Syndax Pharmaceuticals (SNDX) 10-Q 6 Aug 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Aug. 05, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Trading Symbol	SNDX
Entity Registrant Name	Syndax Pharmaceuticals, Inc.
Entity Central Index Key	0001395937
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		38,549,198
Entity Shell Company	false
Title of 12(b) Security	Common Stock
Security Exchange Name	NASDAQ
Entity File Number	001-37708
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	32-0162505
Entity Address, Address Line One	35 Gatehouse Drive
Entity Address, Address Line Two	Building D
Entity Address, Address Line Three	Floor 3
Entity Address, City or Town	Waltham
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02451
City Area Code	781
Local Phone Number	419-1400
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 53,611	$ 24,609
Restricted cash	115
Short-term investments	133,142	35,166
Prepaid expenses and other current assets	4,939	2,556
Total current assets	191,807	62,331
Property and equipment, net	237	281
Right-of-use asset, net	502	716
Other assets	82	197
Total assets	192,628	63,525
Current liabilities:
Accounts payable	1,832	6,178
Accrued expenses and other current liabilities	8,691	10,195
Current portion of deferred revenue	1,517	1,517
Current portion of right-of-use liability	427	478
Total current liabilities	12,467	18,368
Long-term liabilities:
Deferred revenue, less current portion	12,375	13,133
Right-of-use liability, less current portion	240	419
Loan payable	19,896
Other long-term liabilities	3	5
Total long-term liabilities	32,514	13,557
Total liabilities	44,981	31,925
Commitments
Stockholders’ equity:
Preferred stock, $0.001 par value, 10,000,000 shares authorized; 0 shares outstanding at June 30, 2020 and December 31, 2019
Common stock, $0.0001 par value, 100,000,000 shares authorized; 38,512,744 and 27,140,484 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively	4	3
Additional paid-in capital	675,294	527,067
Accumulated other comprehensive income	117
Accumulated deficit	(527,768)	(495,470)
Total stockholders’ equity	147,647	31,600
Total liabilities and stockholders’ equity	$ 192,628	$ 63,525

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	38,512,744	27,140,484
Common stock, shares outstanding	38,512,744	27,140,484

Condensed Consolidated Statemen

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue:
Total revenues	$ 379	$ 379	$ 758	$ 758
Type of revenue [extensible list]	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember
Operating expenses:
Research and development	$ 10,943	$ 12,290	$ 20,505	$ 23,569
General and administrative	6,046	3,463	11,963	7,374
Total operating expenses	16,989	15,753	32,468	30,943
Loss from operations	(16,610)	(15,374)	(31,710)	(30,185)
Other (expense) income:
Interest expense	(638)		(1,087)
Interest income	225	501	558	953
Other (expense) income	(39)	(43)	(59)	14
Total other (expense) income	(452)	458	(588)	967
Net loss	(17,062)	(14,916)	(32,298)	(29,218)
Other comprehensive loss:
Unrealized gain on marketable securities	69	50	117	83
Comprehensive loss	(16,993)	(14,866)	(32,181)	(29,135)
Net loss attributable to common stockholders	$ (17,062)	$ (14,916)	$ (36,204)	$ (29,218)
Net loss per share attributable to common stockholders—basic and diluted	$ (0.42)	$ (0.47)	$ (0.97)	$ (1)
Weighted-average number of common shares used to compute net loss per share attributable to common stockholders—basic and diluted	40,609,205	31,605,279	37,468,922	29,327,029

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (32,298)	$ (29,218)
Adjustments to reconcile net loss to net cash from operating activities:
Depreciation	45	(404)
Amortization and accretion of investments	(193)
Non-cash operating lease expense	214
Non-cash interest expense	166
Stock-based compensation	3,959	2,930
Other	(1)	(1)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(2,384)	(2,665)
Accounts payable	(4,346)	838
Deferred revenue	(758)	(758)
Accrued expenses and other liabilities	(1,736)	(78)
Net cash used in operating activities	(37,332)	(29,356)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of short-term investments	(131,125)	(59,894)
Proceeds from sales and maturities of short-term investments	33,460	53,715
Net cash used in investing activities	(97,665)	(6,179)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from debt agreement, net	19,730
Proceeds from Employee Stock Purchase Plan	149	72
Proceeds from stock option exercises	1,353	151
Net cash provided by financing activities	163,999	28,432
NET INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	29,002	(7,103)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH—beginning of period	24,724	33,985
CASH, CASH EQUIVALENTS AND RESTRICTED CASH —end of period	53,726	26,882
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid for interest	629
At-the-Market Offering [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net		830
Private Placement [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net	$ 142,767	$ 27,379

Nature of Business

Nature of Business	6 Months Ended
	Jun. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Business	1. Nature of Business Syndax Pharmaceuticals, Inc. (“we,” “us,” “our” or the “Company”) is a clinical stage biopharmaceutical company developing an innovative pipeline of cancer therapies. We were incorporated in Delaware in 2005. We base our operations in Waltham, Massachusetts and we operate in one segment.

Basis of Presentation

Basis of Presentation	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	2. Basis of Presentation The Company has prepared the accompanying condensed consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”). Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. The interim unaudited condensed financial statements have been prepared on the same basis as the annual audited financial statements and in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of June 30, 2020, and the results of operations and comprehensive loss for the three and six months ended June 30, 2020 and 2019, and cash flows for the six months ended June 30, 2020 and 2019. The results for the three and six months ended June 30, 2020 are not necessarily indicative of the results to be expected for the year ending December 31, 2020, any other interim periods, or any future year or period. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2019, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K that was filed with the Securities and Exchange Commission (“SEC”) on March 5, 2020. In 2011, the Company established a wholly owned subsidiary in the United Kingdom. There have been no activities for this entity to date. In 2014, the Company established a wholly owned U.S. subsidiary, Syndax Securities Corporation. The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	3. Summary of Significant Accounting Policies Significant Accounting Policies The Company’s significant accounting policies, which are disclosed in the audited consolidated financial statements for the year ended December 31, 2019 and the notes thereto are included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 5, 2020. Since the date of that filing, there have been no material changes to the Company’s significant accounting policies except as noted below. Significant Risks and Uncertainties With the global spread of the ongoing COVID-19 pandemic in 2020, the Company has implemented business continuity plans designed to address and mitigate the impact of the COVID-19 pandemic on our business. The Company anticipate that the COVID-19 pandemic could have an impact on the clinical development timelines for one or more of our clinical programs. The extent to which the COVID-19 pandemic impacts the Company’s business, clinical development, manufacturing of clinical and commercial drug substance and drug product, and regulatory efforts, the corporate development objectives and the value of and market for the Company’s common stock, will depend on future developments that are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration of the pandemic, travel restrictions, quarantines, social distancing and business closure requirements in the U.S., Europe and other countries, and the effectiveness of actions taken globally to contain and treat the disease. The global economic slowdown, the overall disruption of global healthcare systems and the other risks and uncertainties associated with the pandemic could have a material adverse effect on its business, financial condition, results of operations and growth prospects. In addition, the Company is subject to other challenges and risks specific to its business and ability to execute on the strategy, as well as risks and uncertainties common to companies in the pharmaceutical industry with development and commercial operations, including, without limitation, risks and uncertainties associated with: obtaining regulatory approval of our late-stage product candidate; delays or problems in the supply of the Company’s products, loss of single source suppliers or failure to comply with manufacturing regulations; identifying, acquiring or in-licensing additional products or product candidates; pharmaceutical product development and the inherent uncertainty of clinical success; and the challenges of protecting and enhancing the Company’s intellectual property rights; complying with applicable regulatory requirements. In addition, to the extent the ongoing COVID-19 pandemic adversely affects the Company’s business and results of operations, it may also have the effect of heightening many of the other risks and uncertainties discussed above. Debt Issuance Cost Debt issuance costs consist of payments made to secure commitments under certain debt financing arrangements. These amounts are recognized as interest expense over the period of the financing arrangement using the effective interest method. If the financing arrangement is canceled or forfeited, or if the utility of the arrangement to the Company is otherwise compromised, these costs are recognized as interest expense immediately. The Company’s consolidated financial statements present debt issuance costs related to a recognized debt liability as a direct reduction from the carrying amount of that debt liability. Derivative Financial Instruments The Company accounts for derivative financial instruments as either equity or liabilities in accordance with Accounting Standards Codification Topic 815, Derivatives and Hedging, based on the characteristics and provisions of each instrument. Embedded derivatives are required to be bifurcated from the host instruments and recorded at fair value if the derivatives are not clearly and closely related to the host instruments on issuance date. The Company did not have any material embedded derivatives that required bifurcation upon issuance or as of June 30, 2020. Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of costs and expenses during the reporting period. The Company bases estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. The Company evaluates its estimates and assumptions on an ongoing basis. The Company’s actual results may differ from these estimates under different assumptions or conditions. Management anticipates that the COVID-19 pandemic will have an impact on the clinical and pre-clinical development timelines for the Company’s clinical and pre-clinical programs. Estimates and assumptions about future events and their effects cannot be determined with certainty and therefore require the exercise of judgment. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, assumptions and judgments or revise the carrying value of its assets or liabilities. These estimates may change as new events occur and additional information is obtained and are recognized in the consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the Company’s financial statements.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	6 Months Ended
	Jun. 30, 2020
Revenue From Contract With Customer [Abstract]
Revenue from Contracts with Customers	4. Revenue from Contracts with Customers On December 19, 2014 (the “Effective Date”), the Company entered into a license agreement with Kyowa Kirin, Co., Ltd. (the KKC License Agreement), under which the Company granted KKC an exclusive license to develop and commercialize entinostat in Japan and Korea. Under the terms of the KKC License Agreement, the Company will be responsible for the manufacture and supply of the products during the development activities. In addition to the license and manufacturing obligations, the Company is obligated to provide KKC access to know-how and regulatory information the Company may develop over the life of the entinostat patent. Lastly, to the extent additional intellectual property is developed during the term of the agreement, KKC will receive the right to the intellectual property when and if available. KKC will conduct the development, regulatory approval filings, and commercialization activities of entinostat in Japan and Korea. KKC paid the Company $25.0 million upfront, which included a $7.5 million equity investment and a $17.5 million non-refundable cash payment. In addition, to the extent certain development and commercial milestones are achieved, KKC will be required to pay the Company up to $75.0 million in milestone payments over the term of the license agreement. The term of the agreement commenced on the Effective Date and, unless earlier terminated in accordance with the terms of the agreement, will continue on a country-by-country and product-by-product basis, until the later of: (i) the date all valid claims of the last effective patent among the Company’s patents expires or is abandoned, withheld, or is otherwise invalidated in such country; and (ii) 15 years from the date of the first commercial sale of a product in the Japan or Korea. The equity purchase and the up-front payment of the license fee were accounted for separately. The Company allocated the amount of consideration equal to the fair value of the shares on the Effective Date, which resulted in $7.7 million of proceeds allocated to the equity purchase and the remaining consideration of $17.3 million allocated to the up-front license fee. In October 2017, the Company announced that KKC enrolled the first Japanese patient into a local pivotal study of entinostat for the treatment of hormone receptor positive, human epidermal growth factor receptor 2 negative breast cancer. In accordance with the terms of the license agreement, KKC paid the Company a $5.0 million milestone payment which the Company received in December 2017. The Company determined that the performance obligations associated with the KKC License Agreement include (i) the combined license, rights to access and use materials and data, and rights to additional intellectual property, and (ii) the clinical supply obligation. All other goods or services promised to KKC are immaterial in the context of the agreement. Under ASC 606, the identification of the clinical supply obligation as a distinct performance obligation separate and apart from the license performance obligation resulted in a change in the performance period. The start of the performance period under ASC 606 was determined to be the contract inception date, December 19, 2014. The clinical supply was identified as a separate performance obligation under ASC 606 as (i) the Company is not providing a significant serv ice of integration whereby the clinical s upply and other promises are inputs into a combined output, (ii) the c linical s upply does not significantly modify or customize the other promises nor is it significantly modified or cust omized by them, and (iii) the clinical s upply is not highly interdependent or highly interrelated with the other promises in the a greement as KK C co uld choose not to purchase the clinical s upply from the Company without significantly affecting the other promised goods or services. The Company further concluded that the clinical supply represented an immaterial performance obligation and therefore the entire $ 17.3 million allocated to the upfront payment was allocated to the combined license and will be recognized ratably over the performance period, representing contract inception though 2029 . In 2017, KK C achieved a development milestone, and was required to pay the Company $ 5.0 million. The Company is recognizing the development milestone consideration over the performance period coinciding with the license to intellectual property. As the Company determined that its performance obligations associated with the KK C Agreement at contract inception were not distinct and represented a single performance obligation, and that the obligations for goods and services provided would be completed over the performance period of the agreement, any payments received by the Company from KK C , including the upfront payment and progress-dependent development and regulatory milestone payments, are recognized as revenue using a time-based proportional performance model over the contract term (December 2014 through 2029) of the collaboration, within license fees. To date no commercial milestone payments or royalties have been achieved. Contract liabilities consisted of deferred revenue, as presented on the consolidated balance sheet, as of June 30, 2020. Deferred revenue related to the KKC License Agreement was $13.9 million as of June 30, 2020 and will be recognized over the remainder of the contract term. The Company will continue to monitor the impact of the results of E2112 on the KKC License Agreement. As of the date of these financial statements the agreement remains in force.

