View Filing Data

Print Document View Excel Document

Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2017	Aug. 10, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q2
Trading Symbol	SNDX
Entity Registrant Name	SYNDAX PHARMACEUTICALS INC
Entity Central Index Key	0001395937
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		22,219,978

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 22,988	$ 23,844
Restricted cash	101	151
Short-term investments	106,967	81,486
Prepaid expenses and other current assets	4,111	3,029
Total current assets	134,167	108,510
Property and equipment, net	260	260
Other assets	239	243
Total assets	134,666	109,013
Current liabilities:
Accounts payable	3,362	2,375
Accrued expenses and other current liabilities	6,923	6,771
Current portion of deferred revenue	1,220	1,220
Total current liabilities	11,505	10,366
Long-term liabilities:
Deferred revenue, less current portion	13,610	14,220
Other long-term liabilities	214	288
Total long-term liabilities	13,824	14,508
Total liabilities	25,329	24,874
Commitments
Stockholders' equity:
Preferred stock, $0.001 par value, 10,000,000 shares authorized; 0 shares outstanding at June 30, 2017 and December 31, 2016
Common stock, $0.0001 par value, 100,000,000 shares authorized; 22,219,843 and 18,215,181 shares outstanding at June 30, 2017 and December 31, 2016, respectively	2	2
Additional paid-in capital	441,218	389,374
Accumulated other comprehensive income	36	56
Accumulated deficit	(331,919)	(305,293)
Total stockholders' equity	109,337	84,139
Total liabilities and stockholders' equity	$ 134,666	$ 109,013

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2017	Dec. 31, 2016
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 outstanding	22,219,843	18,215,181

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue:
License fees	$ 305	$ 305	$ 610	$ 610
Total revenues	305	305	610	610
Operating expenses:
Research and development	9,862	6,131	19,414	10,917
General and administrative	4,285	2,808	8,215	7,080
Total operating expenses	14,147	8,939	27,629	17,997
Loss from operations	(13,842)	(8,634)	(27,019)	(17,387)
Other income (expense):
Interest income, net	290	276	549	420
Change in fair value of common stock warrant liability				(1,703)
Other expense	(87)		(140)	(18)
Total other income (expense)	203	276	409	(1,301)
Net loss	(13,639)	(8,358)	(26,610)	(18,688)
Other comprehensive (loss) income:
Unrealized (losses) gains on marketable securities	38	(36)	(20)	164
Comprehensive loss	(13,601)	(8,394)	(26,630)	(18,524)
Net loss attributable to common stockholders	$ (13,639)	$ (8,358)	$ (26,610)	$ (21,286)
Net loss per share attributable to common stockholders-basic and diluted	$ (0.70)	$ (0.47)	$ (1.41)	$ (1.91)
Weighted-average number of common shares used to compute net loss per share attributable to common stockholders-basic and diluted	19,497,581	17,769,514	18,868,089	11,155,525

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (26,610)	$ (18,688)
Adjustments to reconcile net loss to net cash from operating activities:
Depreciation, amortization and accretion	79	57
Stock-based compensation	2,825	2,969
Change in fair value of warrants and derivative		1,720
Other	8
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(1,082)	(394)
Accounts payable	800	(54)
Deferred revenue	(610)	(610)
Accrued expenses and other liabilities	122	1,707
Net cash (used in) provided by operating activities	(24,468)	(13,293)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment		(206)
Changes in restricted cash	50
Purchases of short-term investments	(87,989)	(109,932)
Proceeds from sales and maturities of short-term investments	62,447	62,377
Net cash used in investing activities	(25,492)	(47,761)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock in initial public stock offering, net		52,318
Proceeds from issuance of common stock in follow on public stock offering, net	48,836
Proceeds from stock option exercises	269
Other	(1)	(2)
Net cash provided by financing activities	49,104	52,316
NET DECREASE IN CASH AND CASH EQUIVALENTS	(856)	(8,738)
CASH AND CASH EQUIVALENTS-beginning of period	23,844	23,179
CASH AND CASH EQUIVALENTS-end of period	22,988	14,441
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Interest paid		2
SUPPLEMENTAL DISCLOSURES OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Property and equipment purchases included in accounts payable and accrued expenses	41	51
Accretion of dividends on convertible preferred stock		2,598
Issuance costs included in accounts payable and accrued expenses	161	170
Vesting of restricted stock	$ 59	21
Reclassification of common stock warrant liability to additional paid-in capital		4,551
Conversion of preferred stock to common stock upon closing of initial public offering		$ 328,941

