[SCHEDULE 13G] Cullinan Therapeutics, Inc. SEC Filing

Rhea-AI Filing Summary

Citadel Advisors LLC and related Citadel entities, along with founder Kenneth Griffin, disclosed a new passive stake in Cullinan Therapeutics, Inc. (CGEM) via Schedule 13G. The group now beneficially owns 3,009,126 common shares, or 5.1% of CGEM’s 59,014,667 shares outstanding as of 30 July 2025. Citadel Advisors, Citadel Advisors Holdings LP and Citadel GP LLC jointly hold 2,511,191 shares (4.3%), while market-making affiliate Citadel Securities controls 497,935 shares (0.8%). All voting and dispositive power is reported as shared; none of the entities has sole power over the stock. The filing is made under Rule 13d-1(b)/(c), signalling the position is currently passive rather than activist. Kenneth Griffin is deemed a control person through his ownership of the various Citadel general-partner entities. No intent to influence control of the issuer is stated, and the certification confirms the shares were not acquired for activist purposes. The disclosure provides investors with the first confirmation that a high-profile hedge-fund complex has crossed the 5% threshold in CGEM.

Positive

• High-profile institutional ownership: Citadel and Kenneth Griffin now hold 5.1% of CGEM, signalling confidence and increasing institutional visibility.

Negative

• None.

Insights

Equity Analyst

TL;DR: Citadel’s 5.1% passive stake introduces a well-capitalised holder and may improve liquidity, modestly positive for sentiment.

Citadel’s entry is meaningful because hedge-fund positions often signal fundamental conviction or event-driven interest. Although 5.1% is below activist levels, it positions Citadel among CGEM’s top holders, expanding institutional ownership and potentially tightening the float. The absence of sole voting power or activist intent keeps governance risk low. For valuation, no immediate EPS or cash-flow impact occurs, yet the market commonly interprets such filings as a vote of confidence, which can compress the cost of capital. Impact rating: modestly positive.

Corporate Governance Specialist

TL;DR: Passive 13G filing limits governance implications; monitor only if Citadel converts to 13D.

Because the group certified passive intent, there is no current push for board seats or strategic change. Voting and dispositive powers are shared across multiple Citadel entities, diluting any single-entity influence. However, Kenneth Griffin controls the structure, so a future shift to a 13D could quickly aggregate influence. Investors should track subsequent filings for threshold changes or amendments that might indicate an activist posture.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Cullinan Therapeutics, Inc.

(Name of Issuer)

Common Stock, par value $0.0001 per share (the "Shares")

(Title of Class of Securities)

230031106

(CUSIP Number)

07/30/2025

(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. 230031106

1

Names of Reporting Persons

Citadel Advisors LLC

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

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 2,511,191.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,511,191.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,511,191.00

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)

4.3 %

12

Type of Reporting Person (See Instructions)

IA, HC, OO

Comment for Type of Reporting Person: The percentages reported in this Schedule 13G are based upon 59,014,667 Shares outstanding as of April 30, 2025 (according to the issuer's Form 10-Q as filed with the Securities and Exchange Commission on May 8, 2025). Except as described in the preceding sentence, all Shares for the holdings of the reporting persons reported in this Schedule 13G are as of the opening of the market on August 6, 2025.

SCHEDULE 13G

CUSIP No. 230031106

1

Names of Reporting Persons

Citadel Advisors Holdings LP

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

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 2,511,191.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,511,191.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,511,191.00

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)

4.3 %

12

Type of Reporting Person (See Instructions)

HC, PN

SCHEDULE 13G

CUSIP No. 230031106

1

Names of Reporting Persons

Citadel GP LLC

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

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 2,511,191.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,511,191.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,511,191.00

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)

4.3 %

12

Type of Reporting Person (See Instructions)

HC, OO

SCHEDULE 13G

CUSIP No. 230031106

1

Names of Reporting Persons

Citadel Securities LLC

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

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 497,935.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 497,935.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

497,935.00

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)

0.8 %

12

Type of Reporting Person (See Instructions)

BD, OO

SCHEDULE 13G

CUSIP No. 230031106

1

Names of Reporting Persons

Citadel Securities Group LP

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

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 497,935.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 497,935.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

497,935.00

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)

0.8 %

12

Type of Reporting Person (See Instructions)

HC, PN

SCHEDULE 13G

CUSIP No. 230031106

1

Names of Reporting Persons

Citadel Securities GP LLC

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

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 497,935.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 497,935.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

497,935.00

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)

0.8 %

12

Type of Reporting Person (See Instructions)

HC, OO

SCHEDULE 13G

CUSIP No. 230031106

1

Names of Reporting Persons

Kenneth Griffin

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

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 3,009,126.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 3,009,126.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

3,009,126.00

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)

