Law Firms Seek Lead Plaintiffs in Gossamer Bio Securities Suit Before June 1 Deadline

Overview

• Gossamer announced on February 23 that its Phase 3 PROSERA study of seralutinib missed the primary six‑minute‑walk distance goal, reporting a placebo‑adjusted gain of +13.3 meters with p=0.0320 which did not meet the trial's prespecified alpha.
• The February 23 disclosure sent Gossamer shares down by more than 80% in a single trading day and the company later told investors that it had fallen below Nasdaq's $1 minimum bid‑price requirement as of February 24.
• Multiple plaintiff firms have filed complaints and are publicly soliciting eligible investors to move for lead‑plaintiff status by the June 1, 2026 deadline to represent the putative class that purchased stock between June 16, 2025 and February 20, 2026.
• The lawsuits allege Gossamer misled investors about PROSERA's trial design and site monitoring, saying Latin American sites enrolled heavily treated, lower‑risk patients whose strong placebo performance diluted the pooled treatment effect.
• No class has been certified and the allegations are unproven, but the litigation could affect investor recoveries and the company’s ability to remain listed on Nasdaq if the listing shortfall is not cured.