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Prepaid Expenses and Other Current Assets

Significant Agreements

5. Significant Agreements

Merck KGaA – Pfizer Collaboration – On December 31, 2015, the Company entered into a clinical trial collaboration and supply agreement with Ares Trading, S.A., a subsidiary of Merck KGaA, Darmstadt, Germany, and Pfizer Inc. (the “Alliance”) under which it will conduct a clinical trial evaluating entinostat in combination with an investigational monoclonal antibody, avelumab, in patients with ovarian cancer. Avelumab is being developed collaboratively by the Alliance, which are together treated as a single party for purposes of this agreement. The Company will be the sponsor of the clinical trial. The Alliance will supply avelumab for use in the clinical trial. During the term of the trial or the term of the agreement, whichever is shorter, each party has agreed not to initiate any clinical trial in combination with such party’s drug and a third party drug for the treatment of ovarian cancer if the third party drug has the same target and mechanism of action as the other party’s drug, subject to certain exceptions. To the extent any inventions arise from the clinical trial, each party will solely own inventions relating to its drug alone, and the parties will jointly own any inventions relating to the combination of the two drugs. In most cases, data from the trial will be jointly owned. However, each party will solely own certain sample analysis data generated from clinical samples obtained from trial participants. Either party may terminate the agreement for the other party’s uncured material breach. In addition, either party may terminate the agreement if it determines that the trial may unreasonably affect patient safety, or if a regulatory authority takes an action that prevents such party from supplying its drug, or if such party decides to discontinue development of its drug. The Alliance may also terminate the agreement if the Company fails to make any changes to the clinical trial protocol that are reasonably requested by the Alliance to address a perceived safety issue.

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. To the extent additional intellectual property is developed during the term of the agreement, KHK will receive a license 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. Unless terminated earlier in accordance with the terms of the agreement, it 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 upfront 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 upfront 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 will be 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. For the three months ended March 31, 2016, the Company recognized $0.3 million of revenue associated with the KHK License Agreement. As of March 31, 2016, there was $16.4 million of deferred revenue related to the KHK License Agreement, which is classified as current or long-term in the condensed consolidated balance sheets.

Eastern Cooperative Oncology Group – In March 2014, the Company entered into a clinical trial agreement (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. As of March 31, 2016, the Company’s aggregate payment obligations under this agreement were approximately $20.6 million; and the Company’s remaining payment obligations are approximately $17.6 million over an estimated period of approximately five years. In April 2016, the ECOG Agreement was amended to provide additional study activities and the contractual obligation increased $0.5 million.

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 FDA or 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.

The total shares exercisable under the warrant, the fair value associated with the warrant and the Black-Scholes option-pricing model assumptions used to value the shares of common stock issuable pursuant to the warrant were as follows:


	Total Shares of Common Stock Issuable Under the Warrant		Average Exercise Price		Fair Value of Common Stock		Estimated Volatility			Risk-Free Interest Rate			Estimated Dividend Yield			Estimated Remaining Contractual Life (in years)		Fair Value of Warrant Liability
(In thousands, except share and per share data)
March 31, 2015		136,563	$	1.54	$	6.88		73	%		1.72	%		0.0	%		7.25	$	825
March 8, 2016		357,840	$	1.54	$	13.55		69	%		1.82	%		0.0	%		10.00	$	4,551

Fair Value Measurements

3 Months Ended

Mar. 31, 2016

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
	Total Carrying Value		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(In thousands)
December 31, 2015
Assets:
Cash equivalents	$	23,154	$	9,208	$	13,946	$	—
Short-term investments		63,310		—		63,310		—

Total assets	$	86,464	$	9,208	$	77,256	$	—

Liabilities:
Derivative liability	$	133	$	—	$	—	$	133
Common stock warrant liability		2,848		—		—		2,848

Total liabilities	$	2,981	$	—	$	—	$	2,981

March 31, 2016
Assets:
Cash equivalents	$	21,890	$	18,354	$	3,536	$	—
Short-term investments		110,483		—		110,483		—

