New Evidence Reinforces Nirsevimab’s Efficacy as a Single-Dose Long-Acting Antibody Providing Season-Long RSV Protection for Infants

Today, Sanofi announced that the latest clinical trial data analysis of nirsevimab, a long-acting antibody therapy for respiratory syncytial virus (RSV), showed that in children entering their first RSV season, nirsevimab reduced the risk of lower respiratory tract infections (LRTI) requiring treatment due to RSV infection by 79.5%. The press release noted that nirsevimab is the first passive immunization therapy that provides sustained immune protection throughout the RSV season with a single injection for all infants.

RSV is a common infectious pathogen that can cause seasonal epidemics of LRTI, including bronchiolitis and pneumonia. Globally, it is the leading cause of infant hospitalization. Nirsevimab, a long-acting antibody jointly developed by Sanofi and AstraZeneca, is designed to be more potent and longer-lasting. It employs a passive immunization mechanism, allowing infants to quickly gain immunity against RSV through a single intramuscular injection, with the potential for protection throughout the entire epidemic season. It has already received Breakthrough Therapy Designation from the U.S. FDA.

This pre-specified pooled analysis combined data from the pivotal Phase 3 MELODY trial and the Phase 2b trial. The analysis showed that, compared to placebo, nirsevimab reduced the risk of LRTI (including bronchiolitis and pneumonia) requiring medical attention due to RSV infection by 79.5% (95% CI, 65.9~87.7, p<0.0001).

Another post-hoc analysis found that infants treated with nirsevimab had RSV neutralizing antibody levels in their blood 50 times the baseline level after 151 days. After 361 days of treatment, the RSV neutralizing antibody levels were still 19 times those in the placebo group, suggesting that protection for infants may extend beyond 151 days.

"RSV remains the most common cause of LRTI in infants, causing seasonal epidemics annually. These new analyses further support the potential of nirsevimab to provide protection for all infants throughout the RSV season with a single dose, which could bring about a paradigm shift in RSV prevention," said Dr. Eric Simões, Clinical Professor at the University of Colorado School of Medicine.

References:

[1] Press Release: New nirsevimab data analyses reinforce efficacy against RSV. Retrieved May 11, 2022, from https://www.sanofi.com/en/media-room/press-releases/2022/2022-05-11-08-00-00-2440425

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