Long-Acting Monoclonal Antibody Shows Potential to Offer RSV protection for all Infants

Nirsevimab showed 74.5 percent efficacy against medically attended lower respiratory tract infections caused by a respiratory syncytial virus (RSV) in healthy infants, according to an international, randomized, placebo-controlled Phase 3 clinical trial. It is the first potential immunization against RSV in the general infant population, with a single dose providing safe protection across the entire RSV season. Results were published in the New England Journal of Medicine.

RSV is a common contagious virus that causes seasonal epidemics of lower respiratory tract infections, leading to bronchiolitis and pneumonia in infants. Lurie Children’s was among the highest US sites in the trial.

Nirsevimab is an investigational long-acting Monoclonal Antibody, being developed by AstraZeneca and Sanofi, designed to protect all infants through their first RSV season with a single dose. Monoclonal Antibody do not require the activation of the immune system to help offer rapid and direct protection against disease. The only available preventative option for RSV is palivizumab, which is limited to high-risk infants and provides one-month protection, requiring five injections to cover an RSV season.

A separate Phase 2/3 trial, also published in the New England Journal of Medicine, evaluated the safety of nirsevimab in infants with congenital heart disease, chronic lung disease, and prematurity entering their first RSV season nirsevimab had similar safety and tolerability profile compared to palivizumab. Results in this population of infants indicated similar protection against RSV to healthy term and late preterm infants.