Merck & Co. (MRK) received a positive opinion from the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP) on December 12 2025, recommending approval of an expanded indication for its PAH drug WINREVAIR (sotatercept). The recommendation covers adults with pulmonary arterial hypertension (PAH) in World Health Organization Functional Class II, III, and IV, extending the drug’s use beyond the current EU approval for WHO FC II‑III patients.
The CHMP decision is grounded in the Phase 3 ZENITH trial, which demonstrated a 76 % reduction in the risk of major morbidity and mortality events in patients with WHO FC III or IV PAH. The trial was stopped early for efficacy, and the data now support inclusion of the most severe patient group, WHO FC IV, thereby broadening the addressable market for WINREVAIR across all 27 EU member states and additional European countries such as Iceland, Liechtenstein, and Norway.
From a commercial perspective, the expanded indication is expected to lift WINREVAIR’s sales momentum. Full‑year 2024 sales reached $419 million, and Q3 2025 sales were $360 million, a 10 % year‑over‑year increase driven by strong uptake in the newly eligible FC IV cohort. Merck’s management projects full‑year 2025 worldwide sales between $64.1 billion and $65.6 billion, with the PAH franchise contributing a growing share of the company’s $64.2 billion global revenue in 2024.
Merck’s senior vice president of general medicine, Dr. Joerg Koglin, emphasized that the expanded indication “recognizes the impact of WINREVAIR on morbidity and mortality in adult patients with PAH, extending the overall use of the drug to include WHO FC IV patients.” The company sees the CHMP recommendation as a key step toward diversifying its portfolio beyond the oncology blockbuster Keytruda, whose patent protection is set to expire in 2028. WINREVAIR is the first activin‑signaling inhibitor approved for PAH worldwide, and the EU expansion positions Merck as the sole provider of this therapeutic class in the region.
The PAH market, which serves roughly 90,000 patients globally and carries a 43 % five‑year mortality rate, is highly competitive. By adding WHO FC IV patients, Merck gains a competitive edge over other PAH therapies that do not cover this severe subgroup. The company’s strategy to grow its cardio‑pulmonary portfolio is reinforced by the CHMP recommendation, and the timing aligns with a recent U.S. label update in October 2025 that also broadened the drug’s indication.
The CHMP recommendation is a regulatory milestone that will likely lead to a final European Commission decision in the first quarter of 2026, after which Merck can accelerate commercial rollout across the EU. The expanded indication is expected to increase the drug’s addressable market, strengthen Merck’s competitive position, and provide a new revenue stream as the company continues to diversify beyond Keytrude.
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