Gossamer Bio Files First NDA for Seralutinib in PAH

What Happened
Gossamer Bio, Inc. announced on September 23, 2026 that it submitted a New Drug Application (NDA) to the U.S. Food and Drug Administration (FDA) for seralutinib for the treatment of pulmonary arterial hypertension (PAH). This is the company’s first NDA submission. The filing is supported by the Phase 3 PROSERA study (as one adequate and well‑controlled investigation), confirmatory evidence from the Phase 2 TORREY study, and supportive analyses. Gossamer noted it held a Pre‑NDA Type B meeting with the FDA in June 2026; FDA meeting minutes characterized the PROSERA statistical significance and treatment‑effect magnitude as review issues rather than filing issues and provided feedback on submission format and content. The FDA will decide whether to accept the NDA for filing after its initial review, which the company expects could occur later in 2026.

Key Details

• NDA submission date announced: September 23, 2026.
• First NDA in company history; primary support from Phase 3 PROSERA and Phase 2 TORREY studies.
• June 2026 Pre‑NDA Type B meeting: FDA described key efficacy questions as review‑level (not filing) issues and gave feedback on submission format.
• Company expects the FDA’s filing decision may occur later in 2026; substantive review will determine acceptability of efficacy and safety evidence.

Why It Matters
This submission is a major regulatory milestone: NDA acceptance and eventual approval would be required before seralutinib could be marketed for PAH. For investors, the next near‑term catalyst is the FDA’s determination whether to accept the NDA for filing; acceptance does not guarantee approval, since the FDA will still evaluate the totality of efficacy and safety data during substantive review. The company’s filing also reiterates standard forward‑looking risks (including reliance on seralutinib, potential need for more capital, and the possibility the FDA may not accept or approve the NDA), which investors should consider.