Merck announced results from its phase 2b/3 trial of clesrovimab (MK-1654), an investigational monoclonal antibody aimed at preventing respiratory syncytial virus (RSV) in infants.
The trial showed a reduction of over 84% in RSV-related hospitalizations and more than 90% in lower respiratory infection hospitalizations among healthy preterm and full-term infants over a five-month period.
Clesrovimab is designed to provide RSV protection with a single dose for infants during their first RSV season, regardless of weight. The trial met its primary and secondary endpoints, with no RSV-related deaths, and adverse events were similar between the clesrovimab and placebo groups. Additional data indicated an 88% reduction in severe RSV cases during the study period.
Merck also shared interim results from a phase 3 trial comparing clesrovimab to palivizumab, showing comparable safety and efficacy profiles. The company plans to submit the findings to global health authorities for potential approval ahead of the 2025-26 RSV season.