Nature of Business	6 Months Ended
Nature of Business	Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	1. Nature of Business Syndax Pharmaceuticals, Inc. (the Company) is a clinical stage biopharmaceutical company developing an innovative pipeline of combination therapies in multiple cancer indications. The Company’s lead product candidate, entinostat, is currently being evaluated in a Phase 3 clinical trial for advanced hormone receptor positive, human epidermal growth factor receptor 2 negative breast cancer. The U.S. Food and Drug Administration granted Breakthrough Therapy designation to entinostat when given in combination with exemestane following positive results from the Company’s ENCORE 301 Phase 2b clinical trial. Given its potential ability to block the function of immune suppressive cells in the tumor microenvironment, the Company is evaluating entinostat as a combination therapeutic in Phase 1b/2 clinical trials with Merck & Co., Inc. for non-small cell lung cancer, melanoma and microsatellite stable colorectal cancer; with Genentech, Inc. for triple negative breast cancer; and with Merck KGaA, Darmstadt, Germany, and Pfizer Inc. for ovarian cancer. The Company’s second product candidate, SNDX-6352, is a monoclonal antibody that targets the colony stimulating factor-1 receptor to enhance the body’s immune response against tumors that have shown sensitivity to immunotherapy. The Company is evaluating SNDX-6352 in a Phase 1 clinical trial. The Company plans to continue to leverage the technical and business expertise of our management team and scientific collaborators to license, acquire and develop additional cancer therapies to expand our pipeline. In March 2016, the Company completed its initial public offering (“IPO”) whereby it sold 4,809,475 shares of common stock at the initial public offering price of $12.00 per share, which included 409,475 shares issued pursuant to the underwriters’ partial exercise of their over-allotment option to purchase additional shares of common stock. The aggregate net proceeds received by the Company from the offering were $50.5 million, net of underwriting discounts and commissions of $4.0 million and offering expenses of $3.1 million. Upon the closing of the IPO, all outstanding shares of the Company’s outstanding convertible preferred stock converted into 12,872,551 shares of common stock; and the Company’s outstanding warrant liability to purchase 357,840 shares of the Company’s common stock valued at $4.6 million was reclassified to additional paid-in capital. In connection with the closing of the Company’s IPO, the Company filed an amended and restated certificate of incorporation and adopted amended and restated bylaws, both of which were approved by the Company’s board of directors and stockholders on September 28, 2015 and February 24, 2016, respectively. Pursuant to the amended and restated certificate of incorporation, the Company is now authorized to issue 100,000,000 shares of common stock and 10,000,000 shares of preferred stock. In May 2017, the Company completed a follow-on public offering whereby the Company sold 3,950,190 shares of common stock at a price of $13.25 per share, which included 200,190 shares issued pursuant to the underwriters’ partial exercise of their option to purchase additional shares of common stock. The aggregate net proceeds received by the Company from the offering were approximately $48.7 million, net of underwriting discounts and commissions and estimated offering expenses payable by the Company. Since its inception, the Company has devoted its efforts principally to research and development and raising capital. The Company is subject to risks common to companies in the development stage, including, but not limited to, successful development of therapeutics, obtaining additional funding, protection of proprietary therapeutics, compliance with government regulations, fluctuations in operating results, dependence on key personnel and collaborative partners, and risks associated with industry changes. The Company’s long-term success is dependent upon its ability to successfully develop and market its product candidates, expand its oncology drug pipeline, earn revenue, obtain additional capital when needed, and ultimately, achieve profitable operations. The Company anticipates that it will be two or more years before either entinostat or SNDX-6352 is approved, if ever, and the Company begins to generate revenue from sales of either entinostat or SNDX-6352. Accordingly, management expects to incur substantial losses on the ongoing development of entinostat and SNDX-6352 and does not expect to achieve positive cash flow from operations for the foreseeable future, if ever. As a result, the Company will continue to require additional capital to move forward with its business plan. While certain amounts of this additional capital were raised in the past, there can be no assurance that funds necessary beyond these amounts will be available in amounts or on terms sufficient to ensure ongoing operations. The Company’s management believes that the cash, cash equivalents and short-term investments balances as of June 30, 2017 should enable the Company to maintain its planned operations for at least the next 12 months. The Company’s ability to fund all of its planned operations internally beyond that date, including the completion of its ongoing and planned clinical trial activities, may be substantially dependent upon whether the Company can obtain sufficient funding on terms acceptable to the Company. Proceeds from additional capital transactions would allow the Company to accelerate and/or expand its planned research and development activities. In the event that sufficient funds are not available, the Company may be required to delay or reduce expenditures to conserve cash, which could involve scaling back or curtailing development and general and administrative activities.

Basis of Presentation	6 Months Ended
Basis of Presentation	Jun. 30, 2017
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, 2017, and the results of operations and comprehensive loss for the three and six months ended June 30, 2017 and 2016, and cash flows for the six months ended June 30, 2017 and 2016. The results for the three and six months ended June 30, 2017 are not necessarily indicative of the results to be expected for the year ending December 31, 2017, 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, 2016, 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 14, 2017. 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 Accounting Policies	6 Months Ended
Summary of Significant Accounting Policies	Jun. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	3. Summary of Significant Accounting Policies Significant Accounting Policies The Company’s significant accounting policies are disclosed in the audited consolidated financial statements for the year ended December 31, 2016 and the notes thereto, which are included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 14, 2017, have had no material changes during the six months ended June 30, 2017. 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. Other Assets Other assets consist of deferred issuance costs, long-term security deposits and noncurrent restricted cash. Deferred issuance costs consist primarily of direct incremental legal and accounting fees relating to the IPO and other public offerings, which are deferred until completion of the offering, at which time they are reclassified to additional paid-in capital as a reduction of the offering proceeds. In the event that the offering is terminated, all costs deferred will be expensed immediately. As of June 30, 2017, and 2016, the Company had no capitalized deferred issuance costs. Research and Development In instances where the Company has entered into cost-sharing arrangements, all research and development costs reimbursed by the collaborators are accounted for as reductions to research and development expense. For the six months ended June 30, 2017, the Company incurred $1.0 million in external costs related to cost-sharing collaborations, of which $0.5 million has been recorded as a reduction to research and development expense. No external costs related to cost-sharing collaborations were incurred for the six months ended June 30, 2016. Recently Issued and Adopted Accounting Pronouncements In May 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting (“ASU 2017-09”). ASU 2017-09 provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. An entity should account for the effects of a modification unless all of the following are met: (1) the fair value (or calculated value or intrinsic value, if such an alternative measurement method is used) of the modified award is the same as the fair value (or calculated value or intrinsic value, if such an alternative measurement method is used) of the original award immediately before the original award is modified. If the modification does not affect any of the inputs to the valuation technique that the entity uses to value the award, the entity is not required to estimate the value immediately before and after the modification; (2) the vesting conditions of the modified award are the same as the vesting conditions of the original award immediately before the original award is modified; (3) the classification of the modified award as an equity instrument or a liability instrument is the same as the classification of the original award immediately before the original award is modified. ASU 2017-09 will be effective for the Company on January 1, 2018. The Company does not expect the adoption of this standard to have a material impact on its consolidated financial statements. In November 2016, the FASB issued ASU 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash” (“ASU 2016-18”). ASU 2016-18 requires that restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The statement of cash flows must also explain the change during the period in the total of cash, cash equivalents, and restricted cash or restricted cash equivalents. ASU 2016-18 will be effective for the Company on January 1, 2018. The Company does not expect the adoption of this standard to have a material impact on its consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”). ASU 2016-09 simplifies several aspects related to the accounting for share-based payment transactions, including the accounting for income taxes, forfeitures, statutory tax withholding requirements and classification on the statement of cash flows. The Company adopted ASU 2016-09 on January 1, 2017, and it did not have a material impact on its condensed consolidated balance sheet, condensed consolidated statement of comprehensive loss and condensed statement of cash flows. As part of the adoption of this guidance, the Company adopted a policy to account for forfeitures as they occur. In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842).” Under ASU 2016-02, lessees will be required to recognize, for all leases of 12 months or more, a liability to make lease payments and a right-of-use asset representing the right to use the underlying asset for the lease term. Additionally, the guidance requires improved disclosures to help users of financial statements better understand the nature of an entity’s leasing activities. This ASU is effective for public reporting companies for interim and annual periods beginning after December 15, 2018, with early adoption permitted, and must be adopted using a modified retrospective approach. The standard will be effective for the Company on January 1, 2019. The Company is in the process of evaluating the effect of the new guidance on the Company’s consolidated financial statements and related disclosures. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”). ASU 2014-09 supersedes the revenue recognition requirements of FASB Accounting Standards Codification (“ASC”) Topic 605, Revenue Recognition and most industry-specific guidance throughout the Accounting Standards Codification, resulting in the creation of FASB ASC Topic 606, Revenue from Contracts with Customers. ASU 2014-09 requires entities to recognize revenue in a way that depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services. Adoption will be permitted using either a retrospective or modified retrospective approach. In July 2015, FASB voted to delay the effective date of the standard by one year to the first quarter of 2018 to provide companies sufficient time to implement the standard. Early adoption will be permitted. The Company plans to adopt ASU 2014-09 on January 1, 2018. In preparation for adoption of ASC 606, we have formed a project team and engaged a third-party professional services firm to assist us with our evaluation. We have completed the assessment phase and are working through the next phases of the adoption project. We are continuing to evaluate which transition approach to use and assessing the effect the adoption of ASC 606 will have on our results of operations, financial position and related disclosures. Our preliminary assessment is that the impact of ASC 606 on our revenue recognition is minimal, but it is too early to make a final determination of transition method and effect of adoption given the many facets of this adoption that need to be considered.

