Gossamer Study Finds Seralutinib Has Long-Lasting Effects in PAH

Gossamer Bio Inc. has released new data showing its inhaled kinase inhibitor, seralutinib, has long-lasting effects on pulmonary arterial hypertension (PAH).

The new data from an open-label extension trial were unveiled last week at the Pulmonary Vascular Research Institute’s 2025 Annual Congress in Rio de Janeiro. The company also presented preclinical data suggesting seralutinib work synergistically with Merck & Co.’s recently approved Winrevair (sotatercept). Faheem Hasnain, Gossamer’s chairman and CEO, said he was “immensely proud” of the preclinical data.

Gossamer presented three PAH posters at the conference. Two of the presentations dealt with the open-label extension of the phase 2 TORREY Trial, in which 86 adult patients with World Health Organization (WHO) group 1 PAH were randomly assigned to receive either seralutinib or placebo, in addition to background therapy. The original study showed seralutinib led to significant reductions in pulmonary vascular resistance (PVR) after 24 weeks.

Seventy-four patients enrolled in the extension trial. By week 72, data were available for 55 of those participants. Of the 55 participants, 28 were treated with seralutinib for all 72 weeks, and 17 participants demonstrated a reduction in pulmonary vascular resistance of more than 15%.

One poster focused on the sustainability of the pulmonary vascular resistance benefit, and found that improvement continued throughout the extension period. In those with pulmonary vascular resistance responses, the trial showed a median PVR improvement of 32%, with the range spanning from a 17% improvement to a 62% improvement. Responders also saw improvement in their scores on the six-minute walking distance (6MWD) assessment.

The investigators said improvements in mean pulmonary arterial pressure and cardiac output likely contributed to the responses.

The authors also sought to demonstrate the long-term effects of seralutinib by tracking circulating biomarkers. An exploratory analysis of the TORREY study found seralutinib altered some 380 circulating biomarkers at 12 and/or 24 weeks of therapy. Many of those biomarkers were found to be relevant to PAH, including endoglin, collagen 1A1, interleukin 10, and FMS related receptor tyrosine kinase 1 (FLT1).

The investigators found that, among those patients who began the trial in the seralutinib cohort and continued taking the therapy (23 patients), 169 of the 380 protein changes (45%) noted at week 24 continued at week 72. Among the 22 patients who crossed over from placebo, 152 of 380 protein changes (40%) were recapitulated at “nominal significance” after 48 weeks of seralutinib in the extension trial.

The investigators said they will prospectively validate the findings in the phase 3 PROSERA trial, which is currently enrolling patients.