Syros Pharmaceuticals (SYRS) 10-K 7 Mar 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Feb. 28, 2019	Jun. 29, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	SYROS PHARMACEUTICALS, INC.
Trading Symbol	SYRS
Entity Central Index Key	1,556,263
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		32,766,624
Entity Public Float			$ 258,458,840
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Entity Small Business	true
Entity Ex Transition Period	true
Entity Emerging Growth Company	true
Entity Shell Company	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 49,886	$ 32,205
Marketable securities	49,793	39,844
Prepaid expenses and other current assets	1,417	917
Restricted cash, current portion	638	193
Total current assets	101,734	73,159
Property and equipment, net	3,861	3,938
Other long-term assets	881	1,101
Restricted cash, net of current portion	290	290
Total assets	106,766	78,488
Current liabilities:
Accounts payable	3,309	2,283
Accrued expenses	13,893	9,728
Deferred revenue, current portion	1,926
Deferred rent, current portion	392	355
Capital lease obligations, current portion	9	47
Total current liabilities	19,529	12,413
Deferred rent, net of current portion	353	745
Deferred revenue, net of current portion	8,276
Capital lease obligations, net of current portion	22	6
Commitments and contingencies (see Note 10)
Stockholders' equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at December 31, 2018 and December 31, 2017; 0 shares issued and outstanding at December 31, 2018 and December 31, 2017
Common stock, $0.001 par value; 200,000,000 shares authorized at December 31, 2018 and December 31, 2017; 33,765,864 and 26,423,375 shares issued and outstanding at December 31, 2018 and December 31, 2017, respectively	34	26
Additional paid-in capital	296,100	220,606
Accumulated other comprehensive loss	(3)	(42)
Accumulated deficit	(217,545)	(155,266)
Total stockholders' equity	78,586	65,324
Total liabilities and stockholders' equity	$ 106,766	$ 78,488

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	33,765,864	26,423,375
Common stock, shares outstanding	33,765,864	26,423,375

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Revenue	$ 2,050	$ 1,101	$ 317
Operating expenses:
Research and development	50,182	41,896	37,817
General and administrative	16,164	13,891	10,463
Total operating expenses	66,346	55,787	48,280
Loss from operations	(64,296)	(54,686)	(47,963)
Other income, net	2,017	676	220
Net loss	(62,279)	(54,010)	(47,743)
Accrued dividends on preferred stock			(3,681)
Net loss applicable to common stockholders	$ (62,279)	$ (54,010)	$ (51,424)
Net loss per share applicable to common stockholders- basic and diluted	$ (1.91)	$ (2.13)	$ (4.05)
Weighted-average number of common shares used in net loss per share applicable to common stockholders- basic and diluted	32,656,237	25,406,845	12,696,414

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (62,279)	$ (54,010)	$ (47,743)
Other comprehensive gain (loss):
Unrealized holding gains (losses) on marketable securities	39	(33)	(9)
Comprehensive loss	$ (62,240)	$ (54,043)	$ (47,752)

CONSOLIDATED STATEMENTS OF CONV

CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Stock Purchase Agreement	At The Market	Follow-On Offering [Member]	Private Placement	Series A convertible preferred stock	Series B convertible preferred stock	Common Stock [Member]	Common Stock [Member]Stock Purchase Agreement	Common Stock [Member]At The Market	Common Stock [Member]Follow-On Offering [Member]	Common Stock [Member]Private Placement	Common Stock [Member]Series A convertible preferred stock	Common Stock [Member]Series B convertible preferred stock	Additional Paid‑In Capital	Additional Paid‑In CapitalStock Purchase Agreement	Additional Paid‑In CapitalAt The Market	Additional Paid‑In CapitalFollow-On Offering [Member]	Additional Paid‑In CapitalPrivate Placement	Additional Paid‑In CapitalSeries A convertible preferred stock	Additional Paid‑In CapitalSeries B convertible preferred stock	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance at Dec. 31, 2015	$ (47,964)							$ 2							$ 5,547								$ (53,513)
Balance (in shares) at Dec. 31, 2015						30,350,000	16,893,931
Balance at Dec. 31, 2015						$ 29,015	$ 52,998
Balance (in shares) at Dec. 31, 2015								2,363,018
Issuance of convertible preferred stock, net of issuance costs							$ 39,794
Issuance of convertible preferred stock, net of issuance costs (in shares)							12,714,150
Conversion of convertible preferred stock into common stock						$ (29,015)	$ (92,792)
Conversion of convertible preferred stock into common stock (in shares)						(30,350,000)	(29,608,081)
Conversion of convertible preferred stock into common stock (in shares)													8,093,326	7,895,474
Conversion of convertible preferred stock into common stock						$ 29,015	$ 92,792						$ 8	$ 8						$ 29,007	$ 92,784
Exercise of stock options and vesting of restricted stock awards	395														395
Exercise of stock options and vesting of restricted stock awards (in shares)								429,070
Issuance of common stock, net of issuance costs	49,882							$ 5							49,877
Issuance of common stock, net of costs and fees (in shares)								4,600,000
Stock-based compensation expense	4,234														4,234
Other comprehensive gain (loss)	(9)																					$ (9)
Net loss	(47,743)																						(47,743)
Balance at Dec. 31, 2016	80,602							$ 23							181,844							(9)	(101,256)
Balance (in shares) at Dec. 31, 2016								23,380,888
Exercise of stock options and vesting of restricted stock awards	1,799														1,799
Exercise of stock options and vesting of restricted stock awards (in shares)								449,896
Issuance of common stock, net of issuance costs	32,547							$ 3							32,544
Issuance of common stock, net of costs and fees (in shares)								2,592,591
Stock-based compensation expense	4,419														4,419
Other comprehensive gain (loss)	(33)																					(33)
Net loss	(54,010)																						(54,010)
Balance at Dec. 31, 2017	$ 65,324							$ 26							220,606							(42)	(155,266)
Balance (in shares) at Dec. 31, 2017	26,423,375							26,423,375
Exercise of stock options	$ 626														626
Exercise of stock options, Shares	214,532							214,533
Issuance of common stock, net of issuance costs		$ 7,648	$ 16,538	$ 42,700	$ 1,380				$ 1	$ 1	$ 6					$ 7,647	$ 16,537	$ 42,694	$ 1,380
Issuance of common stock, net of costs and fees (in shares)									793,021	1,373,677	4,816,753	144,505
Stock-based compensation expense	$ 6,610														6,610
Other comprehensive gain (loss)	39																					39
Net loss	(62,279)																						(62,279)
Balance at Dec. 31, 2018	$ 78,586							$ 34							$ 296,100							$ (3)	$ (217,545)
Balance (in shares) at Dec. 31, 2018	33,765,864							33,765,864

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock [Member] | Stock Purchase Agreement
Issuance costs	$ 100
Common Stock [Member] | At The Market
Issuance costs	107
IPO | Common Stock [Member]
Issuance costs			$ 7,600
Follow-On Offering [Member] | Common Stock [Member]
Issuance costs	$ 3,300
Private Placement | Common Stock [Member]
Issuance costs		$ 2,400
Series B convertible preferred stock
Issuance costs			$ 206

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Net loss	$ (62,279)	$ (54,010)	$ (47,743)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,604	1,527	1,273
Loss on disposal of fixed assets			4
Stock-based compensation expense	6,610	4,419	4,234
Net amortization of premiums and discounts on marketable securities	(642)	(102)	6
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(500)	131	(508)
Accounts receivable		867	(317)
Other long-term assets	(34)	(365)	(482)
Accounts payable	888	141	(404)
Accrued expenses	4,191	3,533	3,685
Deferred revenue	10,202	(550)
Deferred rent and lease incentive	(355)	(320)	(284)
Net cash used in operating activities	(40,315)	(44,729)	(40,536)
Investing activities
Purchases of property and equipment	(1,384)	(821)	(2,322)
Proceeds from the disposition of property and equipment	9
Purchases of marketable securities	(96,768)	(41,770)	(25,020)
Maturities of marketable securities	87,500	27,000
Net cash used in investing activities	(10,643)	(15,591)	(27,342)
Financing activities
Payments on capital lease obligations	(50)	(168)	(135)
Proceeds from issuance of common stock through employee benefit plans	626	1,799	395
Proceeds from issuance of convertible preferred stock, net of issuance costs			39,813
Proceeds from issuance of common stock in public offerings and private placements, net of issuance costs	68,508	32,306	50,484
Net cash provided by financing activities	69,084	33,937	90,557
Increase (decrease) in cash, cash equivalents and restricted cash	18,126	(26,383)	22,679
Cash and cash equivalents, Beginning of period	32,688	59,071	36,392
Cash and cash equivalents, End of period	50,814	32,688	59,071
Supplemental disclosure of cash flow information:
Cash paid for interest	2	9	19
Non-cash investing and financing activities
Conversion of convertible preferred stock into common stock			82,013
Property and equipment received but unpaid as of period end	268	143	349
Assets acquired under capital lease	$ 28		$ 17
Offering costs incurred but unpaid as of period end		$ 13