Net Loss per Share Attributable to Common Stockholders

6 Months Ended

Jun. 30, 2017

Earnings Per Share [Abstract]

Net Loss per Share Attributable to Common Stockholders

4. 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,
	2017			2016			2017			2016
	(In thousands, except share and per share data)
Numerator—basic and diluted:
Net loss	$	(13,639	)	$	(8,358	)	$	(26,610	)	$	(18,688	)
Accretion of convertible preferred stock dividends		—			—			—			(2,598	)

Net loss attributable to common stockholders—basic and diluted	$	(13,639	)	$	(8,358	)	$	(26,610	)	$	(21,286	)

Net loss per share attributable to common stockholders—basic and diluted	$	(0.70	)	$	(0.47	)	$	(1.41	)	$	(1.91	)

Denominator—basic and diluted:
Weighted-average common shares used to compute net loss per share—basic and diluted		19,497,581			17,769,514			18,868,089			11,155,525

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,
	2017		2016
Options to purchase common stock		3,281,644		2,715,428
Common stock warrant		357,840		357,840
Restricted stock subject to future vesting		0		11,612

Significant Agreements	6 Months Ended
Significant Agreements	Jun. 30, 2017
Equity [Abstract]
Significant Agreements	5. Significant Agreements UCB Biopharma Sprl In July 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 SNDX-6352, an IND-ready anti-CSF-1R monoclonal antibody. The Company made a nonrefundable upfront payment of $5.0 million to UCB in the third quarter of 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 SNDX-6352, 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 SNDX-6352, except that UCB is performing a limited set of transitional chemistry, manufacturing and control tasks related to SNDX-6352. 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 of these findings, the upfront payment of $5.0 million has been recorded as research and development expense in the consolidated statement of comprehensive loss. Kyowa Hakko Kirin Co., Ltd. On December 19, 2014 (the “Effective Date”), the Company entered into a license agreement (the “KHK License Agreement”) with Kyowa Hakko Kirin Co., Ltd. (“KHK”), under which the Company granted KHK an exclusive license to develop and commercialize entinostat in Japan and Korea. Under the terms of the KHK 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 KHK 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, KHK will receive the right to the intellectual property when and if available. KHK will conduct the development, regulatory approval filings, and commercialization activities of entinostat in Japan and Korea. KHK paid the Company $25.0 million upfront, which included a $7.5 million equity investment of 536,049 shares of Series B-1 convertible preferred stock and a $17.5 million non-refundable cash payment. In addition, to the extent certain development and commercial milestones are achieved, KHK 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 purchase of the Series B-1 and the up-front payment of the license fee were accounted for separately. The Company allocated the amount of consideration related to Series B-1 equal to the fair value of the Series B-1 shares on the Effective Date based on a share price of $14.39 per share, which resulted in $7.7 million of proceeds allocated to the Series B-1 and the remaining consideration of $17.3 million allocated to the up-front license fee. The fair value of the Series B-1 of $14.39 per share was based on a contemporaneous valuation. The Company received $7.5 million and issued the Series B-1 in January 2015 and received the remaining $17.5 million in February 2015. On the date of issuance, the Company recorded accretion of $5.4 million to record the Series B-1 at its redemption value. The Company has concluded that this agreement is within the scope of ASC 605-25, Revenue Recognition, Multiple-Element Arrangements. Pursuant to this guidance, the Company identified the following deliverables: (i) licenses, (ii) clinical supply and manufacturing obligations, (iii) rights to access and use materials and data, and (iv) rights to additional intellectual property. All other potential deliverables included in the arrangement have been deemed either contingent or inconsequential or perfunctory, individually and in the aggregate. Moreover, the Company has evaluated all deliverables included in the KHK License Agreement and determined that there are two units of accounting in connection with its obligations at inception under the KHK License Agreement: (i) license unit of accounting and (ii) rights to additional intellectual property. The first three deliverables identified above comprise the license unit of accounting. The Company concluded that the stand-alone selling price for the rights to additional intellectual property unit of account is immaterial. As such, the entire $17.3 million allocated to the upfront payment was allocated to the license unit of accounting. The arrangement consideration allocated to the license unit of accounting will be recognized as revenue ratably over the Company’s expected services period (currently expected to be through 2029) commencing on the date of the first delivery of the clinical trial materials. In June 2015, the Company began delivering clinical materials to KHK and commenced recognizing revenue from the upfront consideration of $17.3 million. During the six months ended June 30, 2017 and 2016, the Company recognized $0.6 million of revenue associated with the KHK License Agreement. As of June 30, 2017, there was $14.8 million of deferred revenue related to the KHK License Agreement, which is classified as current or long-term in the consolidated balance sheets. In October 2016, the Company entered into a clinical trial co-funding agreement with KHK under which the Company will expand its clinical trial agreement with Eastern Cooperative Oncology Group (the “ECOG Agreement”) to include enrollments from sites in Korea. 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 will provide a fixed level of financial support for the clinical trial through an upfront payment of $695,000 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. During the second quarter of 2016, the ECOG Agreement was amended to provide additional study activities and the contractual obligation increased by $0.8 million. During the first quarter of 2017, the ECOG Agreement was amended to expand the study to include enrollments from sites in Korea and to provide additional study activities and the contractual obligation increased by $2.0 million. As of June 30, 2017, the Company’s aggregate payment obligations under this agreement were approximately $23.4 million; and its remaining payment obligations are approximately $13.7 million over an estimated period of approximately four 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. In June 2014, a development milestone was achieved, and the Company recorded $2.0 million of research and development expense, which has been fully paid. In connection with the Bayer Agreement, the Company issued to Bayer a warrant to purchase the number of shares of the Company’s common stock equal to 1.75% of the shares of common stock outstanding on a fully diluted basis as of the earlier of the date the warrant is exercised or the closing of the IPO. The warrant contains anti-dilution protection to maintain Bayer’s potential ownership at 1.75% of the shares of common stock outstanding on a fully diluted basis, which requires that the actual number of shares of common stock issuable pursuant to the warrant be increased or decreased for any changes in the fully diluted shares of common stock outstanding. The warrant is exercisable at an exercise price of $1.54 per share and expires upon the earlier of the 10-year anniversary of the closing of the IPO or the date of the consummation of a disposition transaction. The warrant was classified as a long-term liability and recorded at fair value with the changes in the fair value recorded in other expense. The Company used the Black-Scholes option-pricing model to determine the fair value of the warrant. Upon the closing of the IPO, the anti-dilution protection for the warrant expired, resulting in the reclassification of the warrant liability to additional paid-in capital. The warrant was re-measured using current assumptions just prior to the reclassification.

