0000950170-24-089241 | 10-Q | XBRL Viewer | Syndax Pharmaceuticals INC

Basis of Presentation	6 Months Ended
Jun. 30, 2024
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, or 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, 2024, and the results of operations and comprehensive loss for the three and six months ended June 30, 2024 and 2023, and cash flows for the six months ended June 30, 2024 and 2023. The results for the three and six months ended June 30, 2024 are not necessarily indicative of the results to be expected for the year ending December 31, 2024, 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, 2023, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K as filed with the Securities and Exchange Commission, or the SEC, on February 27, 2024. In 2011, the Company established a wholly owned subsidiary in the United Kingdom, which the Company dissolved in June 2024. In 2014, the Company established a wholly owned U.S. subsidiary, and in 2021, the Company established a wholly owned subsidiary in the Netherlands. To date, there have been no material activities for these entities. All intercompany balances and transactions have been eliminated in consolidation.

Basis of Presentation

6 Months Ended

Jun. 30, 2024

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, or 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, 2024, and the results of operations and comprehensive loss for the three and six months ended June 30, 2024 and 2023, and cash flows for the six months ended June 30, 2024 and 2023. The results for the three and six months ended June 30, 2024 are not necessarily indicative of the results to be expected for the year ending December 31, 2024, 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, 2023, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K as filed with the Securities and Exchange Commission, or the SEC, on February 27, 2024.

In 2011, the Company established a wholly owned subsidiary in the United Kingdom, which the Company dissolved in June 2024. In 2014, the Company established a wholly owned U.S. subsidiary, and in 2021, the Company established a wholly owned subsidiary in the Netherlands. To date, there have been no material activities for these entities. All intercompany balances and transactions have been eliminated in consolidation.

Stockholders' Equity

6 Months Ended

Jun. 30, 2024

Equity [Abstract]

Stockholders' Equity

11. Stockholders’ Equity

The following table presents the changes in stockholders’ equity for the three and six months ended June 30, 2024:


(In thousands, except share data)	Common Stock $0.0001 Par Value				Additional Paid-In Capital		Accumulated Other Comprehensive (Loss)/Income			Accumulated Deficit			Total Stockholders’ Equity
	Shares		Amount
Balance as of December 31, 2023		84,826,632	$	8	$	1,456,370	$	218		$	(902,400	)	$	554,196
Stock purchase under ESPP		35,463		—		—		—			—			—
Stock-based compensation expense		—		—		8,899		—			—			8,899
Unrealized loss on investments		—		—		—		(974	)		—			(974	)
Vesting of RSUs		3,750		—		—		—			—			—
Employee withholdings ESPP		—		—		309		—			—			309
Proceeds from exercise of stock options		113,841		—		1,859		—			—			1,859
Net loss		—		—		—		—			(72,400	)		(72,400	)
Balance as of March 31, 2024		84,979,686	$	8	$	1,467,437	$	(756	)	$	(974,800	)	$	491,889
Stock-based compensation expense		—		—		9,896		—			—			9,896
Unrealized loss on investments		—		—		—		(61	)		—			(61	)
Vesting of RSUs		1,603		—		—		—			—			—
Employee withholdings ESPP		—		—		237		—			—			237
Proceeds from exercise of stock options		47,340		—		439		—			—			439
Par value adjustment		—		1		—		—			—			1
Net loss		—		—		—		—			(68,063	)		(68,063	)
Balance as of June 30, 2024		85,028,629	$	9	$	1,478,009	$	(817	)	$	(1,042,863	)	$	434,338

The following table presents the changes in stockholders’ equity for the three and six months ended June 30, 2023:


(In thousands, except share data)	Common Stock $0.0001 Par Value				Additional Paid-In Capital			Accumulated Other Comprehensive (Loss)/Income			Accumulated Deficit			Total Stockholders’ Equity
	Shares		Amount
Balance as of December 31, 2022		68,111,385	$	7	$	1,161,288		$	(806	)	$	(693,040	)	$	467,449
Stock purchase under ESPP		16,537		—		—			—			—			—
Stock-based compensation expense		—		—		6,238			—			—			6,238
Unrealized gain on short-term investments		—		—		—			470			—			470
Vesting of RSUs		5,000		—		—			—			—			—
Employee withholdings ESPP		—		—		196			—			—			196
Prefunded warrants, exercise		85,998		—		—			—			—			—
Proceeds from exercise of stock options		276,506		—		2,278			—			—			2,278
Net loss		—		—		—			—			(41,126	)		(41,126	)
Balance as of March 31, 2023		68,495,426	$	7	$	1,170,000		$	(336	)	$	(734,166	)	$	435,505
Stock-based compensation expense		—		—		8,065			—			—			8,065
Unrealized loss on short-term investments		—		—		—			(238	)		—			(238	)
Vesting of RSUs		1,602		—		—			—			—			—
Employee withholdings ESPP		—		—		179			—			—			179
Prefunded warrants, exercise		771,133		—		(1	)		—			—			(1	)
Proceeds from exercise of stock options		163,037		—		1,146			—			—			1,146
Net loss		—		—		—			—			(44,615	)		(44,615	)
Balance as of June 30, 2023		69,431,198	$	7	$	1,179,389		$	(574	)	$	(778,781	)	$	400,041

At-the Market Program

In May 2023, the Company entered into a sales agreement with Cowen and Company, or TD Cowen, under which the Company could, from time to time, issue and sell shares of its common stock having aggregate sales proceeds of up to $200.0 million, in a series of one or more ATM equity offerings, or the 2023 ATM Program. TD Cowen is not required to sell any specific share amounts but acts as the Company’s sales agent, using commercially reasonable efforts consistent with its normal trading and sales practices. Pursuant to the sales agreement, shares will be sold pursuant to the previous shelf registration statement on Form S-3ASR (Registration No. 333-277424), which became automatically effective upon the filing on February 27,2024. The Company’s common

stock will be sold at prevailing market prices at the time of the sale, and as a result, prices may vary. For the period ended June 30, 2024, the Company sold no shares of common stock under the 2023 ATM Program.

