Gossamer Bio is a clinical-stage biopharmaceutical company focused on a single lead asset: seralutinib, an inhaled kinase inhibitor being developed for pulmonary arterial hypertension (PAH) and pulmonary hypertension associated with interstitial lung disease (PH-ILD). PAH is a rare, progressive disease caused by abnormal cellular proliferation and vascular remodeling in the pulmonary arteries, ultimately leading to right heart failure. Unlike approved PAH therapies, which are vasodilators, seralutinib targets the underlying cellular mechanisms driving disease progression by blocking PDGFR, CSF1R, and c-KIT signaling pathways. Seralutinib completed a Phase 3 trial (PROSERA) in early 2026, showing a 13.3-meter placebo-adjusted improvement in six-minute walk distance, but narrowly missed its pre-specified statistical threshold; Gossamer is now seeking FDA feedback on potential regulatory paths forward. Gossamer also has an ongoing Phase 3 trial in PH-ILD, though enrollment was paused following the PROSERA results. Gossamer is pre-revenue and funds operations through equity, debt, and a collaboration with Chiesi, under which Chiesi paid Gossamer $160M in development cost reimbursement and is eligible to share U.S. commercial profits equally while holding exclusive rights outside the U.S. in exchange for mid-to-high teens royalties on net sales. Gossamer in-licensed seralutinib from Pulmokine, to whom it owes tiered royalties and milestone payments. Gossamer has no internal manufacturing and relies on third-party contract manufacturers.