Business Context and Reporting Period
Company: Gossamer Bio, Inc. (GOSS)
Filing Type: Form 8-K (Current Report)
Date: February 23, 2026
Event: Announcement of topline results from the Phase 3 PROSERA study of seralutinib for pulmonary arterial hypertension (PAH).
Key Financial Metrics
This filing is a Current Report (Form 8-K) focused on clinical trial results and does not contain financial statements. The filing text does not provide clear values for revenue, profit, cash flow, margins, debt, or liquidity.
Material Changes and Clinical Results
Primary Endpoint Results
- Study Design: 390 patients randomized (197 seralutinib, 193 placebo); 55% on triple/quadruple therapy.
- 6-Minute Walk Distance (6MWD) at Week 24:
- Seralutinib median change: +28.2 meters.
- Placebo median change: +13.5 meters.
- Treatment effect: +13.3 meters (p=0.0320).
- Outcome: Did not meet the prespecified statistical threshold (α = 0.025); key secondary endpoints cannot be evaluated for statistical significance in the overall population.
Subgroup and Secondary Endpoint Results
- Intermediate/High-Risk Subgroup (REVEAL 2 Lite Score ≥ 6): Placebo-adjusted 6MWD improvement of +20.0 meters (p=0.0207). Three of four key secondary endpoints met p-values below 0.0125.
- NT-proBNP (Week 24): Estimated location shift of -120.4 ng/L vs. placebo (p=0.0002) in the overall population; -265.8 ng/L in the high-risk subgroup.
- Connective Tissue Disease-Associated PAH (CTD-APAH): Placebo-adjusted 6MWD gain of +37.0 meters (p=0.0104).
- Other Secondary Endpoints: Time-to-clinical worsening, clinical improvement, and risk score reduction favored seralutinib in the overall population.
Safety Profile
- Treatment-Emergent Adverse Events (TEAEs): 86.5% (seralutinib) vs. 80.5% (placebo).
- Serious Adverse Events (SAEs): 16.0% (seralutinib) vs. 18.9% (placebo).
- Transaminase Elevations (≥3x ULN): 13% (seralutinib) vs. 1% (placebo).
- Most Common Adverse Event: Cough (37.0% of seralutinib patients).
Guidance, Outlook, and Risks
Management Commentary and Next Steps
- Regulatory Path: The Company expects to meet with the U.S. FDA to discuss the path forward for seralutinib in PAH.
- Operational Impact: Enrollment in the Phase 3 SERANATA Study is paused to evaluate the impact of PROSERA results, specifically regarding regional discrepancies in placebo response.
- Additional Data: CT functional respiratory imaging (FRI) substudy results are expected in the coming weeks.
Risks and Contingencies
- Development Uncertainty: The Company may not identify a viable development path forward, which could limit commercial opportunity or require additional capital.
- Workforce Evaluation: The Company may need to evaluate its current workforce based on potential development paths.
- Data Limitations: Topline results are based on preliminary analysis and may change following comprehensive review.
- Capital Resources: The Company may use capital resources sooner than expected.
Investor Verification Checklist
- Verify the FDA meeting date and the specific feedback received regarding the development path for seralutinib.
- Monitor the decision timeline regarding the paused SERANATA Study enrollment.
- Review the upcoming CT functional respiratory imaging (FRI) substudy results for additional efficacy insights.
- Assess the Company's capital runway and potential need for additional financing given the pause in enrollment and potential workforce adjustments.
- Examine the detailed safety data regarding transaminase elevations and cough in the full clinical study report.