Gossamer Bio (Nasdaq: GOSS) announced on July 27 that FDA meeting minutes from a mid-June Pre-NDA Type B meeting support a September 2026 NDA submission for seralutinib in pulmonary arterial hypertension — and simultaneously reacquired worldwide rights to the drug from Italy-based Chiesi Farmaceutici, consolidating full commercial and development control ahead of that filing.
The regulatory update resolves the central uncertainty hanging over the program since February, when topline results from the Phase III PROSERA study showed seralutinib produced a placebo-adjusted improvement in six-minute walk distance of +13.3 meters at week 24 (p=0.0320), narrowly missing the pre-specified alpha threshold of 0.025. The FDA has now characterized both the degree of statistical significance and the magnitude of the treatment effect as review issues rather than filing issues — a distinction that allows Gossamer to proceed with an NDA anchored on PROSERA as the single adequate and well-controlled study, supported by confirmatory evidence from the Phase II TORREY study. If accepted for filing, a decision could come in Q3 2027.
Seralutinib is an inhaled inhibitor of PDGFRα/β, CSF1R, and c-KIT — receptor tyrosine kinases implicated in pulmonary vascular remodeling — delivered via dry powder inhaler to maximize pulmonary exposure while limiting systemic effects. The non-vasodilatory, anti-proliferative mechanism distinguishes it from every currently approved PAH therapy, which act through vasodilatory pathways including endothelin receptor antagonism, PDE5 inhibition, prostacyclin signaling, and soluble guanylate cyclase stimulation. The closest mechanistic parallel in the approved landscape is Merck's Winrevair (sotatercept-csrk), approved in March 2024, which targets activin signaling to address vascular remodeling — though through a biologic rather than inhaled small-molecule approach.
The rights reacquisition from Chiesi dissolves the prior 50/50 US profit share and returns ex-US rights to Gossamer at no upfront cash cost. Chiesi makes a one-time USD 5 million payment to Gossamer, settling outstanding collaboration costs. In return, Chiesi receives a capped royalty on worldwide net sales, with no further obligation once the cap is reached, plus specified regulatory and commercial milestones. The structure gives Gossamer full control over pricing, lifecycle strategy, and commercialization across all geographies — a meaningful shift from the shared economics that governed the program through PROSERA.