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StocksMediumUpdated×2•Originally published 5 May 2026•Updated 7 May 2026•

1 min read

Gossamer Bio Faces Class Action Lawsuit After 80% Stock Crash on Trial Failure

Key Facts

1A securities class action lawsuit was filed against Gossamer Bio and an executive for investors who acquired securities between June 16, 2025, and February 20, 2026.

2The company announced in February 2026 that Phase 3 PROSERA study top-line results failed to meet the primary endpoint of six-minute-walk distance change.

27 days ago

Version History

Version 227 days ago

What changed: Added specific class action period dates, the exact announcement date of the clinical failure, and technical details regarding the failed primary endpoint.

Version 128 days ago

What changed: Added details regarding the filing law firm and the established lead plaintiff deadline of June 1, 2026.

Gossamer Bio is facing a securities class action lawsuit filed by Hagens Berman Sobol Shapiro LLP on behalf of investors who acquired GOSS securities between June 16, 2025, and February 20, 2026. The legal action follows the company's official announcement on February 23, 2026, regarding disappointing top-line results from its Phase 3 PROSERA study. Specifically, the trial failed to meet its primary endpoint of change in six-minute-walk distance at week 24, triggering a massive 80% collapse in GOSS shares. A lead plaintiff deadline of June 1, 2026, has been established for investor participation in the litigation. The lawsuit alleges that the company and its executives misled the public regarding the clinical trial's viability prior to the disclosure. Market participants are closely monitoring how these proceedings will impact the company's liquidity and operational stability following the clinical failure.