Gossamer Bio stock plummets 80% due to failed trial

2026-02-24 04:15:21

Investing.com – Gossamer Bio (NASDAQ:GOSS) stock plummeted 80% on Monday after the company’s seralutinib failed to meet the primary endpoint in the Phase 3 PROSERA trial for pulmonary arterial hypertension.

The drug showed a 13.3-meter improvement in six-minute walk distance (adjusted for placebo) at week 24, with a p-value of 0.0320, not reaching the pre-specified significance threshold of 0.025. Patients treated with seralutinib had a median change from baseline of 28.2 meters, compared to 13.5 meters in the placebo group.

Although the primary endpoint was not met, seralutinib demonstrated activity in certain patient subgroups. In a pre-specified high-risk subgroup of 234 patients, the drug achieved a 20.0-meter improvement in six-minute walk distance (adjusted for placebo), with a p-value of 0.0207. The treatment effect was most pronounced in North America, with a 25.9-meter improvement over placebo, though it did not reach statistical significance.

A key secondary endpoint showed that seralutinib reduced NT-proBNP levels by 120.4 ng/L at week 24 compared to placebo. In patients with connective tissue disease-related pulmonary arterial hypertension, the drug increased six-minute walk distance by 37.0 meters (adjusted for placebo).

The drug was generally well tolerated, with 86.5% of patients on seralutinib reporting treatment-related adverse events, compared to 80.5% in the placebo group. Cough was the most common adverse event, occurring in 37.0% of seralutinib patients.

Gossamer Bio plans to meet with the U.S. FDA to discuss the future development path for seralutinib. The company is pausing enrollment in its SERANATA study to assess the impact of the PROSERA results, especially regional differences in placebo response. Among the trial population, 55% of patients were on triple or quadruple background therapy for pulmonary arterial hypertension, and 61% were on background prostacyclin therapy.

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