Total assets	$	132,373	$	18,354	$	114,019	$	—

Cash equivalents of $18.4 million as of March 31, 2016 and $9.2 million as of December 31, 2015 consisted of 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 $3.5 million as of March 31, 2016 and $13.9 million as of December 31, 2015 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 $110.5 million as of March 31, 2016 and $63.3 million as of December 31, 2015 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 March 31, 2016, 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, 2016 and 2015; and 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, 2016, 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 Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(In thousands)
December 31, 2015
Commercial paper	$	28,980	$	48	$	—		$	29,028
Corporate bonds		34,302		—		(20	)		34,282

	$	63,282	$	48	$	(20	)	$	63,310

March 31, 2016
Commercial paper	$	66,152	$	221	$	—		$	66,373
Corporate bonds		44,103		8		(1	)		44,110

	$	110,255	$	229	$	(1	)	$	110,483

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, 2014	$	693		$	126
Change in fair value		132			4

Balance—March 31, 2015	$	825		$	130


	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—March 31, 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 is 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 is payable in June 2018 is included in other long-term liabilities.

Prepaid Expenses and Other Current Assets

3 Months Ended

Mar. 31, 2016

Text Block [Abstract]

7. Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following:


	March 31, 2016		December 31, 2015
	(In thousands)
Short-term deposits	$	654	$	805
Prepaid insurance		573		34
Interest receivable on short-term investments		345		258
Prepaid clinical supplies		321		210
Other		152		157

Total prepaid expenses and other current assets	$	2,045	$	1,464

Accrued Expenses and Other Current Liabilities

3 Months Ended

Mar. 31, 2016

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

8. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:


	March 31, 2016		December 31, 2015
	(In thousands)
Accrued clinical costs	$	2,306	$	574
Accrued professional fees		613		561
Accrued compensation and related costs		454		698
Other		217		342

Total accrued expenses	$	3,590	$	2,175

Convertible Preferred Stock

3 Months Ended

Mar. 31, 2016

Convertible Preferred Stock

9. Convertible Preferred Stock

Convertible preferred stock consisted of the following as of December 31, 2015:


	Preferred Shares Designated		Issuance Date	Preferred Shares Issued and Outstanding		Liquidation Preference		Carrying Value
(In thousands, except share and per share data)
Series A-1		3,160,975	March 2013		2,801,745	$	48,032	$	65,666
Series B		3,382,113	March and August 2013		272,240	$	2,933	$	5,084
Series B-1		3,965,411	March, April, July, August and November 2013 and January 2015		3,568,020	$	96,348	$	96,348
Series C-1		6,090,481	June and August 2015		6,090,461	$	152,015	$	152,015

Total								$	319,113

Series A		3,512,194	March and August 2013		700,435	$	—	$	7,231

Upon the closing of the IPO, all of the outstanding shares of the Company’s convertible preferred stock were converted into 12,872,551 shares of its common stock. As of March 31, 2016, the Company does not have any convertible preferred stock issued or outstanding.

Stock-Based Compensation

3 Months Ended

Mar. 31, 2016

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

Stock-Based Compensation

10. Stock-Based Compensation

In September 2015, the Company’s board of directors adopted its 2015 Omnibus Incentive Plan (“2015 Plan”), which was subsequently approved by its stockholders and became effective upon the closing of the IPO on March 8, 2016. The 2015 Plan replaces the 2007 Stock Plan (“2007 Plan”). The 2015 Plan allows for the granting of incentive stock options, nonqualified stock options, stock appreciate rights, restricted stock, unrestricted stock, stock units, dividend equivalent rights, performance awards, annual incentive awards, and other equity-based awards to the Company’s executives and other employees, non-employee members of the board of directors, and consultants of the Company. Any options or awards outstanding under the Company’s 2007 Plan remain outstanding and effective. Any shares of common stock related to awards outstanding under the 2007 Plan which thereafter terminate by expiration, forfeiture, cancellation or otherwise without the issuance of such shares will be added to, and included in, the 2015 Plan reserve amount. The Company initially reserved 1,750,000 shares of its common stock for the issuance of awards under the 2015 Plan. The 2015 Plan provides that the number of shares reserved and available for issuance under the 2015 Plan will automatically increase each January 1, beginning on January 1, 2017, by 4% of the outstanding number of shares of common stock on the immediately preceding December 31 or such lesser number of shares as determined by the Company’s board of directors. As of March 31, 2016, there were 1,750,000 shares available for issuance under the 2015 Plan.