Pre-Funded Warrants

In December 2021, the Company sold pre-funded warrants to purchase 1,142,856 shares of common stock. As of June 30, 2024, 285,714 pre-funded warrants were considered issued and outstanding.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478448/946-505-50-6

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480237/815-40-50-6

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/505/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-16

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

+ Details

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Class of Stock [Line Items]
Beginning balance	$ 491,889	$ 554,196	$ 435,505	$ 467,449	$ 554,196	$ 467,449
Stock-based compensation expense	9,896	8,899	8,065	6,238
Unrealized loss on investments	(61)	(974)	$ (238)	470	(817)	232
Prefunded warrants, exercise, shares			(1)
Employee withholdings ESPP	237	309	$ 179	196
Proceeds from exercise of stock options	439	1,859	1,146	2,278
Par value adjustment	1
Net Income (Loss)	(68,063)	(72,400)	(44,615)	(41,126)	(140,463)	(85,741)
Ending balance	434,338	491,889	400,041	435,505	434,338	400,041
Common Stock [Member]
Class of Stock [Line Items]
Beginning balance	$ 8	$ 8	$ 7	$ 7	$ 8	$ 7
Beginning balance, shares	84,979,686	84,826,632	68,495,426	68,111,385	84,826,632	68,111,385
Stock purchase under ESPP, shares		35,463		16,537
Vesting of RSUs, shares	1,603	3,750	1,602	5,000
Prefunded warrants, exercise, shares			771,133	85,998
Proceeds from exercise of stock options, shares	47,340	113,841	163,037	276,506
Par value adjustment	$ 1
Ending balance	$ 9	$ 8	$ 7	$ 7	$ 9	$ 7
Ending balance, shares	85,028,629	84,979,686	69,431,198	68,495,426	85,028,629	69,431,198
Additional Paid-In Capital [Member]
Class of Stock [Line Items]
Beginning balance	$ 1,467,437	$ 1,456,370	$ 1,170,000	$ 1,161,288	$ 1,456,370	$ 1,161,288
Stock-based compensation expense	9,896	8,899	$ 8,065	6,238
Prefunded warrants, exercise, shares			(1)
Employee withholdings ESPP	237	309	$ 179	196
Proceeds from exercise of stock options	439	1,859	1,146	2,278
Ending balance	1,478,009	1,467,437	1,179,389	1,170,000	1,478,009	1,179,389
Accumulated Other Comprehensive(Loss) / Income [Member]
Class of Stock [Line Items]
Beginning balance	(756)	218	(336)	(806)	218	(806)
Unrealized loss on investments	(61)	(974)	(238)	470
Ending balance	(817)	(756)	(574)	(336)	(817)	(574)
Accumulated Deficit [Member]
Class of Stock [Line Items]
Beginning balance	(974,800)	(902,400)	(734,166)	(693,040)	(902,400)	(693,040)
Net Income (Loss)	(68,063)	(72,400)	(44,615)	(41,126)
Ending balance	$ (1,042,863)	$ (974,800)	$ (778,781)	$ (734,166)	$ (1,042,863)	$ (778,781)

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 105,396	$ 295,394
Short-term investments	319,701	275,304
Short-term deposits	7,170	6,885
Other receivable	9,582	0
Prepaid expenses and other current assets	4,207	3,293
Total current assets	446,056	580,876
Long-term investments	29,516	29,829
Property and equipment, net	2	8
Right-of-use asset, net	1,000	1,487
Restricted cash	217	217
Other assets	156	463
Total assets	476,947	612,880
Current liabilities:
Accounts payable	11,568	9,961
Collaboration payable, net	3,102	7,232
Accrued expenses and other current liabilities	26,809	39,856
Current portion of right-of-use liability	981	1,035
Current portion of capital lease	12	12
Total current liabilities	42,472	58,096
Long-term liabilities:
Right-of-use liability, less current portion	133	578
Capital lease, less current portion	4	10
Total long-term liabilities	137	588
Total liabilities	42,609	58,684
Commitments and contingencies (Note 12)
Stockholders’ equity:
Preferred stock, $0.001 par value, 10,000,000 shares authorized; 0 shares outstanding at June 30, 2024 and December 31, 2023	0	0
Common stock, $0.0001 par value, 200,000,000 shares authorized; 85,028,629 and 84,826,632 shares issued and outstanding at June 30, 2024 and December 31, 2023, respectively	9	8
Additional paid-in capital	1,478,009	1,456,370
Accumulated other comprehensive (loss) gain	(817)	218
Accumulated deficit	(1,042,863)	(902,400)
Total stockholders’ equity	434,338	554,196
Total liabilities and stockholders’ equity	$ 476,947	$ 612,880

Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2024
Accounting Policies [Abstract]
Significant Accounting Policies	The Company’s significant accounting policies, which are disclosed in the audited consolidated financial statements for the year ended December 31, 2023, and the notes thereto are included in the Company’s Annual Report on Form 10-K that was filed with the SEC on February 27, 2024. Since the date of filing, there have been no material changes to the Company’s significant accounting policies except as noted below.
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. Estimates and assumptions about future events and their effects cannot be determined with certainty and therefore require the exercise of judgment. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, assumptions and judgments or revise the carrying value of its assets or liabilities. These estimates may change as new events occur and additional information is obtained and are recognized in the consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the Company’s condensed consolidated financial statements.
Significant Risks and Uncertainties	Significant Risks and Uncertainties We are subject to challenges and risks specific to our business and our ability to execute on our strategy, as well as risks and uncertainties common to companies in the pharmaceutical industry with development and commercial operations, including, without limitation, risks and uncertainties associated with: obtaining regulatory approval of our late-stage product candidate; delays or problems in the supply of our products, loss of single source suppliers or failure to comply with manufacturing regulations; identifying, acquiring or in-licensing additional products or product candidates; pharmaceutical product development and the inherent uncertainty of clinical success; the challenges of protecting and enhancing our intellectual property rights; and complying with applicable regulatory requirements.
Recently Issued and Adopted Accounting Pronouncements	Recently Issued and Adopted Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board, or FASB, or other accounting standard setting bodies that we adopt as of the specified effective date. Unless otherwise discussed below, we do not believe that the adoption of recently issued standards have or may have a material impact on our consolidated statements or disclosures. Segment Reporting In December 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which requires all public entities, including public entities with a single reportable segment, to provide in interim and annual periods one or more measures of segment profit or loss used by the chief operating decision maker to allocate resources and assess performance. Additionally, the standard requires disclosures of significant segment expenses and other segment items as well as incremental qualitative disclosures. The guidance in this update is effective for fiscal years beginning after December 15, 2023, and interim periods after December 15, 2024. The Company is currently in the process of evaluating the effects of this pronouncement on our related disclosures.

