US pharmaceutical company Merck & Co Inc (NYSE:MRK), known as MSD outside the US and Canada, announced on Monday that the US Food and Drug Administration (FDA) has approved an updated indication for Winrevair (sotatercept-csrk) to treat adults with pulmonary arterial hypertension (PAH, WHO Group 1).

The approval, based on results from the Phase 3 ZENITH trial, expands the label to include reductions in key clinical worsening events such as hospitalisation for PAH, lung transplantation, and death.

In the ZENITH study, which enrolled 172 participants, adding Winrevair to background therapy reduced the risk of major morbidity and mortality by 76% compared to placebo. The composite primary endpoint -- time to first occurrence of all-cause death, lung transplantation, or hospitalisation for PAH -- occurred in 17% of Winrevair-treated patients versus 55% of those on placebo. The trial was stopped early due to overwhelming efficacy.

Winrevair, an activin signalling inhibitor, was first approved in March 2024 following the STELLAR study. Merck noted that the ZENITH data further support the therapy's benefit-risk profile across a broad range of adult patients with PAH.

Healthcare providers are advised to monitor haemoglobin and platelet levels during treatment due to potential risks of erythrocytosis and thrombocytopenia. The most common adverse reactions included infections, epistaxis, diarrhoea, and telangiectasia.