Merck announces positive results from phase 2b/3 trial of clesrovimab, an investigational RSV preventative monoclonal antibody for infan

Merck (MSD outside the US and Canada) announced positive topline results from its phase 2b/3 trial (MK-1654-004) of clesrovimab (MK-1654), an investigational monoclonal antibody for RSV prevention in infants. The trial met its primary safety and efficacy goals, reducing RSV-related medically attended lower respiratory infections (MALRI) through Day 150. Results will be presented at an upcoming congress, and Merck plans to file with global regulators.

MK-1654-004 (NCT04767373) is a phase 2b/3 double-blind, randomized, placebo-controlled study evaluating clesrovimab's safety and efficacy in preterm and full-term infants. Participants received either clesrovimab or a placebo. The primary endpoints were RSV-associated MALRI incidence and safety, including adverse events (AEs) and serious adverse events (SAEs).

Clesrovimab is a long-acting monoclonal antibody designed to protect infants from RSV with a single dose. RSV is a major cause of hospitalization in infants and can lead to severe respiratory illnesses, contributing to about 101,000 deaths annually in children under five.