Gossamer Bio Phase 3 miss adds regulatory uncertainty, says Leerink

Gossamer Bio (GOSS) reported Phase 3 PROSERA data in pulmonary arterial hypertension that missed its primary endpoint, with a placebo-adjusted six-minute walk distance of +13.3M at week 24, below the prespecified alpha threshold and Leerink’s base-case expectation, the analyst tells investors in a research note. While a higher-risk subgroup showed +20M improvement and 48-week data suggest separation from placebo, the miss introduces regulatory uncertainty, prompting the company to pause SERANATA enrollment and plan FDA discussions on the next steps, Leerink says.