Merck (NYSE: MRK), known as MSD outside of the United States and Canada, announced the U.S. Food and Drug Administration (FDA) has accepted the Biologics License Application (BLA) for clesrovimab (MK-1654), the company’s investigational prophylactic long-acting monoclonal antibody designed to protect infants from respiratory syncytial virus (RSV) disease during their first RSV season. The FDA has set a Prescription Drug User Fee Act (PDUFA), or target action, date of June 10, 2025.

“Despite recent advances in RSV prevention, unmet needs remain for additional effective interventions to help protect infants and continue to help address the burden RSV places on families and the healthcare system. This regulatory milestone, along with promising results from our pivotal studies demonstrating efficacy in the prevention of RSV disease, marks important progress toward our goal of having clesrovimab available in time for the 2025-26 RSV season,” said Dr. Paula Annunziato, senior vice president, infectious diseases and vaccines, Global Clinical Development, Merck Research Laboratories. “We look forward to working alongside the FDA on the review of clesrovimab, which, if approved, would be the first and only single dose immunization for infants regardless of weight designed to protect them for the duration of their first RSV season.”

The application is supported by results from the pivotal Phase 2b/3 CLEVER trial (MK-1654-004), a randomized placebo-controlled trial evaluating a single dose of clesrovimab administered to healthy preterm and full-term infants (birth to 1 year of age), and interim results from the ongoing Phase 3 SMART trial (MK-1654-007) evaluating the safety and efficacy of clesrovimab versus palivizumab in infants and children at increased risk for severe RSV disease. Data from these trials were presented during IDWeek in October 2024.

If approved, Merck anticipates that clesrovimab would be available for ordering by physicians and healthcare administrators by July 2025, with shipments to arrive in time for the 2025 RSV season.