The Law Offices of Frank R. Cruz announces that a class action lawsuit has been filed on behalf of shareholders who purchased or otherwise acquired Gossamer Bio, Inc. (“Gossamer” or the “Company”) (NASDAQ: GOSS) securities between June 16, 2025 and February 20, 2026, inclusive (the “Class Period”). Gossamer investors have until June 1, 2026 to file a lead plaintiff motion.

What Happened?

On February 23, 2026, Gossamer disclosed that results for its Phase 3 PROSERA study of seralutinib for the treatment of pulmonary arterial hypertension had failed to meet the primary endpoint, citing patients at Latin American sites performing particularly well on placebo due to enrollment of a heavily-treated lower-risk population.

On this news, Gossamer’s stock price fell $1.71, or 80.3%, to close at $0.42 per share on February 23, 2026, thereby injuring investors.

What Is The Lawsuit About?

The complaint filed in this class action alleges that throughout the Class Period, Defendants made materially false and/or misleading statements, as well as failed to disclose material adverse facts about the Company’s business, operations, and prospects. Specifically, Defendants failed to disclose to investors that: (1) patients at the Latin American sites were largely heavily-treated and lower risk and, ultimately, performed particularly well on the placebo, thus, Gossamer’s Phase 3 PROSERA study failed to meet the primary endpoint of improved six-minute walk distance at week 24; and (2) as a result, Defendants’ positive statements about the Company’s business, operations, and prospects were materially misleading and/or lacked a reasonable basis at all relevant times.