Net Loss per Share Attributable

Net Loss per Share Attributable to Common Stockholders	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Net Loss per Share Attributable to Common Stockholders	5. Net Loss per Share Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding for the period. Because the Company has reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods. The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company: Three Months Ended June 30 , Six Months Ended June 30 , 2020 2019 2020 2019 (In thousands, except share and per share data) (In thousands, except share and per share data) Numerator—basic and diluted: Net loss $ (17,062 ) $ (14,916 ) $ (32,298 ) $ (29,218 ) Deemed dividend due to warrant reset — — (3,906 ) — Net loss attributable to common stockholders—basic and diluted $ (17,062 ) $ (14,916 ) $ (36,204 ) $ (29,218 ) Net loss per share attributable to common stockholders—basic and diluted $ (0.42 ) $ (0.47 ) $ (0.97 ) $ (1.00 ) Denominator—basic and diluted: Weighted-average number of common shares used to compute net loss per share attributable to common stockholders—basic and diluted 40,609,205 31,605,279 37,468,922 29,327,029 The following potentially dilutive securities have been excluded from the computation of diluted weighted-average shares outstanding because such securities have an antidilutive impact due to losses reported (in common stock equivalent shares): June 30, 2020 2019 Options to purchase common stock 6,857,741 5,770,616 Warrants to purchase common stock 1,105,908 4,595,039 Employee Stock Purchase Plan 24,214 18,848 Non-vested restricted stock units (RSUs) 15,000 — In June 2018, the Company signed an exchange agreement with an investor under which the investor exchanged 2,000,000 shares of common stock for 2,000,000 warrants. Further, as discussed in Note 13, in March 2019, the Company sold 2,095,039 shares of common stock as well as 2,500,000 pre-funded warrants and 4,595,039 Series 1 and Series 2 warrants. The pre-funded warrants are exercisable into shares of common stock for $0.0001 per share. In May 2020, a holder of pre-funded warrants exchanged 280,335 warrants for 280,332 shares of common stock in a cashless exercise. Additionally, in May 2020, holders of Series 1 and Series 2 warrants, exercised 3,489,131 warrants and received 1,512,229 shares of common stock in a cashless exercise. As of June 30, 2020, there were 552,953 shares of our common stock issuable upon the exercise of Series 1 warrants outstanding, at an exercise price of $10.00 per share, and there were 552,955 shares of our common stock issuable upon the exercise of Series 2 warrants outstanding, at an exercise price of $13.00 per share.

