Common Stock, $0.001 par value

Dianthus Therapeutics, Inc.

7 TIMES SQUARE, NEW YORK, NY, 10036

This statement is filed on behalf of each of the following person (collectively, the "Reporting Persons"): i. Avidity Partners Management LP; ii. Avidity Partners Management (GP) LLC; iii. Avidity Capital Partners Fund (GP) LP; iv. Avidity Capital Partners (GP) LLC; v. Avidity Private Master Fund I LP; and vi. Michael Gregory. The foregoing persons are hereinafter sometimes collectively referred to as the "Reporting Persons." Any disclosures herein with respect to a Reporting Persons is made by such Reporting Persons. The filing of this statement should not be construed in and of itself as an admission by any Reporting Person as to beneficial ownership of the securities reported herein. The Reporting Persons have entered into a joint filing agreement, filed as Exhibit A to this Amendment No. 3 to Schedule 13D, pursuant to which the Reporting Persons agreed to file the Schedule 13D and any amendments thereto in accordance with the provisions of Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended.

The address of the principal business office of each of the Reporting Persons is 2828 N Harwood Street, Suite 1220, Dallas, Texas 75201.

The principal business of Avidity Partners Management LP is managing investments. Avidity Partners Management (GP) LLC is the general partner of Avidity Partners Management LP. Avidity Capital Partners Fund (GP) LP serves as the general partner of private investment funds managed by Avidity Partners Management LP, including Avidity Private Master Fund I LP. Avidity Capital Partners (GP) LLC is the general partner of Avidity Capital Partners Fund (GP) LP. Mr. Gregory is the managing member of Avidity Partners Management (GP) LLC and Avidity Capital Partners (GP) LLC.

None of the Reporting Persons have been a party to any civil proceeding of a judicial or administrative body of competent jurisdiction resulting in any judgment, decree or final order enjoining them from engaging in future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws during the last five years.

i. Avidity Partners Management LP is a Delaware limited partnership; ii. Avidity Partners Management (GP) LLC is a Delaware limited liability company; iii. Avidity Capital Partners Fund (GP) LP is a Delaware limited partnership; iv. Avidity Capital Partners (GP) LLC is a Delaware limited liability company; v. Avidity Private Master Fund I LP is a Cayman Islands exempted limited partnership; and vi. Michael Gregory is a citizen of the United States of America.

The information set forth in Items 2, 3 and 4 is hereby incorporated by reference into this Item 5. The aggregate number of shares of Common Stock and the percentage of total outstanding shares of Common Stock beneficially owned by the Reporting Persons is set forth below. References to percentage ownerships of shares of Common Stock in this statement are based on 42,876,015 shares of Common Stock outstanding as of November 3, 2025 as reported in the Issuer's Form 10-Q filed with the Securities and Exchange Commission on November 5, 2025. The filing of this statement shall not be construed as an admission that a Reporting Person beneficially owns those shares held by any other Reporting Person.

Avidity Partners Management LP, Avidity Partners Management (GP) LLC, Avidity Capital Partners Fund (GP) LP, Avidity Capital Partners (GP) LLC and Michael Gregory have shared power to vote or to direct the vote and shared power to dispose or to direct the disposition of 2,104,184 shares of the Common Stock reported in (a) above.

Avidity Private Master Fund I LP has shared power to vote or to direct the vote and shared power to dispose or to direct the disposition of 1,899,593 shares of the Common Stock reported in (a) above. The transactions in the Common Stock by the Reporting Persons during the past sixty days in respect of the Issuer are set forth on Exhibit B. All of the securities in this Schedule 13D are owned by advisory clients of Avidity Partners Management LP. Other than Avidity Private Master Fund I LP, no such client(s) is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the Common Stock in an amount equal to more than five percent of the class. The Reporting Persons no longer beneficially own 5% or more of the total outstanding shares of Common Stock. Consequently, this Amendment No. 3 is the final amendment to the Schedule 13D and constitutes an "exit filing" for the Reporting Persons.