Another RSV Monoclonal Antibody Candidate Protects Infants

Globally, respiratory syncytial virus (RSV) is the leading cause of hospitalization for healthy infants under a year old and causes an estimated 101,000 deaths a year in children under five.

To address this significant health risk, Merck today announced positive topline results from its Phase 2b/3 clinical trial evaluating clesrovimab (MK-1654), the company’s investigational prophylactic monoclonal antibody (mAb) designed to protect infants from respiratory syncytial virus (RSV) disease.

Clesrovimab met its primary safety and efficacy endpoints in the trial, including reducing medically attended lower respiratory infections caused by RSV through Day 150. 

Clesrovimab is being studied in infants (pre-term and full-term) to provide rapid, durable protection through their first RSV season with a single, fixed-dose administration.

“RSV is highly contagious and can cause inflammation in the airways of infants, leading to difficulty breathing. As a widespread illness globally, RSV is the leading cause of hospitalization for healthy infants,” said Dr. Paula Annunziato, senior vice president of infectious diseases and vaccines, Global Clinical Development, Merck Research Laboratories, in a press release on July 23, 2024.

“We are encouraged by these findings and look forward to working with regulators to provide a new option to help address the impact of RSV on infants and their families."

For the 2024-2025 RSV season, the U.S. FDA-approved Beyfortus™ (Nirsevimab) mAb offers passive immunization to prevent lower respiratory tract infections caused by the RSV to infants experiencing their first or second RSV season and those with congenital heart disease or chronic lung disease.

Additionally, one vaccine has been approved for pregnant women, which offers RSV protection to newborns.