Sec Form 4 Filing - Fairmount Funds Management LLC @ Dianthus Therapeutics, Inc. /DE/ - 2024-01-22

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Fairmount Funds Management LLC 2. Issuer Name and Ticker or Trading Symbol Dianthus Therapeutics, Inc. /DE/ [ DNTH] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 200 BARR HARBOR DRIVE, SUITE 400 3. Date of Earliest Transaction (MM/DD/YY) 01/22/2024 (Street) WEST CONSHOHOCKEN, PA19428 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 01/22/2024 A 834,334 ( 1 ) A $ 12 2,762,837 I See footnote ( 2 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Pre-Funded Warrants (Right to Buy) $ 0.001 01/22/2024 A 832,333 ( 3 ) ( 4 ) ( 4 ) Common Stock 832,333 $ 11.999 832,333 I See footnote ( 5 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Fairmount Funds Management LLC 200 BARR HARBOR DRIVE, SUITE 400 WEST CONSHOHOCKEN, PA19428 X X Kiselak Tomas 200 BARR HARBOR DRIVE, SUITE 400 WEST CONSHOHOCKEN, PA19428 X X Harwin Peter Evan 200 BARR HARBOR DRIVE, SUITE 400 WEST CONSHOHOCKEN, PA19428 X X Signatures /s/ Tomas Kiselak, Managing Member of Fairmount Funds Management LLC 01/24/2024 Signature of Reporting Person Date /s/ Tomas Kiselak 01/24/2024 Signature of Reporting Person Date /s/ Peter Harwin 01/24/2024 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Consists of 834,334 shares of common stock purchased by Fairmount Healthcare Fund II LP ("Fund II") from the Issuer in a private placement, which transaction is exempt from Section 16(b) in accordance with Rule 16b-3(d)(1) promulgated under the Securities Exchange Act of 1934, as amended (the "Exchange Act"). ( 2 )Consists of (i) 58,857 shares of common stock held of record by Fairmount Healthcare Fund LP ("Fund I"), (ii) 2,641,834 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. ( 3 )Consists of Pre-Funded Warrants to purchase up to 832,333 shares of common stock purchased by Fund II from the Issuer in a private placement, which transaction is exempt from Section 16(b) in accordance with Rule 16b-3(d)(1) promulgated under the Exchange Act. ( 4 )The Pre-Funded Warrants have no expiration date and are exercisable at any time after the date of issuance. A holder of Pre-Funded Warrants may not exercise the Pre-Funded Warrant if the holder, together with its affiliates, would beneficially own more than 9.99% of the number of shares of common stock outstanding immediately after giving effect to such exercise. ( 5 )Consists of Pre-Funded Warrants to purchase up to 832,333 shares of common stock held of record by Fund II. Fairmount is the investment manager for Fund II. The general partner of Fairmount is 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.

Remarks: 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.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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