Fair Value Measurements

6 Months Ended

Jun. 30, 2017

Fair Value Disclosures [Abstract]

Fair Value Measurements

6. 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 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		Significant
			Prices		Other		Significant
	Total		in Active		Observable		Unobservable
	Carrying		Markets		Inputs		Inputs
	Value		(Level 1)		(Level 2)		(Level 3)
	(In thousands)
June 30, 2017
Assets:
Cash and cash equivalents	$	22,988	$	10,738	$	12,250	$	—
Short-term investments		106,967		—		106,967		—

Total assets	$	129,955	$	10,738	$	119,217	$	—

December 31, 2016
Assets:
Cash and cash equivalents	$	23,844	$	17,089	$	6,755	$	—
Short-term investments		81,486		—		81,486		—

Total assets	$	105,330	$	17,089	$	88,241	$	—

Cash equivalents of $10.7 million as of June 30, 2017 and $17.1 million as of December 31, 2016 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 $12.3 million as of June 30, 2017 and $6.8 million as of December 31, 2016 consisted of highly rated corporate bonds 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 $107.0 million as of June 30, 2017 and $81.5 million as of December 31, 2016 consisted of commercial paper and highly rated corporate bonds 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, 2017, 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, 2017 and 2016. 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, 2017, 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, 2017
Commercial paper	$	35,219	$	73	$	—		$	35,292
Corporate bonds		71,712		1		(38	)		71,675

	$	106,931	$	74	$	(38	)	$	106,967

December 31, 2016
Commercial paper	$	30,125	$	61	$	—		$	30,186
Corporate bonds		51,305		6		(11	)		51,300

	$	81,430	$	67	$	(11	)	$	81,486

A roll-forward of the recurring fair value measurements of the common stock warrant liability and the derivative liability categorized with Level 3 inputs is as follows:


	Common Stock Warrant Liability			Derivative Liability
	(In thousands)
Balance — December 31, 2015	$	2,848		$	133
Change in fair value		1,703			17
Reclassification		(4,551	)		(150	)

Balance — June 30, 2016	$	—		$	—

The common stock warrant liability was recorded at fair value determined by using the Black-Scholes option-pricing model. This method of valuation involves using inputs such as the fair value of the Company’s common stock, stock price volatility, the contractual term of the warrant, risk-free interest rates and dividend yields. Due to the nature of these inputs, the valuation of the warrants was considered a Level 3 measurement. Upon the closing of the IPO, the warrant was reclassified to additional paid-in capital. See Note 5 for further discussion of the accounting for the Bayer common stock warrant as well as for a summary of the significant inputs and assumptions used to determine the fair value of the warrant. The derivative liability related to the contingent success fee owed under the term loans. Upon the completion of an IPO or upon the occurrence of certain change of control or liquidation events, the Company was required to pay a $0.2 million success fee. The Company had recorded the success fee as a derivative financial liability. The initial fair value of the derivative of $0.1 million had been recorded as a debt discount. The term loans were paid in full in October 2015; however, the liability for the success fee survived the repayment of the term loans. Upon completion of the IPO this is no longer accounted for as a derivative, and the success fee of $0.2 million that was payable in June 2018 was included in other long-term liabilities. The success fee was paid in full in March 2017.

Prepaid Expenses and Other Current Assets

6 Months Ended

Jun. 30, 2017

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Prepaid Expenses and Other Current Assets

7. Prepaid Expenses and Other Current Assets


	June 30, 2017		December 31, 2016
	(In thousands)
Short-term deposits	$	2,007	$	1,630
Prepaid insurance		504		168
Interest receivable on short-term investments		419		306
Reimbursable costs		438		262
Prepaid clinical supplies		457		461
Other		286		202

Total prepaid expenses and other current assets	$	4,111	$	3,029

Stock-Based Compensation

6 Months Ended

Jun. 30, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation

8. Stock-Based Compensation

In January 2017, the number of shares of common stock available for issuance under the 2015 Omnibus Incentive Plan (“2015 Plan”), was increased by 728,948 shares due to the automatic increase provision of the 2015 Plan. As of June 30, 2017, the total number of shares of common stock available for issuance under the 2015 Plan was 1,427,340. The Company recognized stock-based compensation expense related to the issuance of stock option awards to employees and non-employees in the condensed consolidated statements of comprehensive loss as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
	(In thousands)
Research and development	$	347	$	256	$	630	$	479
General and administrative		1,101		523		2,195		2,490

Total	$	1,448	$	779	$	2,825	$	2,969

During the six months ended June 30, 2017, the Company granted 842,390 stock options to certain executives and employees. The grant date fair value of these options was $5.5 million, or $6.50 per share on a weighted-average basis, and will be recognized as compensation expense over the requisite service period of three to four years.

