficiency of cash resources to fund operating plan	12 months
Accumulated deficit	$ 215,158	$ 194,681

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies - Additional Information (Details)	3 Months Ended
	Mar. 31, 2020segment
Accounting Policies [Abstract]
Number of segments	1

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Liabilities Recognized at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	$ 46,079	$ 53,043
Fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets at fair value	156,320	101,552
Fair value measurements | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets at fair value	102,203	91,653
Fair value measurements | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets at fair value	54,117	9,899
Fair value measurements | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets at fair value	0	0
Shorter maturity | Fair value measurements | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	31,821	40,782
Shorter maturity | Fair value measurements | Money market funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents		40,782
Shorter maturity | Fair value measurements | Money market funds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	0	0
Shorter maturity | Fair value measurements | Money market funds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	0	0
Shorter maturity | Fair value measurements | Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	7,998
Shorter maturity | Fair value measurements | Government agency securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	7,998
Shorter maturity | Fair value measurements | Government agency securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	0
Shorter maturity | Fair value measurements | Government agency securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents	0
Shorter maturity | Fair value measurements | Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents		2,000
Shorter maturity | Fair value measurements | Government agency securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents		0
Shorter maturity | Fair value measurements | Government agency securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents		2,000
Shorter maturity | Fair value measurements | Government agency securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, cash equivalents		0
Longer maturity | Fair value measurements | Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, investments available-for-sale securities	36,868	34,499
Longer maturity | Fair value measurements | Government agency securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, investments available-for-sale securities	36,868	34,499
Longer maturity | Fair value measurements | Government agency securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, investments available-for-sale securities	0	0
Longer maturity | Fair value measurements | Government agency securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, investments available-for-sale securities	0	0
Longer maturity | Fair value measurements | Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, investments available-for-sale securities	76,647	18,896
Longer maturity | Fair value measurements | Government agency securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, investments available-for-sale securities	22,530	10,997
Longer maturity | Fair value measurements | Government agency securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, investments available-for-sale securities	54,117	7,899
Longer maturity | Fair value measurements | Government agency securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, investments available-for-sale securities	0	0
Corporate equity securities | Fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, marketable equity securities	2,986	5,375
Corporate equity securities | Fair value measurements | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, marketable equity securities	2,986	5,375
Corporate equity securities | Fair value measurements | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, marketable equity securities	0	0
Corporate equity securities | Fair value measurements | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, marketable equity securities	$ 0	$ 0

Cash, Cash Equivalents, Inves_3

Cash, Cash Equivalents, Investments and Marketable Equity Securities - Cash Equivalents and Short-term and Long-term Investments (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Cash and Cash Equivalents
Amortized cost, cash and cash equivalents	$ 46,079	$ 53,043	$ 60,262
Fair value, cash and cash equivalent	46,079	53,043
Government agency securities
Debt Securities
Amortized cost, investments available for sale	36,586	34,475
Unrealized Gains	282	24
Unrealized Losses	0	0
Fair value, available-for-sale securities	36,868	34,499
Government agency securities
Debt Securities
Amortized cost, investments available for sale	76,360	18,874
Unrealized Gains	287	22
Unrealized Losses	0	0
Fair value, available-for-sale securities	76,647	18,896
Investments, available for sale
Debt Securities
Amortized cost, investments available for sale	112,946	53,349
Unrealized Gains	569	46
Unrealized Losses	0	0
Fair value, available-for-sale securities	113,515	53,395
Marketable equity securities
Marketable Securities
Amortized Cost	10,451	10,451
Unrealized Gains	0	0
Unrealized Losses	(7,465)	(5,076)
Fair Value	2,986	5,375
Cash
Cash and Cash Equivalents
Amortized cost, cash and cash equivalents	6,260	10,261
Fair value, cash and cash equivalent	6,260	10,261
Money market funds
Cash and Cash Equivalents
Amortized cost, cash and cash equivalents	31,821	40,782
Fair value, cash and cash equivalent	31,821	40,782
Government agency securities
Cash and Cash Equivalents
Amortized cost, cash and cash equivalents	7,998	2,000
Fair value, cash and cash equivalent	$ 7,998	$ 2,000
Measurement Input, Expected Term | Government agency securities
Debt Securities
Average maturity	173 days	108 days
Measurement Input, Expected Term | Government agency securities
Debt Securities
Average maturity	130 days	74 days
Measurement Input, Expected Term | Government agency securities
Cash and Cash Equivalents
Cash and Cash Equivalents, Term	30 days	8 days

Cash, Cash Equivalents, Inves_4

Cash, Cash Equivalents, Investments and Marketable Equity Securities - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Debt securities, realized gain	$ 0	$ 0
Debt securities, realized loss	0	0
Equity securities, realized gain	0	0
Equity securities, realized loss	0	0
Other than temporary impairment losses, investments	$ 0	$ 0

Restricted Cash (Details)

Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 46,079	$ 53,043	$ 60,262
Restricted cash	1,157	1,157	1,157
Total cash, cash equivalents and restricted cash shown in the statements of cash flows	$ 47,236	$ 54,200	$ 61,419	$ 18,927

