The Schall Law Firm is seeking investors who purchased Gossamer Bio, Inc. (NASDAQ: GOSS) securities between June 16, 2025 and February 20, 2026 to join a class action lawsuit alleging securities fraud. The company allegedly made false and misleading statements regarding its Phase 3 PROSERA study design, specifically concealing adverse facts about placebo response controls at certain testing sites.

A securities class action lawsuit has been filed against Gossamer Bio (GOSS) alleging executives concealed placebo response risks in the Phase 3 PROSERA trial for seralutinib. The trial failed to meet its primary endpoint on February 23, 2026, causing an 80% stock price decline. The complaint claims management misled investors about trial design and patient recruitment despite knowing of significant placebo effects, particularly at Latin American sites.

Rosen Law Firm has issued deadline notices for securities class action lawsuits against Gossamer Bio, Upstart Holdings, and POET Technologies. Investors with losses exceeding $100K are encouraged to secure counsel before upcoming deadlines. The lawsuits allege false and misleading statements regarding clinical trial design and other material facts.

Gossamer Bio (GOSS) faces a securities class action lawsuit after its Phase 3 PROSERA trial for seralutinib failed to meet its primary endpoint, causing an 80% stock price drop. The lawsuit alleges the company misled investors about trial design and patient recruitment, particularly regarding heavily-treated patients in Latin America sites showing outsized placebo responses that compressed treatment efficacy.

A class action lawsuit has been filed against Gossamer Bio, Inc. (NASDAQ: GOSS) for allegedly providing materially false and misleading statements regarding its Phase 3 PROSERA study for pulmonary arterial hypertension treatment. The company is accused of expressing confidence in the trial design while concealing adverse facts about placebo response controls at Latin American testing sites, causing investors to purchase securities at artificially inflated prices. Investors who purchased shares between June 16, 2025, and February 20, 2026, have until June 1, 2026, to apply as lead plaintiff.

Rosen Law Firm is notifying investors in Gossamer Bio, Inc., FS KKR Capital Corp., and Regencell Bioscience Holdings Limited of ongoing securities class action lawsuits. The firm is seeking lead plaintiffs with losses exceeding $100,000 before the June 1, 2026 deadline. The Gossamer case alleges defendants made false statements about their Phase 3 PROSERA study design while concealing material adverse facts.

Gossamer Bio (GOSS) faces a securities class action lawsuit after its Phase 3 PROSERA trial for seralutinib failed to meet its primary endpoint, causing an 80% stock price drop. The lawsuit alleges the company misled investors about trial design and patient recruitment, particularly regarding heavily-treated patients in Latin America sites showing outsized placebo responses that compressed treatment efficacy.

A class action lawsuit has been filed against Gossamer Bio, Inc. alleging that the company made materially false and misleading statements regarding its Phase 3 PROSERA study results while concealing material adverse facts about the study design, particularly regarding placebo response control at Latin American testing sites. The lawsuit covers investors who purchased Gossamer securities between June 16, 2025 and February 20, 2026.

Rosen Law Firm is encouraging investors who purchased securities in Gossamer Bio, Upstart Holdings, and FS KKR Capital Corp. during specified periods to join class action lawsuits. The firm is seeking a lead plaintiff for the Gossamer case by June 1, 2026, with allegations involving false statements regarding a Phase 3 clinical study.

A class action lawsuit has been filed against Gossamer Bio, Inc. alleging that the company made materially false and misleading statements regarding its Phase 3 PROSERA study results while concealing design flaws and inadequate placebo control at Latin American testing sites. The lawsuit covers investors who purchased Gossamer securities between June 16, 2025 and February 20, 2026, claiming the stock traded at artificially inflated prices.

Pomerantz Law Firm has filed class action lawsuits against Gossamer Bio, Inc. and other companies for alleged securities fraud. Gossamer's stock plummeted 80.13% on February 23, 2026, after its Phase 3 PROSERA study for seralutinib failed to meet its primary endpoint for treating pulmonary arterial hypertension. Investors with losses are urged to contact the firm by the June 1, 2026 deadline to potentially become lead plaintiffs.

Over 50 pharmaceutical companies are advancing 55+ pipeline drugs for pulmonary arterial hypertension (PAH) treatment. Recent developments include United Therapeutics' ralinepag meeting Phase III endpoints with 55% risk reduction, Gossamer Bio's seralutinib Phase III results, GSK's acquisition of 35Pharma for HS235, and Inhibikase Therapeutics enrolling patients in Phase III IMPROVE-PAH trial. Multiple novel mechanisms of action are being explored to address persistent clinical gaps in PAH management.