Nature of Business

Nature of Business	12 Months Ended
	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Business	1. Nature of Business Syros Pharmaceuticals, Inc. (the "Company"), a Delaware corporation formed in November 2011, is a biopharmaceutical company pioneering an understanding of the non-coding regulatory region of the genome to advance a new wave of medicines that control the expression of genes. The Company is subject to a number of risks similar to those of other early stage companies, including dependence on key individuals; risks inherent in the development and commercialization of medicines to treat human disease; competition from other companies, many of which are larger and better capitalized; risks relating to obtaining and maintaining necessary intellectual property protection; and the need to obtain adequate additional financing to fund the development of its product candidates and discovery activities. If the Company is unable to raise capital when needed or on favorable terms, it would be forced to delay, reduce, eliminate or out-license certain of its research and development programs or future commercialization rights to its product candidates. During the year ended December 31, 2018, the Company issued and sold an aggregate of 1,373,677 shares of its common stock to the public pursuant to its at-the-market sales facility, resulting in aggregate proceeds of $16.6 million. In February 2018, the Company issued and sold an aggregate of 4,188,481 shares of its common stock in a public offering at a price of $9.55 per share, resulting in gross proceeds of $40.0 million before deducting underwriting commissions and fees of approximately $2.9 million. The underwriters exercised their option to purchase an additional 628,272 shares at a price per share of $9.55, resulting in additional gross proceeds of $6.0 million before deducting underwriting commissions and fees of approximately $0.4 million. In February 2018, the Company also completed a private placement of 144,505 shares of common stock to Incyte Corporation (“Incyte”), for aggregate proceeds of $1.4 million. In January 2018, the Company completed a private placement of 793,021 shares of common stock to Incyte for aggregate proceeds of $10.0 million in connection with entry into a target discovery collaboration with Incyte (see Note 3). The Company has incurred significant annual net operating losses in every year since its inception. It expects to continue to incur significant and increasing net operating losses for at least the next several years. The Company’s net losses were $62.3 million, $54.0 million and $47.7 million for the years ended December 31, 2018, 2017 and 2016, respectively. As of December 31, 2018, the Company had an accumulated deficit of $217.5 million. The Company has not generated any revenues from product sales, has not completed the development of any product candidate and may never have a product candidate approved for commercialization. The Company has financed its operations to date primarily through the sale of equity securities. The Company has devoted substantially all of its financial resources and efforts to research and development and general and administrative expense to support such research and development. The Company’s net losses may fluctuate significantly from quarter to quarter and year to year. Net losses and negative cash flows have had, and will continue to have, an adverse effect on the Company’s stockholders' equity and working capital. The Company believes that its cash, cash equivalents and marketable securities of $99.7 million as of December 31, 2018 will be sufficient to allow the Company to fund its current operating plan for a period of at least 12 months past the issuance date of these consolidated financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The Company’s consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative U.S. GAAP as found in the ASC and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). In connection with preparing for its initial public offering, the Company effected a one-for-3.75 reverse stock split of the Company’s common stock. The reverse stock split became effective on June 17, 2016. The par value and authorized shares of common stock and convertible preferred stock were not adjusted as a result of the reverse stock split. All share and per share amounts in the financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital. The financial statements have also been retroactively adjusted to reflect adjustments to the conversion price for each series of convertible preferred stock effected in connection with the reverse stock split. Principles of Consolidation The accompanying consolidated financial statements include the accounts of Syros Pharmaceuticals, Inc. and its wholly owned subsidiary, Syros Securities Corporation, which is a Massachusetts corporation formed by the Company in December 2014 to exclusively engage in buying, selling and holding securities on its own behalf. All intercompany transactions and balances have been eliminated in consolidation. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Management considers many factors in selecting appropriate financial accounting policies and in developing the estimates and assumptions that are used in the preparation of the financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, which include, but are not limited to, expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates and whether historical trends are expected to be representative of future trends. Management’s estimation process often may yield a range of potentially reasonable estimates and management must select an amount that falls within that range of reasonable estimates. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, estimates related to revenue recognition, stock-based compensation expense, accrued expenses and income taxes. Actual results may differ from those estimates or assumptions. Segment Information 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 operating decision maker view the Company's operations and manage its business in one operating segment. The Company operates only in the United States. Cash and Cash Equivalents The Company considers all highly liquid instruments that have original maturities of three months or less when acquired to be cash equivalents. Cash equivalents, which consist of money market funds that invest in U.S. Treasury obligations, as well as overnight repurchase agreements, are stated at fair value. The Company maintains its bank accounts at one major financial institution. Off-Balance Sheet Risk and Concentrations of Credit Risk The Company has no financial instruments with off-balance sheet risk, such as foreign exchange contracts, option contracts, or other foreign hedging arrangements. Financial instruments that potentially subject the Company to concentrations of credit risk primarily consist of cash equivalents and marketable securities. Under its investment policy, the Company limits amounts invested in such securities by credit rating, maturity, industry group, investment type and issuer, except for securities issued by the U.S. government. The Company is not exposed to any significant concentrations of credit risk from these financial instruments. The goals of the Company’s investment policy, in order of priority, are safety and preservation of principal and liquidity of investments sufficient to meet cash flow requirements. Fair Value of Financial Instruments ASC 820, Fair Value Measurement ASC 820 identified fair value as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 established a three-tier fair value hierarchy that distinguishes between the following: Level 1—Quoted market prices (unadjusted) in active markets for identical assets or liabilities. Level 2—Inputs other than quoted prices included within Level 1 that are either directly or indirectly observable, such as quoted market prices, interest rates and yield curves. Level 3—Unobservable inputs developed using estimates or assumptions developed by the Company, which reflect those that a market participant would use. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized as Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amounts reflected in the consolidated balance sheets for cash and cash equivalents, prepaid expenses, other current assets, accounts payable, accrued expenses and deferred revenue approximate their fair values, due to their short-term nature. Property and Equipment Property and equipment consists of laboratory equipment, computer equipment, furniture and fixtures and leasehold improvements, all of which are stated at cost, less accumulated depreciation. Expenditures for maintenance and repairs that do not improve or extend the lives of the respective assets are recorded to expense as incurred. Major betterments are capitalized as additions to property and equipment. Depreciation and amortization is recognized over the estimated useful lives of the assets using the straight-line method. Construction-in-progress is stated at cost, which relates to the cost of research equipment not yet placed into service. No depreciation expense is recorded on construction-in-progress until such time as the relevant assets are completed and put into use. Impairment of Long-Lived Assets The Company continually evaluates long-lived assets for potential impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparing the book values of the assets to the expected future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book values of the assets exceed their fair value. The Company has not recognized any impairment losses from inception through December 31, 2018. Other Long-Term Assets At December 31, 2018, other long-term assets consisted of advance payments made to the contract research organization responsible for conducting the Company’s clinical trials of SY-1425 and SY-1365. At December 31, 2017, other long-term assets primarily consisted of deferred issuance costs, which included direct and incremental legal and accounting fees related to a shelf registration statement filed in July 2017, as well as advance payments made to the contract research organization responsible for conducting the Company’s clinical trials of SY-1425 and SY-1365. Revenue Recognition To date the Company’s only revenue has consisted of collaboration and license revenue. The Company has not generated any revenue from product sales and does not expect to generate any revenue from product sales for the foreseeable future. For the year ended December 31, 2018, the Company recognized approximately $2.1 million of revenue, all of which was attributable to its target discovery collaboration with Incyte. For the years ended December 31, 2017 and 2016, the Company recognized $1.1 million and $0.3 million of revenue, respectively, all of which was attributable to a research agreement with a multinational pharmaceutical company that expired in accordance with its terms in March 2017. On January 1, 2018, the Company adopted ASC 606, Revenue from Contracts with Customers (“ASC 606”) ASC 606 applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of ASC 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. From time to time, the Company may enter into agreements that are within the scope of ASC 606. The terms of these arrangements typically include payment to the Company of one or more of the following: non-refundable, up-front license fees; development, regulatory and commercial milestone payments; and royalties on net sales of licensed products. Each of these payments results in license and collaboration revenues, except for revenues from royalties on net sales of licensed products, which will be classified as royalty revenues. The Company analyzes its collaboration arrangements to assess whether they are within the scope of ASC 808, Collaborative Arrangements Prior to the adoption of ASC 606, the Company recognized revenue in accordance with ASC Topic 605, Revenue Recognition (“ASC 605”). Accordingly, revenue was recognized when all of the following criteria are met: • persuasive evidence of an arrangement exists; • delivery has occurred or services have been rendered; • the seller’s price to the buyer is fixed or determinable; and • collectability is reasonably assured. Amounts received prior to satisfying the revenue recognition criteria were recognized as deferred revenue in the Company’s consolidated balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified in current liabilities. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion. The Company analyzed arrangements with multiple deliverables based on the guidance in ASC Topic 605-25, Revenue Recognition—Multiple Element Arrangements The Company recognized arrangement consideration allocated to each unit of accounting when all of the revenue recognition criteria in ASC 605 are satisfied for that particular unit of accounting. In the event that a deliverable did not represent a separate unit of accounting, the Company recognized revenue from the combined unit of accounting over the contractual or estimated performance period for the undelivered items, which is typically the term of its research and development obligations. If there was no discernible pattern of performance or objectively measurable performance measures do not exist, then the Company recognized revenue under the arrangement on a straight-line basis over the period it expects to complete its performance obligations or upon completion when the final act is of such significance to the overall arrangement that performance has not substantively occurred until the completion of that act. Conversely, if the pattern of performance over which the service is provided to the customer could not be determined and objectively measurable performance measures exist, then the Company recognizeed revenue under the arrangement using the proportional performance method. Research and Development Expenditures relating to research and development are expensed in the period incurred. Research and development expenses consist of both internal and external costs associated with the development of the Company’s gene control platform and product candidates. Research and development costs include salaries and benefits, materials and supplies, external research, preclinical and clinical development expenses, stock-based compensation expense and facilities costs. Facilities costs primarily include the allocation of rent, utilities, depreciation and amortization. In certain circumstances, the Company is required to make nonrefundable advance payments to vendors for goods or services that will be received in the future for use in research and development activities. In such circumstances, the nonrefundable advance payments are deferred and capitalized, even when there is no alternative future use for the research and development, until related goods or services are provided. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the work being performed, including the phase or completion of the event, invoices received and costs. Significant judgements and estimates may be made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company may in-license the rights to develop and commercialize product candidates. For each in-license transaction the Company evaluates whether it has acquired processes or activities along with inputs that would be sufficient to constitute a “business” as defined under U.S. GAAP. A “business” as defined under U.S. GAAP consists of inputs and processes applied to those inputs that have the ability to create outputs. Although businesses usually have outputs, outputs are not required for an integrated set of activities to qualify as a business. When the Company determines that it has not acquired sufficient processes or activities to constitute a business, any up-front payments, as well as milestone payments, are immediately expensed as acquired research and development in the period in which they are incurred. Stock-Based Compensation Expense The Company accounts for its stock-based compensation awards in accordance with ASC 718, Compensation—Stock Compensation The amount of stock-based compensation expense recognized during a period is based on the fair value of the portion of the awards that are ultimately expected to vest. The Company accounts for forfeitures as they occur instead of estimating forfeitures at the time of grant. Ultimately, the actual expense recognized over the vesting period will be for only those options that vest. The Company expenses the fair value of its stock-based awards to employees on a straight-line basis over the associated service period, which is generally the vesting period. For stock-based awards granted to non-employees, stock-based compensation expense is recognized over the vesting period during which services are rendered by such non-employees. At the end of each financial reporting period prior to vesting, the fair value of these awards is remeasured using the then-current fair value of such awards. For stock-based awards that contain performance-based milestones, the Company records stock-based compensation expense in accordance with the accelerated attribution model. Management evaluates when the achievement of a performance-based milestone is probable based on the expected satisfaction of the performance conditions as of the reporting date. For certain of the Company’s performance-based awards, notwithstanding any vesting in accordance with the achievement of performance-based milestones, such awards vest in full on the sixth anniversary of the vesting commencement date. Income Taxes The Company accounts for income taxes in accordance with ASC Topic 740, Income Taxes The Company accounts for uncertain tax positions using a more-likely-than-not threshold for recognizing and resolving uncertain tax positions. The evaluation of uncertain tax positions is based on factors including, but not limited to, changes in the law, the measurement of tax positions taken or expected to be taken in tax returns, the effective settlement of matters subject to audit, new audit activity, and changes in facts or circumstances related to a tax position. In December 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Cuts and Jobs Act of 2017. The Company has recognized the provisional tax impacts related the revaluation of deferred tax assets and liabilities and included these amounts in its financial statements for the year ended December 31, 2017. The Company has no foreign operations and, therefore, does not have an associated liability from the repatriation tax on accumulated earnings in the Tax Cuts and Jobs Act. The Company did not record any adjustments in the year ended December 31, 2018 to these provisional amounts that were material to the financial statements. As of December 31, 2018, the Company's accounting treatment is complete. Net Loss per Share Basic net loss per share applicable to common stockholders is calculated by dividing net loss applicable to common stockholders by the weighted average shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share applicable to common stockholders is calculated by adjusting the weighted average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock method and the if-converted method. For purposes of the dilutive net loss per share applicable to common stockholders calculation, convertible preferred stock, stock options, and unvested restricted stock are considered to be common stock equivalents but are excluded from the calculation of diluted net loss per share applicable to common stockholders, as their effect would be anti-dilutive; therefore, basic and diluted net loss per share applicable to common stockholders were the same for all periods presented. The following common stock equivalents were excluded from the calculation of diluted net loss per share applicable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect. As of December 31, 2018 2017 2016 Stock options 3,732,643 2,846,668 2,543,435 Unvested restricted stock — — 4,885 3,732,643 2,846,668 2,548,320 The weighted average number of common shares used in net loss per share applicable to common stockholders on a basic and diluted basis were 32,656,237, 25,406,845 and 12,696,414 shares for the years ended December 31, 2018, 2017 and 2016, respectively. Recent Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) Leases Targeted Improvements In June 2018, the FASB issued ASU No. 2018-07, Compensation -Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurements (Topic 820) , Recently Adopted Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, (ASC 606) In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) , In November 2016, the FASB issued ASU No. 2016-18, Restricted Cash In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business .