Summary of Significant Accounting Policies	6 Months Ended
Summary of Significant Accounting Policies	Jun. 30, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	3. Summary of Significant Accounting Policies The Company’s significant accounting policies, which are disclosed in the audited consolidated financial statements for the year ended December 31, 2023, and the notes thereto are included in the Company’s Annual Report on Form 10-K that was filed with the SEC on February 27, 2024. Since the date of filing, there have been no material changes to the Company’s significant accounting policies except as noted below. 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. Estimates and assumptions about future events and their effects cannot be determined with certainty and therefore require the exercise of judgment. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, assumptions and judgments or revise the carrying value of its assets or liabilities. These estimates may change as new events occur and additional information is obtained and are recognized in the consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the Company’s condensed consolidated financial statements. Significant Risks and Uncertainties We are subject to challenges and risks specific to our business and our ability to execute on our strategy, as well as risks and uncertainties common to companies in the pharmaceutical industry with development and commercial operations, including, without limitation, risks and uncertainties associated with: obtaining regulatory approval of our late-stage product candidate; delays or problems in the supply of our products, loss of single source suppliers or failure to comply with manufacturing regulations; identifying, acquiring or in-licensing additional products or product candidates; pharmaceutical product development and the inherent uncertainty of clinical success; the challenges of protecting and enhancing our intellectual property rights; and complying with applicable regulatory requirements. Recently Issued and Adopted Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board, or FASB, or other accounting standard setting bodies that we adopt as of the specified effective date. Unless otherwise discussed below, we do not believe that the adoption of recently issued standards have or may have a material impact on our consolidated statements or disclosures. Segment Reporting In December 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which requires all public entities, including public entities with a single reportable segment, to provide in interim and annual periods one or more measures of segment profit or loss used by the chief operating decision maker to allocate resources and assess performance. Additionally, the standard requires disclosures of significant segment expenses and other segment items as well as incremental qualitative disclosures. The guidance in this update is effective for fiscal years beginning after December 15, 2023, and interim periods after December 15, 2024. The Company is currently in the process of evaluating the effects of this pronouncement on our related disclosures.

Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2024

Fair Value Disclosures [Abstract]

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

The table below presents information about the Company’s assets and liabilities that are regularly measured and carried at fair value and indicate the level within the fair value hierarchy of valuation techniques the Company utilized to determine such fair values (in thousands):


	Fair Value Measurements Using
			Quoted
			Prices		Significant
			(unadjusted)		Other		Significant
	Total		in Active		Observable		Unobservable
	Carrying		Markets		Inputs		Inputs
	Value		(Level 1)		(Level 2)		(Level 3)
	(In thousands)
June 30, 2024
Assets:
Cash and cash equivalents	$	105,396	$	105,396	$	—	$	—
Short-term investments		319,701		—		319,701		—
Long-term investments		29,516		—		29,516		—
Total assets	$	454,613	$	105,396	$	349,217	$	—
December 31, 2023
Assets:
Cash and cash equivalents	$	295,394	$	295,394	$	—	$	—
Short-term investments		275,304		—		275,304		—
Long-term investments		29,829		—		29,829		—
Total assets	$	600,527	$	295,394	$	305,133	$	—

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, 2024
Commercial paper	$	125,696	$	—	$	(73	)	$	125,623
Corporate bonds		40,037		—		(68	)		39,969
US Treasury		177,303		—		(669	)		176,634
Federal bonds		6,998		—		(7	)		6,991
	$	350,034	$	—	$	(817	)	$	349,217
December 31, 2023
Commercial paper	$	160,657	$	149	$	—		$	160,806
Corporate bonds		47,150		62		—			47,212
US Treasury		68,111		46		—			68,157
Federal bonds		28,998		—		(40	)		28,958
	$	304,916	$	257	$	(40	)	$	305,133

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-9

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

+ Details

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Jun. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Net Loss per Share Attributable to Common Stockholders

6 Months Ended

Jun. 30, 2024

Earnings Per Share [Abstract]

Net Loss per Share Attributable to Common Stockholders

5. Net Loss per Share Attributable to Common Stockholders

Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding for the period. Because the Company has reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods. The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company:


	Three Months Ended June 30,						Six Months Ended June 30,
	2024			2023			2024			2023
	(In thousands, except share and per share data)						(In thousands, except share and per share data)
Numerator—basic and diluted:
Net loss	$	(68,063	)	$	(44,615	)	$	(140,463	)	$	(85,741	)
Net loss attributable to common stockholders—basic and diluted	$	(68,063	)	$	(44,615	)	$	(140,463	)	$	(85,741	)
Net loss per share attributable to common stockholders—basic and diluted	$	(0.80	)	$	(0.64	)	$	(1.65	)	$	(1.23	)
Denominator—basic and diluted:
Weighted-average number of common shares used to compute net loss per share attributable to common stockholders—basic and diluted		85,274,829			69,638,427			85,244,015			69,539,209

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,
	2024		2023
Options to purchase common stock		12,226,274		10,429,475
Employee Stock Purchase Plan		29,426		15,331
Non-vested restricted stock units (RSUs)		1,486,146		526,736

For additional information related to the Company’s common stock see Note 10.

Fair Value Measurements

6 Months Ended

Jun. 30, 2024

Fair Value Disclosures [Abstract]

Fair Value Measurements

7. Fair Value Measurements

The carrying amounts of cash and cash equivalents, restricted cash, accounts payable, and accrued expenses approximated their estimated fair values due to the short-term nature of these financial instruments. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value are performed in a manner to maximize the use of observable inputs and minimize the use of unobservable inputs. The accounting standard describes a fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable, that may be used to measure fair value, which are the following:

Level 1— Quoted prices (unadjusted) in active markets that are accessible at the market date for identical unrestricted assets or liabilities.

Level 2— Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs for which all significant inputs are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3— Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.


	Fair Value Measurements Using
			Quoted
			Prices		Significant
			(unadjusted)		Other		Significant
	Total		in Active		Observable		Unobservable
	Carrying		Markets		Inputs		Inputs
	Value		(Level 1)		(Level 2)		(Level 3)
	(In thousands)
June 30, 2024
Assets:
Cash and cash equivalents	$	105,396	$	105,396	$	—	$	—
Short-term investments		319,701		—		319,701		—
Long-term investments		29,516		—		29,516		—
Total assets	$	454,613	$	105,396	$	349,217	$	—
December 31, 2023
Assets:
Cash and cash equivalents	$	295,394	$	295,394	$	—	$	—
Short-term investments		275,304		—		275,304		—
Long-term investments		29,829		—		29,829		—
Total assets	$	600,527	$	295,394	$	305,133	$	—

There have been no material impairments of our assets measured and carried at fair value during the period ended June 30, 2024 and 2023. In addition, there have been no changes in valuation techniques during the periods ended June 30, 2024 and 2023. The fair value of Level 1 instruments classified as cash equivalents are valued using quoted market prices in active markets. The fair value of Level 2 instruments classified as cash equivalents and short and long-term investments are determined based on quoted prices in active markets, which are either directly or indirectly observable as of the reporting date with fair value being determined using models or other valuation methodologies.

