State Street Corporation (SNDX) discloses 5.66M-share, 6.4% holding in Syndax

Rhea-AI Filing Summary

State Street Corporation reported a significant ownership position in Syndax Pharmaceuticals Inc. common stock. State Street and its investment management subsidiaries reported that they beneficially own 5,658,465 shares of Syndax common stock, representing 6.4% of the class as of June 30, 2026. The filing states no sole voting or dispositive power, with shared voting power over 5,408,786 shares and shared dispositive power over 5,658,465 shares. The position is held through entities including SSGA Funds Management, Inc., State Street Bank and Trust Company, and several State Street Global Advisors entities. The filing notes that no other person is known to have rights to more than 5% of the class through this holding.

Key Figures

Shares beneficially owned: 5,658,465 shares Percent of class: 6.4% Shared voting power: 5,408,786 shares +2 more

5 metrics

Shares beneficially owned 5,658,465 shares Beneficial ownership of Syndax common stock reported by State Street

Percent of class 6.4% Portion of Syndax common stock class beneficially owned by State Street

Shared voting power 5,408,786 shares Shares of Syndax over which State Street has shared voting power

Shared dispositive power 5,658,465 shares Shares of Syndax over which State Street has shared dispositive power

Date of ownership information 06/30/2026 Date as of which the ownership percentages and share counts apply

Key Terms

beneficially owned, shared voting power, shared dispositive power, Schedule 13G

4 terms

beneficially owned financial

"Ownership (a) | Amount beneficially owned: 5658465.00"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

shared voting power financial

"Shared power to vote or to direct the vote: 5,408,786"

Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.

shared dispositive power financial

"Shared power to dispose or to direct the disposition of: 5,658,465"

Schedule 13G regulatory

"Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 08/07/2026 - 11:00 AM Accepted by SEC EDGAR 08/07/2026 - 10:59 AM Learn about SEC filing dates

FAQ

How much of Syndax Pharmaceuticals (SNDX) does State Street Corporation own?

State Street Corporation reports beneficial ownership of 5,658,465 shares of Syndax Pharmaceuticals common stock, representing 6.4% of the outstanding class as of June 30, 2026.

What voting power does State Street have in Syndax Pharmaceuticals (SNDX)?

State Street reports no sole voting power and shared voting power over 5,408,786 shares of Syndax common stock, reflecting its role across affiliated investment management entities.

What dispositive power does State Street report over SNDX shares?

State Street reports no sole dispositive power and shared dispositive power over 5,658,465 shares of Syndax common stock, matching its total beneficially owned position.

Which State Street entities hold the Syndax Pharmaceuticals (SNDX) stake?

The stake is held through affiliates including SSGA Funds Management, Inc., State Street Bank and Trust Company, and several State Street Global Advisors entities listed in the ownership disclosure.

Does any other person have rights to more than 5% of SNDX through State Street’s holdings?

The filing states “Not Applicable” for persons with rights to dividends or sale proceeds, indicating no identified other person with an interest relating to more than 5% of the class through this position.

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)

06/30/2026

(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)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 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 5,408,786.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 5,658,465.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

5,658,465.00

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)

6.4 %

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 Number(s): 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: 5658465.00
(b)	Percent of class: 6.4 %
(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: 5,408,786
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 5,658,465
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 BANK AND TRUST COMPANY (BK);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:	08/07/2026