SCHEDULE: Fairmount Funds Exits Major Stake in Dianthus Therapeutics

Fairmount Funds Management LLC and its affiliates have reduced their beneficial ownership in Dianthus Therapeutics, Inc. to below 5%, marking an exit filing.

Summary

• Fairmount Funds Management LLC, Fairmount Healthcare Fund II L.P., Peter Harwin, and Tomas Kiselak (the "Reporting Persons") filed Amendment No. 4 to their Schedule 13D for Dianthus Therapeutics, Inc.
• The Reporting Persons collectively beneficially own 2,139,635 shares of Common Stock, representing 4.9% of the outstanding class.
• This ownership comprises 2,137,191 shares of Common Stock and pre-funded warrants to purchase up to 2,444 shares of Common Stock.
• On November 21, 2025, Fairmount Healthcare Fund II L.P. sold 1,170,000 shares of Common Stock in a block trade at a price of $39.50 per share.
• Following this sale, the Reporting Persons no longer beneficially own 5% or more of the outstanding Common Stock, making this an "exit filing."
• Fund II also provided notice to the Company on November 24, 2025, to decrease the beneficial ownership limitation for the Pre-Funded Warrants from 9.99% to 4.99%.
• The percentage of class is calculated based on 42,878,549 shares of Common Stock outstanding, which includes 42,876,015 shares as of November 3, 2025, and the 2,444 shares underlying the Pre-Funded Warrants.

Sentiment

Score: 3

Explanation: The filing indicates a significant reduction in ownership by a major institutional investor, culminating in an 'exit filing.' This divestment, especially a large block sale, can be perceived negatively by the market as it suggests a lack of continued conviction or a strategic shift away from the company by a sophisticated holder.

Negatives

• A significant institutional investor, Fairmount Healthcare Fund II L.P., sold 1,170,000 shares of Common Stock, indicating a reduction in their investment.
• The Reporting Persons have reduced their stake below the 5% threshold, leading to an "exit filing," which could be interpreted as a loss of confidence by a major holder.

Risks

• The Reporting Persons may, at any time, review, reconsider, and change their position or purpose regarding their investment in Dianthus Therapeutics, Inc.
• They may seek to influence management or the board of directors of the Company.

Future Outlook

The Reporting Persons currently have no present plans or proposals for actions described in Item 4 of Schedule 13D, but they may, at any time, review, reconsider, and change their position or purpose, and may seek to influence the Company's management or board of directors.

Industry Context

NA

Stakeholder Impact

• Shareholders may perceive the significant reduction in ownership by a major institutional investor as a negative signal, potentially impacting investor confidence and the company's stock price.

Next Steps

• The Reporting Persons may, at any time, review, reconsider, and change their investment position or purpose regarding Dianthus Therapeutics, Inc.

Key Dates

Recommendation

The filing details a significant block sale by a major institutional investor, Fairmount Healthcare Fund II L.P., reducing their stake below 5% and marking an 'exit filing.' While this is a notable change in ownership structure, the filing itself does not provide new fundamental information about Dianthus Therapeutics, Inc.'s operations, financial health, or strategic direction. The sale represents a decision by a specific investor to divest, which could be for various reasons unrelated to the company's intrinsic value. Therefore, a 'hold' recommendation is appropriate, advising investors to maintain their current position while awaiting further company-specific news or a clearer understanding of the implications of this ownership change on market sentiment and future performance.

Keywords

Dianthus Therapeutics, Fairmount Funds Management, Schedule 13D, Beneficial Ownership, Stock Sale, Pre-Funded Warrants, Institutional Investor, Equity Stake, Exit Filing, Biotechnology