Gossamer Bio, Inc. (NASDAQ:GOSS) (the "Company" or "Gossamer"), a biopharmaceutical company focused on the development and commercialization of seralutinib for the treatment of pulmonary arterial hypertension (PAH) and pulmonary hypertension associated with interstitial lung disease (PH-ILD), today announced the final tender results of its previously announced exchange offer (the "Exchange Offer") to exchange any and all of its 5.00% Convertible Senior Notes due 2027 (the "Existing Convertible Notes") for a pro rata portion of (i) up to $72.0 million in aggregate principal amount of its new 7.50% Convertible Senior Secured First Lien Notes due 2030 (the "New Convertible Notes"), (ii) up to 317,647,058 shares of its common stock (the "Common Stock") or, in lieu of issuing shares of Common Stock to the extent such shares would cause any holders of Existing Convertible Notes that are "qualified institutional buyers" as defined in Rule 144A under the Securities Act ("Eligible Holders") to beneficially own greater than 9.99% of the outstanding Common Stock, prefunded warrants to purchase shares of Common Stock (the "Prefunded Warrants" and, together with the Common Stock, the "Equity Securities") and (iii) with respect to Eligible Holders who tender prior to the Extended Early Tender Date (as defined below), warrants to purchase shares of Common Stock (the "Purchase Warrants" and, together with the New Convertible Notes and Equity Securities, the "Offered Securities").

As previously announced, as of 5:00 p.m., New York City time, on June 2, 2026 (the "Extended Early Tender Date"), $181,052,000 in aggregate principal amount of Existing Convertible Notes was validly tendered in the Exchange Offer and not validly withdrawn (such notes, the "Early Tendered Notes") and related consents to the Proposed Amendments (as defined below) were validly delivered and not validly withdrawn as of such time, and the Company and the Required Supporting Noteholders agreed to amend the condition to the Exchange Offer that a minimum of 98% of the aggregate principal amount of Existing Convertible Notes be validly tendered to a minimum of 90.5% of the aggregate principal amount of Existing Convertible Notes be validly tendered. As a result, early settlement of Offered Securities in exchange for the Early Tendered Notes validly tendered and not validly withdrawn as of the Extended Early Tender Date occurred on June 4, 2026, and the Company entered into a supplemental indenture eliminating substantially all of the restrictive covenants in the indenture governing the Existing Convertible Notes, as well as certain events of default and related provisions applicable to the Existing Convertible Notes (the "Proposed Amendments").

As of 5:00 p.m., New York City time, on June 16, 2026, based on information provided by D.F. King & Co., Inc., which is acting as the exchange agent and information agent for the Exchange Offer, no additional Existing Convertible Notes were validly tendered in the Exchange Offer. As a result, $18,948,000 in aggregate principal amount of the Existing Convertible Notes will remain outstanding following this Exchange Offer.