SCHEDULE: RA Capital Discloses 5.9% Stake in Disc Medicine

RA Capital Management and its affiliates have reported a 5.9% passive ownership stake in Disc Medicine, Inc., totaling 2,228,924 shares.

Summary

• RA Capital Management, L.P., Peter Kolchinsky, Rajeev Shah, and RA Capital Healthcare Fund, L.P. (collectively, the "Reporting Persons") have filed a Schedule 13G.
• The Reporting Persons collectively beneficially own 2,228,924 shares of Disc Medicine, Inc.'s common stock.
• This ownership represents 5.9% of the total outstanding common stock, based on 37,750,162 shares outstanding as of October 31, 2025.
• The shares are primarily held by RA Capital Healthcare Fund, L.P., with RA Capital Management, L.P. serving as the investment adviser.
• Peter Kolchinsky and Rajeev Shah are controlling persons of RA Capital Management GP, LLC, the general partner of RA Capital.
• The Reporting Persons expressly disclaim status as a "group" for purposes of this Schedule 13G and certify that the securities were not acquired for the purpose of changing or influencing control of the issuer.

Sentiment

Score: 7

Explanation: The disclosure of a 5.9% passive stake by RA Capital Management, a specialized healthcare investor, is generally viewed positively as it signals institutional confidence in Disc Medicine's long-term prospects and potential value.

Positives

• A significant institutional investor, RA Capital Management, a specialized healthcare-focused firm, has taken a 5.9% stake in Disc Medicine, indicating confidence in the company's long-term prospects.
• The investment is classified as passive, suggesting a belief in the company's current strategic direction without intent to influence control.

Risks

• The filing itself does not detail risks of the issuer, but rather the nature of the ownership. The primary risk for the reporting persons is the investment risk associated with Disc Medicine's stock performance.

Future Outlook

The filing is a disclosure of current ownership and does not contain forward-looking statements or guidance regarding Disc Medicine, Inc.'s future performance or operations.

Management Comments

• The Reporting Persons expressly disclaim status as a 'group' for purposes of this Schedule 13G.
• RA Capital, Dr. Kolchinsky, and Mr. Shah disclaim beneficial ownership of the securities reported in this Schedule 13G other than for the purpose of determining their obligations under Section 13(d) of the Act.
• The Fund has delegated to RA Capital the sole power to vote and the sole power to dispose of all securities held in the Fund's portfolio, and disclaims beneficial ownership for purposes of Section 13(d) of the Act due to this delegation.
• The securities were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer.

Industry Context

RA Capital Management is a prominent investment firm focused on the healthcare and life sciences sectors. Their significant stake in Disc Medicine, a biotechnology company, aligns with broader industry trends of specialized funds investing in innovative drug development and therapeutic companies. This investment signals RA Capital's belief in Disc Medicine's potential within the competitive biotech landscape.

Stakeholder Impact

• Shareholders: May view the significant institutional investment as a positive signal, potentially increasing confidence and attracting further investment.
• Management: The presence of a large passive investor like RA Capital could provide a degree of stability and validation for the company's strategic direction.

Next Steps

• The filing does not outline specific future actions or milestones for Disc Medicine, Inc. or the Reporting Persons beyond the ongoing passive investment.

Key Dates

Recommendation

While the disclosure of a significant passive stake by a reputable healthcare investor like RA Capital Management is a positive signal, indicating institutional confidence, this filing alone does not provide sufficient operational or financial data to warrant a 'buy' or 'sell' recommendation. It primarily confirms a substantial, non-controlling investment. Investors should 'hold' and await further operational updates and financial results from Disc Medicine to make a more informed decision.

Keywords

Disc Medicine, RA Capital Management, Schedule 13G, Beneficial Ownership, Common Stock, Institutional Investor, Healthcare Fund, Passive Investment, Biotechnology, Pharmaceuticals