There were 45,930 options exercised during the six months ended June 30, 2017, resulting in total proceeds of $0.3 million. The intrinsic value of the options exercised was $0.2 million. In accordance with the Company’s policy, the shares were issued from a pool of shares reserved for issuance under the 2007 and 2015 Plans.

As of June 30, 2017, there was $10.6 million of unrecognized compensation cost related to employee and non-employee unvested stock options and unvested restricted stock share-based compensation arrangements granted under the 2015 and 2007 Plans, which is expected to be recognized over a weighted-average remaining service period of 2.6 years. Stock compensation costs have not been capitalized by the Company.

Upon the closing of the IPO on March 8, 2016, the vesting of certain options granted to two of the Company’s executives immediately vested, in accordance with their employment agreements. The Company recorded $0.7 million of additional stock compensation expense related to this accelerated vesting in March 2016.

Employee Stock Purchase Plan	6 Months Ended
Employee Stock Purchase Plan	Jun. 30, 2017
Postemployment Benefits [Abstract]
Employee Stock Purchase Plan	9. Employee Stock Purchase Plan In January 2017, the number of shares of common stock available for issuance under the 2015 Employee Stock Purchase Plan (“2015 ESPP”), was increased by 182,237 shares as a result of the automatic increase provision of the 2015 ESPP. As of June 30, 2017, the total number of shares of common stock available for issuance under the 2015 ESPP was 432,237. The first offering period has been approved and commences on August 1, 2017 to finish on January 31, 2018.

Stockholders' Equity

6 Months Ended

Jun. 30, 2017

Equity [Abstract]

Stockholders' Equity

10. Stockholders’ Equity

The following table presents the changes in stockholders’ equity for the six months ended June 30, 2017:


	Common Stock $0.0001 Par Value				Additional Paid-In Capital		Accumulated Other Comprehensive Income			Accumulated Deficit			Total Stockholders’ Equity


	Shares		Amount
	(In thousands, except share and per share data)
Balance as of December 31, 2016		18,215,181	$	2	$	389,374	$	56		$	(305,293	)	$	84,139
Proceeds from follow-on offering, net of offering costs of $3,665		3,950,190		—		48,675		—			—			48,675
Proceeds from exercise stock options		45,929		—		269		—			—			269
Vesting of restricted stock		8,543				59		—			—			59
Stock-based compensation expense		—		—		2,825		—			—			2,825
Unrealized gain on short-term investments		—		—		—		(20	)		—			(20	)
Cumulative effect adjustment of adopting ASU 2016-09		—		—		16		—			(16	)		—
Net loss		—		—		—		—			(26,610	)		(26,610	)

Balance as of June 30, 2017		22,219,843	$	2	$	441,218	$	36		$	(331,919	)	$	109,337

Income Taxes	6 Months Ended
Income Taxes	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes The Company has not recorded any net tax provision for the periods presented due to the losses incurred and the need for a full valuation allowance on net deferred tax assets. The difference between the income tax expense at the U.S. federal statutory rate and the recorded provision is primarily due to the valuation allowance provided on all deferred tax assets.

Related-Party Transactions	6 Months Ended
Related-Party Transactions	Jun. 30, 2017
Related Party Transactions [Abstract]
Related-Party Transactions	12. Related-Party Transactions The Company’s chief executive officer and member of the board of directors is also a managing director at MPM Asset Management, LLC, which holds an investment in the Company’s common stock.

Subsequent Event	6 Months Ended
Subsequent Event	Jun. 30, 2017
Subsequent Events [Abstract]
Subsequent Event	13. Subsequent Event The Company considers events and transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. Company has completed an evaluation all subsequent events through the date of this filing of this Quarterly Report on Form 10-Q.

Basis of Presentation (Policies)	6 Months Ended
Basis of Presentation (Policies)	Jun. 30, 2017
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 are disclosed in the audited consolidated financial statements for the year ended December 31, 2016 and the notes thereto, which are included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 14, 2017, have had no material changes during the six months ended June 30, 2017.
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.
Other Assets	Other Assets Other assets consist of deferred issuance costs, long-term security deposits and noncurrent restricted cash. Deferred issuance costs consist primarily of direct incremental legal and accounting fees relating to the IPO and other public offerings, which are deferred until completion of the offering, at which time they are reclassified to additional paid-in capital as a reduction of the offering proceeds. In the event that the offering is terminated, all costs deferred will be expensed immediately. As of June 30, 2017, and 2016, the Company had no capitalized deferred issuance costs.
Research and Development	Research and Development In instances where the Company has entered into cost-sharing arrangements, all research and development costs reimbursed by the collaborators are accounted for as reductions to research and development expense. For the six months ended June 30, 2017, the Company incurred $1.0 million in external costs related to cost-sharing collaborations, of which $0.5 million has been recorded as a reduction to research and development expense. No external costs related to cost-sharing collaborations were incurred for the six months ended June 30, 2016.
Recently Issued and Adopted Accounting Pronouncements	Recently Issued and Adopted Accounting Pronouncements In May 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting (“ASU 2017-09”). ASU 2017-09 provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. An entity should account for the effects of a modification unless all of the following are met: (1) the fair value (or calculated value or intrinsic value, if such an alternative measurement method is used) of the modified award is the same as the fair value (or calculated value or intrinsic value, if such an alternative measurement method is used) of the original award immediately before the original award is modified. If the modification does not affect any of the inputs to the valuation technique that the entity uses to value the award, the entity is not required to estimate the value immediately before and after the modification; (2) the vesting conditions of the modified award are the same as the vesting conditions of the original award immediately before the original award is modified; (3) the classification of the modified award as an equity instrument or a liability instrument is the same as the classification of the original award immediately before the original award is modified. ASU 2017-09 will be effective for the Company on January 1, 2018. The Company does not expect the adoption of this standard to have a material impact on its consolidated financial statements. In November 2016, the FASB issued ASU 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash” (“ASU 2016-18”). ASU 2016-18 requires that restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The statement of cash flows must also explain the change during the period in the total of cash, cash equivalents, and restricted cash or restricted cash equivalents. ASU 2016-18 will be effective for the Company on January 1, 2018. The Company does not expect the adoption of this standard to have a material impact on its consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”). ASU 2016-09 simplifies several aspects related to the accounting for share-based payment transactions, including the accounting for income taxes, forfeitures, statutory tax withholding requirements and classification on the statement of cash flows. The Company adopted ASU 2016-09 on January 1, 2017, and it did not have a material impact on its condensed consolidated balance sheet, condensed consolidated statement of comprehensive loss and condensed statement of cash flows. As part of the adoption of this guidance, the Company adopted a policy to account for forfeitures as they occur. In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842).” Under ASU 2016-02, lessees will be required to recognize, for all leases of 12 months or more, a liability to make lease payments and a right-of-use asset representing the right to use the underlying asset for the lease term. Additionally, the guidance requires improved disclosures to help users of financial statements better understand the nature of an entity’s leasing activities. This ASU is effective for public reporting companies for interim and annual periods beginning after December 15, 2018, with early adoption permitted, and must be adopted using a modified retrospective approach. The standard will be effective for the Company on January 1, 2019. The Company is in the process of evaluating the effect of the new guidance on the Company’s consolidated financial statements and related disclosures. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”). ASU 2014-09 supersedes the revenue recognition requirements of FASB Accounting Standards Codification (“ASC”) Topic 605, Revenue Recognition and most industry-specific guidance throughout the Accounting Standards Codification, resulting in the creation of FASB ASC Topic 606, Revenue from Contracts with Customers. ASU 2014-09 requires entities to recognize revenue in a way that depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services. Adoption will be permitted using either a retrospective or modified retrospective approach. In July 2015, FASB voted to delay the effective date of the standard by one year to the first quarter of 2018 to provide companies sufficient time to implement the standard. Early adoption will be permitted. The Company plans to adopt ASU 2014-09 on January 1, 2018. In preparation for adoption of ASC 606, we have formed a project team and engaged a third-party professional services firm to assist us with our evaluation. We have completed the assessment phase and are working through the next phases of the adoption project. We are continuing to evaluate which transition approach to use and assessing the effect the adoption of ASC 606 will have on our results of operations, financial position and related disclosures. Our preliminary assessment is that the impact of ASC 606 on our revenue recognition is minimal, but it is too early to make a final determination of transition method and effect of adoption given the many facets of this adoption that need to be considered.

