Market reactionShares fell 10% on Nov 5.
Gossamer Bio is developing seralutinib, an inhaled drug for pulmonary arterial hypertension (PAH); it is not approved and is under FDA review.
Gossamer submitted an NDA for seralutinib in PAH in September 2026, although Phase 3 PROSERA narrowly missed its primary endpoint (13.3-meter walk gain, p=0.032 against a 0.025 threshold). FDA called the statistical shortfall a review issue rather than a filing issue. If FDA accepts the filing in 2026, the August private placement adds $125 million and funds operations into 2028. Without it, cash lasts into the first quarter of 2027, and the 10-Q reports going-concern doubt.
Thesis checklist
1 risk needs attention
Why it is in this state
The evidence, what would weaken it and the source filing
Why it is in this state
The evidence, what would weaken it and the source filing
Why it is in this state
The evidence, what would weaken it and the source filing
Next decision point
Tests: FDA accepts the NDA for filing
Does FDA accept the seralutinib NDA for review?
Strong, inconclusive and weak outcomes
What to look for in the result and how each would move the checklist
Price and material events
Select an event marker to read the update below. Marker colors show Thesis status.
Gossamer filed seralutinib on a missed Phase 3; FDA's filing decision unlocks $125 million
Phase 3 miss, rights reacquired, NDA planned anyway: approvability on marginal data is the only question that matters
PAH drug missed its Phase 3 primary endpoint, yet FDA cleared an NDA filing path — approvability on borderline data is the only question that matters
Seralutinib's NDA path hinges on FDA accepting a missed primary endpoint dataset supported by robust secondary and subgroup signals
About this history: every entry shows when the Thesis moved and what it said. The reasoning behind each move (the evidence, the analysis and the source filing) and the earnings write-ups are part of a subscription.
Dates, trials and completed outcomes are open to everyone. What each upcoming milestone hinges on is part of a subscription.
Drug pages: Seralutinib
Disease areas: Lung and respiratory diseases
Catalyst calendar · Upcoming FDA decisions · Thesis changes
Competitive landscape
7 peers tracked
Cash: Market-data provider estimate; measurement period unavailable.
Debt: Market-data provider estimate; a complete comparable filing balance is unavailable.
Quarterly burn: Estimated from trailing free cash flow; measurement period unavailable.
Net cash and estimated runway require verified matching measurement periods. Missing debt components are not assumed to be zero.
Runway: No underlying guidance available.