Merck's Winrevair Poised for Strong Growth in 2025 Despite Initial Slow Uptake

Merck's pulmonary arterial hypertension (PAH) drug Winrevair is expected to see significant growth in 2025, according to a recent survey conducted by Leerink Partners. The drug, which was the primary target in Merck's $11.5 billion acquisition of Acceleron in 2021, has shown promise despite a slower-than-expected initial uptake following its FDA approval in March 2024.

Real-World Safety Profile Boosts Confidence

The Leerink survey, which included 51 cardiologists and 53 pulmonologists treating approximately one-third of the U.S. PAH patient population, revealed that the real-world safety profile of Winrevair is better than initially anticipated. This finding has alleviated concerns about bleeding risks that were highlighted in earlier clinical trials.

"The real-world safety is better than expected," Leerink analysts noted, while acknowledging that more data is needed to fully assess the drug's long-term safety profile. This improved safety perception is expected to contribute to increased adoption of Winrevair in the coming year.

Market Penetration and Growth Potential

Currently, Winrevair is prescribed to about 10% of PAH patients under the care of surveyed physicians, indicating "large headroom for Winrevair growth," according to Leerink. The drug generated $149 million in sales during the third quarter of 2024, a solid start but below initial expectations for a treatment projected to reach $3 billion in peak sales.

Leerink analysts believe that early market access challenges and cautious prescribing practices due to bleeding risk concerns contributed to the slower initial uptake in 2024. However, as physicians gain more experience with the drug and Merck better characterizes the risk profile, opinions are expected to shift in favor of Winrevair.

Competitive Landscape and Future Outlook

Winrevair enters a competitive market dominated by Johnson & Johnson's Uptravi and Opsumit, the latter of which generated $2 billion in revenue in 2023. The PAH treatment landscape has also seen recent additions, such as the FDA approval of Opsynvi, a combination tablet of Opsumit and United Therapeutics' Adcirca.

As Merck continues to position Winrevair in this competitive field, the company may need to reassess its dosing strategy. Leerink analysts suggest that Merck's estimate of one-third of patients requiring a two-vial dosage might be "overly optimistic," as survey respondents indicated that adverse events were often mitigated through dosing pauses or reductions.

With improved real-world safety data and growing physician experience, Winrevair appears well-positioned to overcome its initial challenges and gain significant market share in the treatment of pulmonary arterial hypertension throughout 2025 and beyond.