SCHEDULE: Citadel Discloses 9.99% Stake in MEI Pharma, Inc.

Citadel entities, including Kenneth Griffin, have disclosed a combined beneficial ownership of 9.99% in MEI Pharma, Inc., totaling 3,245,888 shares.

Summary

• Citadel Advisors LLC, Citadel Advisors Holdings LP, and Citadel GP LLC collectively beneficially own 3,167,695 shares, representing 9.75% of MEI Pharma, Inc.'s common stock.
• Citadel Securities LLC, Citadel Securities Group LP, and Citadel Securities GP LLC collectively beneficially own 78,193 shares, representing 0.24% of the common stock.
• Kenneth Griffin, through his control over the Citadel entities, beneficially owns an aggregate of 3,245,888 shares, which constitutes 9.99% of the common stock.
• The percentages are calculated based on 32,491,374 shares outstanding, which includes 29,879,755 shares outstanding as of July 22, 2025, 2,084,509 shares issued from warrant exercises, and 527,110 shares issuable from warrant conversions.
• All reporting persons hold shared voting and shared dispositive power over their respective beneficially owned shares, with no sole power.
• The acquisition of these securities was not for the purpose of changing or influencing the control of MEI Pharma, Inc., other than activities solely in connection with a nomination under Rule 14a-11.

Sentiment

Score: 7

Explanation: The disclosure of a significant stake by a prominent institutional investor like Citadel can be viewed positively by the market, indicating institutional interest and potential validation of the company's prospects, even if the investment is passive.

Positives

• Significant institutional investment from Citadel, a prominent financial firm, indicates a notable level of interest in MEI Pharma, Inc.
• The 9.99% stake held by Kenneth Griffin and associated entities represents a substantial vote of confidence from a major investor.

Risks

• The beneficial ownership includes shares issuable upon conversion of warrants, which could lead to future dilution if exercised.

Future Outlook

The filing does not provide forward-looking statements or guidance regarding MEI Pharma, Inc.'s operational or financial performance.

Management Comments

• The securities referred to 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 Rule 14a-11.

Industry Context

This Schedule 13G filing indicates a significant passive investment by a major hedge fund and market maker in a biotechnology company. Such disclosures are common for institutional investors crossing the 5% beneficial ownership threshold, signaling their position in a public company without necessarily implying an intent to influence management or control.

Stakeholder Impact

• Shareholders: The disclosure of a large institutional stake may influence investor sentiment and potentially the stock price, signaling significant institutional interest.

Key Dates

Keywords

MEI Pharma, Citadel, Kenneth Griffin, Beneficial Ownership, Schedule 13G, Institutional Investor, Common Stock, Biotechnology, Pharmaceuticals, Warrants