Trial results for PAH treatment seralutinib expected early 2026
Enrollment of nearly 400 patients in Phase 3 study now complete
Enrollment is now complete — with nearly 400 participants with pulmonary arterial hypertension (PAH) — in the Phase 3 PROSERA clinical trial that’s testing the PAH treatment candidate seralutinib against a placebo in adults.
Top-line results from PROSERA are expected in February 2026, according to Gossamer Bio, which is developing seralutinib in collaboration with the Chiesi Group as a treatment for PAH and pulmonary hypertension associated with interstitial lung disease.
The study is designed to be registrational, meaning that if the results are positive, the findings could support applications seeking regulatory approval of seralutinib for PAH.
“Completing enrollment for the Phase 3 PROSERA study represents an important step forward in our mission to develop seralutinib as a potential first-in-class treatment option for PAH,” Faheem Hasnain, CEO, chairman and cofounder of Gossamer Bio, said in a company press release. “We are deeply grateful to the patients, caregivers, and investigators who made this possible through their dedication and partnership.”
Hasnain added that the company is “eager to be able to share topline results from this registrational study early next year.”
PAH is marked by the narrowing of the arteries that carry blood through the lungs, which puts atypical strain on the heart. This narrowing occurs as a result of the cells that line these blood vessels growing abnormally. Seralutinib is an inhaled therapy designed to block the activity of signaling molecules that contribute to this abnormal cell growth.
Trial testing seralutinib as PAH treatment at 190 sites worldwide
The Phase 3 PROSERA trial (NCT05934526) has now enrolled 390 adults with PAH. Participants in the trial are being randomly assigned to take seralutinib or the placebo, inhaled twice daily for almost a year.
Preliminary data show that almost 1 in 5 participants are from North America, and that approximately 3 in 4 are in functional class III, which means these individuals experience limitations such as shortness of breath during normal household activities.
The study’s main goal is to evaluate the effect of treatment on the six-minute walk test (6MWT) after 24 weeks, or about six months. The 6MWT, which simply measures how far a person can walk in six minutes, is a common measure used to assess exercise capacity in people who can walk. The PROSERA trial also will be assessing other outcomes, such as the time to clinical worsening over the course of the study.
Results from an earlier Phase 2 study called TORREY (NCT04456998) showed that seralutinib, when added to standard-of-care treatment for PAH, was significantly better than a placebo at reducing pulmonary vascular resistance — the resistance that must be overcome for blood to flow. Further benefits included a drop in pulmonary arterial pressure, an increase in cardiac output, which is a measure of how much blood is pumped by the heart, and an increase in the distance covered in walking for six minutes.
Building on insights from the Phase 2 TORREY study, we focused on selecting a patient population that aligns closely with the study’s objectives and is more likely to exhibit a clinically significant benefit in 24 weeks.
According to Gossamer, patients enrolled in PROSERA were selected based on findings from TORREY. The goal was to select a patient population that’s most likely to show benefits with seralutinib treatment.
“Given the preliminary baseline characteristics of PROSERA, we firmly believe that we have accomplished this patient selection goal,” Hasnain said. “Building on insights from the Phase 2 TORREY study, we focused on selecting a patient population that aligns closely with the study’s objectives and is more likely to exhibit a clinically significant benefit in 24 weeks.”
The study is being conducted across 190 locations worldwide.
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