A tale of two drug trials

Two companies have announced the results of clinical trials of drugs for pulmonary arterial hypertension recently, neatly illustrating successful and unsuccessful results.

Last week, Gossamer Bio announced that their drug, seralutinib, failed to meet the primary endpoint of its phase 3 PROSERA clinical trial. Gossamer’s stock price dropped precipitously. Interestingly, one of the reasons the study failed may have been an unusually good response to the placebo in some locations, and not a poor response to seralutinib at all! The study did have some promising results, so Gossamer is still looking for a path forward for seralutinib, particularly in the United States.

This week, United Therapeutics announced that its phase 3 ADVANCE OUTCOMES study of the drug ralinepag did meet its primary endpoint, with results indicating it reduced the risk of clinical worsening by 55% compared to placebo. The company’s stock is trading near its 52-week high price, and they will seek approval for ralinepag in the US later in 2026.

Together, these contrasting outcomes are a reminder that while the path to new pulmonary arterial hypertension treatments is rarely straightforward, each trial—whether it meets its endpoint or not—moves the field a step closer to better options for patients.