Significant Agreements

Significant Agreements	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Significant Agreements	6. Significant Agreements Vitae Pharmaceuticals, Inc. In October 2017, the Company entered into a license agreement (the “AbbVie License Agreement”) with Vitae Pharmaceuticals, Inc. (“Vitae”), which was a subsidiary of Allergan plc (“Allergan”) prior to Allergan’s acquisition by AbbVie Inc. (“AbbVie”), under which Vitae granted the Company an exclusive, sublicensable, worldwide license to a portfolio of preclinical, orally available, small molecule inhibitors of the interaction of Menin with the Mixed Lineage Leukemia (“MLL”) protein (the “Menin Assets”). The Company made a nonrefundable upfront payment of $5.0 million to Allergan in the fourth quarter of 2017. Additionally, subject to the achievement of certain milestone events, the Company may be required to pay AbbVie up to $99.0 million in one-time development and regulatory milestone payments over the term of the AbbVie License Agreement. In the event that the Company or any of its affiliates or sublicensees commercializes the Menin Assets, the Company will also be obligated to pay AbbVie low single to low double-digit royalties on sales, subject to reduction in certain circumstances, as well as up to an aggregate of $70.0 million in potential one-time, sales-based milestone payments based on achievement of certain annual sales thresholds. Under certain circumstances, the Company may be required to share a percentage of non-royalty income from sublicensees, subject to certain deductions, with AbbVie. The Company is solely responsible for the development and commercialization of the Menin Assets. Each party may terminate the AbbVie License Agreement for the other party’s uncured material breach or insolvency; and the Company may terminate the AbbVie License Agreement at will at any time upon advance written notice to AbbVie. AbbVie may terminate the AbbVie License Agreement if the Company or any of its affiliates or sublicensees institutes a legal challenge to the validity, enforceability, or patentability of the licensed patent rights. Unless terminated earlier in accordance with its terms, the AbbVie License Agreement will continue on a country-by-country and product-by-product basis until the later of: (i) the expiration of all of the licensed patent rights in such country; (ii) the expiration of all regulatory exclusivity applicable to the product in such country; and (iii) 10 years from the date of the first commercial sale of the product in such country. As of the date of the AbbVie License Agreement, the asset acquired had no alternative future use nor had it reached a stage of technological feasibility. As the processes or activities that were acquired along with the license do not constitute a “business,” the transaction has been accounted for as an asset acquisition. In June 2019, the Company achieved certain development and regulatory milestones. As a result, in June 2019, the Company recorded $4.0 million as research and development expense. The $4.0 million plus accrued interest was paid in May 2020. UCB Biopharma Sprl In 2016, the Company entered into a license agreement (the “UCB License Agreement”) with UCB Biopharma Sprl (“UCB”), under which UCB granted to the Company a worldwide, sublicenseable, exclusive license to UCB6352, which the Company refers to as axatilimab, an investigational new drug (“IND”) ready anti-CSF-1R monoclonal antibody. The Company made a nonrefundable upfront payment of $5.0 million to UCB in 2016. Additionally, subject to the achievement of certain milestone events, the Company may be required to pay UCB up to $119.5 million in one-time development and regulatory milestone payments over the term of the UCB License Agreement. In the event that the Company or any of its affiliates or sublicensees commercializes axatilimab, the Company will also be obligated to pay UCB low double-digit royalties on sales, subject to reduction in certain circumstances, as well as up to an aggregate of $250.0 million in potential one-time, sales-based milestone payments based on achievement of certain annual sales thresholds. Under certain circumstances, the Company may be required to share a percentage of non-royalty income from sublicensees, subject to certain deductions, with UCB. The Company is solely responsible for the development and commercialization of axatilimab, except that UCB is performing a limited set of transitional chemistry, manufacturing and control tasks related to axatilimab. Each party may terminate the UCB License Agreement for the other party’s uncured material breach or insolvency; and the Company may terminate the UCB License Agreement at will at any time upon advance written notice to UCB. UCB may terminate the UCB License Agreement if the Company or any of its affiliates or sublicensees institutes a legal challenge to the validity, enforceability, or patentability of the licensed patent rights. Unless terminated earlier in accordance with its terms, the UCB License Agreement will continue on a country-by-country and product-by-product basis until the later of: (i) the expiration of all of the licensed patent rights in such country; (ii) the expiration of all regulatory exclusivity applicable to the product in such country; and (iii) 10 years from the date of the first commercial sale of the product in such country. As of the date of the UCB License Agreement, the asset acquired had no alternative future use nor had it reached a stage of technological feasibility. As the processes or activities that were acquired along with the license do not constitute a “business,” the transaction has been accounted for as an asset acquisition. In July 2020, the Company met a clinical milestone under the UCB License Agreement associated with the Phase 1 dose-finding study, and will be required to pay UCB $2.0 million. Eastern Cooperative Oncology Group In March 2014, the Company entered into the ECOG Agreement with Eastern Cooperative Oncology Group, a contracting entity for the Eastern Cooperative Oncology Group—American College of Radiology Imaging Network Cancer Research Group (“ECOG-ACRIN”), that describes the parties’ obligations with respect to the NCI-sponsored pivotal Phase 3 clinical trial of entinostat. Under the terms of the ECOG Agreement, ECOG-ACRIN will perform this clinical trial in accordance with the clinical trial protocol and a mutually agreed scope of work. The Company is providing a fixed level of financial support for the clinical trial through an upfront payment of $0.7 million and a series of payments of up to $1.0 million each that are comprised of milestone payments through the completion of enrollment and time-based payments through the completion of patient monitoring post-enrollment. In addition, the Company is obligated to supply entinostat and placebo to ECOG-ACRIN for use in the clinical trial. From the second quarter of 2016 through the fourth quarter of 2018, the Company has entered into a number of amendments to the agreement to provide for additional study activities resulting in an increase of the contractual obligation of $5.1 million. The Company has agreed to provide this additional financial support to fund the additional activities required to ensure that the E2112 clinical trial will satisfy FDA registration requirements. In May 2020, the Company announced that the E2112 trial did not achieve the primary endpoint of demonstrating a statistically significant overall survival benefit over hormone therapy alone. As a result the Company has decided to deprioritize the entinostat program to focus resources on advancing the remainder of its pipeline. As of June 30, 2020, the Company’s aggregate payment obligations under this agreement are approximately $24.7 million; and its estimated remaining payment obligations are approximately $3.8 million, which are estimated to be paid over a period of approximately two years. Data and inventions from the Phase 3 clinical trial are owned by ECOG-ACRIN. The Company has access to the data generated in the clinical trial, both directly from ECOG-ACRIN under the ECOG Agreement as well as from the NCI. Additionally, ECOG-ACRIN has granted the Company a non-exclusive royalty-free license to any inventions or discoveries that are derived from entinostat as a result of its use during the clinical trial, along with a first right to negotiate an exclusive license to any of these inventions or discoveries. Either party may terminate the ECOG Agreement in the event of an uncured material breach by the other party or if the U.S. Food and Drug Administration (“FDA”) or National Cancer Institute (“NCI”) withdraws the authorization to perform the clinical trial in the United States. The parties may jointly terminate the ECOG Agreement if the parties agree that safety-related issues support termination of the clinical trial. The Company records the appropriate clinical trial expenses in its financial statements by matching those expenses with the period in which the services and efforts are expended. The Company accounts for these expenses according to the progress of the clinical trial as measured by patient enrollment and the timing of various aspects of the clinical trial. The Company determines accrual estimates through financial models, taking into account discussion with applicable personnel and ECOG-ACRIN as to the progress or state of consummation of the clinical trial or the services completed. Bayer Pharma AG (formerly known as Bayer Schering Pharma AG) In March 2007, the Company entered into a license agreement (the “Bayer Agreement”) with Bayer Schering Pharma AG (“Bayer”) for a worldwide, exclusive license to develop and commercialize entinostat and any other products containing the same active ingredient. Under the terms of the Bayer Agreement, the Company paid a nonrefundable upfront license fee of $2.0 million and is responsible for the development and marketing of entinostat. The Company recorded the $2.0 million license fee as research and development expense during the year ended December 31, 2007, as it had no alternative future use. The Company will pay Bayer royalties on a sliding scale based on net sales, if any, and make future milestone payments to Bayer of up to $150.0 million in the event that certain specified development and regulatory goals and sales levels are achieved.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	7. Fair Value Measurements The carrying amounts of cash and cash equivalents, restricted cash, accounts payable, and accrued expenses approximated their estimated fair values due to the short-term nature of these financial instruments. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value are performed in a manner to maximize the use of observable inputs and minimize the use of unobservable inputs. The accounting standard describes a fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable, that may be used to measure fair value, which are the following: Level 1— Quoted prices (unadjusted) in active markets that are accessible at the market date for identical unrestricted assets or liabilities. Level 2— Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs for which all significant inputs are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3— Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. During the periods presented, the Company has not changed the manner in which it values assets and liabilities that are measured at fair value using Level 3 inputs. The Company recognizes transfers between levels of the fair value hierarchy as of the end of the reporting period. There were no transfers within the hierarchy for any of periods presented. A summary of the assets and liabilities carried at fair value in accordance with the hierarchy defined above is as follows: Fair Value Measurements Using Quoted Prices Significant (unadjusted) Other Significant Total in Active Observable Unobservable Carrying Markets Inputs Inputs Value (Level 1) (Level 2) (Level 3) (In thousands) June 30, 2020 Assets: Cash and cash equivalents $ 53,611 $ 53,611 $ — $ — Short-term investments 133,142 — 133,142 — Total assets $ 186,753 $ 53,611 $ 133,142 $ — December 31, 2019 Assets: Cash and cash equivalents $ 24,609 $ 23,439 $ 1,170 $ — Short-term investments 35,166 — 35,166 — Total assets $ 59,775 $ 23,439 $ 36,336 $ — Cash and cash equivalents of $53.6 million and $23.4 million as of June 30, 2020 and December 31, 2019, respectively, consisted of overnight investments and money market funds and are classified within Level 1 of the fair value hierarchy because they are valued using quoted market prices in active markets. Cash equivalents of $1.2 million as of December 31, 2019, consisted of highly rated corporate bonds and commercial paper and are classified within Level 2 of the fair value hierarchy because pricing inputs are other than quoted prices in active markets, which are either directly or indirectly observable as of the reporting date, and fair value is determined through the use of models or other valuation methodologies. Short-term investments of $133.1 million and $35.2 million as of June 30, 2020 and December 31, 2019, respectively, consisted of commercial paper, highly rated corporate bonds and asset backed securities and are classified within Level 2 of the fair value hierarchy because pricing inputs are other than quoted prices in active markets, which are either directly or indirectly observable as of the reporting date, and fair value is determined through the use of models or other valuation methodologies. The short-term investments are classified as available-for-sale securities. As of June 30, 2020, the remaining contractual maturities of the available-for-sale securities were less than one year, and the balance in the Company’s accumulated other comprehensive income was comprised solely of activity related to the Company’s available-for-sale securities. There were no realized gains or losses recognized on the sale or maturity of available-for-sale securities during the six months ended June 30, 2020 and 2019. As a result, the Company did not reclassify any amounts out of accumulated other comprehensive income for the same periods. The Company has a limited number of available-for-sale securities in insignificant loss positions as of June 30, 2020, which the Company does not intend to sell and has concluded it will not be required to sell before recovery of the amortized cost for the investment at maturity. The following table summarizes the available-for-sale securities: Amortized Unrealized Unrealized Cost Gains Losses Fair Value (In thousands) June 30, 2020 Commercial paper $ 104,308 $ 108 $ (15 ) $ 104,401 Corporate bonds 28,716 27 (2 ) 28,741 $ 133,024 $ 135 $ (17 ) $ 133,142 December 31, 2019 Commercial paper $ 15,675 $ 5 $ — $ 15,680 Corporate bonds 18,361 — (5 ) 18,356 Asset-backed securities 2,300 — — 2,300 $ 36,336 $ 5 $ (5 ) $ 36,336

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	6 Months Ended
	Jun. 30, 2020
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Current Assets	8. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following: June 30, 2020 December 31, 2019 (In thousands) Short-term deposits $ 2,968 $ 1,297 Prepaid clinical supplies 147 166 Interest receivable on investments 222 116 Reimbursable costs 23 416 Prepaid insurance 1,210 214 Other 369 347 Total prepaid expenses and other current assets $ 4,939 $ 2,556

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	6 Months Ended
	Jun. 30, 2020
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	9. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following: June 30, 2020 December 31, 2019 (In thousands) Accrued professional fees $ 295 $ 403 Accrued compensation and related costs 2,029 2,800 Accrued clinical costs 5,657 6,726 Other 710 266 Total accrued expenses and other current liabilities $ 8,691 $ 10,195

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	10. Stock-Based Compensation In January 2020, the number of shares of common stock available for issuance under the 2015 Omnibus Incentive Plan (“2015 Plan”), was increased by 1,085,619 shares due to the automatic annual provision to increase shares available under the 2015 Plan. As of June 30, 2020, the total number of shares of common stock available for issuance under the 2015 Plan was 714,953. The Company recognized stock-based compensation expense related to the issuance of stock option awards to employees and non-employees and related to the 2015 Employee Stock Purchase Plan (“ESPP”) in the condensed consolidated statements of comprehensive loss as follows: Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 (In thousands) Research and development $ 561 $ 537 $ 1,093 $ 1,071 General and administrative 1,568 801 2,866 1,859 Total $ 2,129 $ 1,338 $ 3,959 $ 2,930 Compensation expense by type of award in the three and six months ended June 30, 2020 and 2019 was as follows: Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 (In thousands) Stock options $ 2,086 $ 1,308 $ 3,880 $ 2,867 Employee Stock Purchase Plan 43 30 79 63 Total $ 2,129 $ 1,338 $ 3,959 $ 2,930 During the six months ended June 30, 2020, the Company granted 1,412,825 stock options to certain executives, consultants, and employees having service-based vesting conditions. The grant date fair value of the options granted in the six months ended June 30, 2020, was $11.1 million, or $7.85 per share on a weighted-average basis and will be recognized as compensation expense over the requisite service period of three to four years. In April 2020, the Company granted 74,000 stock options to certain employees to purchase shares of common stock that contain a performance-based vesting criterion related to filing a New Drug Application with the FDA. In May 2020, these options were cancelled. No expense had been recognized related to this award. In 2019, the Company granted 583,000 stock options to certain employees to purchase shares of common stock that contain certain performance-based vesting criteria, primarily related to the achievement of certain clinical and regulatory development milestones related to product candidates. Recognition of stock-based compensation expense associated with these performance-based stock options commences when the performance condition is considered probable of achievement, using management’s best estimates, which consider the inherent risk and uncertainty regarding the future outcomes of the milestones. During the six months ended June 30, 2020, 141,490 options were exercised for cash proceeds of $1.4 million. During the six months ended June 30, 2019, 22,167 options were exercised for cash proceeds of $0.2 million. As of June 30, 2020, there was $17.2 million of unrecognized compensation cost related to employee and non-employee unvested stock options and RSUs granted under the 2015 and 2007 Plans, which is expected to be recognized over a weighted-average remaining service period of 2.8 years. Stock compensation costs have not been capitalized by the Company. Restricted stock units During the six months ended June 30, 2020, the Company granted 15,000 shares of the Company’s restricted stock units. The shares are scheduled to vest in equal annual tranches over a four-year

