Syndax Pharmaceuticals (SNDX) 10-Q 11 May 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 10, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
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	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		48,248,559
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 (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 64,386	$ 115,243
Restricted cash		115
Short-term investments	206,949	177,822
Prepaid expenses and other current assets	7,612	5,684
Total current assets	278,947	298,864
Property and equipment, net	176	192
Right-of-use asset, net	434	290
Other assets	115	1,267
Total assets	279,672	300,613
Current liabilities:
Accounts payable	6,529	3,508
Accrued expenses and other current liabilities	11,414	11,246
Current portion of deferred revenue	1,517	1,517
Current portion of right-of-use liability	476	316
Current portion of term loan	4,632	2,285
Total current liabilities	24,568	18,872
Long-term liabilities:
Deferred revenue, less current portion	11,237	11,617
Right-of-use liability, less current portion	60	101
Loan payable	15,602	17,834
Other long-term liabilities		1
Total long-term liabilities	26,899	29,553
Total liabilities	51,467	48,425
Commitments
Stockholders’ equity:
Preferred stock, $0.001 par value, 10,000,000 shares authorized; 0 shares outstanding at March 31, 2021 and December 31, 2020
Common stock, $0.0001 par value, 100,000,000 shares authorized; 48,248,559 and 47,881,223 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively	5	5
Additional paid-in capital	824,542	820,815
Accumulated other comprehensive income (loss)	9	(4)
Accumulated deficit	(596,351)	(568,628)
Total stockholders’ equity	228,205	252,188
Total liabilities and stockholders’ equity	$ 279,672	$ 300,613

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
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	48,248,559	47,881,223
Common stock, shares outstanding	48,248,559	47,881,223

Condensed Consolidated Statemen

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue:
Total revenues	$ 379	$ 379
Type of revenue [extensible list]	us-gaap:LicenseMember	us-gaap:LicenseMember
Operating expenses:
Research and development	$ 21,870	$ 9,562
General and administrative	5,672	5,917
Total operating expenses	27,542	15,479
Loss from operations	(27,163)	(15,100)
Other expense, net:
Interest expense	(623)	(449)
Interest income	120	333
Other (expense) income	(57)	(20)
Total other (expense) income	(560)	(136)
Net loss	(27,723)	(15,236)
Other comprehensive income:
Unrealized gain on marketable securities	13	48
Comprehensive loss	(27,710)	(15,188)
Net loss attributable to common stockholders	$ (27,723)	$ (19,142)
Net loss per share attributable to common stockholders—basic and diluted	$ (0.54)	$ (0.56)
Weighted-average number of common shares used to compute net loss per share attributable to common stockholders —basic and diluted	51,499,831	34,328,640

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (27,723)	$ (15,236)
Adjustments to reconcile net loss to net cash from operating activities:
Depreciation	16	23
Amortization and accretion of investments	113	(110)
Non-cash operating lease expense	101	108
Non-cash interest expense	114	62
Stock-based compensation	2,767	1,829
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(660)	(2,530)
Accounts payable	3,021	2,820
Deferred revenue	(379)	(379)
Accrued expenses and other liabilities	41	(2,512)
Net cash used in operating activities	(22,589)	(15,925)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of short-term investments	(66,728)	(34,938)
Proceeds from sales and maturities of short-term investments	37,500	15,885
Net cash used in investing activities	(29,228)	(19,053)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from debt agreement, net		19,730
Proceeds from Employee Stock Purchase Plan	79	64
Proceeds from stock option exercises	881	338
Net cash provided by financing activities	960	54,998
NET (DECREASE) INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(50,857)	20,020
CASH, CASH EQUIVALENTS AND RESTRICTED CASH—beginning of period	115,358	24,724
CASH, CASH EQUIVALENTS AND RESTRICTED CASH —end of period	64,501	44,744
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid for interest	$ 493	126
SUPPLEMENTAL DISCLOSURES OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Issuance costs debt included in accounts payable and accrued expenses		82
Private Placement [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net		$ 34,866

