Sec Form 3 Filing - Fairmount Funds Management LLC @ Jade Biosciences, Inc. - 2025-04-28

FORM 3 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 Jade Biosciences, Inc. [ JBIO] 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) 04/28/2025 (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 564,551 ( 1 ) ( 2 ) I By Fairmount Healthcare Fund II L.P. ( 3 ) Common Stock 2,655,817 ( 1 ) ( 2 ) I By Fairmount Healthcare Co-Invest IV L.P. ( 3 )

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 Series A Non-Voting Convertible Preferred Stock ( 4 ) ( 4 ) ( 4 ) Common Stock 12,622,000 ( 1 ) ( 5 ) I By Fairmount Healthcare Fund II L.P. ( 3 ) Pre-funded Warrant $ 0.0001 ( 6 ) ( 6 ) Common Stock 4,935,159 ( 1 ) ( 7 ) I By Fairmount Healthcare Fund II L.P. ( 3 )

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 Fairmount Healthcare Fund II L.P. 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 05/01/2025 Signature of Reporting Person Date /s/ Tomas Kiselak, Managing Member of Fairmount Healthcare Fund II L.P. 05/01/2025 Signature of Reporting Person Date /s/ Tomas Kiselak 05/01/2025 Signature of Reporting Person Date /s/ Peter Harwin 05/01/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Effective as of April 28, 2025 (the "Effective Time"), (i) a wholly-owned subsidiary of Aerovate Therapeutics, Inc. ("Aerovate") merged with and into Jade Biosciences, Inc. ("Jade") with Jade continuing as a wholly owned subsidiary of Aerovate and the surviving corporation of the merger, (ii) immediately thereafter, Jade merged with and into a second wholly-owned subsidiary of Aerovate ("Second Merger Sub"), with Second Merger Sub being the surviving entity of the merger and (iii) immediately thereafter, Second Merger Sub merged with and into Aerovate, with Aerovate being the surviving entity of the merger (collectively, the "Merger"). At the Effective Time, Aerovate changed its name to "Jade Biosciences, Inc." (hereinafter, the "Issuer"). ( 2 )Represents the number of shares of the Issuer's common stock received by the Reporting Person in the Merger in exchange for the shares of Jade's common stock held by the Reporting Person prior to the Merger. Each share of Jade's common stock held at the Effective Time was exchanged for 0.6311 shares of the Issuer's common stock. ( 3 )Fairmount Funds Management LLC ("Fairmount") is the investment manager for Fairmount Healthcare Fund II LP and Fairmount Healthcare Co-Invest IV L.P. Peter Harwin and Tomas Kiselak are the managers of Fairmount. Fairmount, Mr. Harwin, and Mr. Kiselak disclaim beneficial ownership of any of the reported securities, except to the extent of their pecuniary interest therein. ( 4 )Shares of Series A Non-Voting Convertible Preferred Stock of the Issuer, par value $0.0001 per share (the "Issuer Preferred Stock") are convertible into shares of the Issuer's common stock at any time at the option of the holder thereof, based on the Conversion Ratio and subject to certain limitations, including the Beneficial Ownership Limitation (as such terms are defined in the Certificate of Designation for the Issuer Preferred Stock filed with the Securities and Exchange Commission as Exhibit 3.7 to the Issuer's Form 8-K filed on May 1, 2025). The Issuer Preferred Stock has no expiration date. ( 5 )Represents the number of shares of the Issuer's common stock underlying 12,622 shares of Issuer Preferred Stock received by the Reporting Person in the Merger in exchange for the shares of Jade's Series Seed Convertible Preferred Stock ("Jade Preferred Stock") held by the Reporting Person prior to the Merger. Each share of Jade Preferred Stock held at the Effective Time was exchanged for 0.0006311 shares of Issuer Preferred Stock. ( 6 )The pre-funded warrants to purchase shares of the Issuer's common stock (the "Issuer Pre-Funded Warrants") have no expiration date and are exercisable at any time after the date of issuance. A holder of Issuer Pre-Funded Warrants may not exercise the Issuer 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. ( 7 )Represents the number of Issuer Pre-Funded Warrants received by the Reporting Person in the Merger in exchange for pre-funded warrants to purchase shares of Jade's common stock (the "Jade Pre-Funded Warrants") held by the Reporting Person prior to the Merger. Each Jade Pre-Funded Warrant held at the Effective Time was exchanged for 0.6311 Issuer Pre-Funded Warrants.

Remarks: Exhibit 24 - Power of Attorney Fairmount, Fairmount Healthcare Fund II LP and Fairmount Healthcare Co-Invest IV L.P. 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 manager of Fairmount.

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

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