The Company’s short and long-term investments are classified as available-for-sale securities. As of June 30, 2024, the remaining contractual maturities of the available-for-sale securities were 1 to 16 months, and the balance in the Company’s accumulated other comprehensive loss 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 and six months ended June 30, 2024 and 2023. As a result, the Company did not reclassify any amounts out of accumulated other comprehensive loss for the same periods. The Company has a limited number of available-for-sale securities that are not in significant loss positions as of June 30, 2024, which the Company does not intend to sell, and it 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, 2024
Commercial paper	$	125,696	$	—	$	(73	)	$	125,623
Corporate bonds		40,037		—		(68	)		39,969
US Treasury		177,303		—		(669	)		176,634
Federal bonds		6,998		—		(7	)		6,991
	$	350,034	$	—	$	(817	)	$	349,217
December 31, 2023
Commercial paper	$	160,657	$	149	$	—		$	160,806
Corporate bonds		47,150		62		—			47,212
US Treasury		68,111		46		—			68,157
Federal bonds		28,998		—		(40	)		28,958
	$	304,916	$	257	$	(40	)	$	305,133

Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2024	Jul. 25, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
Trading Symbol	SNDX
Entity Registrant Name	Syndax Pharmaceuticals, Inc.
Entity Central Index Key	0001395937
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock
Security Exchange Name	NASDAQ
Entity File Number	001-37708
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	32-0162505
Entity Address, Address Line One	35 Gatehouse Drive
Entity Address, Address Line Two	Building D
Entity Address, Address Line Three	Floor 3
Entity Address, City or Town	Waltham
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02451
City Area Code	781
Local Phone Number	419-1400
Document Quarterly Report	true
Document Transition Report	false
Entity Common Stock, Shares Outstanding		85,096,358

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (140,463)	$ (85,741)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	6	6
Accretion of investments	(7,470)	(7,685)
Non-cash operating lease expense	486	259
Stock-based compensation	18,795	14,303
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(890)	459
Collaboration (payable) receivable, net	(4,129)	3,967
Other receivable	(9,582)	0
Accounts payable	1,607	6,629
Accrued expenses and other liabilities	(13,553)	(6,796)
Net cash used in operating activities	(155,193)	(74,599)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of short and long-term investments	(167,385)	(142,593)
Proceeds from sales and maturities of short-term investments	129,736	236,415
Net cash (used in) provided by investing activities	(37,649)	93,822
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from Employee Stock Purchase Plan	546	374
Proceeds from stock option exercises	2,298	3,424
Net cash provided by financing activities	2,844	3,798
NET (DECREASE) INCREASE CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(189,998)	23,021
CASH, CASH EQUIVALENTS AND RESTRICTED CASH—beginning of period	295,611	74,471
CASH, CASH EQUIVALENTS AND RESTRICTED CASH —end of period	$ 105,613	$ 97,492

Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2024

Equity [Abstract]

Summary of Changes in Stockholders' Equity

The following table presents the changes in stockholders’ equity for the three and six months ended June 30, 2024:


(In thousands, except share data)	Common Stock $0.0001 Par Value				Additional Paid-In Capital		Accumulated Other Comprehensive (Loss)/Income			Accumulated Deficit			Total Stockholders’ Equity
	Shares		Amount
Balance as of December 31, 2023		84,826,632	$	8	$	1,456,370	$	218		$	(902,400	)	$	554,196
Stock purchase under ESPP		35,463		—		—		—			—			—
Stock-based compensation expense		—		—		8,899		—			—			8,899
Unrealized loss on investments		—		—		—		(974	)		—			(974	)
Vesting of RSUs		3,750		—		—		—			—			—
Employee withholdings ESPP		—		—		309		—			—			309
Proceeds from exercise of stock options		113,841		—		1,859		—			—			1,859
Net loss		—		—		—		—			(72,400	)		(72,400	)
Balance as of March 31, 2024		84,979,686	$	8	$	1,467,437	$	(756	)	$	(974,800	)	$	491,889
Stock-based compensation expense		—		—		9,896		—			—			9,896
Unrealized loss on investments		—		—		—		(61	)		—			(61	)
Vesting of RSUs		1,603		—		—		—			—			—
Employee withholdings ESPP		—		—		237		—			—			237
Proceeds from exercise of stock options		47,340		—		439		—			—			439
Par value adjustment		—		1		—		—			—			1
Net loss		—		—		—		—			(68,063	)		(68,063	)
Balance as of June 30, 2024		85,028,629	$	9	$	1,478,009	$	(817	)	$	(1,042,863	)	$	434,338

The following table presents the changes in stockholders’ equity for the three and six months ended June 30, 2023:


(In thousands, except share data)	Common Stock $0.0001 Par Value				Additional Paid-In Capital			Accumulated Other Comprehensive (Loss)/Income			Accumulated Deficit			Total Stockholders’ Equity
	Shares		Amount
Balance as of December 31, 2022		68,111,385	$	7	$	1,161,288		$	(806	)	$	(693,040	)	$	467,449
Stock purchase under ESPP		16,537		—		—			—			—			—
Stock-based compensation expense		—		—		6,238			—			—			6,238
Unrealized gain on short-term investments		—		—		—			470			—			470
Vesting of RSUs		5,000		—		—			—			—			—
Employee withholdings ESPP		—		—		196			—			—			196
Prefunded warrants, exercise		85,998		—		—			—			—			—
Proceeds from exercise of stock options		276,506		—		2,278			—			—			2,278
Net loss		—		—		—			—			(41,126	)		(41,126	)
Balance as of March 31, 2023		68,495,426	$	7	$	1,170,000		$	(336	)	$	(734,166	)	$	435,505
Stock-based compensation expense		—		—		8,065			—			—			8,065
Unrealized loss on short-term investments		—		—		—			(238	)		—			(238	)
Vesting of RSUs		1,602		—		—			—			—			—
Employee withholdings ESPP		—		—		179			—			—			179
Prefunded warrants, exercise		771,133		—		(1	)		—			—			(1	)
Proceeds from exercise of stock options		163,037		—		1,146			—			—			1,146
Net loss		—		—		—			—			(44,615	)		(44,615	)
Balance as of June 30, 2023		69,431,198	$	7	$	1,179,389		$	(574	)	$	(778,781	)	$	400,041