5.1 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Cullinan Therapeutics, Inc.
(b)	Address of issuer's principal executive offices: One Main Street, Suite 1350 Cambridge, MA, 02142
Item 2.
(a)	Name of person filing: This Schedule 13G is being jointly filed by Citadel Advisors LLC ("Citadel Advisors"), Citadel Advisors Holdings LP ("CAH"), Citadel GP LLC ("CGP"), Citadel Securities LLC ("Citadel Securities"), Citadel Securities Group LP ("CALC4"), Citadel Securities GP LLC ("CSGP") and Mr. Kenneth Griffin (collectively with Citadel Advisors, CAH, CGP, Citadel Securities, CALC4 and CSGP, the "Reporting Persons") with respect to the Shares of the above-named issuer owned by Citadel Multi-Strategy Equities Master Fund Ltd., a Cayman Islands company ("CM"), Citadel CEMF Investments Ltd., a Cayman Islands limited company ("CCIL"), and Citadel Securities. Such owned Shares may include other instruments exercisable for or convertible into Shares. Citadel Advisors is the portfolio manager for CM and CCIL. CAH is the sole member of Citadel Advisors. CGP is the general partner of CAH. CALC4 is the non-member manager of Citadel Securities. CSGP is the general partner of CALC4. Mr. Griffin is the President and Chief Executive Officer of CGP, and owns a controlling interest in CGP and CSGP. The filing of this statement shall not be construed as an admission that any of the Reporting Persons is the beneficial owner of any securities covered by the statement other than the securities actually owned by such person (if any).
(b)	Address or principal business office or, if none, residence: The address of each of the Reporting Persons is 830 Brickell Plaza, Miami, Florida 33131.
(c)	Citizenship: Each of Citadel Advisors, CGP, Citadel Securities and CSGP is organized as a limited liability company under the laws of the State of Delaware. Each of CALC4 and CAH is organized as a limited partnership under the laws of the State of Delaware. Mr. Griffin is a U.S. citizen.
(d)	Title of class of securities: Common Stock, par value $0.0001 per share (the "Shares")
(e)	CUSIP No.: 230031106
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: 1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC may be deemed to beneficially own 2,511,191 Shares. 2. Citadel Securities LLC may be deemed to beneficially own 497,935 Shares. 3. Each of Citadel Securities Group LP and Citadel Securities GP LLC may be deemed to beneficially own 497,935 Shares. 4. Mr. Griffin may be deemed to beneficially own 3,009,126 Shares.
(b)	Percent of class: 1. The number of Shares that each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC may be deemed to beneficially own constitutes 4.3% of the Shares outstanding. 2. The number of Shares that Citadel Securities LLC may be deemed to beneficially own constitutes 0.8% of the Shares outstanding. 3. The number of Shares that each of Citadel Securities Group LP and Citadel Securities GP LLC may be deemed to beneficially own constitutes 0.8% of the Shares outstanding. 4. The number of Shares that Mr. Griffin may be deemed to beneficially own constitutes 5.1% of the Shares outstanding.
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 0 2. Citadel Securities LLC: 0 3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 0 4. Mr. Griffin: 0
	(ii) Shared power to vote or to direct the vote: 1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 2,511,191 2. Citadel Securities LLC: 497,935 3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 497,935 4. Mr. Griffin: 3,009,126
	(iii) Sole power to dispose or to direct the disposition of: 1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 0 2. Citadel Securities LLC: 0 3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 0 4. Mr. Griffin: 0
	(iv) Shared power to dispose or to direct the disposition of: 1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 2,511,191 2. Citadel Securities LLC: 497,935 3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 497,935 4. Mr. Griffin: 3,009,126
Item 5.	Ownership of 5 Percent or Less of a Class.
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	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.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	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 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.

Citadel Advisors LLC

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	08/06/2025

Citadel Advisors Holdings LP

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	08/06/2025

Citadel GP LLC

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	08/06/2025

Citadel Securities LLC

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	08/06/2025

Citadel Securities Group LP

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	08/06/2025

Citadel Securities GP LLC

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	08/06/2025

Kenneth Griffin

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, attorney-in-fact*
Date:	08/06/2025

Comments accompanying signature: * Seth Levy is signing on behalf of Kenneth Griffin as attorney-in-fact pursuant to a power of attorney previously filed with the Securities and Exchange Commission, and hereby incorporated by reference herein. The power of attorney was filed as an attachment to a filing by Citadel Advisors LLC on Schedule 13G for Allakos Inc. on October 13, 2023.

Exhibit Information

Exhibit 99.1 - Joint Filing Agreement

FAQ

How many Cullinan Therapeutics (CGEM) shares does Citadel now own?

Citadel entities collectively report 3,009,126 shares beneficially owned.

What percentage of CGEM’s outstanding shares does the stake represent?

The group’s holdings equal 5.1% of the 59,014,667 shares outstanding.

Why did Citadel file a Schedule 13G instead of a 13D?

A 13G indicates a passive investment; Citadel certified it does not seek to influence control of CGEM.

Which Citadel entity holds the largest portion of the CGEM stake?

Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC together hold 2,511,191 shares (4.3%).

When did Citadel cross the 5% ownership threshold in CGEM?

The event date triggering the filing is listed as July 30, 2025.