Nature of Business

Nature of Business	3 Months Ended
	Mar. 31, 2021
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	3 Months Ended
	Mar. 31, 2021
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 March 31, 2021, and the results of operations and comprehensive loss and cash flows for the three months ended March 31, 2021 and 2020. The results for the three months ended March 31, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021, 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, 2020, 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 12, 2021. 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	3 Months Ended
	Mar. 31, 2021
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, 2020 and the notes thereto are included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 12, 2021. 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 We have implemented business continuity plans designed to address and mitigate the impact of the COVID-19 pandemic on our business. We 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 our business, our clinical development, manufacturing of clinical and commercial drug substance and drug product, and regulatory efforts, our corporate development objectives and the value of and market for our 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 our business, financial condition, results of operations and growth prospects. In addition, we are subject to other challenges and risks specific to our business and our ability to execute on our 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 our 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 our intellectual property rights; complying with applicable regulatory requirements. In addition, to the extent the ongoing COVID-19 pandemic adversely affects our business and results of operations, it may also have the effect of heightening many of the other risks and uncertainties discussed above. 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. We anticipate that the COVID-19 pandemic will have an impact on the clinical and pre-clinical development timelines for our 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	3 Months Ended
	Mar. 31, 2021
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 service of integration whereby the clinical supply and other promises are inputs into a combined output, (ii) the clinical supply does not significantly modify or customize the other promises nor is it significantly modified or customized by them, and (iii) the clinical supply is not highly interdependent or highly interrelated with the other promises in the agreement as KKC could choose not to purchase the clinical supply 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, KKC 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 KKC 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 KKC, 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. Contract liabilities consisted of deferred revenue, as presented on the consolidated balance sheet, as of March 31, 2021. Deferred revenue related to the KKC License Agreement was $12.8 million as of March 31, 2021 and will be recognized over the remainder of the contract term. For the three months ended March 31, 2021 and 2020, the Company recognized $0.4 million, respectively, as revenue.

Net Loss per Share Attributable

Net Loss per Share Attributable to Common Stockholders	3 Months Ended
	Mar. 31, 2021
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 March 31, 2021 2020 (In thousands, except share and per share data) Numerator—basic and diluted: Net loss $ (27,723 ) $ (15,236 ) Deemed dividend due to warrant reset — (3,906 ) Net loss attributable to common stockholders—basic and diluted $ (27,723 ) $ (19,142 ) Net loss per share attributable to common stockholders—basic and diluted $ (0.54 ) $ (0.56 ) Denominator—basic and diluted: Weighted-average number of common shares used to compute net loss per share attributable to common stockholders—basic and diluted 51,499,831 34,328,640 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): March 31, 2021 2020 Options to purchase common stock 7,404,823 6,897,802 Warrants to purchase common stock — 4,595,039 Employee Stock Purchase Plan 8,214 24,214 Non-vested restricted stock units (RSUs) 124,083 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 12, 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. During the first quarter of 2021, 250,000 pre-funded warrants were exchanged for shares of common stock in a cash exercise. As of March 31, 2021, 3,307,952 pre-funded warrants were outstanding.

Significant Agreements

Significant Agreements	3 Months Ended
	Mar. 31, 2021
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., which is now a subsidiary of AbbVie, Inc. (“AbbVie”), under which AbbVie 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 AbbVie 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 amount was paid in 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. As a result, in 2016, the upfront payment of $5.0 million was recorded as research and development expense in the consolidated statements of operations. In July 2020, the Company achieved certain development and regulatory milestones. As a result, in July 2020, the Company recorded $2.0 million as research and development expense, which has been fully paid. In March 2021, the Company recorded $2.0 million as research and development expense for the achievement of a certain development milestone. This amount was recorded in accounts payable as of March 31, 2021. 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 p roviding 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 $ 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 March 31, 2021, the Company’s aggregate payment obligations under this agreement are approximately $24.7 million; and its remaining payment obligations are approximately $3.2 million, which are estimated to be paid over a period of approximately one year. As of March 31, 2021, the Company has accrued $2.3 million related to the ECOG Agreement. 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	3 Months Ended
	Mar. 31, 2021
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 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) March 31, 2021 Assets: Cash and cash equivalents $ 64,386 $ 64,386 $ — $ — Short-term investments 206,949 — 206,949 — Total assets $ 271,335 $ 64,386 $ 206,949 $ — December 31, 2020 Assets: Cash and cash equivalents $ 115,243 $ 110,246 $ 4,997 $ — Short-term investments 177,822 — 177,822 — Total assets $ 293,065 $ 110,246 $ 182,819 $ — Cash and cash equivalents of $64.4 million and $110.2 million as of March 31, 2021 and December 31, 2020, 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 $5.0 million as of December 31, 2020, 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 $206.9 million and The short-term investments are classified as available-for-sale securities. As of March 31, 2021, 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 three months ended March 31, 2021 and 2020. 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 March 31, 2021, 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) March 31, 2021 Commercial paper $ 160,222 $ 19 $ (5 ) $ 160,236 Corporate bonds 21,226 — (8 ) 21,218 US Treasury 25,492 4 (1 ) 25,495 $ 206,940 $ 23 $ (14 ) $ 206,949 December 31, 2020 Commercial paper $ 154,176 $ 13 $ (16 ) $ 154,173 Corporate bonds 22,617 2 (3 ) 22,616 US Treasury 6,030 — — 6,030 $ 182,823 $ 15 $ (19 ) $ 182,819

