Bragar Eagel & Squire, P.C., a prominent law firm specializing in stockholder rights, has filed a class action lawsuit against Gossamer Bio, Inc. (NASDAQ:GOSS) in the United States District Court for the Southern District of California. This lawsuit is on behalf of investors who purchased Gossamer securities from June 16, 2025, to February 20, 2026. The complaint alleges that Gossamer misled investors by providing overly positive statements about its Phase 3 PROSERA study, which evaluates seralutinib for treating pulmonary arterial hypertension (PAH). Specifically, the firm claims that Gossamer concealed material adverse facts about the study's design, particularly regarding the placebo response at Latin American testing sites, leading to artificially inflated stock prices. Investors affected by these developments are urged to contact Bragar Eagel & Squire for legal guidance before the June 1, 2026 deadline to apply for lead plaintiff status in the lawsuit.