Merck Secures FDA Nod for New RSV Antibody Enflonsia in Infants

Merck MRK announced FDA approval for its prophylactic long-acting monoclonal antibody, clesrovimab, for the prevention of RSV in newborns and infants born during or entering their first RSV season. The drug will be marketed under the brand name Enflonsia.

The FDA’s decision came a day ahead of the previously announced target date of June 10, 2025. The approval is based on data from the pivotal phase IIb/III CLEVER study, which showed that treatment with a single dose of Enflonsia significantly reduced the incidence of RSV disease and hospitalization in healthy preterm and full-term infants.

Merck plans to launch Enflonsia in the United States ahead of the upcoming 2025-26 RSV season and expects ordering for the shots to start next month. Per a Reuters article, Merck will price the antibody at $556 per dose.

Merck’s Stock Performance

Year to date, Merck’s shares have lost 20% compared with the industry’s 1% decline.

Other RSV Antibodies/Vaccines Available in the Market

Once commercially launched, Merck’s Enflonsia will face stiff competition from AstraZeneca AZN/Sanofi’s SNY RSV antibody Beyfortus, which was also approved for a similar indication in 2023. This AstraZeneca-Sanofi antibody achieved blockbuster status in its first full-year sales in 2024.

Coincidentally, on the same day Enflonsia received approval, Sanofi revealed an aggressive effort to increase the supply of the AstraZeneca-partnered Beyfortus, including a plan to start shipping the antibody early in the third quarter of 2025.

While there are multiple vaccines approved for preventing RSV in the United States, the only one approved for immunizing infants is Pfizer’s PFE Abrysvo. Unlike Beyfortus and Enflonsia, which can be administered directly, the Pfizer vaccine protects infants through maternal immunization. Most of the marketed RSV vaccines, including Pfizer’s, are approved for use in older adults aged 60 years and above.

MRK’s Cholesterol Drug Meets Goal in Two Late-Stage Studies

In a separate press release, Merck announced topline data from two phase III studies, CORALreef HeFH and CORALreef AddOn, which evaluated their investigational oral PCSK9 inhibitor, enlicitide decanoate, in adults with hyperlipidemia who had been previously treated with a statin.

Both studies met their primary and key secondary endpoints, showing statistically significant and clinically meaningful greater reductions in low-density lipoprotein cholesterol (LDL-C) after treatment with enlicitide. While the CORALreef HeFH evaluated the drug against a placebo, the CORALreef AddOn assessed the drug against other oral non-statin therapies.

Merck & Co., Inc. Price

 

Merck & Co., Inc. price | Merck & Co., Inc. Quote

MRK’s Zacks Rank

Merck currently carries a Zacks Rank #3 (Hold). You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here.

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