State Street (SNDX holder) discloses 5.3% Syndax Pharmaceuticals ownership stake

Rhea-AI Filing Summary

STATE STREET CORPORATION reported a significant ownership stake in Syndax Pharmaceuticals Inc. common stock. As of 12/31/2025, it beneficially owned 4,596,552 shares, representing 5.3% of the company’s common stock.

State Street reported no sole voting or dispositive power, but shared voting power over 4,341,322 shares and shared dispositive power over 4,596,552 shares. The position is certified as being held in the ordinary course of business and not for influencing control of Syndax.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

SYNDAX PHARMACEUTICALS INC

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

87164F105

(CUSIP Number)

12/31/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 87164F105

1

Names of Reporting Persons

STATE STREET CORPORATION

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

MASSACHUSETTS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 4,341,322.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 4,596,552.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

4,596,552.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.3 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

Item 1.
(a)	Name of issuer: SYNDAX PHARMACEUTICALS INC
(b)	Address of issuer's principal executive offices: 35 GATEHOUSE DRIVE BUILDING D, 3RD FLOOR, WALTHAM, MASSACHUSETTS, 02451
Item 2.
(a)	Name of person filing: STATE STREET CORPORATION;
(b)	Address or principal business office or, if none, residence: ONE CONGRESS STREET, SUITE 1, BOSTON MA 02114, UNITED STATES
(c)	Citizenship: MA
(d)	Title of class of securities: COMMON STOCK
(e)	CUSIP No.: 87164F105
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 4596552.00
(b)	Percent of class: 5.3 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 0
	(ii) Shared power to vote or to direct the vote: 4,341,322
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 4,596,552
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. NOT APPLICABLE
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. SSGA FUNDS MANAGEMENT, INC. (IA);STATE STREET GLOBAL ADVISORS EUROPE LIMITED (IA);STATE STREET GLOBAL ADVISORS LIMITED (IA);STATE STREET GLOBAL ADVISORS TRUST COMPANY (IA);STATE STREET GLOBAL ADVISORS, LTD. (IA);
Item 8.	Identification and Classification of Members of the Group.
	If a group has filed this schedule pursuant to §240.13d-1(b)(1)(ii)(K), so indicate under Item 3(k) and attach an exhibit stating the identity and Item 3 classification of each member of the group. If a group has filed this schedule pursuant to §240.13d-1(c) or §240.13d-1(d), attach an exhibit stating the identity of each member of the group. NOT APPLICABLE
Item 9.	Notice of Dissolution of Group.
	Notice of dissolution of a group may be furnished as an exhibit stating the date of the dissolution and that all further filings with respect to transactions in the security reported on will be filed, if required, by members of the group, in their individual capacity. See Item 5. NOT APPLICABLE

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

STATE STREET CORPORATION

Signature:	ELIZABETH SCHAEFER
Name/Title:	SENIOR VICE PRESIDENT, CHIEF ACCOUNTING OFFICER
Date:	02/09/2026

FAQ

What ownership stake does State Street report in Syndax Pharmaceuticals (SNDX)?

State Street Corporation reports beneficial ownership of 4,596,552 shares of Syndax Pharmaceuticals common stock, representing 5.3% of the outstanding class as of December 31, 2025. This makes State Street a significant institutional holder of SNDX shares.

How much voting power does State Street have in SNDX shares?

State Street reports no sole voting power, but shared voting power over 4,341,322 shares of Syndax Pharmaceuticals common stock. This means voting decisions on these shares are exercised jointly, consistent with State Street’s role as an institutional asset manager.

How many Syndax (SNDX) shares can State Street dispose of?

State Street reports no sole dispositive power, but shared dispositive power over 4,596,552 shares of Syndax common stock. Shared dispositive power indicates State Street participates in decisions about selling or otherwise disposing of these shares on behalf of clients.

Is State Street’s Syndax (SNDX) stake intended to influence control?

State Street certifies the shares were acquired and are held in the ordinary course of business and not for the purpose or effect of changing or influencing control of Syndax. The holding is characterized as a passive institutional investment position.

Who is the reporting person for this 5.3% Syndax (SNDX) ownership?

The reporting person is State Street Corporation, organized in Massachusetts, with a principal office at One Congress Street, Suite 1, Boston, MA 02114. Several State Street Global Advisors entities are identified as relevant investment adviser subsidiaries.

What subsidiaries are associated with State Street’s SNDX holdings?

Associated entities include SSGA Funds Management, Inc., State Street Global Advisors Europe Limited, State Street Global Advisors Limited, State Street Global Advisors Trust Company, and State Street Global Advisors, Ltd., each identified as investment advisers involved with the reported holdings.