[SCHEDULE 13G] MEI Pharma, Inc. SEC Filing

Rhea-AI Filing Summary

Citadel-related entities and Kenneth Griffin have disclosed a near-10% passive stake in MEI Pharma (MEIP). A Schedule 13G filed for the 22 Jul 2025 event shows aggregate beneficial ownership of 3,245,888 common shares, equal to 9.99 % of the 32,491,374 shares outstanding.

• Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC jointly own 3,167,695 shares (9.75%) with shared voting and dispositive power.
• Citadel Securities-affiliated vehicles hold 78,193 shares (0.24%).
• Stake size includes 2,084,509 shares issued and 527,110 shares still issuable from the voluntary exercise or conversion of warrants; each warrant is subject to a 9.99 % ownership cap.
• The filing is on Schedule 13G, indicating the position is passive; the certification explicitly states there is no intent to influence control of MEIP.
• All reporting persons share a business address: 830 Brickell Plaza, Miami, FL.

The disclosure introduces a high-profile institutional holder but does not signal an activist agenda or immediate strategic change for MEI Pharma.

Positive

• High-profile institutional ownership: Citadel and Kenneth Griffin now hold 9.99 % of MEIP, potentially supporting liquidity and investor confidence.

Negative

• Incremental dilution: 2.08 m shares were issued and another 0.53 m are still issuable from warrant conversions tied to Citadel’s stake, modestly increasing the share count.

Insights

Equity Analyst

TL;DR: Large passive stake by Citadel adds liquidity support but no control intent—impact modest.

Citadel’s 9.99 % ownership elevates institutional participation in MEIP, potentially improving trading liquidity and market visibility. Because the position is filed under Schedule 13G—not 13D—and includes a certification of passivity, the probability of governance intervention appears low. The stake derives partly from warrant exercises, which incrementally increased the share count, but the resulting dilution is already reflected in the 32.5 m share base cited. Overall, this is a neutral-to-mildly positive signal: a respected hedge fund has validated MEIP’s valuation yet remains below the 10 % threshold that would trigger additional reporting requirements.

Corporate Governance Specialist

TL;DR: Position capped below 10 %; no activism flags—governance risk unchanged.

The joint filing consolidates seven Citadel entities plus Kenneth Griffin, clarifying control relationships and preventing fragmented disclosures. Shared voting power on all 3.25 m shares means Griffin can influence outcomes if desired, but the 13G certification and lack of sole voting authority mitigate takeover concerns. The warrant cap also limits future ownership beyond 9.99 %, reducing the chance of stealth accumulation. For boards and investors, governance posture remains status-quo; monitoring is advisable but no immediate defensive action is required.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

MEI Pharma, Inc.

(Name of Issuer)

Common Stock, par value $0.00000002 per share (the "Shares")

(Title of Class of Securities)

55279B301

(CUSIP Number)

07/22/2025

(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. 55279B301

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 3,167,695.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 3,167,695.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

3,167,695.00

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)

9.75 %

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 32,491,374 Shares outstanding comprised of (i) 29,879,755 Shares outstanding as of July 22, 2025 (according to the issuer's prospectus as filed with the Securities and Exchange Commission on July 23, 2025), (ii) 2,084,509 Shares issued to affiliates of the reporting persons upon the voluntary exercise of certain warrants held by affiliates of the reporting persons prior to the date hereof, and (iii) 527,110 Shares issuable upon conversion of certain warrants held by affiliates of the reporting persons. 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 July 29, 2025. The applicable warrants are subject to terms that limit exercise, if, after such exercise, the holder and its affiliates and any member of a group with such holder and its affiliates would beneficially own more than 9.99% of the number of shares of Common Stock outstanding immediately after exercise.

SCHEDULE 13G

CUSIP No. 55279B301

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 3,167,695.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 3,167,695.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

3,167,695.00

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)

9.75 %

12

Type of Reporting Person (See Instructions)

HC, PN

SCHEDULE 13G

CUSIP No. 55279B301

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 3,167,695.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 3,167,695.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

3,167,695.00

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)

9.75 %

12

Type of Reporting Person (See Instructions)

HC, OO

SCHEDULE 13G

CUSIP No. 55279B301

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 78,193.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 78,193.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

78,193.00

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)

0.24 %

12

Type of Reporting Person (See Instructions)

BD, OO

SCHEDULE 13G

CUSIP No. 55279B301

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 78,193.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 78,193.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

78,193.00

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)

0.24 %

12

Type of Reporting Person (See Instructions)

HC, PN

SCHEDULE 13G

CUSIP No. 55279B301

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 78,193.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 78,193.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

78,193.00

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)

0.24 %

12

Type of Reporting Person (See Instructions)

HC, OO

SCHEDULE 13G

CUSIP No. 55279B301

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 3,245,888.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 3,245,888.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

3,245,888.00

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)

9.99 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: MEI Pharma, Inc.
(b)	Address of issuer's principal executive offices: 9920 Pacific Heights Blvd., Suite 150 San Diego, CA, 92121
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 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 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 $0.00000002 per share (the "Shares")
(e)	CUSIP No.: 55279B301
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 3,167,695 Shares. 2. Citadel Securities LLC may be deemed to beneficially own 78,193 Shares. 3. Each of Citadel Securities Group LP and Citadel Securities GP LLC may be deemed to beneficially own 78,193 Shares. 4. Mr. Griffin may be deemed to beneficially own 3,245,888 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 9.75% of the Shares outstanding. 2. The number of Shares that Citadel Securities LLC may be deemed to beneficially own constitutes 0.24% 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 0.24% of the Shares outstanding. 4. The number of Shares that Mr. Griffin may be deemed to beneficially own constitutes 9.99% 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: 3,167,695 2. Citadel Securities LLC: 78,193 3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 78,193 4. Mr. Griffin: 3,245,888
	(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: 3,167,695 2. Citadel Securities LLC: 78,193 3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 78,193 4. Mr. Griffin: 3,245,888
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:	07/29/2025

Citadel Advisors Holdings LP

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	07/29/2025

Citadel GP LLC

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	07/29/2025

Citadel Securities LLC

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	07/29/2025

Citadel Securities Group LP

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	07/29/2025

Citadel Securities GP LLC

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	07/29/2025

Kenneth Griffin

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, attorney-in-fact*
Date:	07/29/2025

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 MEI Pharma shares does Citadel own according to the 2025 Schedule 13G?

Citadel-managed entities beneficially own 3,167,695 shares, equal to 9.75 % of outstanding stock.

What is Kenneth Griffin’s total ownership in MEIP?

Including all affiliated vehicles, Kenneth Griffin is deemed to beneficially own 3,245,888 shares (9.99 %).

Is the Citadel position activist or passive?

The filing is on Schedule 13G; the certification states the shares are not held to change or influence control, indicating a passive stake.

Did the stake involve new share issuance?

Yes. The position includes 2,084,509 shares issued and 527,110 shares still issuable from the voluntary exercise or conversion of warrants.

What is the CUSIP for MEI Pharma common stock?

The CUSIP disclosed in the filing is 55279B301.