Investor Notice: Robbins LLP Informs Investors of the Gossamer Bio, Inc. Class Action Lawsuit

SAN DIEGO--(BUSINESS WIRE)--Robbins LLP informs stockholders that a class action was filed on behalf of all investors who purchased or otherwise acquired Gossamer Bio, Inc. (NASDAQ: GOSS) securities between June 16, 2025 and February 20, 2026. Gossamer is a clinical stage biopharmaceutical company focused on the development and commercialization of seralutinib for the treatment of pulmonary hypertension (PH) associated with interstitial lung disease.

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The Allegations: Robbins LLP is Investigating Allegations that Gossamer Bio, Inc. (GOSS) Misled Investors Regarding the Viability of its PROSERA Study

According to the complaint, during the class period, defendants provided investors with material information concerning Gossamer’s Phase 3 PROSERA study evaluating seralutinib for the treatment of pulmonary arterial hypertension (PAH). Defendants’ statements included, among other things, confidence in PROSERA’s trial design. Defendants provided these overwhelmingly positive statements to investors while, at the same time, disseminating false and misleading statements and/or concealing material adverse facts concerning the study design for the Company’s Phase 3 PROSERA study, particularly, controlling for the placebo response at the Latin American testing sites. This caused Plaintiff and other shareholders to purchase Gossamer’s securities at artificially inflated prices.

Plaintiff alleges that the truth emerged on February 23, 2026 when Gossamer published a press release and hosted a Special Call announcing topline results for its Phase 3 PROSERA study, which failed to meet the primary endpoint of improved six-minute walk distance (6MWD) at Week 24, with a +13.3 meter placebo-adjusted gain (p-0.0320) failing to meet the required 0.025 alpha threshold. Gossamer attributed this miss to patients at Latin American sites performing particularly well on placebo due to enrollment of a heavily-treated lower-risk population. On this news, the price of Gossamer’s common stock declined from a closing market price of $2.13 per share on February 20, 2026 to $0.42 per share on February 23, 2025, a decline of over 80% in the span of just a single day.

What Now: You may be eligible to participate in the class action against Gossamer Bio, Inc. Shareholders who wish to serve as lead plaintiff for the class should contact Robbins LLP. The lead plaintiff is a representative party who acts on behalf of other class members in directing the litigation. You do not have to participate in the case to be eligible for a recovery. If you choose to take no action, you can remain an absent class member. For more information, click here.

All representation is on a contingency fee basis. Shareholders pay no fees or expenses.

About Robbins LLP: A recognized leader in shareholder rights litigation, the attorneys and staff of Robbins LLP have been dedicated to helping shareholders recover losses, improve corporate governance structures, and hold company executives accountable for their wrongdoing since 2002.

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