Commitments and Contingencies	6 Months Ended
Commitments and Contingencies	Jun. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	12. Commitments and Contingencies From time to time, the Company may be subject to various claims and proceedings in the ordinary course of business. If the potential loss from any claim, asserted or unasserted, or proceeding is considered probable and the amount is reasonably estimable, the Company will accrue a liability for the estimated loss. There were no contingent liabilities recorded as of June 30, 2024

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, 2024	Jun. 30, 2023
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per common share	12,226,274	10,429,475
Employee Stock Purchase Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per common share	29,426	15,331
Non-Vested Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per common share	1,486,146	526,736

Nature of Business - Additional Information (Detail)	6 Months Ended
Nature of Business - Additional Information (Detail)	Jun. 30, 2024 Segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments	1
State of incorporation	DE

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued clinical study and trial costs	$ 17,516	$ 16,346
Accrued compensation and related costs	7,779	11,172
Accrued professional fees	1,294	1,450
Accrued milestone costs	0	10,000
Other	220	888
Total accrued expenses and other current liabilities	$ 26,809	$ 39,856

Stock-Based Compensation - Share Based Compensation Expense Related to Issuance of Stock Option Awards to Employees and Non Employees Related to Employee Stock Purchase Plan (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 9,896	$ 8,065	$ 18,795	$ 14,303
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	4,318	3,698	8,461	6,476
Selling, General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 5,578	$ 4,367	$ 10,334	$ 7,827

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 1D
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480483/718-10-35-1D

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480483/718-10-35-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(02)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(03)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(04)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(02)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(03)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(v)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

Other Receivables (Additional Information) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2024 USD ($)
Other Receivables, Net, Current [Abstract]
Refundable fee payble	$ 6.1
Payment for fully-refundable fee	6.1
Receivables Related to Achieved Milestones	$ 3.5

Accrued Expenses and Other Current Liabilities

6 Months Ended

Jun. 30, 2024

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

9. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):


	June 30, 2024		December 31, 2023
Accrued clinical study and trial costs	$	17,516	$	16,346
Accrued compensation and related costs		7,779		11,172
Accrued professional fees		1,294		1,450
Accrued milestone costs		—		10,000
Other		220		888
Total accrued expenses and other current liabilities	$	26,809	$	39,856

Prepaid Expenses and Other Current Assets (Tables)

6 Months Ended

Jun. 30, 2024

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

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following (in thousands):


	June 30, 2024		December 31, 2023
Prepaid insurance	$	1,555	$	807
Interest receivable on investments		1,300		1,227
Prepaid subscription		633		769
Prepaid state and local taxes		493		264
Prepaid rent		164		163
Other		62		63
Total prepaid expenses and other current assets	$	4,207	$	3,293

Accrued Expenses and Other Current Liabilities (Tables)

6 Months Ended

Jun. 30, 2024

Payables and Accruals [Abstract]

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):


	June 30, 2024		December 31, 2023
Accrued clinical study and trial costs	$	17,516	$	16,346
Accrued compensation and related costs		7,779		11,172
Accrued professional fees		1,294		1,450
Accrued milestone costs		—		10,000
Other		220		888
Total accrued expenses and other current liabilities	$	26,809	$	39,856

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Jan. 01, 2024	Dec. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 9,896	$ 8,065	$ 18,795	$ 14,303
Proceeds from stock option exercises			2,298	3,424
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 1,999	$ 978	$ 3,616	$ 1,760
2015 Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance	3,798,637		3,798,637		3,393,065
2015 and 2007 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock option and RSUs	$ 101,300		$ 101,300
Weighted average period to recognize compensation expense			2 years 9 months 18 days
2023 Inducement Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance	323,150		323,150
Common stock reserved for issuance						1,100,000

Other Receivables

6 Months Ended

Jun. 30, 2024

Other Receivables, Net, Current [Abstract]

Other Receivables

6. Other Receivables

Contemporaneous with the Company’s New Drug Application, or NDA, submission to the U.S. Food and Drug Administration for revumenib, it was required to pay a $6.1 million refundable fee under the Prescription Drug User Fee Act, or PDUFA. The $6.1 million payment was made in January 2024.

In April 2024, entinostat received marketing approval in China. As of June 30, 2024, the Company has recorded a $3.5 million milestone receivable related to achieved milestones under the license agreement with Eddingpharm.

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid insurance	$ 1,555	$ 807
Interest receivable on investments	1,300	1,227
Prepaid subscriptions	633	769
Prepaid state and local taxes	493	264
Prepaid rent	164	163
Other	62	63
Total prepaid expenses and other current assets	$ 4,207	$ 3,293

Fair Value Measurements - Summary of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 350,034	$ 304,916
Unrealized Gains		257
Unrealized Losses	(817)	(40)
Fair Value	349,217	305,133
Commercial Paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	125,696	160,657
Unrealized Gains		149
Unrealized Losses	(73)
Fair Value	125,623	160,806
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	40,037	47,150
Unrealized Gains		62
Unrealized Losses	(68)
Fair Value	39,969	47,212
U.S. Treasury [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	177,303	68,111
Unrealized Gains		46
Unrealized Losses	(669)
Fair Value	176,634	68,157
Federal Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	6,998	28,998
Unrealized Losses	(7)	(40)
Fair Value	$ 6,991	$ 28,958

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 103
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-103

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481830/320-10-45-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

+ Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

+ Details

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2024	Dec. 31, 2023
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	200,000,000	200,000,000
Common stock, shares issued	85,028,629	84,826,632
Common stock, shares outstanding	85,028,629	84,826,632

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (68,063)	$ (72,400)	$ (44,615)	$ (41,126)	$ (140,463)	$ (85,741)

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-9

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 60
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476176/805-60-65-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 323
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (g)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478666/740-323-65-2

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-28

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482765/220-10-50-6

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-3

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-8

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-4

Reference 17: http://www.xbrl.org/2003/role/exampleRef
-Topic 946
-SubTopic 830
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479168/946-830-55-10

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479105/946-220-45-7

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(9))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(1)(d))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 23: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 32: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483499/205-20-50-7

Reference 34: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 35: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1A

Reference 36: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1B

Reference 37: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

+ Details

Significant Collaborative Research and License Agreements

6 Months Ended

Jun. 30, 2024

Research and Development [Abstract]