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	3 Months Ended
	Mar. 31, 2021
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: March 31, 2021 December 31, 2020 (In thousands) Short-term deposits $ 4,840 $ 4,683 Prepaid insurance 2,052 427 Interest receivable on investments 279 175 Prepaid subscriptions 256 203 Prepaid clinical supplies 58 58 Reimbursable costs 6 24 Other 121 114 Total prepaid expenses and other current assets $ 7,612 $ 5,684

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	3 Months Ended
	Mar. 31, 2021
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: March 31, 2021 December 31, 2020 (In thousands) Accrued clinical costs $ 8,997 $ 7,132 Accrued compensation and related costs 1,579 3,213 Accrued professional fees 471 373 Accrued interest payable 170 170 Other 197 358 Total accrued expenses and other current liabilities $ 11,414 $ 11,246

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	10. Stock-Based Compensation In January 2021, the number of shares of common stock available for issuance under the 2015 Omnibus Incentive Plan (“2015 Plan”) was increased by 1,915,248 shares due to the automatic annual provision to increase shares available under the 2015 Plan. As of March 31, 2021, the total number of shares of common stock available for issuance under the 2015 Plan was 1,259,406. 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 March 31, 2021 2020 (In thousands) Research and development $ 903 $ 532 General and administrative 1,864 1,297 Total $ 2,767 $ 1,829 Compensation expense by type of award in the three months ended March 31, 2021 and 2020 was as follows: Three Months Ended March 31, 2021 2020 (In thousands) Stock options $ 2,346 $ 1,793 Restricted Stock Units 380 — Employee Stock Purchase Plan 41 36 Total $ 2,767 $ 1,829 During the three months ended March 31, 2021, the Company granted 1,202,200 stock options to certain executives and employees having service-based vesting conditions. The grant date fair value of the options granted in the three months ended March 31, 2021, was $18.3 million, or $15.25 per share on a weighted-average basis and will be recognized as compensation expense over the requisite service period of four years. 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. In the fourth quarter of 2020 one of the performance milestones was achieved and of the associated 194,331 stock options, 64,777 stock options vested. The remaining options will vest in the fourth quarter of 2021 and 2022. The Company recorded approximately $64,000 and $50,000 of stock compensation expense associated with these awards for the three months ended March 31, 2021, and 2020, respectively. For the remaining milestones, the performance conditions were not met. Therefore, no expense has been recognized related to these awards for the three months ended March 31, 2021, and 388,669 options were cancelled in 2020. During the three months ended March 31, 2021, 100,954 options were exercised for cash proceeds of approximately $881,000 and 51,034 options were exercised for cash proceeds of approximately $338,000 in the three months ended March 31,2020. As of March 31, 2021, there was $31.7 million of unrecognized compensation cost related to employee and non-employee unvested stock options granted under the 2015 and 2007 Plans, which is expected to be recognized over a weighted-average remaining service period of 3.08 years. Stock compensation costs have not been capitalized by the Company. Restricted stock units During the three months ended March 31, 2021, the Company granted 109,333 shares of the Company’s restricted stock units. The shares are scheduled to vest in equal annual tranches over a four-year

