Merck (MRK) Announces Positive Phase 3 SMART Trial Results for ENFLONSIA (Clesrovimab)

Merck & Co. Inc. (NYSE:MRK) is one of the best value stocks to buy now. On February 19, Merck announced positive second-season findings from the Phase 3 SMART trial evaluating ENFLONSIA (clesrovimab) in infants and children under 2 years of age at increased risk for severe respiratory syncytial virus/RSV. The data focused on vulnerable children, most with chronic lung or congenital heart disease, who received the monoclonal antibody at the start of their second RSV season.

These results showed that the serum concentrations of the antibody in high-risk children were similar to those seen in healthy infants from previous pivotal trials, supporting the potential for extended protection. The safety profile of ENFLONSIA during the second season remained consistent with observations from the first season and previous studies.

Merck (MRK) Announces Positive Phase 3 SMART Trial Results for ENFLONSIA (Clesrovimab)

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Common side effects included irritability, somnolence, and injection-site reactions, with no drug-related serious adverse events reported. ENFLONSIA, which was FDA-approved in June 2025 for infants entering their first RSV season, is a long-acting monoclonal antibody designed to provide five months of protection with a single dose regardless of weight. Merck & Co. Inc. (NYSE:MRK) intends to share these new results with the FDA and other global regulatory authorities to seek an expanded indication for high-risk children entering their second RSV season.

Merck & Co. Inc. (NYSE:MRK) is a healthcare company that offers human health pharmaceuticals for various areas under the Keytruda, Welireg, Gardasil, ProQuad, M-M-R II, Varivax, Vaxneuvance, RotaTeq, Pneumovax 23, Bridion, Dificid, Zerbaxa, Noxafil, Winrevair, Adempas, Verquvo, Lagevrio, Isentress/Isentress HD, Delstrigo, Pifeltro, Belsomra, Januvia, and Janumet brands.

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