Gossamer Bio Shares Plunge 60% After Missing 0.025 P-Value Threshold
Gossamer Bio’s Phase 3 PROSERA trial of seralutinib reported a p-value of 0.032, missing the pre-specified 0.025 threshold and failing its primary endpoint. Shares plunged over 60% following the unexpected miss after management had projected top-line results in February 2026 without disclosing the stricter statistical requirement.
1. Trial Outcome
Gossamer Bio’s Phase 3 PROSERA trial of inhaled seralutinib failed to meet its primary endpoint, delivering a p-value of 0.032 against a pre-specified alpha of 0.025.
2. Market Reaction
The trial failure triggered a sell-off that erased more than 60% of the company’s market value within hours of the announcement.
3. Guidance Disclosure Gap
In May 2025 management projected top-line February 2026 results without revealing that the protocol required a twice-as-stringent 0.025 significance level, raising investor expectations.
4. Investor Litigation
A class action inquiry has been launched, inviting shareholders who incurred losses due to the share collapse to explore legal claims over the undisclosed statistical hurdle.