FDA Accepts Merck’s BLA Application For Clesrovimab, A Long-Acting Antibody To Prevent RSV In Infants

Merck, also known as MSD outside the U.S. and Canada, has announced that the FDA has accepted its Biologics License Application (BLA) for clesrovimab (MK-1654). This investigational monoclonal antibody is designed to provide long-lasting protection for infants against respiratory syncytial virus (RSV) during their first RSV season. The target date for its decision under the Prescription Drug User Fee Act (PDUFA) set by the FDA is June 10, 2025.

Dr. Paula Annunziato, senior vice president of infectious diseases and vaccines, Global Clinical Development, Merck Research Laboratories, said in a statement, “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.”

She also commented, “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 BLA submission is supported by data from the pivotal Phase 2b/3 CLEVER trial (MK-1654-004), which evaluated a single dose of clesrovimab in healthy preterm and full-term infants up to 1 year old. Additional interim results from the ongoing Phase 3 SMART trial (MK-1654-007), comparing clesrovimab to palivizumab in infants and children at higher risk of severe RSV, further support the application. 

Findings from these studies were shared at IDWeek in October 2024. If approved, Merck plans to make clesrovimab available for physician and healthcare provider by July 2025, with shipments scheduled to align with the 2025 RSV season.