Significant Collaborative Research and License Agreements

4. Significant Collaborative Research and License Agreements

Incyte Collaboration

In September 2021, the Company entered into the Incyte License and Collaboration Agreement, or the Incyte License, with Incyte covering the worldwide development and commercialization of axatilimab. Also in September 2021, the Company entered into a share purchase agreement with Incyte, or the Incyte Share Purchase Agreement. These agreements are collectively referred to as the Incyte Agreements. Under the terms of the Incyte Agreements, Incyte received exclusive commercialization rights outside of the United States, subject to certain royalty payment obligations set forth below. In the United States, Incyte and the Company will co-commercialize axatilimab, with the Company having the right to co-promote axatilimab with Incyte, subject to the Company’s exercise of its co-promotion option. Incyte will be responsible for leading all aspects of the commercialization of axatilimab in the United States. The Company and Incyte will share equally the profits and losses from co-commercialization efforts in the United States. The Company and Incyte have agreed to co-develop axatilimab and to share development costs associated with global and U.S. – specific clinical trials, with Incyte responsible for 55% of such costs and the Company responsible for 45% of such costs. Each company will be responsible for funding any of its own independent development activities. Incyte is responsible for 100% of future development costs for trials that are specific to ex-U.S. countries. All development costs related to the collaboration will be subject to a joint development plan.

Under the terms of the Incyte Agreements, in December 2021, Incyte paid the Company a non-refundable cash payment of $117.0 million and the Company issued 1,421,523 shares of common stock with an aggregate purchase price of $35.0 million, or $24.62 per share. Additionally, under the terms of the Incyte Agreements, the Company is eligible to receive up to $220.0 million in future contingent development and regulatory milestones and up to $230.0 million in commercialization milestones as well as tiered royalties ranging in the mid-teens percentage on net sales of the licensed product comprising axatilimab in Europe and Japan and low double digit percentage in the rest of the world outside of the United States. The Company’s right to receive royalties in any particular country will expire upon the last to occur of (a) the expiration of licensed patent rights covering the licensed product in that particular country, (b) a specified period of time after the first post - marketing authorization sale of a licensed product in that country, and (c) the expiration of any regulatory exclusivity for that licensed product in that country.

As of June 30, 2024, the Company has recorded approximately $2.0 million as a collaboration receivable due from Incyte related to the Company’s development and pre-commercialization costs under the Incyte Agreements and has recorded approximately $5.1 million as a collaboration payable due to Incyte for development and pre-commercialization costs incurred by Incyte as of June 30, 2024. Both expense and cost offset are recorded as part of research and development expense and general and administrative expense.

Vitae Pharmaceuticals, Inc.

In October 2017, the Company entered into a license agreement, or the Vitae License Agreement, with Vitae Pharmaceuticals, LLC, or Vitae, a subsidiary of AbbVie, Inc., under which the Company was granted an exclusive, sublicensable, worldwide license to a portfolio of preclinical, orally available, small molecule inhibitors of the Menin–KMT2A binding interaction, or the Menin Assets. Subject to the achievement of certain milestone events, the Company may be required to pay Allergan up to $99.0 million in one-time development and regulatory milestone payments over the term of the Vitae License Agreement. In the event that the Company or any of its affiliates or sublicensees commercializes the Menin Assets, the Company will also be obligated to pay Vitae low single to low double-digit royalties on sales, subject to reduction in certain circumstances, as well as up to an aggregate of $70.0 million in potential one-time, sales-based milestone payments based on achievement of certain annual sales thresholds. The Company is solely responsible for the development and commercialization of the Menin Assets. Each party may terminate the Vitae License Agreement for the other

party’s uncured material breach or insolvency, and the Company may terminate the Vitae License Agreement at any time upon advance written notice to Vitae. Vitae may terminate the Vitae 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 Vitae 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 Vitae 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. Since the effective date of the Vitae License Agreement, the Company achieved certain development and regulatory milestones, resulting in $18.0 million in expense, which includes $8.0 million paid in the three months ended June 30, 2024.

UCB Biopharma Sprl

In 2016, the Company entered into a license agreement, or the UCB License Agreement, as amended from time to time, with UCB Biopharma Sprl, or UCB, under which UCB granted to the Company a worldwide, sublicensable, exclusive license to UCB6352, which the Company refers to as axatilimab, an anti-CSF-1R monoclonal antibody. Subject to the achievement of certain milestone events, the Company may be required to pay UCB up to $119.5 million in one-time development and regulatory milestone payments over the term of the UCB License Agreement. In the event that the Company or any of its affiliates or sublicensees commercializes axatilimab, the Company will also be obligated to pay UCB low double-digit royalties on sales, subject to reduction in certain circumstances, as well as up to an aggregate of $250.0 million in potential one-time, sales-based milestone payments based on achievement of certain annual sales thresholds. Under certain circumstances, the Company may be required to share a percentage of non-royalty income from sublicensees, subject to certain deductions, with UCB. The Company is solely responsible for the development and commercialization of axatilimab, except that UCB was responsible for performing a limited set of transitional chemistry, manufacturing and control tasks related to axatilimab. Each party may terminate the UCB License Agreement for the other party’s uncured material breach or insolvency, and the Company may terminate the UCB License Agreement at any time upon advance written notice to UCB. UCB may terminate the UCB License Agreement if the Company or any of its affiliates or sublicensees institutes a legal challenge to the validity, enforceability, or patentability of the licensed patent rights. Unless terminated earlier in accordance with its terms, the UCB License Agreement will continue on a country-by-country and product-by-product basis until the later of: (i) the expiration of all of the licensed patent rights in such country; (ii) the expiration of all regulatory exclusivity applicable to the product in such country; and (iii) 10 years from the date of the first commercial sale of the product in such country.

As of the date of the UCB License Agreement, the asset acquired had no alternative future use nor had it reached a stage of technological feasibility. As the processes or activities that were acquired along with the license do not constitute a “business,” the transaction has been accounted for as an asset acquisition. As a result, in 2016, the upfront payment of $5.0 million was recorded as research and development expense in the consolidated statements of operations. Additionally, in connection with its most recent amendment of the UCB License Agreement, in the second quarter of 2022 the Company paid UCB $5.8 million, which was recognized as a milestone expense. Since the effective date of the license agreement, the Company achieved certain development and regulatory milestones and has recorded $16.0 million as research and development expense, which includes $10.0 million paid in the three months ended March 31, 2024.