Collaboration and Research Arra

Collaboration and Research Arrangements	12 Months Ended
	Dec. 31, 2018
Incyte
Collaboration and Research Arrangements	3. Collaboration and Research Arrangements Agreements with Incyte Corporation In January 2018, the Company and Incyte entered into a Target Discovery, Research Collaboration and Option Agreement (the “Collaboration Agreement”). Under the Collaboration Agreement, the Company is using its proprietary gene control platform to identify novel therapeutic targets with a focus on myeloproliferative neoplasms, and Incyte has received options to obtain exclusive worldwide rights to intellectual property resulting from the collaboration for the development and commercialization of therapeutic products directed to up to seven validated targets. Incyte will have exclusive worldwide rights to develop and commercialize any therapies under the collaboration that modulate those validated targets. In January 2018, the Company also entered into a Stock Purchase Agreement with Incyte (the “Stock Purchase Agreement”) whereby, for an aggregate purchase price of $10.0 million, Incyte purchased 793,021 shares of the Company’s common stock at $12.61 per share. Under the terms of the Stock Purchase Agreement, the shares were purchased at a 30% premium over the volume-weighted sale price of the shares of the Company’s common stock over the fifteen (15) trading day period immediately preceding the date of the Stock Purchase Agreement. Collaboration Agreement Under the terms of the Collaboration Agreement, Incyte paid the Company $10.0 million in up-front consideration, consisting of $2.5 million in cash and $7.5 million in pre-paid research funding (the “Prepaid Research Amount”). The Company’s activities under the Collaboration Agreement are subject to a joint research plan and, subject to certain exceptions, Incyte is responsible for funding the Company’s activities under the research plan, including amounts in excess of the Prepaid Research Amount. Under the Collaboration Agreement, the Company is required to use commercially reasonable efforts to conduct the research services over a period commencing on the effective date of the Collaboration Agreement and ending upon the completion of specified target validation activities (the "Research Term"). The Company is eligible to receive target selection milestone payments, which extend the period of time in which the options are exercisable, and option exercise fees of up to an aggregate of $54.0 million if Incyte selects the maximum number of targets for validation and exercises its options to obtain exclusive rights to collaboration intellectual property for therapeutic products directed to all seven validated targets. Should any therapeutic product be developed by Incyte against a target as to which Incyte has exercised its option to obtain exclusive rights to collaboration intellectual property, the Company will be eligible to receive milestone payments and, if approved and commercialized, royalty payments from Incyte. For each of the seven validated targets, the Company would become eligible to receive from Incyte a total of up to $50.0 million in development and regulatory milestone payments. If products arising from the collaboration are approved, the Company would become eligible to receive from Incyte, for each validated target, a total of up to $65.0 million in commercial milestone payments. Upon approval and commercialization of any therapeutic product resulting from the collaboration, the Company would become eligible to receive low single-digit royalties on net sales of such product. The term of the Collaboration Agreement began on January 8, 2018 and, unless terminated by a party early, will continue until all royalty obligations for products arising from the collaboration expire. The Collaboration Agreement may be terminated by Incyte for convenience on sixty (60) days’ prior written notice to the Company, or by the Company on thirty (30) days’ written notice in the event Incyte or one of its affiliates or sublicensees challenges the validity or enforceability of certain patent rights controlled by the Company. The Collaboration Agreement may also be terminated by either of the parties on thirty (30) days’ prior written notice in the event of an uncured material breach of the Collaboration Agreement by the other party or immediately in the case of certain bankruptcy events. If the Collaboration Agreement is terminated by Incyte for material breach, then the Company shall refund any unexpended Prepaid Research Amount. Incyte’s right to terminate for convenience and each party’s right to terminate for uncured material breach may be exercised either with respect to the Collaboration Agreement in its entirety or, as applicable, in relation to the relevant validated target and associated therapeutic products. Collaboration Revenue The Company analyzed the Collaboration Agreement to assess whether it is within the scope of ASC 808. As it was determined that the arrangement did not involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities, the Company concluded that the Collaboration Agreement was not within the scope of ASC 808. The Company assessed the Collaboration Agreement and concluded that it represents a contract with a customer within the scope of ASC 606. The Company has identified a single performance obligation which includes a (i) research license that Incyte retains as long as there remains an unexercised option (the “Research License”) and (ii) research and development services provided during the Research Term (the “Research Services”). The Collaboration Agreement includes options to (x) obtain additional time to exercise the license options for certain targets designated as definitive validation targets and (y) obtain license rights to each validated target, both of which were not considered by the Company’s management to be material rights, and therefore not performance obligations, at inception. The Company’s management believes the options do not provide a material right to the customer that it would receive without entering into the contract principally because the option fees are at least equal to the standalone selling price for the underlying goods. The Research License is not considered distinct as Incyte cannot benefit from the Research License without the Research Services that are separately identifiable in the contract. The Research License only allows Incyte to evaluate the targets developed as part of the conduct of the Research Services under the research plan or conduct work allocated to them during the Research Term. Incyte cannot extract any benefit from the Research License without the Research Services, including the provision of data package information, performed by the Company. As such, these two promises are deemed inputs to a combined output (the delivery of data package allowing Incyte to make an option exercise decision) and are bundled into a single performance obligation (the “Research License and Research Service Performance Obligation”). At inception, the total transaction price was determined to be $12.3 million, which consisted of a $2.5 million upfront non-refundable and non-creditable payment, the $7.5 million Prepaid Research Amount and $2.3 million in premium paid on the equity investment made pursuant the Stock Purchase Agreement. The Collaboration Agreement also provides for development and regulatory milestones that are only payable subsequent to the exercise of an option and were therefore excluded from transaction price at inception. The Company intends to re-evaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur. There were no changes to the transaction price during the year ended December 31, 2018. ASC 606 requires an entity to recognize revenue only when it satisfies a performance obligation by transferring a promised good or service to a customer. A good or service is considered to be transferred when the customer obtains control. As the Research License and Research Services represent one performance obligation, the Company has determined that it will satisfy its performance obligation over a period of time as services are performed and Incyte receives the benefit of the services, as the overall purpose of the arrangement is for the Company to perform the services. The Company is recognizing revenue related to the Research License and Research Services Performance Obligation as the underlying services are performed using an input measure over the period the Company expects to complete the performance obligation. The Company measures proportional performance based on an input method using actual costs incurred relative to the total estimated costs of the Research Services. During the year ended December 31, 2018, the Company recognized $2.1 million of deferred revenue under the Collaboration Agreement. As of December 31, 2018, the Company has deferred revenue outstanding under the Collaboration Agreement of approximately $10.2 million, of which $1.9 million and $8.3 million were classified as current and long-term, respectively, on the Company’s consolidated balance sheets. The following table presents the changes in deferred revenue for the year ended December 31, 2018 (in thousands): Year ended December 31, 2018 Balance at Beginning of Period Additions Deductions Balance at End of Period Deferred revenue $ — $ 12,252 $ 2,050 $ 10,202 Other Research Agreements In November 2014, the Company entered into a research agreement with a multinational pharmaceutical company (the “Counterparty”) for purposes of mapping immune cell super-enhancers (“SE”) and transcriptional targets in autoimmune disease. Under the research agreement, the Company is responsible for the conduct of all activities under separate projects, as defined in the research agreement, associated with generating SE and transcriptional maps of the cell/tissue supplied by the Counterparty. Upon the completion of each project, the Counterparty determined whether to commence the next project under the research agreement upon written notification. The research agreement was amended in November 2016 to extend the term to March 31, 2017. The research agreement terminated automatically on March 31, 2017 in accordance with its terms. The Company recognized revenue on a completed performance basis for each project performed under the agreement, as the Company did not have the ability to reasonably estimate the period of performance and the final study report for each project was significant to the overall arrangement. The Company recognized revenue of $1.1 million and $0.3 million during the years ended December 31, 2017 and December 31, 2016, respectively, under the agreement.

Cash, Cash Equivalents and Mark

Cash, Cash Equivalents and Marketable Securities	12 Months Ended
	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Cash, Cash Equivalents and Marketable Securities	4. Cash, Cash Equivalents and Marketable Securities Cash equivalents are highly liquid investments that are readily convertible into cash with original maturities of three months or less when purchased. Marketable securities consist of securities with original maturities greater than 90 days when purchased. The Company classifies these marketable securities 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 loss. Premiums or discounts from par value are amortized to other income over the life of the underlying security. Cash equivalents and marketable securities, available-for-sale, consisted of the following at December 31, 2018 and December 31, 2017 (in thousands): Unrealized Unrealized Fair December 31, 2018 Amortized Cost Gains Losses Value Cash and Cash equivalents: Cash and money market funds $ 34,886 $ — $ — $ 34,886 Overnight repurchase agreements 15,000 — — 15,000 Marketable Securities: U.S. treasury obligations 49,796 — (3 ) 49,793 Total: $ 99,682 $ — $ (3 ) $ 99,679 Unrealized Unrealized Fair December 31, 2017 Amortized Cost Gains Losses Value Cash and Cash equivalents: Cash and money market funds $ 17,205 $ — $ — $ 17,205 Overnight repurchase agreements 15,000 — — 15,000 Marketable Securities: U.S. treasury obligations 39,886 — (42 ) 39,844 Total: $ 72,091 $ — $ (42 ) $ 72,049 Although available to be sold to meet operating needs or otherwise, securities are generally held through maturity. The cost of securities sold is determined based on the specific identification method for purposes of recording realized gains and losses. During the year ended December 31, 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. At December 31, 2018, the Company held seven securities that were in an unrealized loss position. The aggregate fair value of securities held by the Company in an unrealized loss position for less than twelve months as of December 31, 2018 was $34.8 million and there were no securities held by the Company in an unrealized loss position for more than twelve months. The Company has the intent and ability to hold such securities until recovery. The Company determined that there was no material change in the credit risk of the above marketable securities. As a result, the Company determined it did not hold any marketable securities with an other-than temporary impairment as of December 31, 2018.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	5. Fair Value Measurements Assets measured at fair value on a recurring basis as of December 31, 2018 and December 31, 2017 were as follows (in thousands): Active Observable Unobservable Markets Inputs Inputs Description December 31, 2018 (Level 1) (Level 2) (Level 3) Cash and cash equivalents: Cash and money market funds $ 34,886 $ 34,886 $ — $ — Overnight repurchase agreements 15,000 — 15,000 — Marketable securities: U.S. treasury obligations 49,793 49,793 — — $ 99,679 $ 84,679 $ 15,000 $ — Active Observable Unobservable Markets Inputs Inputs Description December 31, 2017 (Level 1) (Level 2) (Level 3) Cash and cash equivalents: Cash and money market funds $ 17,205 $ 17,205 $ — $ — Overnight repurchase agreements 15,000 — 15,000 — Marketable securities: U.S. treasury obligations 39,844 39,844 — — $ 72,049 $ 57,049 $ 15,000 $ —

Restricted Cash

Restricted Cash	12 Months Ended
	Dec. 31, 2018
Cash And Cash Equivalents [Abstract]
Restricted Cash	6. Restricted Cash At December 31, 2018 As of December 31, 2017, the $0.5 million of restricted cash served as the security deposit on the lease of the Company’s current facility in Cambridge, Massachusetts (see Note 10). In April 2018, the Company collected a $0.2 million refund from its landlord in accordance with the terms of the lease agreement and the remaining of $0.3 million is classified as long-term on the Company’s consolidated balance sheets as of December 31, 2018 In August 2018, the Company entered into a manufacturing agreement with a third party for manufacturing services related to one of its product candidates. In accordance with the terms of the manufacturing agreement, the Company was required to provide a letter of credit in the amount of $0.6 million. The letter of credit will expire on September 30, 2019 and is classified as short-term on the Company’s consolidated balance sheets as of December 31, 2018 In accordance with the recently adopted accounting pronouncement ASU 2016-18, the following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheets that sum to the total of the amounts shown in the consolidated statement of cash flows as of December 31, 2018, 2017, 2016 and 2015 (in thousands): December 31, 2018 December 31, 2017 December 31, 2016 December 31, 2015 Cash and cash equivalents $ 49,886 $ 32,205 $ 58,588 $ 35,909 Restricted cash, current portion 638 193 — — Restricted cash, net of current portion 290 290 483 483 Total cash, cash equivalents and restricted cash $ 50,814 $ 32,688 $ 59,071 $ 36,392

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Property and Equipment	7. Property and Equipment Property and Equipment consist of the following as of December 31, 2018 and 2017 (in thousands): Estimated useful life (in years) December 31, 2018 December 31, 2017 Laboratory equipment 5 $ 4,926 $ 3,978 Computer equipment 3 1,080 651 Furniture and fixtures 4 440 396 Leasehold improvements Shorter of 7 years or life of lease 2,717 2,613 $ 9,163 $ 7,638 Less: Accumulated depreciation (5,302 ) (3,700 ) Total property and equipment, net $ 3,861 $ 3,938 Depreciation expense, including depreciation expense for assets recorded under capital leases, for the years ended December 31, 2018, 2017 and 2016 was $1.6 million, $1.5 million and $1.3 million, respectively. Office equipment included assets recorded under capital leases of approximately $0.1 million at December 31, 2018. Laboratory equipment included assets recorded under capital leases of $0.4 million at December 31, 2017 (see Note 9). Accumulated depreciation from assets recorded under capital leases was $0.1 million and $0.2 million at December 31, 2018 and 2017, respectively.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2018
Payables And Accruals Abstract
Accrued Expenses	8. Accrued Expenses Accrued expenses consist of the following as of December 31, 2018 and 2017 (in thousands): December 31, 2018 December 31, 2017 External research and preclinical development $ 10,119 $ 5,875 Employee compensation and benefits 2,985 2,494 Professional fees 618 1,225 Facilities and other 171 134 $ 13,893 $ 9,728

Indebtedness

Indebtedness	12 Months Ended
	Dec. 31, 2018
Debt Disclosure Abstract
Indebtedness	9. Indebtedness Equipment Financing In March 2015, the Company entered into a lease agreement with a vendor for certain laboratory equipment. The Company financed $0.4 million of the amount owed under the lease agreement and was required to make consecutive monthly payments of principal, plus accrued interest at 6.44%, over 36 months through March 2018. All obligations were satisfied following the first quarter of 2018. In the second quarter of 2018, the Company entered into two separate lease agreements with a vendor for certain office equipment. Under these lease agreements, the Company is funding approximately $37,000 and is required to make consecutive monthly payments of principal, plus accrued interest at 4.15%, over 36 and 60 months. All obligations under these lease agreements will be satisfied following the first quarter of 2021 and the second quarter of 2023. During the year ended December 31, 2018, the Company made payments of approximately $52,000, of which $2,000 related to interest. At December 31, 2018, approximately $31,000 of principal was outstanding with respect to lease agreements. The following table sets forth the Company’s future minimum payments due under capital leases as of December 31, 2018: Year 2019 $ 9,936 2020 9,936 2021 6,354 2022 5,160 2023 2,150 $ 33,536

