Gossamer Bio (GOSS) Piper Sandler 36th Annual Healthcare Conference summary

Study progress and timelines

• PROSERA enrollment is on track for completion in late Q1 or early Q2, with data readout planned for Q4 2025.

• Protocol amendments allow patients in the open label extension to access both seralutinib and sotatercept, implemented in late summer 2024.

• Enrollment is predominantly ex-U.S. (about 67–75%), leveraging established PAH clinical infrastructure.

• The study is powered for a 30-meter placebo-adjusted difference in six-minute walk at week 24, with 96% power at 175 patients per arm.

• NDA and MAA filings are targeted for 6–9 months post-topline data, aiming for simultaneous U.S. and EU submissions.

Competitive landscape and market dynamics

• Sotatercept's launch initially slowed U.S. enrollment, but real-world safety concerns have since boosted PROSERA momentum.

• Seralutinib is positioned for earlier and longer use in PAH patients compared to sotatercept, with potential for combination therapy.

• Market research indicates only about 15% of PAH patients have a durable response to sotatercept, leaving a large opportunity for seralutinib.

• KOLs highlight seralutinib's safety, durability, and potential for earlier patient use.

• Combination and sequencing strategies are being explored, with preclinical and open label extension data supporting synergy.

Commercial readiness and partnerships

• Partnership with Chiesi accelerates commercial planning, with Chiesi responsible for ex-U.S. commercialization and a 50/50 U.S. profit share.

• Commercial infrastructure is being built for a potential 2027 launch, with payer engagement underway.

• Chiesi partnership provides capital and expertise, especially for European regulatory navigation and PH-ILD expansion.

• Strategic deal structure allows for potential future monetization or acquisition scenarios.