SCHEDULE 13D/A: Frazier Life Sciences Amends Mirum Pharma Stake

Frazier Life Sciences funds and affiliates updated their beneficial ownership in Mirum Pharmaceuticals, detailing recent share acquisitions and a merger-related stock issuance.

Summary

• Frazier Life Sciences entities and individuals collectively reported beneficial ownership in Mirum Pharmaceuticals, Inc.
• Patrick J. Heron beneficially owns 4,108,404 shares, representing 6.8% of the common stock, including direct holdings, options, and shares held by Frazier Life Sciences IX, L.P. and Frazier Life Sciences X, L.P.
• James N. Topper beneficially owns 4,025,922 shares, representing 6.7% of the common stock, including shares held by Frazier Life Sciences IX, L.P. and Frazier Life Sciences X, L.P.
• The ownership percentages are calculated based on a total of 59,974,732 shares, which includes 51,393,574 shares outstanding on October 31, 2025, plus anticipated shares from the Bluejay Therapeutics acquisition (5,196,009 shares) and two private placements (2,385,149 shares and 1,000,000 shares).
• Recent transactions on January 23, 2026, include Frazier Life Sciences X, L.P. receiving 159,277 shares and Frazier Life Sciences XI, L.P. receiving 286,698 shares due to the Bluejay Therapeutics merger.
• On the same date, Frazier Life Sciences Public Fund, L.P. purchased 536,412 pre-funded warrants at $68.4799 per share, and Frazier Life Sciences X, L.P., Frazier Life Sciences XI, L.P., and Frazier Life Sciences XII, L.P. purchased common stock at $68.48 per share (131,425, 244,232, and 62,931 shares respectively).
• The reporting persons acquired these shares for investment purposes and may adjust their holdings based on market conditions and company prospects.
• A Registration Rights Agreement dated December 7, 2025, grants certain Frazier funds rights to register their shares for resale, with Mirum Pharmaceuticals covering associated fees and expenses.

Sentiment

Score: 6

Explanation: The filing is a routine beneficial ownership update following recent corporate actions (acquisition, private placements). The continued significant investment by Frazier Life Sciences is a moderately positive signal, but the filing itself does not contain new performance-related information to significantly shift sentiment.

Positives

• Frazier Life Sciences funds continue to hold significant stakes, indicating ongoing investor confidence in Mirum Pharmaceuticals.
• The acquisition of Bluejay Therapeutics, Inc. and subsequent private placements suggest strategic growth and capital infusion for Mirum Pharmaceuticals.
• The Registration Rights Agreement facilitates potential future liquidity for the Frazier funds, which can be seen as a positive for their investment strategy.

Risks

• The reporting persons may dispose of or acquire additional shares, which could impact the market price of Mirum Pharmaceuticals' common stock.
• Warrants held by Frazier Life Sciences Public Fund, L.P. are subject to beneficial ownership limitations (9.99%), which could restrict immediate full exercise.

Future Outlook

The reporting persons acquired shares for investment purposes and may adjust their holdings by disposing of or acquiring additional shares based on market conditions, evaluation of the Issuer's business and prospects, and other factors. No present plans for extraordinary corporate transactions, changes in board/management, capitalization/dividend policy, business/corporate structure, charter/bylaws, delisting, or termination of registration are disclosed.

Industry Context

This filing reflects ongoing investment activity in the life sciences sector, particularly in companies like Mirum Pharmaceuticals that are engaged in strategic acquisitions (Bluejay Therapeutics) and capital raising through private placements. The continued significant stake held by Frazier Life Sciences, a prominent venture capital firm, suggests confidence in Mirum's long-term potential within the biotechnology and pharmaceutical industry.

Stakeholder Impact

• Shareholders: The increase in outstanding shares due to the acquisition and private placements could lead to dilution for existing shareholders. The registration rights agreement could lead to future share sales by the reporting persons.
• Investors: Provides transparency on significant institutional ownership and recent investment activities, which can inform investment decisions.

Next Steps

• Mirum Pharmaceuticals has agreed to prepare and file a registration statement with the SEC to register for resale the Registrable Securities held by certain Frazier funds.

Key Dates

Recommendation

This Schedule 13D/A primarily updates beneficial ownership information following Mirum Pharmaceuticals' acquisition of Bluejay Therapeutics and related private placements. While the continued significant investment by Frazier Life Sciences is a positive signal of institutional confidence, the filing itself does not provide new operational or financial performance data to warrant a change in investment stance. The recent capital raises and acquisition are already known events. Investors should hold and monitor Mirum's integration of Bluejay and future financial results.

Keywords

Mirum Pharmaceuticals, Frazier Life Sciences, Schedule 13D/A, Beneficial Ownership, Common Stock, Equity Investment, Biotechnology, Pharmaceuticals, Venture Capital, Bluejay Therapeutics Acquisition, Private Placement, Registration Rights