Employee Stock Purchase Plan

Employee Stock Purchase Plan	6 Months Ended
	Jun. 30, 2020
Postemployment Benefits [Abstract]
Employee Stock Purchase Plan	11. Employee Stock Purchase Plan In January 2020, the number of shares of common stock available for issuance under the ESPP, was increased by 250,000 shares as a result of the automatic increase provision of the ESPP. As of June 30, 2020, the total number of shares of common stock available for issuance under the ESPP was 1,094,393. The issued 12,601 shares during the first six months of 2020. The ESPP is considered a compensatory plan with the related compensation cost expensed over the six-month offering period starting on February 1 and on August 1. The compensation expense related to the ESPP for the three and six months ended June 30, 2020, was approximately $43,000 and $79,000, respectively. The compensation expense related to the ESPP recorded in the three and six months ended June 30, 2019, was approximately $30,000 and $63,000, respectively.

Loan Payable

Loan Payable	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Loan Payable	12. Loan Payable In February 2020, the Company entered into a loan and security agreement (the “Loan Agreement”) with Hercules Capital, Inc. (“Hercules”), which provided for aggregate maximum borrowings of up to $30.0 million, consisting of (i) a term loan of up to $20.0 million, which was funded on February 7, 2020 (the “Initial Advance”), and (ii) subject to Hercules’ investment committee approval, an additional term loan of up to $10.0 million, available for borrowing from February 7, 2020 to December 15, 2020 (the “Tranche 2 Advance”). Borrowings under the Loan Agreement bear interest at an annual rate equal to the greater of (i) 9.85% or (ii) 5.10% plus the Wall Street Journal prime rate. As of June 30, 2020, the Company’s interest rate under the Loan Agreement was 9.85%. Borrowings under the Loan Agreement are repayable in monthly interest-only payments through October 1, 2021. After the interest-only payment period, borrowings under the Loan Agreement are repayable in equal monthly payments of principal and accrued interest until the maturity date of the loan, which is September 1, 2023. At the Company’s option, the Company may prepay all, but not less than all, of the outstanding borrowings, subject to a prepayment premium equal to (i) 2.0% of the principal amount outstanding if the prepayment occurs during the first year following the applicable loan being funded, (ii) 1.5% of the principal amount outstanding if the prepayment occurs during the second year following the applicable loan being funded, and (iii) 1.0% of the principal amount outstanding at any time thereafter but prior to the Maturity Date. In addition, the Company paid a $100,000 facility charge upon closing, which is being expensed over the term of the debt, and will pay a $50,000 facility charge in connection with the Tranche 2 Advance. The Loan Agreement also provides for a final payment, payable upon maturity or the repayment in full of all obligations under the agreement, of up to 4.99% of the aggregate principal amount of the Term Loan Advances (as defined in the Loan Agreement). The final payment will be accrued over the term of the debt. Borrowings under the Loan Agreement are collateralized by substantially all of the Company’s and its subsidiaries personal property and other assets, other than its intellectual property. The Loan Agreement includes a minimum cash covenant of $12.5 million that applies commencing on October 1, 2020, subject to reduction upon satisfaction of certain conditions as set forth in the Loan Agreement. In addition, the Loan Agreement includes customary affirmative and restrictive covenants and representations and warranties, including a covenant against the occurrence of a “change in control,” financial reporting obligations, and certain limitations on indebtedness, liens (including a negative pledge on intellectual property and other assets), investments, distributions (including dividends), collateral, investments, distributions, transfers, mergers or acquisitions, taxes, corporate changes, and deposit accounts. The Loan Agreement also includes customary events of default, including payment defaults, breaches of covenants following any applicable cure period, the occurrence of certain events that could reasonably be expected to have a “material adverse effect” as set forth in the Loan Agreement, cross acceleration to third-party indebtedness and certain events relating to bankruptcy or insolvency. Upon the occurrence of an event of default, a default interest rate of an additional 5.0% may be applied to the outstanding principal balance, and Hercules may declare all outstanding obligations immediately due and payable and take such other actions as set forth in the Loan Agreement. In connection with the Loan Agreement, the Company was required to enter into separate deposit account control agreements with the lender in order to perfect the lender’s security interest in the cash collateral in the Company’s operating accounts. In the event of a default under the Loan Agreement, the lender would have the right to take control of the operating accounts and restrict the Company’s access to the operating accounts and the funds therein. During the three and six months ended June 30, 2020, the Company recognized $0.6 million and $1.0 million, respectively, of interest expense related to the Initial Advance pursuant to the Loan Agreement. As of June 30, 2020, the Company’s maturities of principal obligations under its long-term debt are as follows: Amount Remainder of 2020 $ — 2021 3,057 2022 9,809 2023 7,134 Total principal outstanding 20,000 Amortized final fee 131 Unamortized debt issuance costs (235 ) Total $ 19,896

