According to Gossamer Bio, the Phase 3 PROSERA trial of its seralutinib dry powder inhaler in patients with pulmonary arterial hypertension missed its primary endpoint of change in 6-minute walk distance from baseline. The company notes, however, that the study demonstrated clinically meaningful improvements in a subgroup of higher-risk patients.
Chiesi is partnered with Gossamer on development of the seralutinib DPI. In September 2025, Gossamer announced that it had acquired an option to acquire Respira Therapeutics and Respira’s RT234 vardenafil DPI for the treatment of PAH.
The company says that median change in 6MWD from baseline at Week 24 for patients who received seralutinib was +28.2 m compared to +13.5 m for patients who received a placebo. For intermediate-risk and high-risk patients, Gossamer says that results were consistent with results from the Phase 2 TORREY trial of the DPI in pulmonary arterial hypertension (PAH) in that it “delivered a compelling signal” in the higher risk group.
In light of the results from the PROSERA study, Gossamer said that it is pausing the Phase 3 SERANATA trial of seralutinib in patients with PH-ILD. The company also said that it plans to meet with the FDA regarding the future of seralutinib DPI for the treatment of PAH.
Gossamer Bio Chairman and CEO Faheem Hasnain commented, “While we are disappointed to have narrowly missed the stringent pre-specified statistical threshold for our primary endpoint, the result still clears the traditional 0.05 p-value, and we believe these data clearly demonstrate seralutinib is an active drug in patients with PAH.”
Hasnain continued, “We are also pleased by the clinically meaningful improvements observed in intermediate- and high-risk patients who are at an increased risk of significant morbidity and mortality events and represent a population with a high unmet need. From a clinical development perspective, this is not a narrow or exploratory finding. Seralutinib has once again demonstrated a statistically robust and clinically meaningful signal in higher‑risk patients, consistent with the TORREY Study, which is a clearly defined and readily identifiable population. This finding is compelling on its own.”
Read the Gossamer Bio press release