Net Loss per Share Attributable to Common Stockholders (Tables)

6 Months Ended

Jun. 30, 2017

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,
	2017			2016			2017			2016
	(In thousands, except share and per share data)
Numerator—basic and diluted:
Net loss	$	(13,639	)	$	(8,358	)	$	(26,610	)	$	(18,688	)
Accretion of convertible preferred stock dividends		—			—			—			(2,598	)

Net loss attributable to common stockholders—basic and diluted	$	(13,639	)	$	(8,358	)	$	(26,610	)	$	(21,286	)

Net loss per share attributable to common stockholders—basic and diluted	$	(0.70	)	$	(0.47	)	$	(1.41	)	$	(1.91	)

Denominator—basic and diluted:
Weighted-average common shares used to compute net loss per share—basic and diluted		19,497,581			17,769,514			18,868,089			11,155,525

Potential Dilutive Securities Excluded from Computation of Diluted Net Loss per Common Share


	June 30,
	2017		2016
Options to purchase common stock		3,281,644		2,715,428
Common stock warrant		357,840		357,840
Restricted stock subject to future vesting		0		11,612

Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2017

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		Significant
			Prices		Other		Significant
	Total		in Active		Observable		Unobservable
	Carrying		Markets		Inputs		Inputs
	Value		(Level 1)		(Level 2)		(Level 3)
	(In thousands)
June 30, 2017
Assets:
Cash and cash equivalents	$	22,988	$	10,738	$	12,250	$	—
Short-term investments		106,967		—		106,967		—

Total assets	$	129,955	$	10,738	$	119,217	$	—

December 31, 2016
Assets:
Cash and cash equivalents	$	23,844	$	17,089	$	6,755	$	—
Short-term investments		81,486		—		81,486		—

Total assets	$	105,330	$	17,089	$	88,241	$	—

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, 2017
Commercial paper	$	35,219	$	73	$	—		$	35,292
Corporate bonds		71,712		1		(38	)		71,675

	$	106,931	$	74	$	(38	)	$	106,967

December 31, 2016
Commercial paper	$	30,125	$	61	$	—		$	30,186
Corporate bonds		51,305		6		(11	)		51,300

	$	81,430	$	67	$	(11	)	$	81,486

Summary of Changes in Fair Value of Common Stock Warrant Liability and Derivative Liability Inputs

A roll-forward of the recurring fair value measurements of the common stock warrant liability and the derivative liability categorized with Level 3 inputs is as follows:


	Common Stock Warrant Liability			Derivative Liability
	(In thousands)
Balance — December 31, 2015	$	2,848		$	133
Change in fair value		1,703			17
Reclassification		(4,551	)		(150	)

Balance — June 30, 2016	$	—		$	—

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Prepaid Expenses and Other Current Assets (Tables)

6 Months Ended

Jun. 30, 2017

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Schedule of Prepaid Expenses and Other Current Assets


	June 30, 2017		December 31, 2016
	(In thousands)
Short-term deposits	$	2,007	$	1,630
Prepaid insurance		504		168
Interest receivable on short-term investments		419		306
Reimbursable costs		438		262
Prepaid clinical supplies		457		461
Other		286		202

Total prepaid expenses and other current assets	$	4,111	$	3,029

Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Share Based Compensation Expense Related to Issuance of Stock Option Awards to Employees and Non Employees

The Company recognized stock-based compensation expense related to the issuance of stock option awards to employees and non-employees in the condensed consolidated statements of comprehensive loss as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
	(In thousands)
Research and development	$	347	$	256	$	630	$	479
General and administrative		1,101		523		2,195		2,490

Total	$	1,448	$	779	$	2,825	$	2,969

Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2017

Equity [Abstract]

Summary of Changes in Stockholders' Equity

The following table presents the changes in stockholders’ equity for the six months ended June 30, 2017:


	Common Stock $0.0001 Par Value				Additional Paid-In Capital		Accumulated Other Comprehensive Income			Accumulated Deficit			Total Stockholders’ Equity


