[Form 4] Syndax Pharmaceuticals, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Michael A. Metzger, the Chief Executive Officer and a director of Syndax Pharmaceuticals, Inc. (SNDX), reported option exercise and an immediate sale on 09/08/2025. He exercised 157,307 options at an exercise price of $10.90 to acquire 157,307 shares and then sold the same 157,307 shares under a Rule 10b5-1 plan at prices ranging from $16.21 to $17.06. The filings show beneficial ownership figures of 455,968 shares after the exercise and 298,661 shares after the sale. The report states Metzger has 1,319,634 vested options immediately exercisable and 651,241 unvested options remaining. The option exercised was fully vested.

Positive

• Pre-planned sale under Rule 10b5-1 provides transparency and reduces concerns about opportunistic insider trading.
• Exercise price ($10.90) is well below sale prices ($16.21–$17.06), indicating the CEO realized a positive spread on these shares.
• Significant retained equity exposure: Metzger still has 1,319,634 vested options, maintaining alignment with shareholders.

Negative

• Insider disposition of 157,307 shares reduces the CEO's direct common stock holdings from 455,968 to 298,661 as reported.
• Sale occurred shortly after exercise, which may be viewed by some investors as reducing near-term insider ownership despite retained options.

Insights

Securities/Equity Analyst

TL;DR: CEO exercised vested options and sold shares under a 10b5-1 plan, monetizing gains while retaining substantial vested options.

The transaction is a routine, pre-planned insider liquidity event: exercise at $10.90 followed by sales at $16.21–$17.06 implies a per-share gross spread. The filing discloses large remaining option positions—1,319,634 vested and 651,241 unvested—so Metzger retains significant long-term upside exposure to SNDX equity despite the disposition. For investors, this is informative about insider liquidity but not a company operational disclosure.

Corporate Governance Expert

TL;DR: Use of a Rule 10b5-1 plan signals prearranged selling; disclosure is clear and consistent with governance best practices.

The report explicitly notes the sales were effected pursuant to a 10b5-1 plan limited to grants expiring before September 10, 2025, which supports that trades were pre-planned and not opportunistic. The filing is properly signed and includes the remaining vested and unvested option counts, giving shareholders clear visibility into insider holdings and potential future dilution from option exercises.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

X

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Metzger Michael A

(Last) (First) (Middle)

C/O SYNDAX PHARMACEUTICALS, INC.

730 3RD AVENUE, FLOOR 9

(Street)

NEW YORK NY 10017

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Syndax Pharmaceuticals Inc [ SNDX ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Executive Officer

3. Date of Earliest Transaction (Month/Day/Year)
09/08/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	09/08/2025		M		157,307	A	$10.9	455,968	D
Common Stock	09/08/2025		S(1)		157,307	D	$16.4139(2)	298,661	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock options (Right to buy)	$10.9	09/08/2025		M		157,307		(3)	09/09/2025	Common Stock	157,307	$0	0	D

Explanation of Responses:

1. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 plan adopted by the Reporting Person solely covering equity grants with expiration dates prior to September 10, 2025. Following the sales reported in this Form 4, the Reporting Person has a total of 1,319,634 options to purchase shares of common stock that are vested and immediately exercisable and a total of 651,241 options to purchase shares of common stock that have not yet vested.

2. The sale prices ranged from $16.21 to $17.06.

3. This option is fully vested.

	/s/ Michael A. Metzger	09/08/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What did Michael A. Metzger report on the Form 4 for SNDX?

He exercised 157,307 options at $10.90 and sold 157,307 shares on 09/08/2025 under a Rule 10b5-1 plan.

How many SNDX options does Metzger have vested and unvested?

He has 1,319,634 vested options immediately exercisable and 651,241 unvested options.

At what prices were the shares sold?

Sale prices ranged from $16.21 to $17.06 per share.

How did these transactions change Metzger's reported common stock holdings?

Reported beneficial ownership was 455,968 shares after the exercise and 298,661 shares after the sale.

Were the sales part of a pre-arranged plan?

Yes. The Form 4 states the sales were effected pursuant to a Rule 10b5-1 plan covering certain expiring grants.