Accrued Expenses and Other Li_3

Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued professional fees and other	$ 342	$ 862
Employee compensation and benefits	812	3,222
Research and development expenses	3,107	4,252
Accrued expenses and other liabilities	$ 4,261	$ 8,336

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Unrealized gain (loss) on short-term investments	$ 523	$ 97

Revenue - Additional Informatio

Revenue - Additional Information (Details)	1 Months Ended	3 Months Ended	12 Months Ended
	Feb. 28, 2019USD ($)	Mar. 31, 2020USD ($)segment	Dec. 31, 2018	Dec. 31, 2019USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of segments | segment		1
Contract asset	$ 16,000,000	$ 0		$ 0
Contract liability		10,600,000		$ 10,600,000
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
Indemnification agreement | Disposed of by sale, not discontinued operations | Assets for synthesis and research and development for treating Cystic Fibrosis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Amount released	$ 16,000,000
Escrow release period			18 months

Revenue - Vertex (Details)

Revenue - Vertex (Details) - Disposed of by sale, not discontinued operations - Assets for synthesis and research and development for treating Cystic Fibrosis - USD ($)	1 Months Ended
	Feb. 28, 2019	Mar. 03, 2017
Revenue Recognition, Milestone Method [Line Items]
Cash consideration		$ 160,000,000
Indemnification agreement
Revenue Recognition, Milestone Method [Line Items]
Amount released	$ 16,000,000
Contingent consideration asset, After achievement of milestone events
Revenue Recognition, Milestone Method [Line Items]
Contingent consideration receivable		$ 90,000,000

Revenue - Processa (Details)

Revenue - Processa (Details) - USD ($) $ in Thousands	Mar. 21, 2018	Mar. 19, 2018	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2019
Revenue Recognition, Milestone Method [Line Items]
Shares owned			29,651,595			23,865,075
Allocable arrangement consideration			$ 7	$ 1,005
Processa
Revenue Recognition, Milestone Method [Line Items]
Equity received from sale (in shares)	2,090,301	2,090,301
Shares owned						298,615
Allocable arrangement consideration	$ 10,500		$ 1	$ 1	$ 10,500

Revenue - Cipla (Details)

Revenue - Cipla (Details) - USD ($)	Jan. 16, 2019	Mar. 31, 2020	Mar. 31, 2019
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
License and research and development revenue		$ 7,000	$ 1,005,000
Cipla
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue	$ 1,000,000
Option to purchase inventory, valuation	300,000
License and research and development revenue	1,000,000	$ 0	$ 1,000,000
Cipla | Achievement of Certain Milestones
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Eligible payments receivable	57,000,000
Cipla | First Milestone
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Eligible payments receivable	$ 3,000,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ in Millions	Jan. 01, 2020	Aug. 15, 2019	Mar. 31, 2020
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to unvested options			$ 17
Total unrecognized compensation cost, weighted-average recognition period			2 years 8 months 18 days
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		2 years	2 years 2 months 18 days
Number of RSU shares, granted (in shares)		400,000	409,295
Award vesting percentage		3500.00%
Total unrecognized compensation cost related to restricted stock units			$ 7.4
2014 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares issued under the plan (in shares)	954,603
Common stock available for future award grant (in shares)			1,243,137
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Awards expiration period			10 years

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense Related to All Stock Based Awards Recognized in Statements of Operations and Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2,477	$ 2,929
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,255	1,475
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,222	$ 1,454

Stock-Based Compensation - Esti

Stock-Based Compensation - Estimated Weighted-Average Assumptions of Options Granted (Details)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Payment Arrangement [Abstract]
Expected volatility	68.19%	77.16%
Expected term	6 years	6 years
Risk-free interest rate	1.47%	2.27%
Expected dividend yield	0.00%	0.00%

Stock-Based Compensation - Fair

Stock-Based Compensation - Fair Value of Options (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Payment Arrangement [Abstract]
Weighted average grant date fair value of options granted, per option (in dollars per share)	$ 6.67	$ 9.45
Aggregate grant date fair value of options vested during the period	$ 2,184	$ 2,442
Total cash received from exercises of stock options	435	805
Total intrinsic value of stock options exercised	$ 93	$ 879