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure Abstract
Commitments and Contingencies	10. Commitments and Contingencies Operating Leases In March 2015, the Company entered into an operating lease for approximately 21,488 rentable square feet of office and laboratory space in Cambridge, Massachusetts (the “2015 Lease”), with a lease term commencing in August 2015 and ending in October 2020. The Company has an option to extend the 2015 Lease for five additional years. The 2015 Lease has escalating rent payments and the Company records rent expense on a straight-line basis over its term, including any rent-free periods. The 2015 Lease includes certain lease incentives in the form of tenant allowances. The Company has capitalized the improvements made with the tenant allowance into fixed assets and established a liability for the deferred lease incentive upon delivery of premise to landlord. The Company recorded these incentives as a component of deferred rent and will amortize these incentives as a reduction of rent expense over the lease term. The related fixed assets will be amortized over the lease term. The Company recorded rent expense of $0.9 million for each of the years ended December 31, 2018, 2017 and 2016 related to the 2015 Lease. The 2015 Lease required the Company to issue an original letter of credit in the amount of $0.5 million of which $0.2 million was collected in April 2018 and $0.3 million remains classified as restricted cash as of December 31, 2018 (see Note 6). The following table sets forth the Company’s future minimum payments due under operating leases as of December 31, 2018: Year (in thousands) 2019 $ 1,325 2020 1,130 $ 2,455 On January 8, 2019, the Company entered into a lease (the “2019 Lease”) with respect to approximately 52,859 square feet of space in Cambridge, Massachusetts for a lease term commencing in January 2019 and ending in February 2030. The Company has the option to extend the lease term for one (1) additional ten (10) year period. The initial fixed rental rate is $67.50 per rentable square foot of the premises per annum, and will increase at a rate of three percent (3%) per year, with base rent first becoming due on March 1, 2020. Under the terms of the 2019 Lease, the landlord will provide an allowance in an amount not to exceed $9,514,620 (calculated at a rate of $180 per rentable square foot of the leased premises) toward the cost of completing the initial buildout of the leased premises. The Company will be required pay its share of operating expenses, taxes and any other expenses payable under the 2019 Lease. In connection with the execution of the 2019 Lease, the Company was required to provide the landlord with a letter of credit in the amount of $3.1 million that will expire 95 days after completion of the 2019 Lease. The Company will have the right, under certain conditions, to reduce the amount of the letter of credit to $2.1 million in October 2023. License Agreements TMRC Co. Ltd. In September 2015, the Company entered into an exclusive license agreement with TMRC Co. Ltd. ("TMRC") to develop and commercialize tamibarotene in North America and Europe for the treatment of cancer. This agreement was amended and restated in April 2016. In exchange for this license, the Company agreed to a non-refundable upfront payment of $1.0 million, for which $0.5 million was paid in September 2015 upon execution of the agreement, and the remaining $0.5 million was paid in May 2016. Under the agreement, the Company is also obligated to make payments upon the successful achievement of clinical and regulatory milestones totaling approximately $13.0 million per indication, defined as a distinct tumor type. In September 2016, the Company paid $1.0 million to TMRC for a development milestone achieved upon the successful dosing of the first patient in its Phase 2 clinical trial of SY-1425. In addition, the Company is obligated to pay TMRC a single-digit percentage royalty, on a country-by-country and product-by-product basis, on net product sales of SY-1425 using know-how and patents licensed from TMRC in North America and Europe for a defined royalty term. The Company also entered into a supply management agreement with TMRC under which the Company agreed to pay TMRC a fee for each kilogram of SY-1425 active pharmaceutical ingredient that is produced. The Company made payments of $0.4 million under this supply management agreement during the year ended December 31, 2017. No payments were made under the supply management agreement during the year ended December 31, 2018. Litigation The Company is not party to any litigation and does not have contingency reserves established for any litigation liabilities as of December 31, 2018 December 31, 2017

Stock-Based Payments

Stock-Based Payments	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Payments	11. Stock-Based Payments 2016 Stock Incentive Plan The 2016 Stock Incentive Plan (the “2016 Plan”) was adopted by the board of directors on December 15, 2015 and approved by the stockholders on June 17, 2016, and became effective on July 6, 2016 upon the closing of the Company’s initial public offering (“IPO”). The 2016 Plan replaced the 2012 Equity Incentive Plan (the "2012 Plan"). Any options or awards outstanding under the 2012 Plan remained outstanding and effective. Under the 2016 Plan, the Company may grant incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards. The number of shares of the Company’s common stock reserved for issuance under the 2016 Plan automatically increases on the first day of each calendar year, through the 2025 calendar year, in an amount equal to the least of (i) 1,600,000 shares of common stock, (ii) 4.0% of the outstanding shares of common stock as of such date, or (iii) such lesser amount as specified by the board of directors. This number is subject to adjustment in the event of a stock split, stock dividend or other change in the Company’s capitalization. For the calendar year beginning January 1, 2018, the number of shares reserved for issuance under the 2016 Plan was increased by 1,056,935 shares. At December 31, 2018, 2,836,921 shares remained available for future issuance under the 2016 Plan. Under the 2016 Plan, stock options may not be granted at less than fair value on the date of grant. Terms of stock option agreements, including vesting requirements, are determined by the board of directors, subject to the provisions of the 2016 Plan. Stock option awards granted by the Company generally vest over four years, with 25% vesting on the first anniversary of the vesting commencement date and 75% vesting ratably, on a monthly basis, over the remaining three years. Such awards are exercisable from the date of grant for a period of ten years. The Company may grant performance-based stock option awards for which vesting accelerates upon the achievement of performance-based milestones. For certain of such awards, notwithstanding any vesting in accordance with the achievement of performance-based milestones, such awards may vest in full on the sixth anniversary of the vesting commencement date. 2016 Employee Stock Purchase Plan The 2016 Employee Stock Purchase Plan (the “2016 ESPP”) was adopted by the board of directors on December 15, 2015 and approved by the stockholders on June 17, 2016, and became effective on July 6, 2016 upon the closing of the IPO. The number of shares of the Company’s common stock reserved for issuance under the 2016 ESPP automatically increases on the first day of each calendar year, through the 2025 calendar year, in an amount equal to the least of (i) 1,173,333 shares of the Company’s common stock, (ii) 1.0% of the total number of shares of the Company’s common stock outstanding on the first day of the applicable year, and (iii) an amount determined by the Company’s board of directors. For the calendar year beginning January 1, 2018, the number of shares reserved for issuance under the 2016 ESPP was increased by 264,233 shares. At December 31, 2018, 1,084,756 shares remained available for future issuance under the 2016 ESPP. Stock Options Performance-Based Stock Options The Company has granted stock options to management for which vesting accelerates upon the achievement of performance-based criteria. Milestone events are specific to the Company’s corporate goals, including but not limited to certain clinical development milestones and the Company’s ability to execute on its corporate development and financing strategies. Stock-based compensation expense associated with these performance-based stock options is recognized based on the accelerated attribution model. Management evaluates when the achievement of a performance-based milestone is probable based on the expected satisfaction of the performance conditions as of the reporting date. Notwithstanding any vesting in accordance with the achievement of performance-based milestones, such awards vest in full on the sixth anniversary of the vesting commencement date. During the year ended December 31, 2018, the Company recorded additional stock-based compensation expense of $0.2 million related to the acceleration of vesting of certain stock options associated with the entry into the Collaboration Agreement with Incyte. As of December 31, 2018, there was $1.0 million of unrecognized stock-based compensation expense related to the performance-based stock options granted to management, with an expected recognition period of 3.8 years. The Company has granted options to purchase 75,000 shares of common stock to an advisor that vest upon the achievement of performance-based criteria. As of December 31, 2018, no such performance-based criteria had been achieved. As of December 31, 2018, there was $0.3 million of unrecognized compensation cost related to this option, with a remaining contractual period of 7.7 years. A summary of the status of stock options as of December 31, 2018 and December 31, 2017 and changes during the year ended December 31, 2018 is presented below: Aggregate Weighted Remaining Intrinsic Average Contractual Value Shares Exercise Price Life (in years) (in thousands) Outstanding at December 31, 2017 2,846,668 $ 9.25 8.2 $ 5,713 Granted 1,548,252 10.37 Exercised (214,532 ) 2.92 Cancelled (447,745 ) 10.96 Outstanding at December 31, 2018 3,732,643 $ 9.88 7.9 $ 1,694 Exercisable at December 31, 2018 1,366,881 $ 8.34 6.9 $ 1,569 The intrinsic value of options exercised during the years ended December 31, 2018 Cash received from option exercises during the years ended December 31, 2018 Restricted Common Stock From time to time, upon approval by the Company’s board of directors, certain employees and advisors have been granted restricted shares of common stock with time- and performance-based vesting criteria. These shares of restricted stock are subject to repurchase rights. Accordingly, the Company has recorded the proceeds from the issuance of restricted stock as a liability in the consolidated balance sheets included as a component of accrued expenses or other long-term liabilities based on the scheduled vesting dates. The restricted stock liability is reclassified into stockholders’ equity as the restricted stock vests over time or upon the achievement of performance. As of December 31, 2018, there was no unvested restricted common stock outstanding. The total fair value of restricted stock vested during the years ended December 31, 2017 and 2016, was $1,000 and $0.1 million, respectively, based upon the number of restricted stock awards vested multiplied by the fair value of the Company’s common stock on the grant date. Stock-based Compensation Expense The fair value of each stock option granted was estimated on the date of grant using the Black-Scholes option-pricing model based on the following weighted-average assumptions: Year Ended December 31, 2018 2017 2016 Weighted-average risk-free interest rate 2.56 % 2.07 % 1.36 % Expected dividend yield — % — % — % Expected option term (in years) 6.04 6.05 5.98 Volatility 90.26 % 87.83 % 85.39 % The weighted‑average grant date fair value per share of options granted in the years ended December 31, 2018 The following table summarizes the stock-based compensation expense for stock options and restricted common stock granted to employees and non-employees recorded in the Company’s statements of operations: Year Ended December 31, 2018 2017 2016 Research and development $ 2,412 $ 1,666 $ 2,980 General and administrative 4,198 2,753 1,254 Total stock-based compensation expense $ 6,610 $ 4,419 $ 4,234 As of December 31, 2018, there was $14.8 million of total unrecognized compensation cost related to non-vested stock options granted to employees, which is expected to be recognized over a weighted-average period of 3.0 years. Due to an operating loss, the Company does not record tax benefits associated with stock‑based compensation or option exercises. Tax benefits will be recorded when realized