Loan Payable

Loan Payable	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Loan Payable	11. 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”). The Company elected not to draw the additional term of $10.0 million. 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 March 31, 2021, the Company’s interest rate under the Loan Agreement was 9.85%. The Company is obligated to make 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. 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. As of March 31, 2021, the conditions set forth in the Loan Agreement were met. The cash covenant of $12.5 million was deferred. 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 months ended March 31, 2021 and 2020, the Company recognized $0.6 million and $0.4 million, respectively, of interest expense related to the Initial Advance pursuant to the Loan Agreement. As of March 31, 2021, the Company’s maturities of principal obligations under its long-term debt are as follows: Amount Remainder of 2021 $ 2,285 2022 9,727 2023 7,988 Total principal outstanding 20,000 Amortized final fee 396 Unamortized debt issuance costs (162 ) Total 20,234 Term loan, current portion 4,632 Term loan, less current portion $ 15,602

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Stockholders' Equity	12. Stockholders’ Equity The following table presents the changes in stockholders’ equity for the three months ended March 31, 2021: (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, 2020 47,881,223 $ 5 $ 820,815 $ (4 ) $ (568,628 ) $ 252,188 Stock purchase under ESPP 16,382 — — — — — Stock-based compensation expense — — 2,767 — — 2,767 Unrealized gains on short-term investments — — — 13 — 13 Prefunded warrant exchange 250,000 — — — — — Employee withholdings ESPP — — 79 — — 79 Proceeds from exercise of stock options 100,954 — 881 — — 881 Net loss — — — — (27,723 ) (27,723 ) Balance as of March 31, 2021 48,248,559 $ 5 $ 824,542 $ 9 $ (596,351 ) $ 228,205 The following table presents the changes in stockholders’ equity for the three months ended March 31, 2020: (In thousands, except share data) Common Stock $0.0001 Par Value Additional Paid-In Capital Accumulated Other Comprehensive Income 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 In March 2021, the Company entered into a new sales agreement with Cowen and Company, LLC (“Cowen”) under which the Company may issue and sell shares of its common stock having aggregate sales proceeds of up to $75.0 million from time to time through Cowen, acting as agent, in a series of one or more ATM equity offerings (the “2021 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-3ASR (Registration No. 333-254661), which became automatically effective upon filing on March 24, 2021. 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, the Company sold no additional shares of common stock under the 2021 ATM Program. In August 2019, the Company entered into a 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”). In conjunction with the December 2020 offering, the 2019 ATM Program was cancelled. 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 p re- f unded w arrants together with two series of warrants, Series 1 Warrants and Series 2 Warrants, to purchase an aggregate of shares of the Company’s c ommon s tock ( collectively, the “Series Warrants”). The offering price for the securities was $ 6.00 per share (or $ 5.9999 for each p re- f unded w arrant). 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 were immediately exercisable. Each Series 1 Warrant had an initial exercise price of $12.00 per share of common stock and each Series 2 Warrant had an initial exercise price of $18.00 per share of common stock, in each case subject to certain adjustments. The Series Warrants were to 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. All Series 1 and Series 2 warrants were exercised in 2020. The pre-funded 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. The 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: March 31, 2021 Common stock issuable under pre-funded warrants 3,307,952 Options to purchase common stock 1,259,406 Employee Stock Purchase Plan 1,298,692

Basis of Presentation (Policies

Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2021
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, 2020 and the notes thereto are included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 12, 2021. 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 We have implemented business continuity plans designed to address and mitigate the impact of the COVID-19 pandemic on our business. We 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 our business, our clinical development, manufacturing of clinical and commercial drug substance and drug product, and regulatory efforts, our corporate development objectives and the value of and market for our 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 our business, financial condition, results of operations and growth prospects. In addition, we are subject to other challenges and risks specific to our business and our ability to execute on our 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 our 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 our intellectual property rights; complying with applicable regulatory requirements. In addition, to the extent the ongoing COVID-19 pandemic adversely affects our business and results of operations, it may also have the effect of heightening many of the other risks and uncertainties discussed above.
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. We anticipate that the COVID-19 pandemic will have an impact on the clinical and pre-clinical development timelines for our 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)	3 Months Ended
	Mar. 31, 2021
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 March 31, 2021 2020 (In thousands, except share and per share data) Numerator—basic and diluted: Net loss $ (27,723 ) $ (15,236 ) Deemed dividend due to warrant reset — (3,906 ) Net loss attributable to common stockholders—basic and diluted $ (27,723 ) $ (19,142 ) Net loss per share attributable to common stockholders—basic and diluted $ (0.54 ) $ (0.56 ) Denominator—basic and diluted: Weighted-average number of common shares used to compute net loss per share attributable to common stockholders—basic and diluted 51,499,831 34,328,640
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): March 31, 2021 2020 Options to purchase common stock 7,404,823 6,897,802 Warrants to purchase common stock — 4,595,039 Employee Stock Purchase Plan 8,214 24,214 Non-vested restricted stock units (RSUs) 124,083 15,000