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)$ / sharesshares
Number of Option Shares
Number of options, Outstanding beginning balance (in shares) | shares	4,112,609
Number of options, Granted (in shares) | shares	615,050
Number of options, Exercised (in shares) | shares	(51,237)
Number of options, Forfeited or expired (in shares) | shares	(42,937)
Number of options, Outstanding ending balance (in shares) | shares	4,633,485
Number of options, Exercisable (in shares) | shares	2,718,386
Number of options, Vested and expected to vest (in shares) | shares	4,452,847
Weighted Average Exercise Price per Share
Weighted average exercise price per share, Outstanding at beginning of year (in dollars per share) | $ / shares	$ 15.01
Weighted average exercise price per share, Granted (in dollars per share) | $ / shares	10.87
Weighted average exercise price per share, Exercised (in dollars per share) | $ / shares	8.48
Weighted average exercise price per share, Forfeited or expired (in dollars per share) | $ / shares	19.57
Weighted average exercise price per share, Outstanding ending balance (in dollars per share) | $ / shares	14.49
Weighted average exercise price per share, Exercisable (in dollars per share) | $ / shares	14.26
Weighted average exercise price per share, Vested and expected to vest (in dollars per share) | $ / shares	$ 14.52
Weighted Average Remaining Contractual Term (In years)
Weighted average remaining contractual term, Outstanding	7 years 1 month 21 days
Weighted average remaining contractual term, Exercisable	5 years 11 months 23 days
Weighted average remaining contractual term, Vested and expected to vest	7 years 22 days
Aggregate Intrinsic Value
Aggregate intrinsic value, Outstanding | $	$ 886
Aggregate intrinsic value, Exercisable | $	886
Aggregate intrinsic value, Vested and expected to vest | $	$ 886
Stock options
Aggregate Intrinsic Value
Estimated forfeiture rate	7.00%

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of RSU Activity (Details) - Restricted stock units - $ / shares	Aug. 15, 2019	Mar. 31, 2020
Number of RSU Shares
Number of RSU shares, Outstanding beginning balance (in shares)		393,629
Number of RSU shares, Granted (in shares)	400,000	409,295
Number of RSU shares, Released (in shares)		0
Number of RSU shares, Forfeited (in shares)		(4,168)
Number of RSU shares, Outstanding ending balance (in shares)		798,756
Weighted Average Grant Date Fair Value
Weighted average grant date fair value, Outstanding at beginning of year (in dollars per share)		$ 10.27
Weighted average grant date fair value, Granted (in dollars per share)		10.87
Weighted average grant date fair value, Released (in dollars per share)		0
Weighted average grant date fair value, Forfeited (in dollars per share)		10.27
Weighted average grant date fair value, Outstanding at ending of year (in dollars per share)		$ 10.58

Loss Per Share - Computation of

Loss Per Share - Computation of Basic and Diluted Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Warrants to purchase common shares	1,800
Numerator:
Net loss applicable to common stockholders - basic and diluted	$ (20,477)	$ (21,826)
Denominator:
Weighted-average number of common shares used in net loss per share applicable to common stockholders - basic and diluted (in shares)	29,110	23,508
Net loss per share applicable to common stockholders - basic and diluted (in dollars per share)	$ (0.70)	$ (0.93)
Stock options
Anti-dilutive potential common stock equivalents excluded from the calculation of net income (loss) per share:
Anti-dilutive stock options, restricted stock units, and warrants (in shares)	156	448
Restricted stock units
Anti-dilutive potential common stock equivalents excluded from the calculation of net income (loss) per share:
Anti-dilutive stock options, restricted stock units, and warrants (in shares)	55	187
Warrants
Anti-dilutive potential common stock equivalents excluded from the calculation of net income (loss) per share:
Anti-dilutive stock options, restricted stock units, and warrants (in shares)	61	95

Lease - Additional Information

Lease - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)ft²extension	Dec. 31, 2019USD ($)	Mar. 31, 2019	Jan. 01, 2019USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Area of leased office and laboratory space | ft²	56,000
Term of contract	10 years
Number of extensions | extension	2
Length of extension	5 years
Annual base rent amount	$ 2,800
Annual rent increase, percent	3.00%
Abatement of base rent amount	$ 500
Operating lease liability				$ 16,900
Lease liability, current portion	783	$ 268
Lease liability, net of current portion	15,775	15,996
Operating lease right-of-use assets	9,184	$ 9,252		9,500
Operating lease, expense	600
Operating lease, payments	$ 200
Weighted average remaining lease term	8 years 9 months		9 years 9 months
Weighted average discount rate	13.08%		13.08%
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reduction to accrued rent				2,900
Reduction to incentive to lessee				$ 4,500

Open Market Sale Agreement (Det

Open Market Sale Agreement (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2020	Dec. 31, 2019	Mar. 31, 2020	Mar. 01, 2019
Equity [Abstract]
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%		3.00%
Legal expense maximum				$ 50,000
Number of shares issued in transaction (in shares)		36,167
Proceeds from issuance of common stock	$ 70,100,000	$ 400,000
Professional fees		$ 300,000

Sale of Common Stock and Pre-_2

Sale of Common Stock and Pre-Funded Warrants (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Number of shares issued in transaction (in shares)		36,167
Proceeds from issuance of common stock	$ 70.1	$ 0.4
Underwriting Public Offering
Class of Stock [Line Items]
Number of shares issued in transaction (in shares)	5,735,283
Common stock price per share	$ 9.92
Over-Allotment Option
Class of Stock [Line Items]
Number of shares issued in transaction (in shares)	982,863
Private Placement
Class of Stock [Line Items]
Number of shares issued in transaction (in shares)	1,800,000
Warrants
Class of Stock [Line Items]
Common stock price per share	$ 9.919
Warrant exercise price (in dollars per share)	$ 0.001
Ownership threshold for exercising warrants	19.99%
Proceeds allocated to pre-funded warrants	$ 16.7