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Stockholders' Equity	13. Stockholders’ Equity The following table presents the changes in stockholders’ equity for the six months ended June 30, 2020: (In thousands, except share data) Common Stock $0.0001 Par Value Additional Paid-In Capital Accumulated Other Comprehensive Income / (Loss) Accumulated Deficit Total Stockholders’ Equity Shares Amount Balance as of December 31, 2019 27,140,484 $ 3 $ 527,067 $ — $ (495,470 ) $ 31,600 Stock purchase under ESPP 12,601 — — — — — Stock-based compensation expense — — 1,829 — — 1,829 Proceeds from direct offering, net of $93 offering expenses 3,036,719 — 24,201 — — 24,201 Proceeds from pre-funded common stock warrant from direct offering, net of $41 offering expenses — — 10,665 — — 10,665 Deemed dividend from repricing Series 1 and 2 warrants — — 3,906 — — 3,906 Repricing Series 1 and 2 warrants — — (3,906 ) — — (3,906 ) Proceeds from exercise of stock options 51,034 — 338 — — 338 Unrealized gains on short-term investments — — — 48 — 48 Employee withholdings ESPP — — 64 — — 64 Net loss — — — — (15,236 ) (15,236 ) Balance as of March 31, 2020 30,240,838 $ 3 $ 564,164 $ 48 $ (510,706 ) $ 53,509 Stock-based compensation expense — — 2,130 — — 2,130 Issuance of common stock in exchange for pre-funded warrants 280,332 — — — — — Exercise Series 1 and Series 2 warrants 1,512,229 — — — — — Proceeds from direct offering, net of $7,099 offering expenses 6,388,889 1 107,900 — — 107,901 Proceeds from exercise of stock options 90,456 — 1,015 — — 1,015 Unrealized gains on short-term investments — — — 69 — 69 Employee withholdings ESPP — — 85 — — 85 Net loss — — — — (17,062 ) (17,062 ) Balance as of June 30, 2020 38,512,744 $ 4 $ 675,294 $ 117 $ (527,768 ) $ 147,647 The following table presents the changes in stockholders’ equity for the three months ended June 30 , 201 9 : (In thousands, except share data) Common Stock $0.0001 Par Value Additional Paid-In Capital Accumulated Other Comprehensive Income / (Loss) Accumulated Deficit Total Stockholders’ Equity Shares Amount Balance as of December 31, 2018 24,835,951 $ 2 $ 492,493 $ (25 ) $ (439,423 ) $ 53,047 Stock purchase under ESPP 23,970 — — — — — Proceeds from 'at-the-market' offering, net of $34 offering expenses 140,819 — 830 — — 830 Stock-based compensation expense — — 1,592 — — 1,592 Proceeds from direct offering, net of $1,571 in common stock warrants, $78 offering expenses 2,095,039 1 10,921 — — 10,922 Proceeds from pre-funded common stock warrant from direct offering, net of $1,875 in common stock warrants, $93 offering expenses — — 13,032 — — 13,032 Issuance of common stock warrant with direct offering — — 3,446 — — 3,446 Unrealized gains on short-term investments — — 33 — 33 Employee withholdings ESPP — — 26 — — 26 Net loss — — — — (14,302 ) (14,302 ) Balance as of March 31, 2019 27,095,779 $ 3 $ 522,340 $ 8 $ (453,725 ) $ 68,626 Stock-based compensation expense — — 1,338 — — 1,338 Offering expenses associated with direct offering — — (20 ) — — (20 ) Unrealized gains on short-term investments — — — 50 — 50 Employee withholdings ESPP — — 46 — — 46 Proceeds from exercise stock options 22,167 — 151 — — 151 Net loss — — — — (14,916 ) (14,916 ) Balance as of June 30, 2019 27,117,946 $ 3 $ 523,855 $ 58 $ (468,641 ) $ 55,275 In April 2017, the Company entered into a sales agreement with Cowen and Company, LLC (“Cowen”) under which the Company may issue and sell shares of our common stock having aggregate sales proceeds of up to $50.0 million from time to time through Cowen, acting as agent, in a series of one or more at-the-market (the “2017 ATM Program”) equity offerings. Cowen is not required to sell any specific amount, but acts as our sales agent using commercially reasonable efforts consistent with its normal trading and sales practices. The Company pays Cowen up to 3% of the gross proceeds from any common stock sold through this sales agreement. In the first quarter of 2019, the Company sold 140,819 shares of common stock under the 2017 ATM Program for net proceeds of $0.8 million. In August 2019, the Company entered into a new sales agreement with Cowen under which the Company may issue and sell shares of its common stock having aggregate sales proceeds of up to $50.0 million from time to time through Cowen, acting as agent, in a series of one or more ATM equity offerings (the “2019 ATM Program”). Cowen is not required to sell any specific amount, but acts as the Company’s sales agent using commercially reasonable efforts consistent with its normal trading and sales practices. Shares sold pursuant to the sales agreement will be sold pursuant to a shelf registration statement on Form S-3 (Registration No. 333-233564), which was declared effective on September 10, 2019. The Company’s common stock will be sold at prevailing market prices at the time of the sale; and as a result, prices may vary. In the first quarter of 2020, and through June 30, 2020, the Company sold no additional shares of common stock under the ATM program. In March 2019, the Company issued 2,095,039 shares of its common stock and pre-funded warrants to purchase 2,500,000 shares of common stock to certain investors in a registered direct offering. The pre-funded warrants are exercisable immediately upon issuance at an exercise price of $0.0001 per share and have a term of 20 years. The Company sold the shares of common stock and pre-funded warrants together with two series of warrants, Series 1 Warrants and Series 2 Warrants, to purchase an aggregate of 4,595,039 shares of the Company’s common stock (collectively, the “Series Warrants”). The offering price for the securities was $6.00 per share (or $5.9999 for each Pre-Funded Warrant). The aggregate gross proceeds to the Company from this offering were $ 27.6 million, excluding any proceeds the Company may receive upon exercise of the p re- f unded w arrants and Series Warrants and offering costs of $ 0.2 million . No underwriter or placement agent participated in the offering. The Series Warrants are immediately exercisable. Each Series 1 Warrant has an initial exercise price of $12.00 per share of common stock and each Series 2 Warrant has an initial exercise price of $18.00 per share of common stock, in each case subject to certain adjustments. The Series Warrants expire on the earlier of (i) 90 days following the Company’s confirmation to holders of the Company’s release of positive data confirming the achievement of the specified primary endpoint of overall survival benefit in the E2112 clinical trial in breast cancer patients, or (ii) December 31, 2020. If, prior to the expiration date of the Series Warrant, the Company sells additional capital stock or derivative securities convertible into or exercisable for capital stock, as defined, in one or more related transactions primarily for the purpose of raising capital at a Weighted-Average Price (as described below) below $12.00 per share, then the initial exercise price of the Series Warrants will be automatically reset upon exercise to an exercise price (the “Adjusted Exercise Price”) that is the midpoint between the initial exercise price and the lowest Weighted-Average Price per share at which the Company sells capital stock or derivative securities convertible into or exercisable for capital stock in a subsequent offering prior to the exercise date; provided, however, that the Adjusted Exercise Price will not be reduced below $6.00 per share. The Weighted-Average Price shall be calculated as the weighted-average common stock equivalent price of the equity securities sold in such transaction(s) (excluding any derivative securities with an exercise or conversion price that is above the closing sale price as of the time of pricing such offering(s)). In no event will the exercise price for the Series Warrants be adjusted more than once pursuant to this adjustment mechanism. The Pre-Funded Warrants and the Series Warrants may not be exercised by the holder to the extent that the holder, together with its affiliates, would beneficially own, after such exercise more than 9.99% of the shares of the Company’s common stock then outstanding (subject to the right of the holder to increase or decrease such beneficial ownership limitation upon notice to the Company, provided that such limitation cannot exceed 19.99%) and provided that any increase in the beneficial ownership limitation shall not be effective until 61 days after such notice is delivered. The Series Warrants were classified as a component of permanent equity and were recorded at the issuance date using a relative fair value allocation method. The Series Warrants are equity classified because they are freestanding financial instruments that are legally detachable and separately exercisable from the equity instruments, are immediately exercisable, do not embody an obligation for the Company to repurchase its shares, and permit the holders to receive a fixed number of shares of common stock upon exercise. In addition, such warrants do not provide any guarantee of value or return . In January 2020, the Company sold 3,036,719 shares of common stock, and pre-funded warrants to purchase 1,338,287 shares of common stock. The offering price for the securities was $8.00 per share of common stock or $7.9999 for each pre-funded warrant. As a result of this offering, the exercise price of Series 1 Warrants and Series 2 Warrants outstanding reset from $12.00 per share to $10.00 per share and from $18.00 per share to $13.00, respectively. The Company recorded $3.9 million as a deemed dividend which represents the value transferred to the warrant holders due to the Series Warrant adjustment mechanism being triggered. The deemed dividend was recorded as both an increase and a decrease in Additional Paid-in-Capital and reduced net income available to common stockholders by the same amount. The key inputs to the valuation model included the weighted average volatility of 96.74% and the weighted average expected term of 0.4 years. In May 2020, the Company sold 6,388,889 shares of common stock. The offering price for the securities was $18.00 per share of common stock. The aggregate proceeds to the Company, net of offering cost, were $107.9 million. In May 2020, a holder of pre-funded warrants exchanged 280,335 warrants for 280,332 shares of common stock in a cashless exercise. Additionally, in May 2020, holders of Series 1 and Series 2 warrants, exercised 3,489,131 warrants and received 1,512,229 shares of common stock in a cashless exercise. Company has reserved for future issuance the following shares of common stock related to the potential warrant exercise, exercise of stock options, and the employee stock purchase plan: June 30, 2020 Common stock issuable under pre-funded warrants 5,557,952 Series 1 and 2 warrants 1,105,908 Options to purchase common stock 714,953 Employee Stock Purchase Plan 1,094,393

Related-Party Transactions

Related-Party Transactions	6 Months Ended
	Jun. 30, 2020
Related Party Transactions [Abstract]
Related-Party Transactions	14. Related-Party Transactions The Company’s chief executive officer and member of the board of directors is also an Executive Partner at MPM Asset Management, LLC, which holds an investment in the Company’s common stock.

Basis of Presentation (Policies

Basis of Presentation (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Principles of Consolidation	In 2011, the Company established a wholly owned subsidiary in the United Kingdom. There have been no activities for this entity to date. In 2014, the Company established a wholly owned U.S. subsidiary, Syndax Securities Corporation. The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Significant Accounting Policies	Significant Accounting Policies The Company’s significant accounting policies, which are disclosed in the audited consolidated financial statements for the year ended December 31, 2019 and the notes thereto are included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 5, 2020. Since the date of that filing, there have been no material changes to the Company’s significant accounting policies except as noted below.
Significant Risks and Uncertainties	Significant Risks and Uncertainties With the global spread of the ongoing COVID-19 pandemic in 2020, the Company has implemented business continuity plans designed to address and mitigate the impact of the COVID-19 pandemic on our business. The Company anticipate that the COVID-19 pandemic could have an impact on the clinical development timelines for one or more of our clinical programs. The extent to which the COVID-19 pandemic impacts the Company’s business, clinical development, manufacturing of clinical and commercial drug substance and drug product, and regulatory efforts, the corporate development objectives and the value of and market for the Company’s common stock, will depend on future developments that are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration of the pandemic, travel restrictions, quarantines, social distancing and business closure requirements in the U.S., Europe and other countries, and the effectiveness of actions taken globally to contain and treat the disease. The global economic slowdown, the overall disruption of global healthcare systems and the other risks and uncertainties associated with the pandemic could have a material adverse effect on its business, financial condition, results of operations and growth prospects. In addition, the Company is subject to other challenges and risks specific to its business and ability to execute on the strategy, as well as risks and uncertainties common to companies in the pharmaceutical industry with development and commercial operations, including, without limitation, risks and uncertainties associated with: obtaining regulatory approval of our late-stage product candidate; delays or problems in the supply of the Company’s products, loss of single source suppliers or failure to comply with manufacturing regulations; identifying, acquiring or in-licensing additional products or product candidates; pharmaceutical product development and the inherent uncertainty of clinical success; and the challenges of protecting and enhancing the Company’s intellectual property rights; complying with applicable regulatory requirements. In addition, to the extent the ongoing COVID-19 pandemic adversely affects the Company’s business and results of operations, it may also have the effect of heightening many of the other risks and uncertainties discussed above.
Debt Issuance Cost	Debt Issuance Cost Debt issuance costs consist of payments made to secure commitments under certain debt financing arrangements. These amounts are recognized as interest expense over the period of the financing arrangement using the effective interest method. If the financing arrangement is canceled or forfeited, or if the utility of the arrangement to the Company is otherwise compromised, these costs are recognized as interest expense immediately. The Company’s consolidated financial statements present debt issuance costs related to a recognized debt liability as a direct reduction from the carrying amount of that debt liability.
Derivative Financial Instruments	Derivative Financial Instruments The Company accounts for derivative financial instruments as either equity or liabilities in accordance with Accounting Standards Codification Topic 815, Derivatives and Hedging, based on the characteristics and provisions of each instrument. Embedded derivatives are required to be bifurcated from the host instruments and recorded at fair value if the derivatives are not clearly and closely related to the host instruments on issuance date. The Company did not have any material embedded derivatives that required bifurcation upon issuance or as of June 30, 2020.
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of costs and expenses during the reporting period. The Company bases estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. The Company evaluates its estimates and assumptions on an ongoing basis. The Company’s actual results may differ from these estimates under different assumptions or conditions. Management anticipates that the COVID-19 pandemic will have an impact on the clinical and pre-clinical development timelines for the Company’s clinical and pre-clinical programs. Estimates and assumptions about future events and their effects cannot be determined with certainty and therefore require the exercise of judgment. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, assumptions and judgments or revise the carrying value of its assets or liabilities. These estimates may change as new events occur and additional information is obtained and are recognized in the consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the Company’s financial statements.

