Philadelphia, Pennsylvania--(Newsfile Corp. - April 3, 2026) - National plaintiffs' law firm Berger Montague PC announces a class action lawsuit against Gossamer Bio, Inc. (NASDAQ: GOSS) ("Gossamer" or the "Company") on behalf of investors who purchased or acquired Gossamer shares during the period from June 16, 2025 through February 20, 2026 (the "Class Period").

Investor Deadline: Investors who purchased or acquired Gossamer securities during the Class Period may, no later than June 1, 2026, seek to be appointed as a lead plaintiff representative of the class. To learn your rights, CLICK HERE.

Headquartered in San Diego, Gossamer is a clinical-stage biopharmaceutical company focused on developing therapies for immuno-inflammatory and other diseases.

According to the complaint, throughout the Class Period, Gossamer provided overwhelmingly positive statements to investors about its Phase 3 PROSERA study evaluating seralutinib for the treatment of pulmonary arterial hypertension (PAH). In particular, the Company allegedly failed to adequately disclose how placebo responses at Latin American testing sites could impact trial results.

On February 23, 2026, Gossamer announced 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. The Company attributed this outcome to unusually strong placebo performance among patients at Latin American sites, citing enrollment of a heavily-treated lower-risk population.

Following this announcement, Gossamer's stock declined from $2.13 per share on February 20, 2026 to $0.42 per share on February 23, 2026, a loss of more than 80% in a single trading day.

If you are a Gossamer investor and would like to learn more about this action, CLICK HERE or please contact Berger Montague: Andrew Abramowitz at aabramowitz@bergermontague.com or (215) 875-3015, or Caitlin Adorni at cadorni@bergermontague.com or (267)764-4865.

About Berger Montague
Berger Montague is one of the nation's preeminent law firms focusing on complex civil litigation, class actions, and mass torts in federal and state courts throughout the United States. With more than $2.4 billion in 2025 post-trial judgments alone, the Firm is a leader in the fields of complex litigation, antitrust, consumer protection, defective products, environmental law, employment law, securities, and whistleblower cases, among many other practice areas. For over 55 years, Berger Montague has played leading roles in precedent-setting cases and has recovered over $50 billion for its clients and the classes they have represented. Berger Montague is headquartered in Philadelphia and has offices in Chicago; Malvern, PA; Minneapolis; San Diego; San Francisco; Toronto, Canada; Washington, D.C., and Wilmington, DE.

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Source: Berger Montague