Gossamer Bio, Inc.

Background

Company Name	Gossamer Bio, Inc.
Stock Symbol	GOSS
Class Period	June 16, 2025 to February 20, 2026
Lead Plaintiff Motion Deadline	June 01, 2026

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If you suffered a loss on your Gossamer Bio, Inc. investments or would like to inquire about joining an action to recover your loss under the federal securities laws, please complete the form below. Please note that submission of this form does not by itself form an attorney-client relationship nor does filling out this form mean you have joined any lawsuit.

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Additional Comments

Background

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.

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.

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