Net Loss per Share Attributab_2

Net Loss per Share Attributable to Common Stockholders (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss per Share Attributable to Common Stockholders	The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company: Three Months Ended June 30 , Six Months Ended June 30 , 2020 2019 2020 2019 (In thousands, except share and per share data) (In thousands, except share and per share data) Numerator—basic and diluted: Net loss $ (17,062 ) $ (14,916 ) $ (32,298 ) $ (29,218 ) Deemed dividend due to warrant reset — — (3,906 ) — Net loss attributable to common stockholders—basic and diluted $ (17,062 ) $ (14,916 ) $ (36,204 ) $ (29,218 ) Net loss per share attributable to common stockholders—basic and diluted $ (0.42 ) $ (0.47 ) $ (0.97 ) $ (1.00 ) Denominator—basic and diluted: Weighted-average number of common shares used to compute net loss per share attributable to common stockholders—basic and diluted 40,609,205 31,605,279 37,468,922 29,327,029
Potential Dilutive Securities Excluded from Computation of Diluted Net Loss per Common Share	The following potentially dilutive securities have been excluded from the computation of diluted weighted-average shares outstanding because such securities have an antidilutive impact due to losses reported (in common stock equivalent shares): June 30, 2020 2019 Options to purchase common stock 6,857,741 5,770,616 Warrants to purchase common stock 1,105,908 4,595,039 Employee Stock Purchase Plan 24,214 18,848 Non-vested restricted stock units (RSUs) 15,000 —

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Schedule of Fair Values of Financial Assets and Liabilities Measured at Fair Value	A summary of the assets and liabilities carried at fair value in accordance with the hierarchy defined above is as follows: Fair Value Measurements Using Quoted Prices Significant (unadjusted) Other Significant Total in Active Observable Unobservable Carrying Markets Inputs Inputs Value (Level 1) (Level 2) (Level 3) (In thousands) June 30, 2020 Assets: Cash and cash equivalents $ 53,611 $ 53,611 $ — $ — Short-term investments 133,142 — 133,142 — Total assets $ 186,753 $ 53,611 $ 133,142 $ — December 31, 2019 Assets: Cash and cash equivalents $ 24,609 $ 23,439 $ 1,170 $ — Short-term investments 35,166 — 35,166 — Total assets $ 59,775 $ 23,439 $ 36,336 $ —
Summary of Available-for-Sale Securities	The following table summarizes the available-for-sale securities: Amortized Unrealized Unrealized Cost Gains Losses Fair Value (In thousands) June 30, 2020 Commercial paper $ 104,308 $ 108 $ (15 ) $ 104,401 Corporate bonds 28,716 27 (2 ) 28,741 $ 133,024 $ 135 $ (17 ) $ 133,142 December 31, 2019 Commercial paper $ 15,675 $ 5 $ — $ 15,680 Corporate bonds 18,361 — (5 ) 18,356 Asset-backed securities 2,300 — — 2,300 $ 36,336 $ 5 $ (5 ) $ 36,336

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	6 Months Ended
	Jun. 30, 2020
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following: June 30, 2020 December 31, 2019 (In thousands) Short-term deposits $ 2,968 $ 1,297 Prepaid clinical supplies 147 166 Interest receivable on investments 222 116 Reimbursable costs 23 416 Prepaid insurance 1,210 214 Other 369 347 Total prepaid expenses and other current assets $ 4,939 $ 2,556

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	6 Months Ended
	Jun. 30, 2020
Payables And Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following: June 30, 2020 December 31, 2019 (In thousands) Accrued professional fees $ 295 $ 403 Accrued compensation and related costs 2,029 2,800 Accrued clinical costs 5,657 6,726 Other 710 266 Total accrued expenses and other current liabilities $ 8,691 $ 10,195

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share Based Compensation Expense Related to Issuance of Stock Option Awards to Employees and Non Employees Related to Employee Stock Purchase Plan	The Company recognized stock-based compensation expense related to the issuance of stock option awards to employees and non-employees and related to the 2015 Employee Stock Purchase Plan (“ESPP”) in the condensed consolidated statements of comprehensive loss as follows: Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 (In thousands) Research and development $ 561 $ 537 $ 1,093 $ 1,071 General and administrative 1,568 801 2,866 1,859 Total $ 2,129 $ 1,338 $ 3,959 $ 2,930
Compensation Expense by Type of Award	Compensation expense by type of award in the three and six months ended June 30, 2020 and 2019 was as follows: Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 (In thousands) Stock options $ 2,086 $ 1,308 $ 3,880 $ 2,867 Employee Stock Purchase Plan 43 30 79 63 Total $ 2,129 $ 1,338 $ 3,959 $ 2,930

Loan Payable (Tables)

Loan Payable (Tables)	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Summary of Maturities of Principal Obligations Under Long-term Debt	As of June 30, 2020, the Company’s maturities of principal obligations under its long-term debt are as follows: Amount Remainder of 2020 $ — 2021 3,057 2022 9,809 2023 7,134 Total principal outstanding 20,000 Amortized final fee 131 Unamortized debt issuance costs (235 ) Total $ 19,896

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Summary of Changes in Stockholders' Equity	The following table presents the changes in stockholders’ equity for the six months ended June 30, 2020: (In thousands, except share data) Common Stock $0.0001 Par Value Additional Paid-In Capital Accumulated Other Comprehensive Income / (Loss) Accumulated Deficit Total Stockholders’ Equity Shares Amount Balance as of December 31, 2019 27,140,484 $ 3 $ 527,067 $ — $ (495,470 ) $ 31,600 Stock purchase under ESPP 12,601 — — — — — Stock-based compensation expense — — 1,829 — — 1,829 Proceeds from direct offering, net of $93 offering expenses 3,036,719 — 24,201 — — 24,201 Proceeds from pre-funded common stock warrant from direct offering, net of $41 offering expenses — — 10,665 — — 10,665 Deemed dividend from repricing Series 1 and 2 warrants — — 3,906 — — 3,906 Repricing Series 1 and 2 warrants — — (3,906 ) — — (3,906 ) Proceeds from exercise of stock options 51,034 — 338 — — 338 Unrealized gains on short-term investments — — — 48 — 48 Employee withholdings ESPP — — 64 — — 64 Net loss — — — — (15,236 ) (15,236 ) Balance as of March 31, 2020 30,240,838 $ 3 $ 564,164 $ 48 $ (510,706 ) $ 53,509 Stock-based compensation expense — — 2,130 — — 2,130 Issuance of common stock in exchange for pre-funded warrants 280,332 — — — — — Exercise Series 1 and Series 2 warrants 1,512,229 — — — — — Proceeds from direct offering, net of $7,099 offering expenses 6,388,889 1 107,900 — — 107,901 Proceeds from exercise of stock options 90,456 — 1,015 — — 1,015 Unrealized gains on short-term investments — — — 69 — 69 Employee withholdings ESPP — — 85 — — 85 Net loss — — — — (17,062 ) (17,062 ) Balance as of June 30, 2020 38,512,744 $ 4 $ 675,294 $ 117 $ (527,768 ) $ 147,647 The following table presents the changes in stockholders’ equity for the three months ended June 30 , 201 9 : (In thousands, except share data) Common Stock $0.0001 Par Value Additional Paid-In Capital Accumulated Other Comprehensive Income / (Loss) Accumulated Deficit Total Stockholders’ Equity Shares Amount Balance as of December 31, 2018 24,835,951 $ 2 $ 492,493 $ (25 ) $ (439,423 ) $ 53,047 Stock purchase under ESPP 23,970 — — — — — Proceeds from 'at-the-market' offering, net of $34 offering expenses 140,819 — 830 — — 830 Stock-based compensation expense — — 1,592 — — 1,592 Proceeds from direct offering, net of $1,571 in common stock warrants, $78 offering expenses 2,095,039 1 10,921 — — 10,922 Proceeds from pre-funded common stock warrant from direct offering, net of $1,875 in common stock warrants, $93 offering expenses — — 13,032 — — 13,032 Issuance of common stock warrant with direct offering — — 3,446 — — 3,446 Unrealized gains on short-term investments — — 33 — 33 Employee withholdings ESPP — — 26 — — 26 Net loss — — — — (14,302 ) (14,302 ) Balance as of March 31, 2019 27,095,779 $ 3 $ 522,340 $ 8 $ (453,725 ) $ 68,626 Stock-based compensation expense — — 1,338 — — 1,338 Offering expenses associated with direct offering — — (20 ) — — (20 ) Unrealized gains on short-term investments — — — 50 — 50 Employee withholdings ESPP — — 46 — — 46 Proceeds from exercise stock options 22,167 — 151 — — 151 Net loss — — — — (14,916 ) (14,916 ) Balance as of June 30, 2019 27,117,946 $ 3 $ 523,855 $ 58 $ (468,641 ) $ 55,275
Schedule of Common Stock Reserved for Future Issuance	Company has reserved for future issuance the following shares of common stock related to the potential warrant exercise, exercise of stock options, and the employee stock purchase plan: June 30, 2020 Common stock issuable under pre-funded warrants 5,557,952 Series 1 and 2 warrants 1,105,908 Options to purchase common stock 714,953 Employee Stock Purchase Plan 1,094,393

Nature of Business - Additional

Nature of Business - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2020Segment
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of operating segments	1
Date of incorporation	Oct. 11, 2005
State of incorporation	DE

Revenue from Contract with Cust

Revenue from Contract with Customers - Additional Information (Detail) - USD ($)	1 Months Ended		6 Months Ended	12 Months Ended
	Oct. 31, 2017	Dec. 19, 2014	Jun. 30, 2020	Dec. 31, 2017	Dec. 31, 2019
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Up-front payment allocated to preferred stock value
Kyowa Kirin Co., Ltd. [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Milestone payment agreement terms			In accordance with the terms of the license agreement
License Agreement [Member] | Kyowa Kirin Co., Ltd. [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
License agreement upfront payment received		$ 25,000,000
Up-front payment allocated to equity purchase		7,500,000
Up-front license fee received		$ 17,500,000
Period of termination after first commercial sale of first licensed product		15 years
Up-front payment allocated to preferred stock value		$ 7,700,000
Up-front payment allocated to license fee		17,300,000
Milestone payment received	$ 5,000,000			$ 5,000,000
Upfront payment allocation to performance obligation			$ 17,300,000
Performance obligation period			2029
Deferred revenue			$ 13,900,000
License Agreement [Member] | Kyowa Kirin Co., Ltd. [Member] | Maximum [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Milestone payment receivable upon achievement of development and commercial milestone		$ 75,000,000