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 March 31,
	2016		2015
	(In thousands)
Research and development	$	223	$	64
General and administrative		1,967		260

Total	$	2,190	$	324

During the three months ended March 31, 2016, the Company granted 150,480 stock options to certain executives and employees. The grant date fair value of these options was $1.0 million, or $6.82 per share on a weighted-average basis, and will be recognized as compensation expense over the requisite service period of three to four years.

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.

As of March 31, 2016, there was $7.9 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 2007 Plan, which is expected to be recognized over a weighted-average remaining service period of 2.8 years. Stock compensation costs have not been capitalized by the Company.

Employee Stock Purchase Plan	3 Months Ended
Employee Stock Purchase Plan	Mar. 31, 2016
Postemployment Benefits [Abstract]
Employee Stock Purchase Plan	11. Employee Stock Purchase Plan In September 2015, the Company’s board of directors adopted its 2015 Employee Stock Purchase Plan (“2015 ESPP”), which was subsequently approved by its stockholders and became effective upon the closing of the IPO on March 8, 2016. The 2016 ESPP authorizes the initial issuance of up to a total of 250,000 shares of the Company’s common stock to participating employees. The Company’s compensation committee will determine the length and duration of the offering periods. As of March 31, 2016, no offering periods have been approved.

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	12. 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	3 Months Ended
Related-Party Transactions	Mar. 31, 2016
Related Party Transactions [Abstract]
Related-Party Transactions	13. Related-Party Transactions In June 2015, the Company hired a Chief Executive Officer who was also appointed as a member of the Board. This individual is also a managing director at MPM Asset Management, LLC, which holds an investment in the Company’s common stock. In September and October 2014, the Company issued $5.0 million of convertible unsecured promissory notes (“2014 Notes”) to stockholders of the Company. As of March 31 2015, an aggregate of $5.0 million of principal outstanding under the 2014 Notes and $0.2 million of related accrued interest were held by stockholders of the Company. Interest expense related to the 2014 Notes held by these stockholders was $0.1 million for three months ended March 31, 2015. The 2014 Notes were converted into 465,563 shares of Series C-1 in June 2015, in conjunction with the Series C-1 financing.

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

Stockholders' Equity (Deficit)

3 Months Ended

Mar. 31, 2016

Stockholders' Equity (Deficit)

14. Stockholders’ Equity (Deficit)

The following table presents the changes in convertible preferred stock and stockholders’ equity (deficit) for the three months ended March 31, 2016:


	Convertible Preferred Stock $0.001 Par Value						Series A Convertible Preferred Stock $0.001 Par Value						Common Stock $0.0001 Par Value				Additional Paid-In Capital			Accumulated Other Comprehensive Income		Accumulated Deficit			Total Stockholders' Equity (Deficit)
	Shares			Amount			Shares			Amount			Shares		Amount		Additional Paid-In Capital			Accumulated Other Comprehensive Income		Accumulated Deficit			Total Stockholders' Equity (Deficit)
							(In thousands, except share and per share data)
Balance as of December 31, 2015		12,732,466		$	319,113			700,435		$	7,231			85,440	$	1	$	—		$	28	$	(259,675	)	$	(252,415	)
Accretion for convertible preferred stock dividends		—			2,598						—			—		—		(1,452	)		—		(1,146	)		(2,598	)
Proceeds from IPO, net of offering costs of $7,186		—			—			—			—			4,809,475		—		50,527			—		—			50,527
Conversion of preferred stock into common stock		(12,732,466	)		(321,711	)		(700,435	)		(7,231	)		12,872,551		1		328,941			—		—			321,711
Reclassification of common stock warrant liability		—			—			—			—			—		—		4,551			—		—			4,551
Vesting of restricted stock		—			—			—			—			1,536		—		10								10
Stock-based compensation expense		—			—			—			—			—		—		2,190			—		—			2,190
Unrealized gain on short-term investments		—			—			—			—			—		—		—			200		—			200
Net loss		—			—			—			—			—		—		—			—		(10,330	)		(10,330	)

Balance as of March 31, 2016		—		$	—			—		$	—			17,769,002	$	2	$	384,767		$	228	$	(271,151	)	$	113,846

Computation of Basic and Diluted Net Loss per Share Attributable to Common Stockholders

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29-31)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Subparagraph (SAB TOPIC 4.C)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

