By FieldPulse Staff · March 21, 2026
Tags: layoffs, cardiology, phase-3, merck
Gossamer Bio eliminated 77 positions — nearly half its workforce — after its Phase 3 PROSERA trial of seralutinib in pulmonary arterial hypertension missed its primary endpoint. The failure removes a key near-term competitive threat to Merck's Winrevair in the rapidly evolving PAH market.
Gossamer Bio announced on March 17, 2026 that it would eliminate approximately 77 employees — close to 48% of its total workforce — after the Phase 3 PROSERA trial of seralutinib in pulmonary arterial hypertension (PAH) failed to meet its primary endpoint. Seralutinib was one of the most closely watched PAH pipeline agents, designed as a direct competitor to Merck's Winrevair (sotatercept), which launched in 2024 as the first new PAH mechanism in over a decade. Sotatercept works by blocking activin signaling to reduce pulmonary vascular remodeling — a fundamentally different approach from the