Net Loss per Share Attributab_3

Net Loss per Share Attributable to Common Stockholders - Computation of Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator—basic and diluted:
Net loss	$ (17,062)	$ (15,236)	$ (14,916)	$ (14,302)	$ (32,298)	$ (29,218)
Net loss attributable to common stockholders—basic and diluted	$ (17,062)		$ (14,916)		$ (36,204)	$ (29,218)
Net loss per share attributable to common stockholders—basic and diluted	$ (0.42)		$ (0.47)		$ (0.97)	$ (1)
Denominator—basic and diluted:
Weighted-average number of common shares used to compute net loss per share attributable to common stockholders—basic and diluted	40,609,205		31,605,279		37,468,922	29,327,029
Warrant [Member]
Numerator—basic and diluted:
Deemed dividend due to warrant reset					$ (3,906)

Net Loss per Share Attributab_4

Net Loss per Share Attributable to Common Stockholders - Potential Dilutive Securities Excluded from Computation of Diluted Net Loss per Common Share (Detail) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per common share	6,857,741	5,770,616
Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per common share	1,105,908	4,595,039
Employee Stock Purchase Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per common share	24,214	18,848
RSUs [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per common share	15,000

Net Loss per Share Attributab_5

Net Loss per Share Attributable to Common Stockholders - Additional Information (Detail) - $ / shares	Jun. 18, 2018	Jun. 30, 2020	May 31, 2020	Jan. 31, 2020	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Earnings Per Share Basic [Line Items]
Common stock, new shares issued		2,095,039	6,388,889	3,036,719
Pre-funded warrants exchange			280,335
Exercise Series 1 and Series 2 warrants			3,489,131
Biotechnology Value Fund, L.P. [Member]
Earnings Per Share Basic [Line Items]
Number of common stock converted to warrants	2,000,000
Number of common stock warrants issued	2,000,000
Pre-Funded Warrants [Member]
Earnings Per Share Basic [Line Items]
Warrant exercise price per share		$ 0.0001		$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Warrant issued		2,500,000		1,338,287
Series 1 and Series 2 Warrants [Member]
Earnings Per Share Basic [Line Items]
Warrant issued		4,595,039
Common Stock [Member]
Earnings Per Share Basic [Line Items]
Common stock, new shares issued					2,095,039
Pre-funded warrants exchange			280,332			280,332
Exercise Series 1 and Series 2 warrants			1,512,229
Series 1 Warrants [Member]
Earnings Per Share Basic [Line Items]
Warrant exercise price per share		$ 10		$ 10	$ 12	$ 10	$ 10	$ 12
Warrant issued							552,953
Series 2 Warrants [Member]
Earnings Per Share Basic [Line Items]
Warrant exercise price per share		$ 13		$ 13	$ 18	$ 13	$ 13	$ 18
Warrant issued							552,955

Significant Agreements - Additi

Significant Agreements - Additional Information (Detail) - USD ($)

1 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

30 Months Ended

Jun. 30, 2019

Oct. 31, 2017

Mar. 31, 2014

Dec. 31, 2007

Mar. 31, 2007

Jun. 30, 2020

Jun. 30, 2019

Dec. 31, 2017

Jun. 30, 2020

Jun. 30, 2019

Dec. 31, 2016

Dec. 31, 2018

Jul. 31, 2020

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Research and development expense

$ 10,943,000

$ 12,290,000

$ 20,505,000

$ 23,569,000

AbbVie License Agreement [Member] | Vitae Pharmaceuticals Inc [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront milestone payable

$ 5,000,000

Potential milestone payments to be made

$ 99,000,000

Aggregate potential milestone payable

$ 70,000,000

License expiration year

10 years

AbbVie License Agreement [Member] | Vitae Pharmaceuticals Inc [Member] | Accrued Milestone Expenses [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Research and development expense

$ 4,000,000

UCB License Agreement [Member] | UCB Biopharma [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront milestone payable

$ 5,000,000

Potential milestone payments to be made

119,500,000

Aggregate potential milestone payable

$ 250,000,000

License expiration year

10 years

UCB License Agreement [Member] | UCB Biopharma [Member] | Subsequent Event [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Clinical milestone payment

$ 2,000,000

Clinical Trial [Member] | Eastern Cooperative Oncology Group [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront milestone payable

$ 700,000

Milestone payment payable

$ 1,000,000

Increase in contractual obligation

$ 5,100,000

Aggregate payment obligation

24,700,000

24,700,000

Estimated remaining contractual obligation

$ 3,800,000

$ 3,800,000

Period of contractual obligation

2 years

License Agreement [Member] | Bayer Pharma AG [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Research and development expense

$ 2,000,000

Up-front license fee paid

$ 2,000,000

License Agreement [Member] | Bayer Pharma AG [Member] | Maximum [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Aggregate payment obligation

$ 150,000,000

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Values of Financial Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	$ 133,142	$ 35,166
Carrying Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	53,611	24,609
Short-term investments	133,142	35,166
Total assets	186,753	59,775
Quoted Prices (Unadjusted) in Active Markets Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	53,611	23,439
Total assets	53,611	23,439
Significant Other Observable Inputs Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents		1,170
Short-term investments	133,142	35,166
Total assets	$ 133,142	$ 36,336

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Fair Value Measurements [Line Items]
Available for sale debt securities fair value	$ 133,142,000		$ 36,336,000
Realized gains or losses recognized on the sale or maturity of available-for-sale securities	0	$ 0
Quoted Prices (Unadjusted) in Active Markets Level 1 [Member]
Fair Value Measurements [Line Items]
Cash and cash equivalents fair value	53,611,000		23,439,000
Quoted Prices (Unadjusted) in Active Markets Level 1 [Member] | Overnight Investments, Money Market Funds and Highly Rated Corporate Bonds Member]
Fair Value Measurements [Line Items]
Cash and cash equivalents fair value	53,600,000		23,400,000
Significant Other Observable Inputs Level 2 [Member]
Fair Value Measurements [Line Items]
Cash and cash equivalents fair value			1,170,000
Significant Other Observable Inputs Level 2 [Member] | Corporate Bonds and Commercial Paper [Member]
Fair Value Measurements [Line Items]
Cash and cash equivalents fair value			1,200,000
Significant Other Observable Inputs Level 2 [Member] | Commercial Paper, Corporate Bonds and Asset Backed Securities [Member] | Short-term Investments [Member]
Fair Value Measurements [Line Items]
Available for sale debt securities fair value	$ 133,100,000		$ 35,200,000

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 133,024	$ 36,336
Unrealized Gains	135	5
Unrealized Losses	(17)	(5)
Fair Value	133,142	36,336
Commercial Paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	104,308	15,675
Unrealized Gains	108	5
Unrealized Losses	(15)
Fair Value	104,401	15,680
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	28,716	18,361
Unrealized Gains	27
Unrealized Losses	(2)	(5)
Fair Value	$ 28,741	18,356
Asset Back Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		2,300
Fair Value		$ 2,300

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Short-term deposits	$ 2,968	$ 1,297
Prepaid clinical supplies	147	166
Interest receivable on investments	222	116
Reimbursable costs	23	416
Prepaid insurance	1,210	214
Other	369	347
Total prepaid expenses and other current assets	$ 4,939	$ 2,556

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued professional fees	$ 295	$ 403
Accrued compensation and related costs	2,029	2,800
Accrued clinical costs	5,657	6,726
Other	710	266
Total accrued expenses and other current liabilities	$ 8,691	$ 10,195

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	Jan. 01, 2020	May 31, 2020	Apr. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Jan. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options exercised, shares				141,490	22,167
Proceeds from stock option exercises				$ 1,353,000	$ 151,000
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option granted to certain executives, consultants and employees				15,000
Shares, vesting period				4 years
Fair value of shares at grant date				142,000
Weighted average grant date fair value per share				$ 9.47
2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance							1,085,619
2015 Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance				714,953
2007 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option granted to certain executives, consultants and employees				1,412,825
Options grant date fair value amount				$ 11,100,000
Weighted average grant date fair value of options				$ 7.85
Recognized compensation expense related to stock option not met				$ 0
Stock compensation expense				$ 100,000
Stock option not met, options cancelled	194,338			194,331
2007 Plan [Member] | Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option granted to certain executives, consultants and employees			74,000			583,000
Recognized compensation expense related to stock option not met		$ 0
2015 and 2007 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock option and RSUs				$ 17,200,000
Weighted average period to recognize compensation expense				2 years 9 months 18 days

Stock-Based Compensation - Shar

Stock-Based Compensation - Share Based Compensation Expense Related to Issuance of Stock Option Awards to Employees and Non Employees Related to Employee Stock Purchase Plan (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 2,129	$ 1,338	$ 3,959	$ 2,930
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	561	537	1,093	1,071
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 1,568	$ 801	$ 2,866	$ 1,859

Stock-Based Compensation - Comp

Stock-Based Compensation - Compensation Expense by Type of Award (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 2,129	$ 1,338	$ 3,959	$ 2,930
Options to Purchase Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	2,086	1,308	3,880	2,867
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 43	$ 30	$ 79	$ 63

Employee Stock Purchase Plan -

Employee Stock Purchase Plan - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Employee Benefit Plans [Line Items]
Compensation expense		$ 2,129	$ 1,338	$ 3,959	$ 2,930
Employee Stock Purchase Plan [Member]
Employee Benefit Plans [Line Items]
Common stock available for issuance	250,000
Number of shares issued under plan				12,601
Compensation expense		$ 43	$ 30	$ 79	$ 63
Employee Stock Purchase Plan [Member] | Maximum [Member]
Employee Benefit Plans [Line Items]
Common stock available for issuance		1,094,393		1,094,393