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes The Company accounts for income taxes under FASB Accounting Standards Codification 740 ("ASC 740"). Deferred income tax assets and liabilities are determined based upon differences between financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. The components of the income tax provision for the years ended December 31, 2018 and 2017 are as follows: Year Ended December 31, 2018 2017 Current $ 24 $ 7 Deferred — — Total $ 24 $ 7 A reconciliation of the U.S. statutory income tax rate to the Company’s effective tax rate is as follows for the years ended December 31, 2018 2017 Year ended December 31, 2018 2017 2016 Federal income tax computed at federal statutory tax rate 21.00 % 34.00 % 34.00 % State income tax, net of federal benefit 6.01 5.35 4.79 Permanent items (0.61 ) (1.57 ) (2.83 ) Federal and state research and development credits 4.79 7.36 2.93 Rate change — (31.79 ) — Other 0.01 0.66 (0.08 ) Change in valuation allowance (31.24 ) (14.02 ) (38.81 ) Effective income tax rate (0.04 ) % (0.01 ) % 0.00 % In December 2017, the Tax Cuts and Jobs Act was signed into law. The new law did not have a significant impact on the Company’s consolidated financial statements for the year ended December 31, 2017 because it maintains a valuation allowance on the majority of its net operating losses and other deferred tax assets. However, the reduction of the U.S. federal corporate tax rate from 35% to 21% resulted in increases to the amounts reflected in the effective tax rate attributable to "change in valuation allowance” and “rate change” in the Company’s effective tax rate reconciliation table above for the year ended December 31, 2017 compared to the year ended December 31, 2016. The change in the U.S. federal corporate tax rate, which is effective January 1, 2018, is also reflected in the Company’s deferred tax table below. Lastly, the Company discussed the impact of SAB 118 on the Company’s consolidated financial statements below. The principal components of the Company’s deferred tax assets and liabilities consist of the following at December 31, 2018 and 2017 (in thousands): Year ended December 31, 2018 2017 Deferred tax assets: Federal and state net operating loss carryforwards $ 51,346 $ 37,411 Tax credit carryforwards 10,558 7,573 Intangible assets 51 56 Stock-based compensation 2,108 1,059 Leasehold incentive 155 240 Other 2,809 1,237 Total deferred tax assets 67,027 47,576 Less valuation allowance (67,027 ) (47,576 ) Net deferred tax assets — — Deferred tax liabilities: Fixed assets — — Total deferred tax liabilities — — Net deferred taxes $ — $ — As of December 31, 2018, the Company had federal net operating loss (“NOL”) carryforwards of approximately $187.5 million and state net operating loss carryforwards of $189.6 million which are available to reduce future taxable income. The Company also had federal tax credits of approximately $8.8 million and state tax credits of $2.3 million which may be used to offset future tax liabilities. Net operating losses generated before 2018 of approximately $135.7 million will expire at various dates through 2037, and net operating losses of approximately $51.7 million, which were generated after 2017 have an indefinite carryforward period. The NOL and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. Net operating loss and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders over a three-year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. The Company has not determined whether an ownership change has occurred and as such, the Company's NOLs may be limited. ASC 740 requires a valuation allowance to reduce the deferred tax assets reported if, based on the weight of the evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. After consideration of all the evidence, both positive and negative, the Company has recorded a valuation allowance against its deferred tax assets at December 31, 2017 and 2018, respectively because the Company's management has determined that it is more likely than not that these assets will not be fully realized. The increase in the valuation allowance of $19.5 million in 2018 and $8.0 million in 2017 primarily relates to the net loss incurred by the Company. The Company’s reserves related to taxes are based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is more likely than not to be realized following resolution of any potential contingencies present related to the tax benefit. As of December 31, 2018 and 2017 the Company had no unrecognized tax benefits or accrued interest or penalties related to unrecognized tax benefits. The Company’s policy is to recognize both interest and penalties related to unrecognized tax benefits in income tax expense. The Company completed a study to document its qualifying research credits for all years except the year ended December 31, 2018. For the year ended December 31, 2018, the Company generated research credits but has not conducted a study to document the qualified activities. This 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 are being presented as an unrecognized tax benefit for the year ended December 31, 2018. A full valuation allowance has been provided against the Company’s research and development credits and, if an adjustment is required, this adjustment would be offset by an adjustment to the deferred tax asset established for the research and development credit carryforwards and the valuation allowance. The federal and state income tax returns are generally subject to examinations for the tax years ended December 31, 2015 through December 31, 2018. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service or state tax authorities to the extent utilized in a future period. The Company files income tax returns in the U.S. federal and Massachusetts jurisdictions. There are currently no federal or state audits in process. In December 2017, the SEC staff issued SAB 118 to address the application of GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Cuts and Jobs Act of 2017. The Company has recognized the provisional tax impacts related the revaluation of deferred tax assets and liabilities and included these amounts in its financial statements for the year ended December 31, 2017. The Company did not record any adjustments in the year ended December 31, 2018 to these provisional amounts that were material to the financial statements. As of December 31, 2018, the Company's accounting treatment is complete.

Defined Contribution Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2018
Defined Contribution Pension And Other Postretirement Plans Disclosure [Abstract]
Defined Contribution Plan	13. Defined Contribution Plan The Company established a defined contribution savings plan under Section 401(k) of the Internal Revenue Code. This plan covers substantially all employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pretax or post-tax basis. Company contributions to the plan may be made at the discretion of the board of directors. Effective September 1, 2017, the Company instituted an employer match of . For the years ended December 31, 2018 and 2017, the Company contributed $0.4 million and $0.3 million, respectively, to the 401(k) Plan

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Event	14. Subsequent Events On January 8, 2019, the Company entered into a lease agreement with respect to approximately 52,859 square feet of space at 35 CambridgePark Drive, Cambridge, Massachusetts (see Note 10).

Selected Quarterly Financial Da

Selected Quarterly Financial Data (unaudited)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (unaudited)	15. Selected Quarterly Financial Data (unaudited) The following table contains selected quarterly financial information for 2018 and 2017. The Company believes that the following information reflects all normal recurring adjustments necessary for a fair statement of the information for the periods presented. The operating results for any quarter are not necessarily indicative of results for any future period. Three Months Ended March 31, 2018 June 30, 2018 September 30, 2018 December 31, 2018 Revenue $ 370 $ 375 $ 412 893 Operating expenses: Research and development 11,116 11,082 12,856 15,128 General and administrative 4,075 3,841 3,876 4,372 Total operating expenses 15,191 14,923 16,732 19,500 Loss from operations (14,821 ) (14,548 ) (16,320 ) (18,607 ) Other income, net 358 501 583 575 Net loss applicable to common stockholders $ (14,463 ) $ (14,047 ) $ (15,737 ) (18,032 ) Net loss per share applicable to common stockholders - basic and diluted $ (0.48 ) $ (0.43 ) $ (0.47 ) (0.54 ) Weighted-average number of common shares used in net loss per share applicable to common stockholders - basic and diluted 30,335,164 32,892,712 33,653,479 33,694,756 Three Months Ended March 31, 2017 June 30, 2017 September 30, 2017 December 31, 2017 Revenue $ 1,101 $ — $ — $ — Operating expenses: Research and development 9,628 10,041 10,447 11,780 General and administrative 3,086 3,472 3,593 3,740 Total operating expenses 12,714 13,513 14,040 15,520 Loss from operations (11,613 ) (13,513 ) (14,040 ) (15,520 ) Other income, net 98 145 215 218 Net loss applicable to common stockholders $ (11,515 ) $ (13,368 ) $ (13,825 ) $ (15,302 ) Net loss per share applicable to common stockholders - basic and diluted $ (0.49 ) $ (0.52 ) $ (0.53 ) $ (0.58 ) Weighted-average number of common shares used in net loss per share applicable to common stockholders - basic and diluted 23,393,448 25,584,147 26,259,216 26,316,550

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company’s consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative U.S. GAAP as found in the ASC and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). In connection with preparing for its initial public offering, the Company effected a one-for-3.75 reverse stock split of the Company’s common stock. The reverse stock split became effective on June 17, 2016. The par value and authorized shares of common stock and convertible preferred stock were not adjusted as a result of the reverse stock split. All share and per share amounts in the financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital. The financial statements have also been retroactively adjusted to reflect adjustments to the conversion price for each series of convertible preferred stock effected in connection with the reverse stock split.
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of Syros Pharmaceuticals, Inc. and its wholly owned subsidiary, Syros Securities Corporation, which is a Massachusetts corporation formed by the Company in December 2014 to exclusively engage in buying, selling and holding securities on its own behalf. All intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Management considers many factors in selecting appropriate financial accounting policies and in developing the estimates and assumptions that are used in the preparation of the financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, which include, but are not limited to, expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates and whether historical trends are expected to be representative of future trends. Management’s estimation process often may yield a range of potentially reasonable estimates and management must select an amount that falls within that range of reasonable estimates. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, estimates related to revenue recognition, stock-based compensation expense, accrued expenses and income taxes. Actual results may differ from those estimates or assumptions.
Segment Information	Segment Information 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 operating decision maker view the Company's operations and manage its business in one operating segment. The Company operates only in the United States.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid instruments that have original maturities of three months or less when acquired to be cash equivalents. Cash equivalents, which consist of money market funds that invest in U.S. Treasury obligations, as well as overnight repurchase agreements, are stated at fair value. The Company maintains its bank accounts at one major financial institution.
Off-Balance Sheet Risk and Concentrations of Credit Risk	Off-Balance Sheet Risk and Concentrations of Credit Risk The Company has no financial instruments with off-balance sheet risk, such as foreign exchange contracts, option contracts, or other foreign hedging arrangements. Financial instruments that potentially subject the Company to concentrations of credit risk primarily consist of cash equivalents and marketable securities. Under its investment policy, the Company limits amounts invested in such securities by credit rating, maturity, industry group, investment type and issuer, except for securities issued by the U.S. government. The Company is not exposed to any significant concentrations of credit risk from these financial instruments. The goals of the Company’s investment policy, in order of priority, are safety and preservation of principal and liquidity of investments sufficient to meet cash flow requirements.
Fair Value of Financial Instruments	Fair Value of Financial Instruments ASC 820, Fair Value Measurement ASC 820 identified fair value as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 established a three-tier fair value hierarchy that distinguishes between the following: Level 1—Quoted market prices (unadjusted) in active markets for identical assets or liabilities. Level 2—Inputs other than quoted prices included within Level 1 that are either directly or indirectly observable, such as quoted market prices, interest rates and yield curves. Level 3—Unobservable inputs developed using estimates or assumptions developed by the Company, which reflect those that a market participant would use. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized as Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amounts reflected in the consolidated balance sheets for cash and cash equivalents, prepaid expenses, other current assets, accounts payable, accrued expenses and deferred revenue approximate their fair values, due to their short-term nature.
Property and Equipment	Property and Equipment Property and equipment consists of laboratory equipment, computer equipment, furniture and fixtures and leasehold improvements, all of which are stated at cost, less accumulated depreciation. Expenditures for maintenance and repairs that do not improve or extend the lives of the respective assets are recorded to expense as incurred. Major betterments are capitalized as additions to property and equipment. Depreciation and amortization is recognized over the estimated useful lives of the assets using the straight-line method. Construction-in-progress is stated at cost, which relates to the cost of research equipment not yet placed into service. No depreciation expense is recorded on construction-in-progress until such time as the relevant assets are completed and put into use.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company continually evaluates long-lived assets for potential impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparing the book values of the assets to the expected future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book values of the assets exceed their fair value. The Company has not recognized any impairment losses from inception through December 31, 2018.
Other Long-Term Assets	Other Long-Term Assets At December 31, 2018, other long-term assets consisted of advance payments made to the contract research organization responsible for conducting the Company’s clinical trials of SY-1425 and SY-1365. At December 31, 2017, other long-term assets primarily consisted of deferred issuance costs, which included direct and incremental legal and accounting fees related to a shelf registration statement filed in July 2017, as well as advance payments made to the contract research organization responsible for conducting the Company’s clinical trials of SY-1425 and SY-1365.
Revenue Recognition	Revenue Recognition To date the Company’s only revenue has consisted of collaboration and license revenue. The Company has not generated any revenue from product sales and does not expect to generate any revenue from product sales for the foreseeable future. For the year ended December 31, 2018, the Company recognized approximately $2.1 million of revenue, all of which was attributable to its target discovery collaboration with Incyte. For the years ended December 31, 2017 and 2016, the Company recognized $1.1 million and $0.3 million of revenue, respectively, all of which was attributable to a research agreement with a multinational pharmaceutical company that expired in accordance with its terms in March 2017. On January 1, 2018, the Company adopted ASC 606, Revenue from Contracts with Customers (“ASC 606”) ASC 606 applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of ASC 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. From time to time, the Company may enter into agreements that are within the scope of ASC 606. The terms of these arrangements typically include payment to the Company of one or more of the following: non-refundable, up-front license fees; development, regulatory and commercial milestone payments; and royalties on net sales of licensed products. Each of these payments results in license and collaboration revenues, except for revenues from royalties on net sales of licensed products, which will be classified as royalty revenues. The Company analyzes its collaboration arrangements to assess whether they are within the scope of ASC 808, Collaborative Arrangements Prior to the adoption of ASC 606, the Company recognized revenue in accordance with ASC Topic 605, Revenue Recognition (“ASC 605”). Accordingly, revenue was recognized when all of the following criteria are met: • persuasive evidence of an arrangement exists; • delivery has occurred or services have been rendered; • the seller’s price to the buyer is fixed or determinable; and • collectability is reasonably assured. Amounts received prior to satisfying the revenue recognition criteria were recognized as deferred revenue in the Company’s consolidated balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified in current liabilities. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion. The Company analyzed arrangements with multiple deliverables based on the guidance in ASC Topic 605-25, Revenue Recognition—Multiple Element Arrangements The Company recognized arrangement consideration allocated to each unit of accounting when all of the revenue recognition criteria in ASC 605 are satisfied for that particular unit of accounting. In the event that a deliverable did not represent a separate unit of accounting, the Company recognized revenue from the combined unit of accounting over the contractual or estimated performance period for the undelivered items, which is typically the term of its research and development obligations. If there was no discernible pattern of performance or objectively measurable performance measures do not exist, then the Company recognized revenue under the arrangement on a straight-line basis over the period it expects to complete its performance obligations or upon completion when the final act is of such significance to the overall arrangement that performance has not substantively occurred until the completion of that act. Conversely, if the pattern of performance over which the service is provided to the customer could not be determined and objectively measurable performance measures exist, then the Company recognizeed revenue under the arrangement using the proportional performance method.
Research and Development	Research and Development Expenditures relating to research and development are expensed in the period incurred. Research and development expenses consist of both internal and external costs associated with the development of the Company’s gene control platform and product candidates. Research and development costs include salaries and benefits, materials and supplies, external research, preclinical and clinical development expenses, stock-based compensation expense and facilities costs. Facilities costs primarily include the allocation of rent, utilities, depreciation and amortization. In certain circumstances, the Company is required to make nonrefundable advance payments to vendors for goods or services that will be received in the future for use in research and development activities. In such circumstances, the nonrefundable advance payments are deferred and capitalized, even when there is no alternative future use for the research and development, until related goods or services are provided. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the work being performed, including the phase or completion of the event, invoices received and costs. Significant judgements and estimates may be made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company may in-license the rights to develop and commercialize product candidates. For each in-license transaction the Company evaluates whether it has acquired processes or activities along with inputs that would be sufficient to constitute a “business” as defined under U.S. GAAP. A “business” as defined under U.S. GAAP consists of inputs and processes applied to those inputs that have the ability to create outputs. Although businesses usually have outputs, outputs are not required for an integrated set of activities to qualify as a business. When the Company determines that it has not acquired sufficient processes or activities to constitute a business, any up-front payments, as well as milestone payments, are immediately expensed as acquired research and development in the period in which they are incurred.
Stock-Based Compensation Expense	Stock-Based Compensation Expense The Company accounts for its stock-based compensation awards in accordance with ASC 718, Compensation—Stock Compensation The amount of stock-based compensation expense recognized during a period is based on the fair value of the portion of the awards that are ultimately expected to vest. The Company accounts for forfeitures as they occur instead of estimating forfeitures at the time of grant. Ultimately, the actual expense recognized over the vesting period will be for only those options that vest. The Company expenses the fair value of its stock-based awards to employees on a straight-line basis over the associated service period, which is generally the vesting period. For stock-based awards granted to non-employees, stock-based compensation expense is recognized over the vesting period during which services are rendered by such non-employees. At the end of each financial reporting period prior to vesting, the fair value of these awards is remeasured using the then-current fair value of such awards. For stock-based awards that contain performance-based milestones, the Company records stock-based compensation expense in accordance with the accelerated attribution model. Management evaluates when the achievement of a performance-based milestone is probable based on the expected satisfaction of the performance conditions as of the reporting date. For certain of the Company’s performance-based awards, notwithstanding any vesting in accordance with the achievement of performance-based milestones, such awards vest in full on the sixth anniversary of the vesting commencement date.
Income Taxes	Income Taxes The Company accounts for income taxes in accordance with ASC Topic 740, Income Taxes The Company accounts for uncertain tax positions using a more-likely-than-not threshold for recognizing and resolving uncertain tax positions. The evaluation of uncertain tax positions is based on factors including, but not limited to, changes in the law, the measurement of tax positions taken or expected to be taken in tax returns, the effective settlement of matters subject to audit, new audit activity, and changes in facts or circumstances related to a tax position. In December 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Cuts and Jobs Act of 2017. The Company has recognized the provisional tax impacts related the revaluation of deferred tax assets and liabilities and included these amounts in its financial statements for the year ended December 31, 2017. The Company has no foreign operations and, therefore, does not have an associated liability from the repatriation tax on accumulated earnings in the Tax Cuts and Jobs Act. The Company did not record any adjustments in the year ended December 31, 2018 to these provisional amounts that were material to the financial statements. As of December 31, 2018, the Company's accounting treatment is complete.
Net Loss per Share	Net Loss per Share Basic net loss per share applicable to common stockholders is calculated by dividing net loss applicable to common stockholders by the weighted average shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share applicable to common stockholders is calculated by adjusting the weighted average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock method and the if-converted method. For purposes of the dilutive net loss per share applicable to common stockholders calculation, convertible preferred stock, stock options, and unvested restricted stock are considered to be common stock equivalents but are excluded from the calculation of diluted net loss per share applicable to common stockholders, as their effect would be anti-dilutive; therefore, basic and diluted net loss per share applicable to common stockholders were the same for all periods presented. The following common stock equivalents were excluded from the calculation of diluted net loss per share applicable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect. As of December 31, 2018 2017 2016 Stock options 3,732,643 2,846,668 2,543,435 Unvested restricted stock — — 4,885 3,732,643 2,846,668 2,548,320 The weighted average number of common shares used in net loss per share applicable to common stockholders on a basic and diluted basis were 32,656,237, 25,406,845 and 12,696,414 shares for the years ended December 31, 2018, 2017 and 2016, respectively.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) Leases Targeted Improvements In June 2018, the FASB issued ASU No. 2018-07, Compensation -Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurements (Topic 820) , Recently Adopted Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, (ASC 606) In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) , In November 2016, the FASB issued ASU No. 2016-18, Restricted Cash In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business .