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2021
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) March 31, 2021 Assets: Cash and cash equivalents $ 64,386 $ 64,386 $ — $ — Short-term investments 206,949 — 206,949 — Total assets $ 271,335 $ 64,386 $ 206,949 $ — December 31, 2020 Assets: Cash and cash equivalents $ 115,243 $ 110,246 $ 4,997 $ — Short-term investments 177,822 — 177,822 — Total assets $ 293,065 $ 110,246 $ 182,819 $ —
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) March 31, 2021 Commercial paper $ 160,222 $ 19 $ (5 ) $ 160,236 Corporate bonds 21,226 — (8 ) 21,218 US Treasury 25,492 4 (1 ) 25,495 $ 206,940 $ 23 $ (14 ) $ 206,949 December 31, 2020 Commercial paper $ 154,176 $ 13 $ (16 ) $ 154,173 Corporate bonds 22,617 2 (3 ) 22,616 US Treasury 6,030 — — 6,030 $ 182,823 $ 15 $ (19 ) $ 182,819

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	3 Months Ended
	Mar. 31, 2021
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: March 31, 2021 December 31, 2020 (In thousands) Short-term deposits $ 4,840 $ 4,683 Prepaid insurance 2,052 427 Interest receivable on investments 279 175 Prepaid subscriptions 256 203 Prepaid clinical supplies 58 58 Reimbursable costs 6 24 Other 121 114 Total prepaid expenses and other current assets $ 7,612 $ 5,684

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2021
Payables And Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following: March 31, 2021 December 31, 2020 (In thousands) Accrued clinical costs $ 8,997 $ 7,132 Accrued compensation and related costs 1,579 3,213 Accrued professional fees 471 373 Accrued interest payable 170 170 Other 197 358 Total accrued expenses and other current liabilities $ 11,414 $ 11,246

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2021
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 March 31, 2021 2020 (In thousands) Research and development $ 903 $ 532 General and administrative 1,864 1,297 Total $ 2,767 $ 1,829
Compensation Expense by Type of Award	Compensation expense by type of award in the three months ended March 31, 2021 and 2020 was as follows: Three Months Ended March 31, 2021 2020 (In thousands) Stock options $ 2,346 $ 1,793 Restricted Stock Units 380 — Employee Stock Purchase Plan 41 36 Total $ 2,767 $ 1,829

Loan Payable (Tables)

Loan Payable (Tables)	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Summary of Maturities of Principal Obligations Under Long-term Debt	As of March 31, 2021, the Company’s maturities of principal obligations under its long-term debt are as follows: Amount Remainder of 2021 $ 2,285 2022 9,727 2023 7,988 Total principal outstanding 20,000 Amortized final fee 396 Unamortized debt issuance costs (162 ) Total 20,234 Term loan, current portion 4,632 Term loan, less current portion $ 15,602