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-Topic 505
-SubTopic 10
-Section S99
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-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

+ Details

Basis of Presentation (Policies)	3 Months Ended
Basis of Presentation (Policies)	Mar. 31, 2016
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.
Reverse Stock Split	On February 24, 2016, the Company effected a 1-for-1.25 reverse stock split of the Company’s outstanding common stock and convertible preferred stock. Stockholders entitled to fractional shares as a result of the reverse stock split will receive a cash payment in lieu of receiving fractional shares. All of the Company’s historical share and per share information shown in the accompanying financial statements and related notes have been retroactively adjusted to give effect to this reverse stock split.
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, 2015 and the notes thereto, which are included in the Prospectus, have had no material changes during the three months ended March 31, 2016.
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 issuance of debt. As of March 31, 2016 and December 31, 2015, the Company had capitalized deferred IPO issuance costs of $0 and $1.6 million, respectively. These costs were deferred until the completion of the IPO, at which time they were reclassified to additional paid-in capital as a reduction of the IPO proceeds.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”). ASU 2014-09 supersedes the revenue recognition requirements of the FASB’s Accounting Standards Codification (“ASC”) Topic 605, Revenue Recognition, and most industry-specific guidance throughout the ASC, 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. In March 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net), (“ASU 2016-08”), which amends ASU 2014-09 to clarify the implementation guidance on principal versus agent considerations (gross versus net revenue presentation). ASU 2016-08 does not change the core principle of the guidance stated in ASU 2014-09, instead, the amendments in this ASU are intended to improve the operability and understandability of the implementation guidance on principal versus agent considerations and whether an entity reports revenue on a gross or net basis. Adoption of both ASU 2016-08 and 2014-09 will be permitted using either a retrospective or modified retrospective approach. In July 2015, the 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. The collective guidance will be effective for the Company on January 1, 2018, with early adoption permitted but not before January 1, 2017. The Company is currently evaluating the method by which it will implement these standards and the impact of the adoption of these standards on the Company’s condensed consolidated financial statements. 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 Company is in the process of evaluating the effect of the new guidance on its condensed consolidated financial statements and disclosures. 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. ASU 2016-09 will be effective for the Company on January 1, 2017 with early adoption permitted. The Company is currently evaluating the impact that the adoption of ASU 2016-09 will have on the Company’s condensed consolidated financial statements.
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. Certain amounts have been reclassified to conform to the current period presentation. 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, 2016, and the results of operations, comprehensive loss, and cash flows for the three months ended March 31, 2016 and 2015. The results for the three months ended March 31, 2016 are not necessarily indicative of the results to be expected for the year ending December 31, 2016, 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, 2015, and the notes thereto, which are included in the Company’s Prospectus that forms a part of the Company’s Registration Statement on Form S-1 (File No. 333-208861), which was filed with the Securities and Exchange Commission (the “SEC”) pursuant to Rule 424 on March 3, 2016 (the “Prospectus”).

Net Loss per Share Attributable to Common Stockholders (Tables)

3 Months Ended

Mar. 31, 2016

Earnings Per Share [Abstract]

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,
	2016			2015
	(In thousands, except share and per share data)
Numerator—basic and diluted:
Net loss	$	(10,330	)	$	(4,911	)
Accretion of convertible preferred stock dividends		(2,598	)		(1,749	)
Accretion of convertible preferred stock to redemption value		—			(5,412	)

Net loss attributable to common stockholders—basic and diluted	$	(12,928	)	$	(12,072	)

Net loss per share attributable to common stockholders—basic and diluted	$	(2.85	)	$	(206.30	)

Denominator—basic and diluted:
Weighted-average common shares used to compute net loss per share—basic and diluted		4,541,536			58,517

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


	March 31,
	2016		2015
Convertible preferred stock		—		6,782,090
Options to purchase common stock		2,717,539		826,455
Common stock warrants		357,840		136,563
Convertible notes and related accrued interest		—		368,805
Restricted stock subject to future vesting		13,148		—

Significant Agreements (Tables)

3 Months Ended

Mar. 31, 2016

Schedule of Assumptions Used to Value Shares of Common Stock Issuable Pursuant to Warrant


