Paris, March 3, 2022. The New England Journal of Medicine (NEJM) today published detailed results from a Phase 3 trial evaluating nirsevimab, the first investigational long-acting antibody designed to protect all infants across the respiratory syncytial virus (RSV) season with a single dose. The trial involved healthy infants born at term or late preterm (35 weeks gestational age or greater) entering their first RSV season and met the primary endpoint, reducing the incidence of medically attended lower respiratory tract infections (LRTI), such as bronchiolitis or pneumonia, caused by RSV by 74.5% (95% CI 49.6 to 87.1; P<0.001) compared to placebo.1,2

A prespecified pooled analysis of RSV-associated hospitalizations in both the Phase 3 and Phase 2b trials was also conducted. In term and preterm infants (greater than 28 weeks gestational age), the proposed dose of nirsevimab demonstrated efficacy of 77.3% (95% CI 50.3 to 89.7; P<0.001) against RSV-associated hospitalizations.1-3 In the Phase 3 MELODY trial alone, a numerical reduction of the risk of RSV-associated hospitalizations was observed, although not statistically significant (62.1%, 95% CI: -8.6 to 86.8; P=0.07).1,2 In the nirsevimab arm, six of 994 infants were hospitalized for RSV LRTI, while eight of 496 infants were hospitalized in the placebo arm.1,2 Nirsevimab is being developed by Sanofi and AstraZeneca.

Associate Professor, Pediatrics, Northwestern University Feinberg School of Medicine and Scientific Director, Clinical and Community Trials, Ann & Robert H. Lurie Children’s Hospital of Chicago, Illinois“We know that RSV has seen a resurgence with the easing of COVID-19 public health measures. This shows us a broad immunization approach is needed to help mitigate the substantial global burden RSV places on infants, their families and healthcare services. These exciting data show that nirsevimab has the potential to offer RSV protection for all infants, which would be a paradigm shift in the approach to this disease.”

The results of the Phase 3 and Phase 2/3 clinical trials, combined with the Phase 2b trial and conducted in different trial populations, demonstrate nirsevimab’s potential to protect all infants across the RSV season with a single dose.1-6

Nirsevimab is the first investigational long-acting antibody designed to protect all infants during their first RSV season. With nirsevimab, the goal is to provide rapid and direct protection to the infant through a single immunization. It is the first potential immunization to show protection against RSV in infants in a Phase 3 trial.1,2 RSV is the most common cause of LRTI, including bronchiolitis and pneumonia, and a leading cause of hospitalizations in all infants.7-9

The safety and tolerability of nirsevimab compared to palivizumab was evaluated in the Phase 2/3 trial, which demonstrated nirsevimab had a similar safety and tolerability profile compared to palivizumab when administered to infants with congenital heart disease, chronic lung disease and prematurity (35 weeks gestational age or fewer) entering their first RSV season.5,6 Safety was assessed by monitoring the occurrence of all treatment emergent adverse events (TEAEs) and treatment emergent serious adverse events (TESAEs) through 360 days post-dose. The serum levels of nirsevimab following dosing at Day 151 in this trial were comparable with those observed in the Phase 3 trial, indicating similar protection in this population to that in the healthy term and late preterm infants is likely.1,2,5,6 Details from the Phase 2/3 trial were also published in NEJM. The study is ongoing, and topline results were presented at RSVVW’21.

https://www.sanofi.com/en/media-room/press-releases/2022/2022-03-03-08-00-00-2395880