RSV Passive Immunization Options Increase in 2025

Since 1998, various respiratory syncytial virus (RSV) monoclonal antibody (mAb) therapies have been approved to prevent serious lower respiratory tract disease caused by RSV in young children.

Over the past two years, a single-dose, long-acting mAb designed to protect infants has been approved in Canada, Europe, and the USA.

As of March 2024, among females with an infant less than 8 months, 41.3% reported that their infant received an approved mAbs.

However, unmet needs remain for effective interventions to help protect more infants from the burden of RSV.

To meet this need, Merck is developing clesrovimab (MK-1654), the company's investigational prophylactic long-acting mAb designed to protect infants from RSV disease during their first RSV season.

Clesrovimab is designed to be administered as the same single dose, regardless of weight, and is being studied in healthy preterm, full-term, and at-risk infants. 

On December 17, 2024, Merck announced the U.S. Food and Drug Administration had accepted the Biologics License Application (BLA) for clesrovimab and set a Prescription Drug User Fee Act date of June 10, 2025.

Dr. Paula Annunziato, senior vice president of infectious diseases and vaccines, Global Clinical Development, Merck Research Laboratories, informed Vax-Before-Travel, "RSV is the leading cause of infant hospitalization in the U.S., and there is a high unmet need for effective immunization to protect both healthy and high-risk infants from RSV."

"Given the significant burden of this disease, we believe it is important to have multiple options to protect against RSV."

"We are confident in the strength of clesrovimab's clinical data, product profile, and potential to help address the significant burden of RSV on infants and families. If approved, clesrovimab would be the first and only immunization designed to help protect infants with a single dose regardless of weight for the duration of their first RSV season," added Annunziato.

If the BLA is approved, Merck anticipates that clesrovimab shipments will be available to arrive in time for the 2025 RSV season.