Sanofi and AstraZeneca’s (AZ) monoclonal antibody (mAb) nirsevimab reached its primary endpoint in a Phase III trial, demonstrating protection against respiratory syncytial virus disease (RSV) in healthy infants.

Nirsevimab, an investigational extended half-life mAb is designed to protect infants entering their first RSV season, when they are at a higher risk for developing severe RSV disease.

In the Phase III MELODY trial, nirsevimab reduced lower respiratory tract infections (LRTI) requiring medical attention due to RSV in healthy preterm and term infants.

There were no clinically meaningful differences observed in the safety results between the nirsevimab and placebo groups, with the overall safety profile for nirsevimab in the trial remaining consistent with previously reported results.

“Respiratory syncytial virus is the leading cause of hospitalisations in all infants,” said Jean-François Toussaint, global head of research and development, Sanofi Pasteur.

“In fact, most hospitalisations occur in otherwise healthy infants born at term. It’s clear all infants need protection from RSV, and we hope nirsevimab becomes an important addition to routine immunisation schedules,” he added.

“Nirsevimab has the potential to provide a significant public health benefit as the first respiratory syncytial virus immunisation for the general infant population, and this data brings us one step closer to delivering nirsevimab to infants worldwide,” said Mene Pangalos, executive vice president, BioPharmaceuticals R&D, AZ.

Sanofi and AZ are also evaluating nirsevimab in a Phase III trial to assess the safety and tolerability of the mAb compared to Sobi’s Synagis (palivizumab) among preterm infants and children with chronic lung disease (CLD) and congenital heart disease (CHD) entering their first and second RSV seasons.