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Summary of Changes in Stockholders' Equity	The following table presents the changes in stockholders’ equity for the three months ended March 31, 2021: (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, 2020 47,881,223 $ 5 $ 820,815 $ (4 ) $ (568,628 ) $ 252,188 Stock purchase under ESPP 16,382 — — — — — Stock-based compensation expense — — 2,767 — — 2,767 Unrealized gains on short-term investments — — — 13 — 13 Prefunded warrant exchange 250,000 — — — — — Employee withholdings ESPP — — 79 — — 79 Proceeds from exercise of stock options 100,954 — 881 — — 881 Net loss — — — — (27,723 ) (27,723 ) Balance as of March 31, 2021 48,248,559 $ 5 $ 824,542 $ 9 $ (596,351 ) $ 228,205 The following table presents the changes in stockholders’ equity for the three months ended March 31, 2020: (In thousands, except share data) Common Stock $0.0001 Par Value Additional Paid-In Capital Accumulated Other Comprehensive Income 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
Schedule of Common Stock Reserved for Future Issuance	The 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: March 31, 2021 Common stock issuable under pre-funded warrants 3,307,952 Options to purchase common stock 1,259,406 Employee Stock Purchase Plan 1,298,692

Nature of Business - Additional

Nature of Business - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2021Segment
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) - Kyowa Kirin Co., Ltd. [Member] - USD ($)	1 Months Ended		3 Months Ended		12 Months Ended
	Oct. 31, 2017	Dec. 19, 2014	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2017
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]
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		$ 400,000	$ 400,000	$ 5,000,000
Upfront payment allocation to performance obligation			$ 17,300,000
Performance obligation period			2029
Deferred revenue			$ 12,800,000
License Agreement [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
	Mar. 31, 2021	Mar. 31, 2020
Numerator—basic and diluted:
Net loss	$ (27,723)	$ (15,236)
Net loss attributable to common stockholders—basic and diluted	$ (27,723)	$ (19,142)
Net loss per share attributable to common stockholders—basic and diluted	$ (0.54)	$ (0.56)
Denominator—basic and diluted:
Weighted-average number of common shares used to compute net loss per share attributable to common stockholders—basic and diluted	51,499,831	34,328,640
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	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
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	7,404,823	6,897,802
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		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	8,214	24,214
Non-Vested Restricted Stock Units (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	124,083	15,000

Net Loss per Share Attributab_5

Net Loss per Share Attributable to Common Stockholders - Additional Information (Detail) - $ / shares	Jun. 18, 2018	Jan. 31, 2020	Mar. 31, 2019	Mar. 31, 2021
Earnings Per Share Basic [Line Items]
Common stock, new shares issued		3,036,719	2,095,039
Pre-funded warrants exchange				250,000
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
Warrant issued		1,338,287	2,500,000
Warrants outstanding				3,307,952
Series 1 and Series 2 Warrants [Member]
Earnings Per Share Basic [Line Items]
Warrant issued			4,595,039

Significant Agreements - Additi

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

1 Months Ended

3 Months Ended

12 Months Ended

30 Months Ended

Mar. 31, 2021

Jul. 31, 2020

Jun. 30, 2019

Oct. 31, 2017

Mar. 31, 2014

Dec. 31, 2007

Mar. 31, 2007

Mar. 31, 2021

Mar. 31, 2020

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2018

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Research and development expense

$ 21,870,000

$ 9,562,000

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

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

Research and development expense

$ 2,000,000

$ 5,000,000

UCB License Agreement [Member] | UCB Biopharma [Member] | Accrued Milestone Expenses [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Research and development expense

$ 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

$ 5,300,000

Aggregate payment obligation

24,700,000

24,700,000

Remaining contractual obligation

3,200,000

$ 3,200,000

Period of contractual obligation

1 year

Accrued contractual obligation

$ 2,300,000

$ 2,300,000

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	Mar. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	$ 206,949	$ 177,822
Carrying Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	64,386	115,243
Short-term investments	206,949	177,822
Total assets	271,335	293,065
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	64,386	110,246
Total assets	64,386	110,246
Significant Other Observable Inputs Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents		4,997
Short-term investments	206,949	177,822
Total assets	$ 206,949	$ 182,819

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Fair Value Measurements [Line Items]
Available for sale debt securities fair value	$ 206,949,000		$ 182,819,000
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	64,386,000		110,246,000
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	64,400,000		110,200,000
Significant Other Observable Inputs Level 2 [Member]
Fair Value Measurements [Line Items]
Cash and cash equivalents fair value			4,997,000
Significant Other Observable Inputs Level 2 [Member] | Corporate Bonds and Commercial Paper [Member]
Fair Value Measurements [Line Items]
Cash and cash equivalents fair value			5,000,000
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	$ 206,900,000		$ 177,800,000

