X0508 4 2023-09-19 0 0001690585 Dianthus Therapeutics, Inc. /DE/ DNTH 0001802528 Fairmount Funds Management LLC 200 BARR HARBOR DRIVE, SUITE 400 WEST CONSHOHOCKEN PA 19428 1 0 1 0 0001830177 Kiselak Tomas 200 BARR HARBOR DRIVE, SUITE 400 WEST CONSHOHOCKEN PA 19428 1 0 1 0 0001663607 Harwin Peter Evan 200 BARR HARBOR DRIVE, SUITE 400 WEST CONSHOHOCKEN PA 19428 1 0 1 0 0 Common Stock 2023-09-19 4 P 0 30000 13.20 A 1873833 I See footnote Consists of 30,000 shares of common stock purchased by Fairmount Healthcare Fund II LP ("Fund II"). Consists of (i) 58,857 shares of common stock held of record by Fairmount Healthcare Fund LP ("Fund I"), (ii) 1,752,830 shares of common stock held of record by Fund II and (iii) 62,146 shares of common stock held of record by Fairmount SPV III, LLC. Fairmount Funds Management LLC ("Fairmount") is the investment manager for Fund I and Fund II and is the Class A Member for Fairmount SPV III, LLC. The general partner of Fairmount is Fairmount Funds Management GP LLC ("Fairmount GP"), of which Peter Harwin and Tomas Kiselak are the managing members. Fairmount, Fairmount GP, Mr. Harwin, and Mr. Kiselak disclaim beneficial ownership of any of the reported securities, except to the extent of their pecuniary interest therein. Fairmount, Fund I, Fund II and Fairmount SPV III, LLC may each be deemed a director by deputization of the Issuer by virtue of the fact that Tomas Kiselak serves on the board of directors of the Issuer and is a Managing Member of Fairmount. /s/ Tomas Kiselak, Managing Member of Fairmount Funds Management LLC 2023-09-21 /s/ Tomas Kiselak 2023-09-21 /s/ Peter Harwin 2023-09-21