Bayer Pharma AG (formerly known as Bayer Schering Pharma AG)

In March 2007, the Company entered into a license agreement with Bayer Schering Pharma AG, or Bayer, for a worldwide, exclusive license to develop and commercialize entinostat and any other products containing the same active ingredient. 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.

Eddingpharm Investment Company Limited

In August 2016, the Company entered into a license agreement with Eddingpharm Investment Company, or Eddingpharm, to develop and commercialize entinostat. Eddingpharm will pay the Company royalties on a sliding scale based on net sales, if any, and make future milestone payments up to $10.0 million in the event that certain specified development and regulatory goals are achieved. In April 2024, certain milestones were achieved and the Company recognized $3.5 million of milestone and license revenue in the three months ended June 30, 2024.

Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Abstract]

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

The Company recognized stock-based compensation expense related to the issuance of stock option awards and restricted stock units to employees and non-employees and related to the Company’s 2015 Employee Stock Purchase Plan, or ESPP, in the condensed consolidated statements of comprehensive loss as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023

Research and development	$	4,318	$	3,698	$	8,461	$	6,476
Selling, general and administrative		5,578		4,367		10,334		7,827
Total	$	9,896	$	8,065	$	18,795	$	14,303

Summary in Compensation Expense by Type of Award

Compensation expense by type of award in the three and six months ended June 30, 2024 and 2023 was as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023

Stock options	$	7,801	$	7,019	$	14,985	$	12,411
RSUs		1,999		978		3,616		1,760
ESPP		96		68		194		132
Total	$	9,896	$	8,065	$	18,795	$	14,303

Fair Value Measurements - Schedule of Fair Values of Financial Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	$ 319,701	$ 275,304
Long-term investments	29,516	29,829
Carrying Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	105,396	295,394
Short-term investments	319,701	275,304
Long-term investments	29,516	29,829
Total assets	454,613	600,527
Quoted Prices (Unadjusted) in Active Markets Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	105,396	295,394
Total assets	105,396	295,394
Significant Other Observable Inputs Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	319,701	275,304
Long-term investments	29,516	29,829
Total assets	$ 349,217	$ 305,133

Stockholders' Equity - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended
	May 31, 2023	Jun. 30, 2024	Dec. 31, 2021
Pre Funded Warrants [Member]
Class Of Stock [Line Items]
Warrants issued (in shares)			1,142,856
Number of pre funded warrants exercised for common stock		285,714
Cowen and Company LLC [Member] \| At The Market Equity Offering Sales Agreement [Member]
Class Of Stock [Line Items]
Proceeds from issuance of common stock	$ 200.0

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 272
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483014/272-10-45-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 272
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482987/272-10-50-1

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(d))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(27)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(2)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(2)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3

+ Details

Prepaid Expenses and Other Current Assets

6 Months Ended

Jun. 30, 2024

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

Prepaid Expenses and Other Current Assets

8. Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following (in thousands):


	June 30, 2024		December 31, 2023
Prepaid insurance	$	1,555	$	807
Interest receivable on investments		1,300		1,227
Prepaid subscription		633		769
Prepaid state and local taxes		493		264
Prepaid rent		164		163
Other		62		63
Total prepaid expenses and other current assets	$	4,207	$	3,293

Net Loss per Share Attributable to Common Stockholders (Tables)

6 Months Ended

Jun. 30, 2024

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,
	2024			2023			2024			2023
	(In thousands, except share and per share data)						(In thousands, except share and per share data)
Numerator—basic and diluted:
Net loss	$	(68,063	)	$	(44,615	)	$	(140,463	)	$	(85,741	)
Net loss attributable to common stockholders—basic and diluted	$	(68,063	)	$	(44,615	)	$	(140,463	)	$	(85,741	)
Net loss per share attributable to common stockholders—basic and diluted	$	(0.80	)	$	(0.64	)	$	(1.65	)	$	(1.23	)
Denominator—basic and diluted:
Weighted-average number of common shares used to compute net loss per share attributable to common stockholders—basic and diluted		85,274,829			69,638,427			85,244,015			69,539,209

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


	June 30,
	2024		2023
Options to purchase common stock		12,226,274		10,429,475
Employee Stock Purchase Plan		29,426		15,331
Non-vested restricted stock units (RSUs)		1,486,146		526,736

Significant Agreements - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended				6 Months Ended		12 Months Ended
	Oct. 31, 2017	Jul. 31, 2016	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2016	Mar. 31, 2007
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense			$ 48,655		$ 34,764		$ 105,147	$ 68,819
Allergan License Agreement Member \| Vitae Pharmaceuticals Inc [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential milestone payments to be made	$ 99,000
Aggregate potential milestone payable	$ 70,000
License expiration year	10 years
Milestone Expenses Paid			8,000				8,000
Development and regulaotry milestones Expenses			$ 18,000				$ 18,000
UCB License Agreement [Member] \| UCB Biopharma [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential milestone payments to be made		$ 119,500
Aggregate potential milestone payable		$ 250,000
License expiration year		10 years
Research and development expense				$ 10,000		$ 16,000			$ 5,000
Milestone payment payable						$ 5,800
License Agreement [Member] \| Bayer Pharma AG [Member] \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate payment obligation										$ 150,000

Commitments and Contingencies (Additional Information) (Details) $ in Thousands	Jun. 30, 2024 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Contingent liabilities	$ 0

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, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Numerator—basic and diluted:
Net Income (Loss)	$ (68,063)	$ (72,400)	$ (44,615)	$ (41,126)	$ (140,463)	$ (85,741)
Net loss attributable to common stockholders - basic	(68,063)		(44,615)		(140,463)	(85,741)
Net loss attributable to common stockholders - diluted	$ (68,063)		$ (44,615)		$ (140,463)	$ (85,741)
Net loss per share attributable to common stockholders—basic	$ (0.8)		$ (0.64)		$ (1.65)	$ (1.23)
Net loss per share attributable to common stockholders— diluted	$ (0.8)		$ (0.64)		$ (1.65)	$ (1.23)
Denominator—basic and diluted:
Weighted-average number of common shares used to compute net loss per share attributable to common stockholders—basic	85,274,829		69,638,427		85,244,015	69,539,209
Weighted-average number of common shares used to compute net loss per share attributable to common stockholders—diluted	85,274,829		69,638,427		85,244,015	69,539,209

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

+ Details

- Definition

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

+ References

+ Details

- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 60
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476176/805-60-65-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-4

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 5
-Subparagraph (SAB Topic 6.B)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-5

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482662/260-10-50-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-10

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-11

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B

+ Details

- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities, and addition from assumption of issuance of common shares for dilutive potential common shares; of income (loss) available to common shareholders.