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Schedule of common stock equivalents excluded from the calculation of diluted net loss per share	The following common stock equivalents were excluded from the calculation of diluted net loss per share applicable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect. As of December 31, 2018 2017 2016 Stock options 3,732,643 2,846,668 2,543,435 Unvested restricted stock — — 4,885 3,732,643 2,846,668 2,548,320

Collaboration and Research Ar_2

Collaboration and Research Arrangements (Tables)	12 Months Ended
	Dec. 31, 2018
Collaborative Arrangement Disclosure [Abstract]
Schedule of changes in deferred revenue	The following table presents the changes in deferred revenue for the year ended December 31, 2018 (in thousands): Year ended December 31, 2018 Balance at Beginning of Period Additions Deductions Balance at End of Period Deferred revenue $ — $ 12,252 $ 2,050 $ 10,202

Cash, Cash Equivalents and Ma_2

Cash, Cash Equivalents and Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Schedule of cash equivalents and marketable securities, available for sale	Cash equivalents and marketable securities, available-for-sale, consisted of the following at December 31, 2018 and December 31, 2017 (in thousands): Unrealized Unrealized Fair December 31, 2018 Amortized Cost Gains Losses Value Cash and Cash equivalents: Cash and money market funds $ 34,886 $ — $ — $ 34,886 Overnight repurchase agreements 15,000 — — 15,000 Marketable Securities: U.S. treasury obligations 49,796 — (3 ) 49,793 Total: $ 99,682 $ — $ (3 ) $ 99,679 Unrealized Unrealized Fair December 31, 2017 Amortized Cost Gains Losses Value Cash and Cash equivalents: Cash and money market funds $ 17,205 $ — $ — $ 17,205 Overnight repurchase agreements 15,000 — — 15,000 Marketable Securities: U.S. treasury obligations 39,886 — (42 ) 39,844 Total: $ 72,091 $ — $ (42 ) $ 72,049

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of assets measured at fair value on a recurring basis	Assets measured at fair value on a recurring basis as of December 31, 2018 and December 31, 2017 were as follows (in thousands): Active Observable Unobservable Markets Inputs Inputs Description December 31, 2018 (Level 1) (Level 2) (Level 3) Cash and cash equivalents: Cash and money market funds $ 34,886 $ 34,886 $ — $ — Overnight repurchase agreements 15,000 — 15,000 — Marketable securities: U.S. treasury obligations 49,793 49,793 — — $ 99,679 $ 84,679 $ 15,000 $ — Active Observable Unobservable Markets Inputs Inputs Description December 31, 2017 (Level 1) (Level 2) (Level 3) Cash and cash equivalents: Cash and money market funds $ 17,205 $ 17,205 $ — $ — Overnight repurchase agreements 15,000 — 15,000 — Marketable securities: U.S. treasury obligations 39,844 39,844 — — $ 72,049 $ 57,049 $ 15,000 $ —

Restricted Cash (Tables)

Restricted Cash (Tables)	12 Months Ended
	Dec. 31, 2018
ASU 2016-18
Restricted Cash
Schedule of reconciliation of cash, cash equivalents, and restricted cash	In accordance with the recently adopted accounting pronouncement ASU 2016-18, the following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheets that sum to the total of the amounts shown in the consolidated statement of cash flows as of December 31, 2018, 2017, 2016 and 2015 (in thousands): December 31, 2018 December 31, 2017 December 31, 2016 December 31, 2015 Cash and cash equivalents $ 49,886 $ 32,205 $ 58,588 $ 35,909 Restricted cash, current portion 638 193 — — Restricted cash, net of current portion 290 290 483 483 Total cash, cash equivalents and restricted cash $ 50,814 $ 32,688 $ 59,071 $ 36,392

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Schedule of property and equipment	Property and Equipment consist of the following as of December 31, 2018 and 2017 (in thousands): Estimated useful life (in years) December 31, 2018 December 31, 2017 Laboratory equipment 5 $ 4,926 $ 3,978 Computer equipment 3 1,080 651 Furniture and fixtures 4 440 396 Leasehold improvements Shorter of 7 years or life of lease 2,717 2,613 $ 9,163 $ 7,638 Less: Accumulated depreciation (5,302 ) (3,700 ) Total property and equipment, net $ 3,861 $ 3,938

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2018
Payables And Accruals Abstract
Schedule of Accrued Expenses	Accrued expenses consist of the following as of December 31, 2018 and 2017 (in thousands): December 31, 2018 December 31, 2017 External research and preclinical development $ 10,119 $ 5,875 Employee compensation and benefits 2,985 2,494 Professional fees 618 1,225 Facilities and other 171 134 $ 13,893 $ 9,728

Indebtedness (Tables)

Indebtedness (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure Abstract
Schedule of monthly future minimum lease payments with respect to the equipment financing arrangement	The following table sets forth the Company’s future minimum payments due under capital leases as of December 31, 2018: Year 2019 $ 9,936 2020 9,936 2021 6,354 2022 5,160 2023 2,150 $ 33,536

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure Abstract
Schedule of the minimum aggregate future lease commitment	The following table sets forth the Company’s future minimum payments due under operating leases as of December 31, 2018: Year (in thousands) 2019 $ 1,325 2020 1,130 $ 2,455

Stock-Based Payments (Tables)

Stock-Based Payments (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of status of stock options and changes during the period	A summary of the status of stock options as of December 31, 2018 and December 31, 2017 and changes during the year ended December 31, 2018 is presented below: Aggregate Weighted Remaining Intrinsic Average Contractual Value Shares Exercise Price Life (in years) (in thousands) Outstanding at December 31, 2017 2,846,668 $ 9.25 8.2 $ 5,713 Granted 1,548,252 10.37 Exercised (214,532 ) 2.92 Cancelled (447,745 ) 10.96 Outstanding at December 31, 2018 3,732,643 $ 9.88 7.9 $ 1,694 Exercisable at December 31, 2018 1,366,881 $ 8.34 6.9 $ 1,569
Schedule of weighted-average assumptions used in Black-Scholes option-pricing model	The fair value of each stock option granted was estimated on the date of grant using the Black-Scholes option-pricing model based on the following weighted-average assumptions: Year Ended December 31, 2018 2017 2016 Weighted-average risk-free interest rate 2.56 % 2.07 % 1.36 % Expected dividend yield — % — % — % Expected option term (in years) 6.04 6.05 5.98 Volatility 90.26 % 87.83 % 85.39 %
Summary of stock-based compensation expense for stock options granted to employee and non-employees	The following table summarizes the stock-based compensation expense for stock options and restricted common stock granted to employees and non-employees recorded in the Company’s statements of operations: Year Ended December 31, 2018 2017 2016 Research and development $ 2,412 $ 1,666 $ 2,980 General and administrative 4,198 2,753 1,254 Total stock-based compensation expense $ 6,610 $ 4,419 $ 4,234

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Summary of components of the income tax provision	The components of the income tax provision for the years ended December 31, 2018 and 2017 are as follows: Year Ended December 31, 2018 2017 Current $ 24 $ 7 Deferred — — Total $ 24 $ 7
Schedule of reconciliation of effective tax rate expense (benefit) for continuing operations and the statutory federal income tax rate	A reconciliation of the U.S. statutory income tax rate to the Company’s effective tax rate is as follows for the years ended December 31, 2018 2017 Year ended December 31, 2018 2017 2016 Federal income tax computed at federal statutory tax rate 21.00 % 34.00 % 34.00 % State income tax, net of federal benefit 6.01 5.35 4.79 Permanent items (0.61 ) (1.57 ) (2.83 ) Federal and state research and development credits 4.79 7.36 2.93 Rate change — (31.79 ) — Other 0.01 0.66 (0.08 ) Change in valuation allowance (31.24 ) (14.02 ) (38.81 ) Effective income tax rate (0.04 ) % (0.01 ) % 0.00 %
Schedule of components of deferred tax assets and liabilities	The principal components of the Company’s deferred tax assets and liabilities consist of the following at December 31, 2018 and 2017 (in thousands): Year ended December 31, 2018 2017 Deferred tax assets: Federal and state net operating loss carryforwards $ 51,346 $ 37,411 Tax credit carryforwards 10,558 7,573 Intangible assets 51 56 Stock-based compensation 2,108 1,059 Leasehold incentive 155 240 Other 2,809 1,237 Total deferred tax assets 67,027 47,576 Less valuation allowance (67,027 ) (47,576 ) Net deferred tax assets — — Deferred tax liabilities: Fixed assets — — Total deferred tax liabilities — — Net deferred taxes $ — $ —