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 206,940	$ 182,823
Unrealized Gains	23	15
Unrealized Losses	(14)	(19)
Fair Value	206,949	182,819
Commercial Paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	160,222	154,176
Unrealized Gains	19	13
Unrealized Losses	(5)	(16)
Fair Value	160,236	154,173
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	21,226	22,617
Unrealized Gains		2
Unrealized Losses	(8)	(3)
Fair Value	21,218	22,616
US Treasury [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	25,492	6,030
Unrealized Gains	4
Unrealized Losses	(1)
Fair Value	$ 25,495	$ 6,030

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Short-term deposits	$ 4,840	$ 4,683
Prepaid insurance	2,052	427
Interest receivable on investments	279	175
Prepaid subscriptions	256	203
Prepaid clinical supplies	58	58
Reimbursable costs	6	24
Other	121	114
Total prepaid expenses and other current assets	$ 7,612	$ 5,684

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued clinical costs	$ 8,997	$ 7,132
Accrued compensation and related costs	1,579	3,213
Accrued professional fees	471	373
Accrued interest payable	170	170
Other	197	358
Total accrued expenses and other current liabilities	$ 11,414	$ 11,246

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended			12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Jan. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options exercised, shares	100,954		51,034
Proceeds from stock option exercises	$ 881,000		$ 338,000
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option granted to certain executives and employees	109,333
Fair value of shares at grant date	2,300,000
Shares, vesting period	4 years
Weighted average grant date fair value per share	$ 21.36
Unvested and outstanding shares	124,083
Weighted average exercise price	$ 20.10
2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance						1,915,248
2015 Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance	1,259,406
2007 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option granted to certain executives and employees	1,202,200
Options grant date fair value amount	$ 18,300,000
Weighted average grant date fair value of options	$ 15.25
Stock compensation expense	$ 64,000		$ 50,000
Recognized compensation expense related to stock option not met	0
Sock option not met, options cancelled				388,669
Fair value of shares at grant date		194,331
Share-based compensation, stock options vested		64,777		64,777
2007 Plan [Member] | Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option granted to certain executives and employees					583,000
2015 and 2007 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock option	$ 31,700,000
Weighted average period to recognize compensation expense	3 years 29 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
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 2,767	$ 1,829
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	903	532
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 1,864	$ 1,297

Stock-Based Compensation - Comp

Stock-Based Compensation - Compensation Expense by Type of Award (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 2,767	$ 1,829
Options to Purchase Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	2,346	1,793
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	380
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 41	$ 36

Loan Payable - Additional Infor

Loan Payable - Additional Information (Detail) - USD ($)	Oct. 01, 2020	Feb. 29, 2020	Mar. 31, 2021	Mar. 31, 2020
Debt Instrument [Line Items]
Interest expense related to the loan agreement			$ 623,000	$ 449,000
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.
Effective interest rate			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
Minimum cash covenant	$ 12,500,000
Cash covenant deferred			$ 12,500,000
Default interest rate	5.00%
Interest expense related to the loan agreement			$ 600,000	$ 400,000
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]
Aggregate maximum borrowings		$ 20,000,000
Hercules [Member] | Loan Agreement [Member] | Additional Term Loan [Member]
Debt Instrument [Line Items]
Aggregate maximum borrowings		10,000,000
Line of credit facility elected not to draw		$ 10,000,000

Loan Payable - Summary of Matur

Loan Payable - Summary of Maturities of Principal Obligations Under Long-term Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Remainder of 2021	$ 2,285
2022	9,727
2023	7,988
Total principal outstanding	20,000
Amortized final fee	396
Unamortized debt issuance costs	(162)
Total	20,234
Current portion of term loan	4,632	$ 2,285
Term loan, less current portion	$ 15,602	$ 17,834