	Total Shares of Common Stock Issuable Under the Warrant		Average Exercise Price		Fair Value of Common Stock		Estimated Volatility			Risk-Free Interest Rate			Estimated Dividend Yield			Estimated Remaining Contractual Life (in years)		Fair Value of Warrant Liability
(In thousands, except share and per share data)
March 31, 2015		136,563	$	1.54	$	6.88		73	%		1.72	%		0.0	%		7.25	$	825
March 8, 2016		357,840	$	1.54	$	13.55		69	%		1.82	%		0.0	%		10.00	$	4,551

Tabular disclosure of warrants or rights issued. Warrants and rights outstanding are derivative securities that give the holder the right to purchase securities (usually equity) from the issuer at a specific price within a certain time frame. Warrants are often included in a new debt issue to entice investors by a higher return potential. The main difference between warrants and call options is that warrants are issued and guaranteed by the company, whereas options are exchange instruments and are not issued by the company. Also, the lifetime of a warrant is often measured in years, while the lifetime of a typical option is measured in months. Disclose the title of issue of securities called for by warrants and rights outstanding, the aggregate amount of securities called for by warrants and rights outstanding, the date from which the warrants or rights are exercisable, and the price at which the warrant or right is exercisable.

Schedule of Fair Values of Financial Assets and Liabilities Measured at Fair Value

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2016

Fair Value Disclosures [Abstract]

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
	Total Carrying Value		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(In thousands)
December 31, 2015
Assets:
Cash equivalents	$	23,154	$	9,208	$	13,946	$	—
Short-term investments		63,310		—		63,310		—

Total assets	$	86,464	$	9,208	$	77,256	$	—

Liabilities:
Derivative liability	$	133	$	—	$	—	$	133
Common stock warrant liability		2,848		—		—		2,848

Total liabilities	$	2,981	$	—	$	—	$	2,981

March 31, 2016
Assets:
Cash equivalents	$	21,890	$	18,354	$	3,536	$	—
Short-term investments		110,483		—		110,483		—

Total assets	$	132,373	$	18,354	$	114,019	$	—

Summary of Available-for-Sale Securities

The following table summarizes the available-for-sale securities:


	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(In thousands)
December 31, 2015
Commercial paper	$	28,980	$	48	$	—		$	29,028
Corporate bonds		34,302		—		(20	)		34,282

	$	63,282	$	48	$	(20	)	$	63,310

March 31, 2016
Commercial paper	$	66,152	$	221	$	—		$	66,373
Corporate bonds		44,103		8		(1	)		44,110

	$	110,255	$	229	$	(1	)	$	110,483

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, 2014	$	693		$	126
Change in fair value		132			4

Balance—March 31, 2015	$	825		$	130


	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—March 31, 2016	$	—		$	—

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.

Schedule of Prepaid Expenses and Other Current Assets

Prepaid Expenses and Other Current Assets (Tables)

3 Months Ended

Mar. 31, 2016

Text Block [Abstract]

Prepaid expenses and other current assets consisted of the following:


	March 31, 2016		December 31, 2015
	(In thousands)
Short-term deposits	$	654	$	805
Prepaid insurance		573		34
Interest receivable on short-term investments		345		258
Prepaid clinical supplies		321		210
Other		152		157

Total prepaid expenses and other current assets	$	2,045	$	1,464

Accrued Expenses and Other Current Liabilities (Tables)

3 Months Ended

Mar. 31, 2016

Payables and Accruals [Abstract]

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:


	March 31, 2016		December 31, 2015
	(In thousands)
Accrued clinical costs	$	2,306	$	574
Accrued professional fees		613		561
Accrued compensation and related costs		454		698
Other		217		342

Total accrued expenses	$	3,590	$	2,175

Convertible Preferred Stock (Tables)

3 Months Ended

Mar. 31, 2016

Schedule of Convertible Preferred Stock

Convertible preferred stock consisted of the following as of December 31, 2015:


	Preferred Shares Designated		Issuance Date	Preferred Shares Issued and Outstanding		Liquidation Preference		Carrying Value
(In thousands, except share and per share data)
Series A-1		3,160,975	March 2013		2,801,745	$	48,032	$	65,666
Series B		3,382,113	March and August 2013		272,240	$	2,933	$	5,084
Series B-1		3,965,411	March, April, July, August and November 2013 and January 2015		3,568,020	$	96,348	$	96,348
Series C-1		6,090,481	June and August 2015		6,090,461	$	152,015	$	152,015

