X0202 SCHEDULE 13G 0001404574 XXXXXXXX LIVE Common Stock, $0.0001 par value 06/04/2026 0001728117 Gossamer Bio, Inc. 38341P102 3115 MERRYFIELD ROW SUITE 120 SAN DIEGO CA 92121 Rule 13d-1(c) 683 Capital Management, LLC DE 0 49868571 0 49868571 49868571 N 9.99 IA The amounts reflected in Rows 5-9 include (a) 39,504,484 shares of Common Stock, (b) 9,102,055 shares of Common Stock issuable upon exercise of warrants currently exercisable, and (c) 1,262,032 shares of Common Stock issuable upon conversion of convertible notes. 683 Capital Partners, LP DE 0 49868571 0 49868571 49868571 N 9.99 PN The amounts reflected in Rows 5-9 include (a) 39,504,484 shares of Common Stock, (b) 9,102,055 shares of Common Stock issuable upon exercise of warrants currently exercisable, and (c) 1,262,032 shares of Common Stock issuable upon conversion of convertible notes. Ari Zweiman X1 0 49868571 0 49868571 49868571 N 9.99 IN The amounts reflected in Rows 5-9 include (a) 39,504,484 shares of Common Stock, (b) 9,102,055 shares of Common Stock issuable upon exercise of warrants currently exercisable, and (c) 1,262,032 shares of Common Stock issuable upon conversion of convertible notes. Gossamer Bio, Inc. 3115 MERRYFIELD ROW, SUITE 120, SAN DIEGO, CALIFORNIA 92121 683 Capital Management, LLC 683 Capital Partners, LP Ari Zweiman Each of the foregoing is referred to as a "Reporting Person" and collectively as the "Reporting Persons." The principal business address for each of the Reporting Persons is 1700 Broadway, Suite 4200, New York, New York 10019. 683 Capital Management, LLC - DELAWARE 683 Capital Partners, LP - DELAWARE Ari Zweiman - UNITED STATES Y As of June 11, 2026, 683 Capital Partners, LP beneficially owned (a) 49,868,571 shares of Common Stock, (b) warrants to purchase 9,102,055 shares of Common Stock which are currently exercisable, and (c) 1,262,032 shares issuable upon conversion of convertible notes. 683 Capital Management, LLC, as the investment manager of 683 Capital Partners, LP, may be deemed to have beneficially owned the (a) 49,868,571 shares of Common Stock, (b) warrants to purchase 9,102,055 shares of Common Stock which are currently exercisable, and (c) 1,262,032 shares issuable upon conversion of convertible notes beneficially owned by 683 Capital Partners, LP. Ari Zweiman, as the Managing Member of 683 Capital Management, LLC, may be deemed to have beneficially owned the (a) 49,868,571 shares of Common Stock, (b) warrants to purchase 9,102,055 shares of Common Stock which are currently exercisable, and (c) 1,262,032 shares issuable upon conversion of convertible notes beneficially owned by 683 Capital Partners, LP. beneficially owned by 683 Capital Management, LLC. The following percentage is based on 488,846,722 shares of common stock ($0.0001 par value) outstanding as of June 5, 2026, as disclosed in the Issuer's Form DEF 14A filed on June 9, 2026, plus (a) 9,102,055 shares of Common Stock issuable upon exercise of currently exercisable warrants and (b) 1,262,032 shares issuable upon conversion of convertible notes, but excludes shares of Common Stock issuable upon conversion of convertible notes in excess of the 9.99% beneficial ownership limitation contained in the indenture governing such notes. As of June 11, 2026, the Reporting Persons may be deemed to have beneficially owned approximately 9.99% of the outstanding Common Shares. 9.99 See Cover Pages Items 5-9. See Cover Pages Items 5-9. See Cover Pages Items 5-9. See Cover Pages Items 5-9. Y Y Y N See Exhibit A. Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11. JOINT FILING AGREEMENT The undersigned hereby agree that the statement on Schedule 13G with respect to the shares of Common Stock, par value $0.0001 per share, of Gossamer Bio, Inc. dated as of June 11, 2026 is, and any further amendments thereto signed by each of the undersigned shall be, filed on behalf of each of the undersigned pursuant to and in accordance with the provisions of Rule 13d-1(k)(2) under the Securities Exchange Act of 1934, as amended. Dated: June 11, 2026 683 CAPITAL MANAGEMENT, LLC By: /s/ Ari Zweiman Ari Zweiman, Managing Member 683 CAPITAL PARTNERS, LP By: /s/ Ari Zweiman Ari Zweiman, Authorized Person /s/ Ari Zweiman Ari Zweiman 683 Capital Management, LLC Ari Zweiman 06/11/2026 683 Capital Partners, LP Ari Zweiman 06/11/2026 Ari Zweiman Ari Zweiman 06/11/2026