Merck's RSV Antibody Clesrovimab Reduces RSV in Infants

Merck, known as MSD outside the United States and Canada, recently shared promising results from their Phase 2b/3 clinical trial, MK-1654-004, evaluating clesrovimab. This investigational monoclonal antibody is designed to shield infants from respiratory syncytial virus (RSV) during their initial RSV season. The findings, which were unveiled at IDWeek 2024 in Los Angeles, demonstrated significant protection against RSV-related hospitalizations in infants.

The MK-1654-004 trial was a placebo-controlled study involving healthy infants, both preterm and full-term, from birth to one year of age. The trial's data showed that the primary goal was met, with consistent efficacy results observed at both the five-month and six-month checkpoints. Importantly, the incidence of adverse events (AEs) and serious adverse events (SAEs) was similar between the clesrovimab and placebo groups, and there were no deaths related to the treatment or RSV during the study.

Dr. Octavio Ramilo, chair of the Department of Infectious Diseases at St. Jude’s Children’s Research Hospital and a key investigator for the MK-1654-004 and MK-1654-007 trials, commented on the significance of these findings. He highlighted that RSV remains a major cause of infant hospitalization and that these encouraging results point to clesrovimab's potential to reduce the burden of RSV on infants and their families.

The trial's primary efficacy endpoint was the reduction in RSV-associated medically attended lower respiratory infections (MALRI) compared to placebo over a 150-day period post-dose. The results showed a 60.4% reduction in such infections, a finding that underscores the potential of clesrovimab to offer substantial protection against RSV.

Secondary endpoints included the reduction of RSV-related hospitalizations and severe respiratory infections over 150 days, with tertiary endpoints assessing the incidence of acute respiratory infections and severe MALRI through the same period. The analysis included additional efficacy measures through Day 180. Safety assessments covered the frequency of injection-related AEs, AEs of special interest (AESIs), and systemic AEs or SAEs.

The ongoing Phase 3 trial, MK-1654-007, is a multicenter, randomized, partially blinded study comparing clesrovimab to palivizumab in infants and children at increased risk for severe RSV disease. This trial includes participants entering their first RSV season who are recommended to receive palivizumab due to conditions such as prematurity, chronic lung disease of prematurity, or significant congenital heart disease. In this interim analysis, 901 participants were involved, with the primary focus on the safety and tolerability of clesrovimab compared to palivizumab. Secondary endpoints are focused on the incidence of RSV-associated medically attended infections and hospitalizations.

Clesrovimab, also known as MK-1654, is an investigational monoclonal antibody designed to provide passive immunization against RSV. It is intended to be administered as a single dose across different weight categories, offering rapid and lasting protection for infants through their first RSV season.

Respiratory syncytial virus (RSV) is a common and highly contagious virus causing seasonal infections akin to the flu. It poses a significant health risk to both infants and older adults, leading to serious respiratory conditions like bronchiolitis and pneumonia. Globally, RSV is the primary cause of hospitalization for infants under one year of age, with an estimated 101,000 deaths annually in children under five. The CDC notes that RSV season in the United States typically begins in the fall and peaks in winter, though timing can vary by region.

Merck, also known as MSD outside the U.S. and Canada, has a long-standing commitment to developing innovative medicines and vaccines. With a history spanning over 130 years, the company continues to focus on research-driven solutions to improve health outcomes globally, fostering a diverse and inclusive workforce and striving for sustainability and health advancements for all communities.