Gossamer Bio ends open-label extension study of inhaled seralutinib for PAH

Gossamer Bio USA, Inc. has terminated its open-label extension study of inhaled seralutinib (GB002) in adults with WHO Group 1 pulmonary arterial hypertension, according to a clinical trial registry update dated October 7, 2026.

The registry record gives the reason for stopping: enrollment had declined and remaining participants had been on study more than three years, so continued study visits and data collection were no longer considered necessary, and this was not expected to affect study interpretation or the overall benefit-risk.¹

The study, known as NCT04816604 with sponsor ID GB002-2102, is designed to evaluate the long-term effects of GB002 (seralutinib) in subjects who previously participated in a GB002 PAH study.¹ It began on April 5, 2021, and both primary completion and overall study completion are listed as September 9, 2026.

The trial enrolled 74 participants in a single-group, open-label, Phase 2 design, with GB002 (seralutinib) inhaled orally twice per day via a generic dry powder inhaler.¹ The primary outcome measured was the number of participants with treatment emergent adverse events, assessed from first dose up to 80 months or availability of commercial product.¹ A secondary outcome tracked change from baseline over time on the Six-Minute Walk Test.¹

Eligible participants were required to have completed a prior GB002 PAH study and been compliant with study procedures through the parent study's end-of-treatment visit.¹ The study recruited across 28 sites in 7 countries: United States, Australia, Czechia, France, Germany, Spain, and United Kingdom.¹