San Francisco, California--(Newsfile Corp. - May 20, 2026) - A securities class action lawsuit has been filed against Gossamer Bio, Inc. (NASDAQ: GOSS) and an executive, seeking to represent investors who purchased or otherwise acquired Gossamer securities between June 16, 2025 and February 20, 2026. The lawsuit follows Gossamer's bombshell announcement on February 23, 2026 that top-line results for its Phase 3 PROSERA study did not meet the primary endpoint (the change from baseline in six-minute-walk distance at week 24).