+ References + Details

Nature of Business

6 Months Ended

Jun. 30, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Nature of Business

1. Nature of Business

Syndax Pharmaceuticals, Inc., is a clinical stage biopharmaceutical company developing an innovative pipeline of cancer therapies. We were incorporated in Delaware in 2005. We have operations in New York, New York and Waltham, Massachusetts and we operate in one segment. References in these notes to condensed consolidated financial statements to “Syndax,” “the Company,” “we,” “us” or “our” refer to Syndax Pharmaceuticals, Inc. and its wholly owned subsidiaries.

Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Fair Value Measurements [Line Items]
Realized gains or losses recognized on the sale or maturity of available-for-sale securities	$ 0	$ 0	$ 0	$ 0

Stock-Based Compensation

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

10. Stock-Based Compensation

In January 2024, the number of shares of common stock available for issuance under the Company’s 2015 Omnibus Incentive Plan, or the 2015 Plan, was increased by 3,393,065 shares of common stock due to the automatic annual provision to increase shares of common stock available under the 2015 Plan. Additionally in December 2023, the Company’s board of directors approved an increase of 1,100,000 shares of common stock available for issuance under the Company’s 2023 Inducement Plan, or Inducement Plan.

As of June 30, 2024, there were 3,798,637 shares of common stock available for issuance under the 2015 Plan and 323,150 shares of common stock available for issuance under the Inducement Plan.


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023

Research and development	$	4,318	$	3,698	$	8,461	$	6,476
Selling, general and administrative		5,578		4,367		10,334		7,827
Total	$	9,896	$	8,065	$	18,795	$	14,303

Compensation expense by type of award in the three and six months ended June 30, 2024 and 2023 was as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023

Stock options	$	7,801	$	7,019	$	14,985	$	12,411
RSUs		1,999		978		3,616		1,760
ESPP		96		68		194		132
Total	$	9,896	$	8,065	$	18,795	$	14,303

As of June 30, 2024, there were $101.3 million of unrecognized compensation costs related to employee and non-employee unvested stock options and RSUs granted under the 2023 Inducement Plan, 2015 Plan and the Company’s 2007 Stock Plan, which are expected to be recognized over a weighted-average remaining service period of 2.8 years.

Stock-Based Compensation - Compensation Expense by Type of Award (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 9,896	$ 8,065	$ 18,795	$ 14,303
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	7,801	7,019	14,985	12,411
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	1,999	978	3,616	1,760
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 96	$ 68	$ 194	$ 132

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Significant Collaborative Research and License Agreements - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended					3 Months Ended				6 Months Ended		12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Oct. 31, 2017	Aug. 31, 2016	Jul. 31, 2016	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2016	Mar. 31, 2007
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and Development Expense						$ 48,655		$ 34,764		$ 105,147	$ 68,819
Milestone and license revenue						3,500		$ 0		3,500	$ 0
Incyte Agreement [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Common stock shares purchased	1,421,523
Purchase price per share	$ 24.62
Proceeds from issuance of common stock	$ 35,000
Collaboration receivable						2,000				2,000
Collaboration expense due to counterparty						5,100				5,100
Incyte Agreement [Member] \| Maximum [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Potential milestone payments to be made		$ 220,000
Commercialization milestones and tiered royalties		$ 230,000
Incyte Agreement [Member] \| Non-Refundable Cash Payments [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront milestone payable	$ 117,000
Allergan License Agreement [Member] \| Vitae Pharmaceuticals Inc [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Potential milestone payments to be made			$ 99,000
Aggregate Potential Milestone Payable			$ 70,000
Milestone Expenses Paid						8,000				8,000
Development and regulaotry milestones Expenses						$ 18,000				18,000
License Agreements Expiration Period			10 years
Ucb License Agreement [Member] \| U C B Biopharma [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and Development Expense							$ 10,000		$ 16,000			$ 5,000
Potential milestone payments to be made					$ 119,500
Aggregate Potential Milestone Payable					$ 250,000
License Agreements Expiration Period					10 years
Milestone Payment Due									$ 5,800
License Agreement [Member] \| Bayer Pharma Ag [Member] \| Maximum [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Aggregate payment obligation													$ 150,000
License Agreement [Member] \| Eddingpharm Investment [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Milestone and license revenue										$ 3,500
License Agreement [Member] \| Eddingpharm Investment [Member] \| Maximum [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Milestone Payment Due				$ 10,000
Global and U.S. [Member] \| Incyte Agreement [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Development costs associated with clinical trials		45.00%
Global and U.S. [Member] \| Incyte Agreement [Member] \| Incyte Corporation [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Development costs associated with clinical trials		55.00%
Ex-U.S. Countries [Member] \| Incyte Agreement [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Development costs associated with clinical trials		100.00%

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Revenue:
Milestone and license revenue	$ 3,500	$ 0	$ 3,500	$ 0
Total revenues	3,500	0	3,500	0
Operating expenses:
Research and development	48,655	34,764	105,147	68,819
Selling, general and administrative	29,061	14,914	52,083	26,875
Total operating expenses	77,716	49,678	157,230	95,694
Loss from operations	(74,216)	(49,678)	(153,730)	(95,694)
Other income (expense), net:
Interest expense	(45)	(35)	(100)	(75)
Interest income	6,284	5,191	13,540	10,268
Other expense	(86)	(93)	(173)	(240)
Total other income, net	6,153	5,063	13,267	9,953
Net loss	(68,063)	(44,615)	(140,463)	(85,741)
Other comprehensive loss:
Unrealized (loss) gain on short-term investments	(61)	(238)	(817)	232
Comprehensive loss	(68,124)	(44,853)	(141,280)	(85,509)
Net loss attributable to common stockholders	$ (68,063)	$ (44,615)	$ (140,463)	$ (85,741)
Net loss per share attributable to common stockholders—basic	$ (0.8)	$ (0.64)	$ (1.65)	$ (1.23)
Net loss per share attributable to common stockholders—diluted	$ (0.8)	$ (0.64)	$ (1.65)	$ (1.23)
Weighted-average number of common shares used to compute net loss per share attributable to common stockholders —basic	85,274,829	69,638,427	85,244,015	69,539,209
Weighted-average number of common shares used to compute net loss per share attributable to common stockholders—diluted	85,274,829	69,638,427	85,244,015	69,539,209