	Shares		Amount
	(In thousands, except share and per share data)
Balance as of December 31, 2016		18,215,181	$	2	$	389,374	$	56		$	(305,293	)	$	84,139
Proceeds from follow-on offering, net of offering costs of $3,665		3,950,190		—		48,675		—			—			48,675
Proceeds from exercise stock options		45,929		—		269		—			—			269
Vesting of restricted stock		8,543				59		—			—			59
Stock-based compensation expense		—		—		2,825		—			—			2,825
Unrealized gain on short-term investments		—		—		—		(20	)		—			(20	)
Cumulative effect adjustment of adopting ASU 2016-09		—		—		16		—			(16	)		—
Net loss		—		—		—		—			(26,610	)		(26,610	)

Balance as of June 30, 2017		22,219,843	$	2	$	441,218	$	36		$	(331,919	)	$	109,337

Nature of Business - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		6 Months Ended
	May 31, 2017	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2017	Dec. 31, 2016
Nature of Business [Line Items]
Proceeds from public stock offering, net of issuance costs				$ 52,318
Common stock, shares authorized			100,000,000			100,000,000
Preferred stock, shares authorized			10,000,000			10,000,000
Aggregate net proceeds received from the offering, net of underwriting discounts and commissions and estimated offering expenses payable			$ 48,836
Minimum [Member] \| Entinostat or SNDX-6352 [Member]
Nature of Business [Line Items]
Anticipated period of approval			2 years
Initial Public Offering [Member]
Nature of Business [Line Items]
Common stock, shares issued		4,809,475
Sale of stock, price per share		$ 12.00
Proceeds from public stock offering, net of issuance costs		$ 50,500
Underwriting discounts and commissions		4,000
Offering expenses		$ 3,100
Convertible preferred stock converted in to common stock		12,872,551
Shares of Common Stock Issuable Under the Warrant		357,840
Reclassification of common stock warrant liability to additional paid-in capital		$ 4,600
Common stock, shares authorized					100,000,000
Preferred stock, shares authorized					10,000,000
Over-Allotment Option [Member]
Nature of Business [Line Items]
Common stock, new shares issued	200,190	409,475
Follow-on Public Offering [Member]
Nature of Business [Line Items]
Common stock, new shares issued	3,950,190
Sale of stock, price per share	$ 13.25
Aggregate net proceeds received from the offering, net of underwriting discounts and commissions and estimated offering expenses payable	$ 48,700

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Summary Of Significant Accounting Policies [Line Items]
Capitalized deferred issuance costs	$ 0	$ 0
Cost-Sharing Collaborations [Member]
Summary Of Significant Accounting Policies [Line Items]
External costs related to cost-sharing collaborations	1,000,000	$ 0
Cost-sharing collaborations recorded as a reduction to research and development expense	$ 500,000

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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator-basic and diluted:
Net loss	$ (13,639)	$ (8,358)	$ (26,610)	$ (18,688)
Accretion of convertible preferred stock dividends				(2,598)
Net loss attributable to common stockholders-basic and diluted	$ (13,639)	$ (8,358)	$ (26,610)	$ (21,286)
Net loss per share attributable to common stockholders-basic and diluted	$ (0.70)	$ (0.47)	$ (1.41)	$ (1.91)
Denominator-basic and diluted:
Weighted-average common shares used to compute net loss per share-basic and diluted	19,497,581	17,769,514	18,868,089	11,155,525

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, 2017	Jun. 30, 2016
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	3,281,644	2,715,428
Common Stock Warrant [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	357,840	357,840
Restricted Stock Subject to Future Vesting [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	0	11,612

Significant Agreements - Additional Information (Detail) - USD ($)		1 Months Ended						3 Months Ended				6 Months Ended		12 Months Ended
	Dec. 19, 2014	Jul. 31, 2016	Feb. 28, 2015	Jan. 31, 2015	Jun. 30, 2014	Mar. 31, 2014	Mar. 31, 2007	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2007
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense								$ 9,862,000			$ 6,131,000	$ 19,414,000	$ 10,917,000
Up-front payment allocated to preferred stock value
License Agreement [Member] \| Kyowa Hakko Kirin Co., Ltd. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License agreement upfront payment received	$ 25,000,000
Period of termination after first commercial sale of first licensed product	15 years
Up-front payment allocated to license fee	$ 17,300,000
Up-front license fee received			$ 17,500,000
Revenue recognized during period												600,000	$ 600,000
Deferred revenue from license agreement								14,800,000				14,800,000
License Agreement [Member] \| Kyowa Hakko Kirin Co., Ltd. [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payment receivable upon achievement of development and commercial milestone	$ 75,000,000
License Agreement [Member] \| Kyowa Hakko Kirin Co., Ltd. [Member] \| Series B-1 [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Preferred stock issued, shares	536,049
Preferred share price per share				$ 14.39
Up-front payment allocated to preferred stock value	$ 7,700,000
Proceeds received from preferred stock issuance				$ 7,500,000
Accretion to redemption value				$ 5,400,000
License Agreement [Member] \| Bayer Pharma AG [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense					$ 2,000,000										$ 2,000,000
Up-front license fee paid							$ 2,000,000
Percentage of shares issuable upon conversion of warrant														1.75%
Warrant expiration period														10 years
Warrant exercisable														$ 1.54
License Agreement [Member] \| Bayer Pharma AG [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate payment obligation							$ 150,000,000
Clinical Trial [Member] \| Eastern Cooperative Oncology Group [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront milestone payable						$ 695,000
Milestone payment payable						$ 1,000,000
Increase in contractual obligation									$ 2,000,000		$ 800,000
Aggregate payment obligation								23,400,000				23,400,000
Remaining contractual obligation								$ 13,700,000				$ 13,700,000
Period of contractual obligation												4 years
UCB License Agreement [Member] \| UCB Biopharma [Member]
Collaborative Arrangements and Non-collaborative 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		$ 5,000,000

Fair Value Measurements - Schedule of Fair Values of Financial Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	$ 106,967	$ 81,486
Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	22,988	23,844
Short-term investments	106,967	81,486
Total assets	129,955	105,330
Quoted Prices in Active Markets Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	10,738	17,089
Total assets	10,738	17,089
Significant Other Observable Inputs Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	12,250	6,755
Short-term investments	106,967	81,486
Total assets	$ 119,217	$ 88,241

