Merck’s RSV antibody clesrovimab protects infants

Merck & Co, also known as MSD outside the US and Canada, has announced promising top-line results from a phase 2b/3 study of its investigational monoclonal antibody, clesrovimab (MK-1654), designed to prevent respiratory syncytial virus (RSV) infections in infants. RSV is a widespread respiratory virus that typically manifests with mild, cold-like symptoms but can lead to severe conditions like bronchiolitis and pneumonia, particularly in young infants. In the UK alone, RSV is responsible for approximately 30,000 hospitalizations annually in children under five years of age.

Merck’s clesrovimab is an extended half-life monoclonal antibody aimed at providing passive immunization to infants during their first RSV season. The MK-1654-004 clinical trial assessed the efficacy and safety of a single dose of clesrovimab compared to a placebo in healthy preterm and full-term infants. The study successfully met its primary endpoints, demonstrating both safety and efficacy by reducing medically-attended lower respiratory tract infections caused by RSV up to day 150 post-administration.

Detailed findings from the study are expected to be shared at an upcoming scientific congress. Merck has also indicated plans to submit these results to global regulatory authorities. Dr. Paula Annunziato, senior vice president of infectious diseases and vaccines at Merck Research Laboratories, highlighted the significance of these results, particularly in light of RSV’s high contagion rate and its potential to cause severe respiratory issues in infants. She expressed enthusiasm about collaborating with regulators to introduce a new preventative option for RSV.

The announcement of Merck's study results coincides with the UK government's recent unveiling of a national vaccination program aimed at shielding infants through maternal immunization, as well as protecting older adults against RSV. The rollout of this program is set to commence next month in Scotland and in September across England, Wales, and Northern Ireland, positioning the UK as the first country globally to implement a national program using the same vaccine—Pfizer’s Abrysvo—for both infants and older adults.

This new initiative involves vaccinating pregnant women over 28 weeks into their pregnancy to help safeguard their newborns. Additionally, it includes a routine vaccination schedule for individuals over the age of 75 and a one-time campaign for those aged 75 to 79. The coordinated effort aims to significantly reduce the incidence of RSV-related hospitalizations and severe illnesses among the most vulnerable populations.