Merck announced on Mar. 30 that its drug Winrevair showed significant improvement in heart function during a mid-stage clinical trial for a rare type of heart failure, and the company plans to move forward with Phase 3 development. The findings were presented at the 2026 Annual Scientific Session and Expo of the American College of Cardiology.
The results are important as they address combined post- and precapillary pulmonary hypertension (CpcPH) due to heart failure with preserved ejection fraction (HFpEF), an area where there is an unmet medical need. Analysts from BMO Capital Markets said that "the latest data ... validate the clinical benefits of Winrevair in patients with combined post- and precapillary pulmonary hypertension (CpcPH) due to heart failure with preserved ejection fraction (HFpEF)." However, they also noted concerns about "the lack of a clear dose response," which could raise questions among investors.
In the Phase 2 CADENCE study, two doses of Winrevair were compared against placebo in over 160 patients. Both doses led to significant reductions in pulmonary vascular resistance, but unexpectedly, the lower dose had a stronger effect than the higher dose. A discussant for Merck attributed this outcome to small sample size and more discontinuations at the higher dose level during their presentation at ACC.
Despite these issues, BMO analysts said they are comfortable with Merck's explanation but acknowledged lingering investor concerns may continue into later stages of research. Guggenheim Partners analysts wrote that "we are encouraged by the potential for Winrevair in this new population," noting their key opinion leaders were "overwhelmingly positive" about expanding use into CpcPH-HFpEF because of market needs.
Winrevair also improved performance on a six-minute walk test—though not enough for statistical significance—and showed numerical improvements in time before first clinical worsening event and disease biomarker levels. Mahesh Patel, vice president of global clinical development at Merck, said: “CADENCE results support that the 0.3 mg/kg dose may optimize the benefit-risk profile of Winrevair” for these patients.
Winrevair was approved for pulmonary arterial hypertension (PAH) in March 2024 as a fusion protein therapeutic targeting activin signaling pathways. Data from last year's ZENITH trial led to expanded approval after showing reduced risk by 76% versus placebo in certain PAH patients; sales reached $1.4 billion in 2025.
