AstraZeneca and Sanofi's nirsevimab has shown a significant reduction in medically-attended lower respiratory tract infections (LRTI) and hospitalisations caused by respiratory syncytial virus (RSV) in healthy preterm infants in a positive Phase IIb trial.

The trial, published in the New England Journal of Medicine, showed for the first time that a single-dose monoclonal antibody (mAb) can “significantly reduce medically-attended RSV LRTI, including bronchiolitis and pneumonia, in infants throughout the full RSV season,” the firm noted.

Nirsevimab is an extended half-life RSV mAb, being developed by AZ and Sanofi as a passive immunisation, with the potential to provide immunity directly to infants and offer immediate protection against RSV.

The drug achieved a statistically significant 70.1% reduction in medically-attended RSV LRTI compared to placebo through 150 days post-dose, thus meeting the primary endpoint.

On the secondary efficacy endpoint, nirsevimab achieved a 78.4% relative reduction in the incidence of hospitalisations due to RSV LRTI compared to placebo through 150 days post-dose.

Also of note, the safety profile for nirsevimab was similar to placebo, with no notable hypersensitivity reactions observed.

“The data for nirsevimab are exciting, as they highlight the potential for this innovative approach to protect infants from RSV with just one injection for the entire season,” said Dr Joseph Domachowske, study author, Professor of Paediatrics and Microbiology and Immunology at the State University of New York Upstate Medical University.

“Nirsevimab offers the important potential to reduce hospitalisations and emergency department and in-office visits, which are a significant burden for healthcare systems.”

“Every year, respiratory syncytial virus leads to more than three million hospitalisations worldwide and to a significant number of emergency visits for children under five, added Mene Pangalos, executive VP, R&D BioPharmaceuticals, AstraZeneca.

“This novel monoclonal antibody has the potential to protect a broad infant population, 90% of whom are infected with the virus before their second birthday.”