Merck & Co.’s Winrevair Approved for PAH in EU

Five months after securing FDA approval for its novel pulmonary arterial hypertension (PAH) treatment, Winrevair (sotatercept), Merck & Co. has achieved another significant milestone with the drug’s approval in Europe. The European Commission has given the green light for Winrevair to be used alongside other PAH therapies to enhance exercise capacity in adult PAH patients classified under WHO Functional Class II to III. This approval follows a positive recommendation from the European Medicines Agency’s drug advisory committee made in June.

Winrevair’s regulatory successes have been complemented by strong early commercial performance. In the second quarter, the drug generated $70 million in U.S. sales, surpassing analysts’ expectations of $60 million. During Merck’s financial earnings presentation in late July, the company highlighted that approximately 40% of the revenue was due to doses administered to patients, while the rest was from distributors stocking up to meet rising demand. Merck acquired Winrevair through its $11.5-billion acquisition of Acceleron Pharma in 2021.

The EU’s approval of Winrevair was based on data from the Phase III STELLAR trial, similar to the data used for the U.S. approval. Marc Humbert, director of the Pulmonary Hypertension Reference Center at Université Paris-Saclay, emphasized that the STELLAR trial’s results support Winrevair’s use as “a new standard of care” for adults with PAH when combined with other therapies. The trial involved 323 patients who were randomized to receive either a subcutaneous injection of Winrevair every three weeks or a placebo. Those treated with Winrevair alongside existing therapy experienced a significant improvement in exercise capacity, as measured by the six-minute walk distance (6MWD). Specifically, patients on Winrevair walked an average of 40.8 meters farther at 24 weeks than those on placebo.

Moreover, the drug showed a remarkable 82% reduction in the risk of death or clinical worsening, a secondary outcome that distinguishes Winrevair from existing PAH treatments. This reduction in mortality risk is a significant advancement for PAH patients, offering a new therapeutic option that not only improves exercise capacity but also presents a potential life-saving benefit.

Despite its promising clinical benefits, there are concerns about Winrevair’s safety profile. A FirstWord poll of U.S. cardiologists and pulmonologists revealed that over half of the responding physicians would likely prescribe Winrevair. However, 64% expressed concerns regarding its safety and monitoring requirements. The drug has the potential to increase haemoglobin levels, which could lead to erythrocytosis, and decrease platelet count, which could result in severe thrombocytopenia. These safety concerns necessitate careful monitoring and management when prescribing Winrevair to patients.

In conclusion, Merck & Co.’s Winrevair has made significant strides both in regulatory approvals and commercial success. Its approval in Europe marks another important step in providing a new treatment option for PAH patients. While the drug has demonstrated substantial improvements in exercise capacity and mortality reduction, safety concerns remain a critical consideration for its widespread adoption.