Selected Quarterly Financial _2

Selected Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Schedule of selected quarterly financial information	Three Months Ended March 31, 2018 June 30, 2018 September 30, 2018 December 31, 2018 Revenue $ 370 $ 375 $ 412 893 Operating expenses: Research and development 11,116 11,082 12,856 15,128 General and administrative 4,075 3,841 3,876 4,372 Total operating expenses 15,191 14,923 16,732 19,500 Loss from operations (14,821 ) (14,548 ) (16,320 ) (18,607 ) Other income, net 358 501 583 575 Net loss applicable to common stockholders $ (14,463 ) $ (14,047 ) $ (15,737 ) (18,032 ) Net loss per share applicable to common stockholders - basic and diluted $ (0.48 ) $ (0.43 ) $ (0.47 ) (0.54 ) Weighted-average number of common shares used in net loss per share applicable to common stockholders - basic and diluted 30,335,164 32,892,712 33,653,479 33,694,756 Three Months Ended March 31, 2017 June 30, 2017 September 30, 2017 December 31, 2017 Revenue $ 1,101 $ — $ — $ — Operating expenses: Research and development 9,628 10,041 10,447 11,780 General and administrative 3,086 3,472 3,593 3,740 Total operating expenses 12,714 13,513 14,040 15,520 Loss from operations (11,613 ) (13,513 ) (14,040 ) (15,520 ) Other income, net 98 145 215 218 Net loss applicable to common stockholders $ (11,515 ) $ (13,368 ) $ (13,825 ) $ (15,302 ) Net loss per share applicable to common stockholders - basic and diluted $ (0.49 ) $ (0.52 ) $ (0.53 ) $ (0.58 ) Weighted-average number of common shares used in net loss per share applicable to common stockholders - basic and diluted 23,393,448 25,584,147 26,259,216 26,316,550

Nature of Business (Details)

Nature of Business (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Feb. 28, 2018	Jan. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock Offering
Net Loss			$ 62,279	$ 54,010	$ 47,743
Accumulated deficit			(217,545)	$ (155,266)
Cash equivalents and marketable securities			99,700
Common Stock [Member]
Stock Offering
Shares issued				2,592,591	4,600,000
Net Loss
Common Stock [Member] | At Market Sales Facility [Member]
Stock Offering
Shares issued			1,373,677
Aggregate gross proceeds			$ 16,600
Common Stock [Member] | Public Offering
Stock Offering
Shares issued	4,188,481
Share price (in dollars per share)	$ 9.55
Aggregate gross proceeds	$ 40,000
Underwriting commissions and fees	$ 2,900
Common Stock [Member] | Over Allotment
Stock Offering
Shares issued	628,272
Share price (in dollars per share)	$ 9.55
Aggregate gross proceeds	$ 6,000
Underwriting commissions and fees	$ 400
Common Stock [Member] | Private Placement
Stock Offering
Shares issued			144,505
Common Stock [Member] | Private Placement | Incyte
Stock Offering
Shares issued	144,505	793,021
Aggregate gross proceeds	$ 1,400	$ 10,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Basis of Presentation (Details)	Jun. 17, 2016
Convertible Preferred Stock
Summary of Significant Accounting Policies
Ratio for reverse stock split	0.2666

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Segment Information and Off Balance Sheet Risk (Details)	12 Months Ended
	Dec. 31, 2018segmentitem
Accounting Policies [Abstract]
Number of operating segments | segment	1
Number of financial instruments with off-balance sheet risk | item	0

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Property and Equipment, Impairment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Equipment and Impairment of Long-Lived Assets
Depreciation	$ 1,604	$ 1,527	$ 1,273
Impairment losses	0	$ 0	$ 0
Construction in progress
Property, Equipment and Impairment of Long-Lived Assets
Depreciation	$ 0

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue	$ 2.1
Research Agreement | Multinational Pharmaceutical Company | Before topic 606
Revenue		$ 1.1	$ 0.3

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Net Loss per Share (Details) - shares	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Anti-dilutive securities
Total shares excluded from diluted net loss per share applicable to common stockholders									3,732,643	2,846,668	2,548,320
Weighted-average number of common shares used in net loss per share applicable to common stockholders- basic and diluted	33,694,756	33,653,479	32,892,712	30,335,164	26,316,550	26,259,216	25,584,147	23,393,448	32,656,237	25,406,845	12,696,414
Stock options
Anti-dilutive securities
Total shares excluded from diluted net loss per share applicable to common stockholders									3,732,643	2,846,668	2,543,435
Unvested Restricted Stock
Anti-dilutive securities
Total shares excluded from diluted net loss per share applicable to common stockholders											4,885

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Recently Adopted Accounting Pronouncements
Revenue	$ 2.1
Restricted cash	0.9	$ 0.5	$ 0.5	$ 0.5	$ 0.5
ASU 2014-09 | Before topic 606
Recently Adopted Accounting Pronouncements
Revenue	$ 2.1

Collaboration and Research Ar_3

Collaboration and Research Arrangements - Stock Purchase Agreement (Details) - Incyte - Stock Purchase Agreement $ / shares in Units, $ in Millions	1 Months Ended
	Jan. 31, 2018USD ($)$ / sharesshares
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate purchase price | $	$ 10
Shares issued | shares	793,021
Share price (in dollars per share) | $ / shares	$ 12.61
Premium to volume-weighted sale price of shares (as a percent)	30.00%
Trading days within which the purchase price represents a thirty percent (30%) premium to the volume-weighted sale price of the shares	15 days

Collaboration and Research Ar_4

Collaboration and Research Arrangements - Collaboration Agreement (Details) - USD ($) $ in Thousands	Jan. 08, 2018	Jan. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue recognized			$ 2,100
Deferred revenue
Deferred revenue			10,202	$ 0
Deferred revenue, current			1,900
Deferred revenue, long-term			$ 8,276
Incyte | Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front consideration		$ 10,000
Up-front consideration, cash		2,500
Up-front consideration, pre-paid research funding		$ 7,500
Maximum target selection milestone payments and option exercise fees the Company is eligible to receive	$ 54,000
Maximum development and regulatory milestone payments the Company is eligible to receive for each of the validated targets	50,000
Maximum commercial milestone payments the Company is eligible to receive for each of the validated targets if products arising from collaboration are approved	$ 65,000
Period of written notice to terminate the agreement by Incyte	60 days
Period of written notice to terminate the agreement by the Company in the event the counterparty or one of its affiliates or sublicenses challenges the validity or enforceability of certain patent rights controlled by the Company	30 days
Period of written notice to terminate the agreement by either of the parties in the event of an uncured material breach of the collaboration agreement by the other party	30 days
Total transaction price	$ 12,300
Upfront non-refundable and non-creditable payment	2,500
Prepaid research amount	7,500
Premium paid on equity investment	$ 2,300

Collaboration and Research Ar_5

Collaboration and Research Arrangements - Deferred revenue liabilities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Changes in deferred revenue liabilities:
Deferred revenue, Balance at Beginning of Period	$ 0
Deferred revenue, Additions	12,252
Deferred revenue, Deductions	2,050
Deferred revenue, Balance at End of Period	$ 10,202

Collaboration and Research Ar_6

Collaboration and Research Arrangements - Other Research Agreements (Details) - USD ($) $ in Thousands	3 Months Ended					12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	$ 893	$ 412	$ 375	$ 370	$ 1,101	$ 2,050	$ 1,101	$ 317
Multinational Pharmaceutical Company | Other Research Agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue							$ 1,100	$ 300

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities (Details)	12 Months Ended
	Dec. 31, 2018USD ($)item	Dec. 31, 2017USD ($)
Cash Equivalents and Marketable Securities
Marketable Securities, Amortized Cost	$ 99,682,000	$ 72,091,000
Marketable Securities, Unrealized Losses	(3,000)	(42,000)
Marketable Securities, Fair Value	99,679,000	72,049,000
Realized gains (losses)	$ 0
Number of investments adjusted for other-than-temporary declines in fair value | item	0
Fair value of securities held by Company in an unrealized loss position for less than twelve months	$ 34,800,000
Number of securities in unrealized loss position for more than twelve months | item	0
Number of securities with an other-than-temporary impairment | item	0
Number of securities in unrealized loss position for less than twelve months | item	7
U.S treasury obligations
Cash Equivalents and Marketable Securities
Marketable Securities, Amortized Cost	$ 49,796,000	39,886,000
Marketable Securities, Unrealized Losses	(3,000)	(42,000)
Marketable Securities, Fair Value	49,793,000	39,844,000
Cash and money market funds
Cash Equivalents and Marketable Securities
Cash Equivalents, Amortized Cost	34,886,000	17,205,000
Cash Equivalents, Fair value	34,886,000	17,205,000
Overnight repurchase agreements
Cash Equivalents and Marketable Securities
Cash Equivalents, Amortized Cost	15,000,000	15,000,000
Cash Equivalents, Fair value	$ 15,000,000	$ 15,000,000

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets measured at fair value on a recurring basis:
Marketable securities	$ 99,679	$ 72,049
U.S treasury obligations
Assets measured at fair value on a recurring basis:
Marketable securities	49,793	39,844
Cash and money market funds
Assets measured at fair value on a recurring basis:
Cash and cash equivalents	34,886	17,205
Overnight repurchase agreements
Assets measured at fair value on a recurring basis:
Cash and cash equivalents	15,000	15,000
Recurring
Assets measured at fair value on a recurring basis:
Total	99,679	72,049
Recurring | U.S treasury obligations
Assets measured at fair value on a recurring basis:
Marketable securities	49,793	39,844
Recurring | Cash and money market funds
Assets measured at fair value on a recurring basis:
Cash and cash equivalents	34,886	17,205
Recurring | Overnight repurchase agreements
Assets measured at fair value on a recurring basis:
Cash and cash equivalents	15,000	15,000
Recurring | Level 1
Assets measured at fair value on a recurring basis:
Total	84,679	57,049
Recurring | Level 1 | U.S treasury obligations
Assets measured at fair value on a recurring basis:
Marketable securities	49,793	39,844
Recurring | Level 1 | Cash and money market funds
Assets measured at fair value on a recurring basis:
Cash and cash equivalents	34,886	17,205
Recurring | Level 2
Assets measured at fair value on a recurring basis:
Total	15,000	15,000
Recurring | Level 2 | Overnight repurchase agreements
Assets measured at fair value on a recurring basis:
Cash and cash equivalents	$ 15,000	$ 15,000

Restricted Cash - Summary (Deta

Restricted Cash - Summary (Details) - USD ($) $ in Thousands	1 Months Ended
	Apr. 30, 2018	Dec. 31, 2018	Aug. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Restricted Cash
Restricted cash		$ 900		$ 500	$ 500	$ 500	$ 500
Restricted cash, current portion		638		193
Restricted cash, long-term		290		290		$ 483	$ 483
Manufacturing Agreement, August 2018
Restricted Cash
Letter of credit outstanding			$ 600
Operating ​Lease, ​March 2015
Restricted Cash
Restricted cash				$ 500
Restricted cash, long-term		$ 300
Refund received from landlord of security deposit on lease	$ 200
Letter of credit outstanding								$ 500

Restricted Cash - Reconciliatio

Restricted Cash - Reconciliation (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	$ 49,886	$ 32,205	$ 58,588	$ 35,909
Restricted cash, current portion	638	193
Restricted cash, net of current portion	290	290	483	483
Total cash, cash equivalents and restricted cash	$ 50,814	$ 32,688	$ 59,071	$ 36,392

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Equipment and Impairment of Long-Lived Assets
Property and equipment	$ 9,163	$ 7,638
Less: Accumulated depreciation	(5,302)	(3,700)
Total property and equipment, net	3,861	3,938
Depreciation	1,604	1,527	$ 1,273
Laboratory equipment
Property, Equipment and Impairment of Long-Lived Assets
Property and equipment	$ 4,926	3,978
Estimated useful life	5 years
Assets recorded under capital leases		400
Assets recorded under capital leases, accumulated depreciation		200
Computer equipment
Property, Equipment and Impairment of Long-Lived Assets
Property and equipment	$ 1,080	651
Estimated useful life	3 years
Furniture and fixtures
Property, Equipment and Impairment of Long-Lived Assets
Property and equipment	$ 440	396
Estimated useful life	4 years
Leasehold improvements
Property, Equipment and Impairment of Long-Lived Assets
Property and equipment	$ 2,717	$ 2,613
Leasehold improvements | Maximum
Property, Equipment and Impairment of Long-Lived Assets
Estimated useful life	7 years
Office Equipment
Property, Equipment and Impairment of Long-Lived Assets
Assets recorded under capital leases	$ 100
Assets recorded under capital leases, accumulated depreciation	$ 100