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Jan. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Class of Stock [Line Items]
Beginning balance	$ 31,600	$ 252,188	$ 31,600
Stock-based compensation expense		2,767	1,829
Proceeds from direct offering, net of $93 offering expenses			24,201
Proceeds from pre-funded common stock warrant from direct offering, net of $41 offering expenses			10,665
Repricing Series 1 and 2 warrants	(3,900)
Unrealized gains on short-term investments		13	48
Employee withholdings ESPP		79	64
Proceeds from exercise of stock options, value		$ 881	$ 338
Proceeds from exercise of stock options, shares		100,954	51,034
Net loss		$ (27,723)	$ (15,236)
Ending balance		228,205	53,509
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	$ 5	$ 3
Beginning balance, Shares	27,140,484	47,881,223	27,140,484
Stock purchase under ESPP, Shares		16,382	12,601
Proceeds from direct offering,net, Shares			3,036,719
Prefunded warrant exchange, shares		250,000
Proceeds from exercise of stock options, shares		100,954	51,034
Ending balance		$ 5	$ 3
Ending balance, Shares		48,248,559	30,240,838
Additional Paid-In Capital [Member]
Class of Stock [Line Items]
Beginning balance	$ 527,067	$ 820,815	$ 527,067
Stock-based compensation expense		2,767	1,829
Proceeds from direct offering, net of $93 offering expenses			24,201
Proceeds from pre-funded common stock warrant from direct offering, net of $41 offering expenses			10,665
Employee withholdings ESPP		79	64
Proceeds from exercise of stock options, value		881	338
Ending balance		824,542	564,164
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		(4)
Unrealized gains on short-term investments		13	48
Ending balance		9	48
Accumulated Deficit [Member]
Class of Stock [Line Items]
Beginning balance	$ (495,470)	(568,628)	(495,470)
Net loss		(27,723)	(15,236)
Ending balance		$ (596,351)	$ (510,706)

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Parenthetical) (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Equity [Abstract]
Direct offering, offering expenses	$ 93
Pre-funded common stock warrants offering expenses	$ 41

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Millions	1 Months Ended				3 Months Ended
	Mar. 31, 2021USD ($)$ / shares	Jan. 31, 2020USD ($)$ / sharesshares	Aug. 31, 2019USD ($)	Mar. 31, 2019USD ($)Seriesofwarrant$ / sharesshares	Mar. 31, 2021$ / sharesshares	Mar. 31, 2019USD ($)$ / sharesshares
Class Of Stock [Line Items]
Common stock, new shares issued | shares		3,036,719		2,095,039
Number of series of warrants | Seriesofwarrant				2
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
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 | shares				2,095,039
Pre-Funded Warrants [Member]
Class Of Stock [Line Items]
Warrants issued (in shares) | shares		1,338,287		2,500,000		2,500,000
Warrant exercise price per share		$ 0.0001		$ 0.0001		$ 0.0001
Warrant term				20 years
Offering price		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) | shares				4,595,039		4,595,039
Warrant term					90 days
Offering price		8		$ 6
Total fair value of warrant | $						$ 3.4
Series 1 Warrants [Member]
Class Of Stock [Line Items]
Warrant exercise price per share	$ 12				$ 12
Series 1 Warrants [Member] | Maximum [Member]
Class Of Stock [Line Items]
Warrant exercise price per share		12
Series 1 Warrants [Member] | Minimum [Member]
Class Of Stock [Line Items]
Warrant exercise price per share		10
Series 2 Warrants [Member]
Class Of Stock [Line Items]
Warrant exercise price per share	$ 18				$ 18
Series 2 Warrants [Member] | Maximum [Member]
Class Of Stock [Line Items]
Warrant exercise price per share		18
Series 2 Warrants [Member] | Minimum [Member]
Class Of Stock [Line Items]
Warrant exercise price per share		$ 13
Series 1 and Series 2 Warrants [Member]
Class Of Stock [Line Items]
Warrants exercised period					2020
At The Market Equity Offering Sales Agreement [Member]
Class Of Stock [Line Items]
Common stock, new shares issued | shares					0
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 | $	$ 75		$ 50

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Common Stock Reserved for Future Issuance (Detail)	Mar. 31, 2021shares
Pre-Funded Warrants [Member]
Class Of Stock [Line Items]
Common stock reserved for future issuance	3,307,952
Options to Purchase Common Stock [Member]
Class Of Stock [Line Items]
Common stock reserved for future issuance	1,259,406
Employee Stock Purchase Plan [Member]
Class Of Stock [Line Items]
Common stock reserved for future issuance	1,298,692