Gossamer Bio's Seralutinib Phase 3 Misses Primary Endpoint, Shows Strong Subgroup Efficacy
GOSS has more than doubled off its 52-week low of $0.76 on elevated volume (1.8× avg).
Summary
Gossamer Bio's Phase 3 PROSERA study for seralutinib in PAH missed its primary endpoint but showed strong efficacy in high-risk patient subgroups, leading the company to seek FDA guidance and pause a related study.
Key Events · Product Development and Regulatory · GOSS
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Primary Endpoint Missed
The Phase 3 PROSERA study of seralutinib in pulmonary arterial hypertension (PAH) did not meet its primary endpoint (change in 6-minute walk distance) at Week 24, with a p-value of 0.0320 against a prespecified threshold of 0.025.
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Strong Subgroup Efficacy
Seralutinib demonstrated a compelling signal in intermediate- and high-risk PAH patients, showing a +20.0m placebo-adjusted improvement in 6MWD (p=0.0207). A robust +37.0m gain was also observed in connective tissue disease-associated PAH (p=0.0104).
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Positive Secondary Endpoints
All four key secondary endpoints favored seralutinib versus placebo in the overall population, including a significant reduction in NT-proBNP (p=0.0002), though formal statistical significance could not be evaluated due to the primary endpoint miss.
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Acceptable Safety Profile
Seralutinib was generally well tolerated, with a safety profile consistent with existing PAH therapies. Common adverse events included cough (37.0% vs 13.7% for placebo) and transaminase elevations (13% vs 1% for placebo).
Analysis · GOSS · Life Sciences
Gossamer Bio announced mixed topline results for its Phase 3 PROSERA study of seralutinib in pulmonary arterial hypertension (PAH). While the study narrowly missed its primary endpoint for the overall patient population, it demonstrated a compelling and clinically meaningful treatment effect in prespecified intermediate- and high-risk subgroups, as well as in patients with connective tissue disease-associated PAH. The company plans to engage with the FDA to discuss these results and evaluate a potential path forward, which introduces uncertainty as evidenced by the pause in enrollment for the ongoing SERANATA study. The generally acceptable safety profile is a positive, but the primary endpoint miss creates a significant hurdle for broad approval.
At the time of this filing, GOSS was trading at $2.06 on NASDAQ in the Life Sciences sector, with a market capitalization of approximately $493M. The 52-week trading range was $0.76 to $3.87. This filing was assessed with negative market sentiment and an importance score of 8 out of 10.