Loan Payable - Additional Infor

Loan Payable - Additional Information (Detail) - USD ($)	Oct. 01, 2020	Feb. 29, 2020	Jun. 30, 2020	Jun. 30, 2020
Debt Instrument [Line Items]
Interest expense related to the loan agreement			$ 638,000	$ 1,087,000
Hercules [Member] | Loan Agreement [Member]
Debt Instrument [Line Items]
Aggregate maximum borrowings		$ 30,000,000
Interest rate description				Borrowings under the Loan Agreement bear interest at an annual rate equal to the greater of (i) 9.85% or (ii) 5.10% plus the Wall Street Journal prime rate.
Interest rate			9.85%	9.85%
Maturity date		Sep. 1, 2023
Percentage of prepayment premium of principal amount outstanding in first year		2.00%
Percentage of prepayment premium of principal amount outstanding in second year		1.50%
Percentage of prepayment premium of principal amount outstanding thereafter prior to maturity date		1.00%
Facility charge paid		$ 100,000
Interest expense related to the loan agreement			$ 600,000	$ 1,000,000
Hercules [Member] | Loan Agreement [Member] | Scenario Forecast [Member]
Debt Instrument [Line Items]
Minimum cash covenant	$ 12,500,000
Default interest rate	5.00%
Hercules [Member] | Loan Agreement [Member] | Wall Street Journal Prime Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		5.10%
Hercules [Member] | Loan Agreement [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate		9.85%
Hercules [Member] | Loan Agreement [Member] | Maximum [Member]
Debt Instrument [Line Items]
Percentage of repayment on aggregate principal amount of term loan advances		4.99%
Hercules [Member] | Loan Agreement [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Term loan		$ 20,000,000
Hercules [Member] | Loan Agreement [Member] | Additional Term Loan [Member]
Debt Instrument [Line Items]
Term loan		10,000,000
Hercules [Member] | Loan Agreement [Member] | Tranche 2 [Member]
Debt Instrument [Line Items]
Facility charge paid		$ 50,000

Loan Payable - Summary of Matur

Loan Payable - Summary of Maturities of Principal Obligations Under Long-term Debt (Detail) $ in Thousands	Jun. 30, 2020USD ($)
Debt Disclosure [Abstract]
2021	$ 3,057
2022	9,809
2023	7,134
Total principal outstanding	20,000
Amortized final fee	131
Unamortized debt issuance costs	(235)
Total	$ 19,896

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended				6 Months Ended
	May 31, 2020	Jan. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Class of Stock [Line Items]
Beginning balance		$ 31,600	$ 53,509	$ 31,600	$ 68,626	$ 53,047	$ 31,600	$ 53,047
Proceeds from 'at-the-market' offering, net, value						830
Stock-based compensation expense			2,130	1,829	1,338	1,592
Offering expenses associated with direct offering					(20)
Issuance of common stock in exchange for pre-funded warrants, shares	280,335
Exercise Series 1 and Series 2 warrants	3,489,131
Proceeds from direct offering, net, value			107,901	24,201		10,922
Proceeds from pre-funded common stock warrant from direct offering, net, value				10,665		13,032
Issuance of common stock warrant with direct offering, value						3,446
Repricing Series 1 and 2 warrants		3,900
Proceeds from exercise of stock options, value			1,015	338	151
Proceeds from exercise of stock options, shares							141,490	22,167
Unrealized gains on short-term investments			69	48	50	33	$ 117	$ 83
Employee withholdings ESPP			85	64	46	26
Net loss			(17,062)	(15,236)	(14,916)	(14,302)	(32,298)	(29,218)
Ending balance			147,647	53,509	55,275	68,626	147,647	55,275
Series 1 and 2 [Member]
Class of Stock [Line Items]
Deemed dividend from repricing Series 1 and 2 warrants				3,906
Repricing Series 1 and 2 warrants				(3,906)
Common Stock [Member]
Class of Stock [Line Items]
Beginning balance		$ 3	$ 3	$ 3	$ 3	$ 2	$ 3	$ 2
Beginning balance, Shares		27,140,484	30,240,838	27,140,484	27,095,779	24,835,951	27,140,484	24,835,951
Stock purchase under ESPP, Shares				12,601		23,970
Proceeds from "at-the-market" offering, net, shares						140,819
Issuance of common stock in exchange for pre-funded warrants, shares	280,332		280,332
Exercise Series 1 and Series 2 warrants	1,512,229
Proceeds from direct offering, net, value			$ 1			$ 1
Proceeds from direct offering,net, Shares			6,388,889	3,036,719		2,095,039
Proceeds from exercise of stock options, shares			90,456	51,034	22,167
Ending balance			$ 4	$ 3	$ 3	$ 3	$ 4	$ 3
Ending balance, Shares			38,512,744	30,240,838	27,117,946	27,095,779	38,512,744	27,117,946
Common Stock [Member] | Series 1 and 2 [Member]
Class of Stock [Line Items]
Exercise Series 1 and Series 2 warrants			1,512,229
Additional Paid-In Capital [Member]
Class of Stock [Line Items]
Beginning balance		$ 527,067	$ 564,164	$ 527,067	$ 522,340	$ 492,493	$ 527,067	$ 492,493
Proceeds from 'at-the-market' offering, net, value						830
Stock-based compensation expense			2,130	1,829	1,338	1,592
Offering expenses associated with direct offering					(20)
Proceeds from direct offering, net, value			107,900	24,201		10,921
Proceeds from pre-funded common stock warrant from direct offering, net, value				10,665		13,032
Issuance of common stock warrant with direct offering, value						3,446
Proceeds from exercise of stock options, value			1,015	338	151
Employee withholdings ESPP			85	64	46	26
Ending balance			675,294	564,164	523,855	522,340	675,294	523,855
Additional Paid-In Capital [Member] | Series 1 and 2 [Member]
Class of Stock [Line Items]
Deemed dividend from repricing Series 1 and 2 warrants				3,906
Repricing Series 1 and 2 warrants				(3,906)
Accumulated Other Comprehensive Income / (Loss) [Member]
Class of Stock [Line Items]
Beginning balance			48		8	(25)		(25)
Unrealized gains on short-term investments			69	48	50	33
Ending balance			117	48	58	8	117	58
Accumulated Deficit [Member]
Class of Stock [Line Items]
Beginning balance		$ (495,470)	(510,706)	(495,470)	(453,725)	(439,423)	(495,470)	(439,423)
Net loss			(17,062)	(15,236)	(14,916)	(14,302)
Ending balance			$ (527,768)	$ (510,706)	$ (468,641)	$ (453,725)	$ (527,768)	$ (468,641)

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Mar. 31, 2019
Equity [Abstract]
At-the-market, offering expenses			$ 34
Direct offering, common stock warrants			1,571
Direct offering, offering expenses	$ 7,099	$ 93	78
Pre-funded common stock warrants			1,875
Pre-funded common stock warrants offering expenses		$ 41	$ 93

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Millions	1 Months Ended						3 Months Ended			6 Months Ended
	Jun. 30, 2020$ / sharesshares	May 31, 2020USD ($)$ / sharesshares	Jan. 31, 2020USD ($)$ / sharesshares	Aug. 31, 2019USD ($)	Mar. 31, 2019USD ($)Seriesofwarrant$ / sharesshares	Apr. 30, 2017USD ($)	Jun. 30, 2020$ / sharesshares	Mar. 31, 2020shares	Mar. 31, 2019USD ($)$ / sharesshares	Jun. 30, 2020$ / shares	Dec. 31, 2019$ / shares
Class Of Stock [Line Items]
Proceeds from issuance of common stock in follow-on public stock offering, net | $		$ 107.9
Common stock, new shares issued	2,095,039	6,388,889	3,036,719
Number of series of warrants | Seriesofwarrant					2
Offering price | $ / shares		$ 18
Gross proceeds from offering | $					$ 27.6
Offering costs | $					$ 0.2
Weighted average expected term			4 months 24 days		1 year 4 months 24 days				1 year 4 months 24 days
Deemed dividend transferred to the warrant holders | $			$ 3.9
Pre-funded warrants exchange		280,335
Exercise Series 1 and Series 2 warrants		3,489,131
Weighted Average Volatility Rate [Member]
Class Of Stock [Line Items]
Warrants and rights outstanding, measurement input			0.9674		0.891				0.891
Common Stock [Member]
Class Of Stock [Line Items]
Common stock, new shares issued					2,095,039
Pre-funded warrants exchange		280,332					280,332
Exercise Series 1 and Series 2 warrants		1,512,229
Pre-Funded Warrants [Member]
Class Of Stock [Line Items]
Warrants issued (in shares)			1,338,287		2,500,000				2,500,000
Warrant exercise price per share | $ / shares	$ 0.0001		$ 0.0001		$ 0.0001		$ 0.0001		$ 0.0001	$ 0.0001
Warrant term					20 years
Offering price | $ / shares			7.9999		$ 5.9999
Maximum period allowed to increase beneficial ownership limitation after notice										61 days
Minimum percentage of common stock can be held upon exercise of warrant										9.99%
Maximum beneficial ownership limitation percentage										19.99%
Series Warrants [Member]
Class Of Stock [Line Items]
Warrants issued (in shares)					4,595,039				4,595,039
Warrant term										90 days
Offering price | $ / shares			8		$ 6
Weighted average price | $ / shares										$ 12
Total fair value of warrant | $									$ 3.4
Series 1 Warrants [Member]
Class Of Stock [Line Items]
Warrant exercise price per share | $ / shares	10		10		12		10		$ 12	10	$ 12
Series 2 Warrants [Member]
Class Of Stock [Line Items]
Warrant exercise price per share | $ / shares	$ 13		$ 13		$ 18		$ 13		$ 18	13	$ 18
Minimum [Member] | Series Warrants [Member]
Class Of Stock [Line Items]
Adjusted exercise price | $ / shares										$ 6
At The Market Equity Offering Sales Agreement [Member]
Class Of Stock [Line Items]
Proceeds from issuance of common stock in follow-on public stock offering, net | $									$ 0.8
Common stock, new shares issued							0	0	140,819
Cowen and Company LLC [Member] | At The Market Equity Offering Sales Agreement [Member]
Class Of Stock [Line Items]
Proceeds from issuance of common stock in follow-on public stock offering, net | $				$ 50		$ 50
Cowen and Company LLC [Member] | At The Market Equity Offering Sales Agreement [Member] | Maximum [Member]
Class Of Stock [Line Items]
Payment percentage of gross proceeds from sales agreement						3.00%

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Common Stock Reserved for Future Issuance (Detail)	Jun. 30, 2020shares
Pre-Funded Warrants [Member]
Class Of Stock [Line Items]
Common stock reserved for future issuance	5,557,952
Series 1 and 2 Warrants [Member]
Class Of Stock [Line Items]
Common stock reserved for future issuance	1,105,908
Options to Purchase Common Stock [Member]
Class Of Stock [Line Items]
Common stock reserved for future issuance	714,953
Employee Stock Purchase Plan [Member]
Class Of Stock [Line Items]
Common stock reserved for future issuance	1,094,393