Total								$	319,113

Series A		3,512,194	March and August 2013		700,435	$	—	$	7,231

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2016

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


	Three Months Ended March 31,
	2016		2015
	(In thousands)
Research and development	$	223	$	64
General and administrative		1,967		260

Total	$	2,190	$	324

Stockholders' Equity (Deficit) (Tables)

3 Months Ended

Mar. 31, 2016

Summary of Changes in Convertible Preferred Stock and Stockholders' Equity (Deficit)

The following table presents the changes in convertible preferred stock and stockholders’ equity (deficit) for the three months ended March 31, 2016:


	Convertible Preferred Stock $0.001 Par Value						Series A Convertible Preferred Stock $0.001 Par Value						Common Stock $0.0001 Par Value				Additional Paid-In Capital			Accumulated Other Comprehensive Income		Accumulated Deficit			Total Stockholders' Equity (Deficit)
	Shares			Amount			Shares			Amount			Shares		Amount		Additional Paid-In Capital			Accumulated Other Comprehensive Income		Accumulated Deficit			Total Stockholders' Equity (Deficit)
							(In thousands, except share and per share data)
Balance as of December 31, 2015		12,732,466		$	319,113			700,435		$	7,231			85,440	$	1	$	—		$	28	$	(259,675	)	$	(252,415	)
Accretion for convertible preferred stock dividends		—			2,598						—			—		—		(1,452	)		—		(1,146	)		(2,598	)
Proceeds from IPO, net of offering costs of $7,186		—			—			—			—			4,809,475		—		50,527			—		—			50,527
Conversion of preferred stock into common stock		(12,732,466	)		(321,711	)		(700,435	)		(7,231	)		12,872,551		1		328,941			—		—			321,711
Reclassification of common stock warrant liability		—			—			—			—			—		—		4,551			—		—			4,551
Vesting of restricted stock		—			—			—			—			1,536		—		10								10
Stock-based compensation expense		—			—			—			—			—		—		2,190			—		—			2,190
Unrealized gain on short-term investments		—			—			—			—			—		—		—			200		—			200
Net loss		—			—			—			—			—		—		—			—		(10,330	)		(10,330	)

Balance as of March 31, 2016		—		$	—			—		$	—			17,769,002	$	2	$	384,767		$	228	$	(271,151	)	$	113,846

Nature of Business - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended
	Mar. 11, 2016	Mar. 08, 2016	Mar. 31, 2016	Dec. 31, 2015
Nature of Business [Line Items]
Entity incorporation date			Oct. 11, 2005
Proceeds from public stock offering, net of issuance costs			$ 53,549
Underwriting discounts and commissions	$ 300
Reclassification of common stock warrant liability to additional paid-in capital			$ 4,551
Common stock, shares authorized			100,000,000	20,800,000
Preferred stock, shares authorized			10,000,000	10,000,000
Initial Public Offering [Member]
Nature of Business [Line Items]
Common stock, shares issued		4,400,000
Sale of stock, price per share		$ 12.00
Proceeds from public stock offering, net of issuance costs		$ 46,000
Underwriting discounts and commissions		3,700
Offering expenses		$ 3,100
Convertible preferred stock converted in to common stock		12,872,551	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, shares issued	409,475
Sale of stock, price per share	$ 12.00
Proceeds from public stock offering, net of issuance costs	$ 4,600

Basis of Presentation - Additional Information (Detail)	Feb. 24, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Stock split, conversion ratio	0.8

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Initial Public Offering [Member]
Summary Of Significant Accounting Policies [Line Items]
Capitalized deferred issuance costs	$ 0.0	$ 1.6

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, 2016	Mar. 31, 2015
Numerator-basic and diluted:
Net loss	$ (10,330)	$ (4,911)
Accretion of convertible preferred stock dividends	(2,598)	(1,749)
Accretion of convertible preferred stock to redemption value		(5,412)
Net loss attributable to common stockholders-basic and diluted	$ (12,928)	$ (12,072)
Net loss per share attributable to common stockholders-basic and diluted	$ (2.85)	$ (206.30)
Denominator-basic and diluted:
Weighted-average common shares used to compute net loss per share-basic and diluted	4,541,536	58,517

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.