- Participants treated with seralutinib recorded a median improvement of 28.2 meters in walking distance, compared with 13.5 meters with placebo.
- The estimated treatment benefit was 13.3 meters, with a p-value of 0.032, falling short of the predefined significance cutoff of 0.025.
- In a predefined subgroup of intermediate- and high-risk individuals, seralutinib delivered a more pronounced benefit.
Gossamer Bio Inc. (GOSS) on Monday released topline findings from its late-stage PROSERA trial evaluating seralutinib in patients with pulmonary arterial hypertension (PAH), offering a mixed picture as the company weighs its regulatory strategy.
The Phase 3 study assessed the experimental therapy over 24 weeks, measuring improvement in six-minute walk distance compared with placebo.
Primary Endpoint Falls Short
The drug did not achieve the predefined statistical bar for its main goal. Participants treated with seralutinib recorded a median improvement of 28.2 meters in walking distance, compared with 13.5 meters among placebo recipients.
The estimated treatment benefit was 13.3 meters, with a p-value of 0.032, falling short of the predefined significance cutoff of 0.025. As a result, the secondary endpoints cannot be formally considered statistically significant, though all four key secondary measures favored seralutinib.
Following the announcement, Gossamer Bio's stock traded over 82% lower on Monday mid-morning. On Stocktwits, retail sentiment around the stock remained in ‘extremely bullish’ territory while message volume shifted to ‘extremely high’ from high’ levels in 24 hours.
Stronger Results In Higher-Risk Patients
In a predefined subgroup of intermediate- and high-risk individuals, seralutinib delivered a more pronounced benefit. That cohort achieved a 20-meter placebo-adjusted increase in walking distance, along with favorable results across most secondary markers.
Patients with connective tissue disease–associated PAH also demonstrated a notable response, with a placebo-adjusted increase of 37 meters in walking distance at 24 weeks.
The company plans to meet with the U.S. Food and Drug Administration to determine a regulatory path forward. Gossamer has paused enrollment in SERANATA study to assess the implications of PROSERA’s outcome.
GOSS stock has declined by over 70% in the last 12 months.
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