Accrued Expenses (Detail)

Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued Liabilities Current [Abstract]
External research and preclinical development	$ 10,119	$ 5,875
Employee compensation and benefits	2,985	2,494
Professional fees	618	1,225
Facilities and other	171	134
Total accrued expenses	$ 13,893	$ 9,728

Indebtedness (Detail)

Indebtedness (Detail) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Jun. 30, 2018	Dec. 31, 2018
Debt Instrument [Line Items]
2,019			$ 9,936
2,020			9,936
2,021			6,354
2,022			5,160
2,023			2,150
Capital Leases, Future Minimum Payments Due			33,536
Equipment Financing Lease | Laboratory equipment
Debt Instrument [Line Items]
Amount financed	$ 400,000
Interest rate (as a percent)	6.44%
Term of financing	36 months
Equipment Financing Lease | Minimum [Member] | Office Equipment
Debt Instrument [Line Items]
Amount financed		$ 37,000
Interest rate (as a percent)		4.15%
Term of financing		36 months
Equipment Financing Lease | Maximum | Office Equipment
Debt Instrument [Line Items]
Term of financing		60 months
Principal and interest payments made during the period			52,000
Interest payments made during the period			2,000
Principal amount outstanding			$ 31,000

Commitments and Contingencies -

Commitments and Contingencies - Operating Leases (Details)	Jan. 08, 2019ft²	Apr. 30, 2018USD ($)	Mar. 31, 2015USD ($)ft²	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
2,019				$ 1,325,000
2,020				1,130,000
Operating Leases, Future Minimum Payments Due				$ 2,455,000
Subsequent Event
Area of office and laboratory space leased | ft² | ft²	52,859
Operating ​Lease, ​March 2015
Area of office and laboratory space leased | ft² | ft²			21,488
Term of option to extend the lease				5 years
Rent expense				$ 900,000	$ 900,000	$ 900,000
Letter of credit outstanding			$ 500,000
Refund received from landlord of security deposit on lease		$ 200,000
Letter of credit outstanding classified as restricted cash				$ 300,000
Operating Lease, January 2019
Term of option to extend the lease				10 years
Letter of credit outstanding				$ 3,100,000
Initial fixed rental rate per rentable square foot of the premises per annum				$ 67.50
Percentage increase in fixed rental rate				3.00%
Maximum allowance towards leased premises				$ 9,514,620
Allowance per square foot of leased premises				$ 180
Letter of credit expiration period				95 days
Operating Lease, January 2019 | Subsequent Event
Area of office and laboratory space leased | ft² | ft²	52,859
Operating Lease, October 2023
Expected letter of credit amount				$ 2,100,000

Commitments and Contingencies_2

Commitments and Contingencies - License Agreements (Details) - TMRC - USD ($) $ in Millions	1 Months Ended			12 Months Ended
	Sep. 30, 2016	May 31, 2016	Sep. 30, 2015	Dec. 31, 2018	Dec. 31, 2017
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front license fee			$ 1
Payment of up-front license fee		$ 0.5	0.5
Payments per indication due upon the successful achievement of clinical and regulatory milestones			$ 13
Payments made upon achievement of development milestone	$ 1
Payments made under the supply management agreement				$ 0	$ 0.4

Stock-Based Payments - 2016 Sto

Stock-Based Payments - 2016 Stock Incentive Plan (Details) - 2016 Plan - shares	Jan. 01, 2018	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares of common stock reserved for issuance of awards on the first day of each calendar year (in shares)		1,600,000
Increase in number of shares of common stock reserved for issuance of awards on the first day of each calendar year, as a percentage of outstanding shares		4.00%
Increase in number of shares of common stock reserved for issuance (in shares)	1,056,935
Common stock available for future issuance (in shares)		2,836,921
Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		4 years
Term of award		10 years
Stock Option | Vesting on one year anniversary of vesting commencement date
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting (as a percent)		25.00%
Stock Option | Vesting ratably on a monthly basis
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		3 years
Vesting (as a percent)		75.00%

Stock-Based Payments - 2016 Emp

Stock-Based Payments - 2016 Employee Stock Purchase Plan (Details) - 2016 ESPP - shares	Jan. 01, 2018	Jul. 06, 2016	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares of common stock reserved for issuance of awards on the first day of each calendar year (in shares)		1,173,333
Increase in number of shares of common stock reserved for issuance of awards on the first day of each calendar year, as a percentage of outstanding shares		1.00%
Increase in number of shares of common stock reserved for issuance (in shares)	264,233
Common stock available for future issuance (in shares)			1,084,756

Stock-Based Payments - Stock Op

Stock-Based Payments - Stock Options (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted and outstanding (in shares)	1,548,252
Aggregate Intrinsic Value
Intrinsic value of options exercised	$ 1.4	$ 4.6	$ 2.4
Cash received from option exercises	0.6	$ 1.8	$ 0.4
Performance-based stock options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional stock-based compensation expense recorded related to achievement of certain performance-based milestones	0.2
Unrecognized compensation costs	$ 1
Period in which compensation costs will be recognized	3 years 9 months 18 days
Performance-based stock options | Advisor
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs	$ 0.3
Period in which compensation costs will be recognized	7 years 8 months 12 days
Granted and outstanding (in shares)	75,000

Stock-Based Payments - Summary

Stock-Based Payments - Summary of Status of Stock Options and Changes During the Period (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at beginning of year (in shares)	2,846,668
Granted (in shares)	1,548,252
Exercised (in shares)	(214,532)
Cancelled (in shares)	(447,745)
Outstanding at end of period (in shares)	3,732,643	2,846,668
Exercisable (in shares)	1,366,881
Outstanding at beginning of year (in dollars per share)	$ 9.25
Granted (in dollars per share)	10.37
Exercised (in dollars per share)	2.92
Cancelled (in dollars per share)	10.96
Outstanding at end of period (in dollars per share)	9.88	$ 9.25
Exercisable (in dollars per share)	$ 8.34
Remaining Contractual Life, Outstanding	7 years 10 months 25 days	8 years 2 months 12 days
Remaining Contractual Life, Exercisable	6 years 10 months 25 days
Aggregate Intrinsic Value, Outstanding at beginning of year	$ 5,713
Aggregate Intrinsic Value, Outstanding at ending of year	1,694	$ 5,713
Aggregate Intrinsic Value, Options Exercisable	$ 1,569

Stock-Based Payments - Restrict

Stock-Based Payments - Restricted Common Stock (Details) - Unvested Restricted Stock - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Shares
Unvested restricted common stock outstanding			0
Additional disclosures
Total fair value of restricted stock vested	$ 1,000	$ 100

Stock-Based Payments - Weighted

Stock-Based Payments - Weighted-Average Assumptions to Estimate Fair Value of Stock Options (Details) - Stock Option - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average risk-free interest rate	2.56%	2.07%	1.36%
Expected option term (in years)	6 years 15 days	6 years 18 days	5 years 11 months 23 days
Volatility	90.26%	87.83%	85.39%
Weighted-average grant date fair value of options granted (in dollars per share)	$ 7.80	$ 8.75	$ 8.58

Stock-Based Payments - Stock-Ba

Stock-Based Payments - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 6,610	$ 4,419	$ 4,234
Stock options
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Unrecognized compensation costs	$ 14,800
Period in which compensation costs will be recognized	3 years
Performance-based stock options
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Unrecognized compensation costs	$ 1,000
Period in which compensation costs will be recognized	3 years 9 months 18 days
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,412	1,666	2,980
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 4,198	$ 2,753	$ 1,254

Income Taxes - Components of In

Income Taxes - Components of Income Tax Provision (Benefit) - (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Current	$ 24	$ 7
Total	$ 24	$ 7

Income Taxes - Reconciliation -

Income Taxes - Reconciliation - (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal income tax computed at federal statutory tax rate	21.00%	34.00%	34.00%
State income tax, net of federal benefit	6.01%	5.35%	4.79%
Permanent items	(0.61%)	(1.57%)	(2.83%)
Federal and state research and development credits	4.79%	7.36%	2.93%
Rate change		(31.79%)
Other	0.01%	0.66%	(0.08%)
Change in valuation allowance	(31.24%)	(14.02%)	(38.81%)
Effective income tax rate	(0.04%)	(0.01%)	0.00%

Income Taxes - Tax Cuts and Job

Income Taxes - Tax Cuts and Jobs Act - (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Federal Statutory Tax Rate
U.S. federal corporate tax rate	21.00%	34.00%	34.00%
Maximum
Federal Statutory Tax Rate
U.S. federal corporate tax rate		35.00%

Income Taxes - Deferred tax ass

Income Taxes - Deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Federal and state net operating loss carryforwards	$ 51,346	$ 37,411
Tax credit carryforwards	10,558	7,573
Intangible assets	51	56
Stock-based compensation	2,108	1,059
Leasehold incentive	155	240
Other	2,809	1,237
Total deferred tax assets	67,027	47,576
Less valuation allowance	$ (67,027)	$ (47,576)

Income Taxes - NOL carryforward

Income Taxes - NOL carryforwards (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Indefinite Carryforward Period
Operating Loss Carryforwards [Line Items]
NOL carryforwards	$ 51.7
Expire at Various Dates Through 2037
Operating Loss Carryforwards [Line Items]
NOL carryforwards		$ 135.7
Federal
Operating Loss Carryforwards [Line Items]
NOL carryforwards	187.5
Tax credits	8.8
State
Operating Loss Carryforwards [Line Items]
NOL carryforwards	189.6
Tax credits	$ 2.3

Income Taxes - Valuation Allowa

Income Taxes - Valuation Allowance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Increase in valuation allowance	$ 19.5	$ 8

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Unrecognized tax benefits	$ 0	$ 0
Accrued interest related to unrecognized tax benefits	0	0
Accrued penalties related to unrecognized tax benefits	$ 0	$ 0

Defined Contribution Plan - (De

Defined Contribution Plan - (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Defined Contribution Plan Disclosure [Line Items]
Employer match (as a percent)		100.00%
Plan Compensation (as a percent)		1.00%
Employee contribution (as a percent)		50.00%
Contribution made by the company	$ 0.4	$ 0.3
Minimum [Member]
Defined Contribution Plan Disclosure [Line Items]
Plan Compensation (as a percent)		1.00%
Maximum
Defined Contribution Plan Disclosure [Line Items]
Plan Compensation (as a percent)		6.00%

Subsequent Events (Details)

Subsequent Events (Details)	Jan. 08, 2019ft²
Subsequent Event
Subsequent Event [Line Items]
Area of office and laboratory space leased | ft²	52,859

Selected Quarterly Financial _3

Selected Quarterly Financial Data (unaudited) - (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 893	$ 412	$ 375	$ 370				$ 1,101	$ 2,050	$ 1,101	$ 317
Operating expenses:
Research and development	15,128	12,856	11,082	11,116	$ 11,780	$ 10,447	$ 10,041	9,628	50,182	41,896	37,817
General and administrative	4,372	3,876	3,841	4,075	3,740	3,593	3,472	3,086	16,164	13,891	10,463
Total operating expenses	19,500	16,732	14,923	15,191	15,520	14,040	13,513	12,714	66,346	55,787	48,280
Loss from operations	(18,607)	(16,320)	(14,548)	(14,821)	(15,520)	(14,040)	(13,513)	(11,613)	(64,296)	(54,686)	(47,963)
Other income, net	575	583	501	358	218	215	145	98	2,017	676	220
Net loss applicable to common stockholders	$ (18,032)	$ (15,737)	$ (14,047)	$ (14,463)	$ (15,302)	$ (13,825)	$ (13,368)	$ (11,515)	$ (62,279)	$ (54,010)	$ (51,424)
Net loss per share applicable to common stockholders - basic and diluted	$ (0.54)	$ (0.47)	$ (0.43)	$ (0.48)	$ (0.58)	$ (0.53)	$ (0.52)	$ (0.49)	$ (1.91)	$ (2.13)	$ (4.05)
Weighted-average number of common shares used in net loss per share applicable to common stockholders - basic and diluted	33,694,756	33,653,479	32,892,712	30,335,164	26,316,550	26,259,216	25,584,147	23,393,448	32,656,237	25,406,845	12,696,414