☒QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June30, 2026 OR TRANSITION REPORT PURSUANT TO SECTION13 OR 15(d)OF THE SECURITIES EXCHANGE ACT OF 1934For the transition period from ________to_________.Commission File Number: 001-38796_________________________ GOSSAMER BIO, INC. (Exact name of Registrant as specified in its charter)._________________________ Delaware(State or other jurisdiction ofincorporation or organization) Securities registered pursuant to Section 12(b) of the Act: Nasdaq Global Select Market Indicate by check mark whether the Registrant (1)has filed all reports required to be filed by Section13 or 15(d) of the Securities ExchangeAct of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2)has beensubject to such filing requirements for the past 90 days:Yes☒No☐ Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant toRule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the Registrant wasrequired to submit such files).Yes☒No☐ Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reportingcompany, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and“emerging growth company” in Rule 12b-2 of the Exchange Act. Large accelerated filer☐Non-accelerated filer☒Emerging growth company☐ Accelerated filer If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complyingwith any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.☐ Table of Contents Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).YES☐NO☒As of August8, 2026, the registrant had 488,846,722 shares of common stock ($0.0001 par value) outstanding. TABLE OF CONTENTS PART I. FINANCIAL INFORMATION Item1Condensed Consolidated Financial Statements (unaudited)Condensed Consolidated Balance Sheetsas of June30, 2026 (unaudited) and December31, 2025Condensed Consolidated Statements of Operations and Comprehensive Lossfor the Three and Six Months ended June30,2026 and 2025 (unaudited)Condensed Consolidated Statements of Stockholders’ Deficitfor the Three and Six Months ended June30, 2026 and 2025(unaudited)Condensed Consolidated Statements of Cash Flowsfor the Six Months ended June30, 2026 and 2025 (unaudited)Notes to Unaudited Condensed Consolidated Financial StatementsItem2Management’s Discussion and Analysis of Financial Condition and Results of OperationsItem3Quantitative and Qualitative Disclosures About Market RiskItem4Controls and Procedures PART II. OTHER INFORMATION Item1Legal ProceedingsItem1ARisk FactorsItem2Unregistered Sales of Equity Securities and Use of ProceedsItem3Defaults Upon Senior SecuritiesItem4Mine Safety DisclosuresItem5Other InformationItem6ExhibitsExhibit IndexSignatures PART I. FINANCIAL INFORMATION ITEM 1. CONDENSED CONSOLIDATED FINANCIAL STATEMENTS (unaudited)GOSSAMER BIO, INC.Condensed Consolidated Balance Sheets(in thousands, except share and par value amounts) GOSSAMER BIO, INC.Condensed Consolidated Statements of Stockholders’ Equity (Deficit)(Unaudited)(in thousands, except share amounts) GOSSAMER BIO, INC.Condensed Consolidated Statements of Cash Flows(Unaudited)(in thousands) GOSSAMER BIO, INC.Notes to Unaudited Condensed Consolidated Financial Statements Note 1 - Description of Business Gossamer Bio, Inc. (including its subsidiaries, referred to as "we," "us," "our,", or the “Company”) is a clinical-stage biopharmaceuticalcompany focused on the development and commercialization of seralutinib for the treatment of pulmonary hypertension ("PH") includingpulmonary arterial hypertension ("PAH") and PH associated with interstitial lung disease ("PH-ILD"). The Company was incorporated in thestate of Delaware on October 25, 2015 (originally as FSG Bio, Inc.) and is based in San Diego, California. The unaudited condensed consolidated financial statements include the accounts of Gossamer Bio, Inc. and its wholly ownedsubsidiaries. All intercompany balances and transactions among the consolidated entity have been eliminated in consolidation. Liquidity and Going Concern The Company has incurred significant operating losses since its inception. As of June30, 2026, the Company had an accumulated deficitof $1,468.7 million. From the Company’s inception through June30, 2026, the Company has funded its operations primarily through equityfinancings, convertible senior notes and the Chiesi Collaboration Agreement (as defined in Note 10 below). The Company’s existing cas