Fair Value Measurements - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Oct. 31, 2015
Fair Value Measurements [Line Items]
Available for sale debt securities fair value	$ 106,967,000		$ 81,486,000
Realized gains or losses recognized on the sale or maturity of available-for-sale securities	0	$ 0
Corporate Bonds [Member]
Fair Value Measurements [Line Items]
Available for sale debt securities fair value	71,675,000		51,300,000
Term Loan [Member]
Fair Value Measurements [Line Items]
Initial fair value of derivative recorded as debt discount				$ 100,000
Initial Public Offering [Member] \| Term Loan [Member] \| Success Fee Payable [Member]
Fair Value Measurements [Line Items]
Success fee payable included in other long-term liabilities	200,000
Quoted Prices in Active Markets Level 1 [Member]
Fair Value Measurements [Line Items]
Cash equivalents fair value	10,738,000		17,089,000
Quoted Prices in Active Markets Level 1 [Member] \| Overnight Investments and Money Market Funds [Member]
Fair Value Measurements [Line Items]
Cash equivalents fair value	10,700,000		17,100,000
Significant Other Observable Inputs Level 2 [Member]
Fair Value Measurements [Line Items]
Cash equivalents fair value	12,250,000		6,755,000
Significant Other Observable Inputs Level 2 [Member] \| Corporate Bonds and Commercial Paper [Member]
Fair Value Measurements [Line Items]
Available for sale debt securities fair value	107,000,000		81,500,000
Significant Other Observable Inputs Level 2 [Member] \| Corporate Bonds [Member]
Fair Value Measurements [Line Items]
Cash equivalents fair value	$ 12,300,000		$ 6,800,000

Fair Value Measurements - Summary of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 106,931	$ 81,430
Unrealized Gains	74	67
Unrealized Losses	(38)	(11)
Fair Value	106,967	81,486
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	35,219	30,125
Unrealized Gains	73	61
Fair Value	35,292	30,186
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	71,712	51,305
Unrealized Gains	1	6
Unrealized Losses	(38)	(11)
Fair Value	$ 71,675	$ 51,300

Fair Value Measurements - Summary of Changes in Fair Value of Common Stock Warrant Liability and Derivative Liability Inputs (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Change in fair value		$ (1,703)
Reclassification		$ 4,551
Significant Unobservable Inputs Level 3 [Member] \| Derivative Liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 133
Change in fair value	17
Reclassification	(150)
Common Stock Warrant Liability [Member] \| Significant Unobservable Inputs Level 3 [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	2,848
Change in fair value	1,703
Reclassification	$ (4,551)

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Short-term deposits	$ 2,007	$ 1,630
Prepaid insurance	504	168
Interest receivable on short-term investments	419	306
Reimbursable costs	438	262
Prepaid clinical supplies	457	461
Other	286	202
Total prepaid expenses and other current assets	$ 4,111	$ 3,029

Stock-Based Compensation - Additional Information (Detail) $ / shares in Units, $ in Thousands		1 Months Ended	6 Months Ended
	Mar. 08, 2017 Executives	Mar. 31, 2016 USD ($)	Jun. 30, 2017 USD ($) $ / shares shares	Jan. 31, 2017 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options exercised, shares \| shares			45,930
Stock options exercised			$ 269
Intrinsic value of options exercised			$ 200
Initial Public Offering [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of company executives \| Executives	2
Additional stock compensation expense		$ 700
2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance \| shares			1,427,340
2015 Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance \| shares				728,948
2007 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option granted to certain executives and employees \| shares			842,390
Options grant date fair value amount			$ 5,500
Weighted average grant date fair value of options \| $ / shares			$ 6.50
2015 and 2007 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock option			$ 10,600
Weighted average period to recognize compensation expense			2 years 7 months 6 days

Stock-Based Compensation - Share Based Compensation Expense Related to Issuance of Stock Option Awards to Employees and Non Employees (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 1,448	$ 779	$ 2,825	$ 2,969
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	347	256	630	479
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 1,101	$ 523	$ 2,195	$ 2,490

Employee Stock Purchase Plan - Additional Information (Detail) - shares	Jun. 30, 2017	Jan. 31, 2017
2015 ESPP [Member]
Employee Benefit Plans [Line Items]
Common stock available for issuance	432,237	182,237

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Class of Stock [Line Items]
Beginning balance				$ 84,139
Proceeds from exercise stock options, value				$ 269
Proceeds from exercise stock options, shares				45,930
Vesting of restricted stock, Value				$ 59
Stock-based compensation expense				2,825
Unrealized gain on short-term investments				(20)
Net loss		$ (13,639)	$ (8,358)	(26,610)	$ (18,688)
Ending balance		109,337		109,337
Common Stock [Member]
Class of Stock [Line Items]
Beginning balance				$ 2
Beginning balance, Shares				18,215,181
Proceeds from exercise stock options, shares				45,929
Vesting of restricted stock, Shares				8,543
Ending balance		$ 2		$ 2
Ending balance, Shares		22,219,843		22,219,843
Additional Paid-In Capital [Member]
Class of Stock [Line Items]
Beginning balance				$ 389,374
Proceeds from exercise stock options, value				269
Vesting of restricted stock, Value				59
Stock-based compensation expense				2,825
Ending balance		$ 441,218		441,218
Accumulated Other Comprehensive Income [Member]
Class of Stock [Line Items]
Beginning balance				56
Unrealized gain on short-term investments				(20)
Ending balance		36		36
Accumulated Deficit [Member]
Class of Stock [Line Items]
Beginning balance				(305,293)
Net loss				(26,610)
Ending balance		$ (331,919)		(331,919)
Follow-on Public Offering [Member]
Class of Stock [Line Items]
Proceeds from follow-on offering, Value				$ 48,675
Proceeds from follow-on offering, shares	3,950,190
Follow-on Public Offering [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Proceeds from follow-on offering, shares				3,950,190
Follow-on Public Offering [Member] \| Additional Paid-In Capital [Member]
Class of Stock [Line Items]
Proceeds from follow-on offering, Value				$ 48,675
Accounting Standards Update 2016-09 [Member] \| Additional Paid-In Capital [Member]
Class of Stock [Line Items]
Cumulative effect adjustment of adopting ASU 2016-09				16
Accounting Standards Update 2016-09 [Member] \| Accumulated Deficit [Member]
Class of Stock [Line Items]
Cumulative effect adjustment of adopting ASU 2016-09				$ (16)

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Parenthetical) (Detail) - Follow-on Public Offering [Member] $ in Thousands	6 Months Ended
	Jun. 30, 2017 USD ($)
Class of Stock [Line Items]
Net offering costs	$ 3,665
Common Stock [Member]
Class of Stock [Line Items]
Net offering costs	$ 3,665

Income Taxes - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Net tax provision	$ 0	$ 0