Nirsevimab

Nirsevimab (MEDI8897) is a recombinant human immunoglobulin G1 kappa (IgG1ĸ) monoclonal antibody used to prevent respiratory syncytial virus (RSV) lower respiratory tract disease in neonates and infants. It binds to the prefusion conformation of the RSV F protein, a glycoprotein involved in the membrane fusion step of the viral entry process, and neutralizes several RSV A and B strains. Compared to palivizumab, another anti-RSV antibody, nirsevimab shows greater potency at reducing pulmonary viral loads in animal models. In addition, nirsevimab was developed as a single-dose treatment for all infants experiencing their first RSV season, whereas palivizumab requires five monthly doses to cover an RSV season. This is due to a modification in the Fc region of nirsevimab that grants it a longer half-time compared to typical monoclonal antibodies.

On November 2022, nirsevimab was approved by the EMA for the prevention of RSV lower respiratory tract disease in newborns and infants. Nirsevimab was also approved by Health Canada on April 19, 2023 and by the FDA in July 17, 2023 for the same indication.

Nirsevimab is indicated for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in neonates and infants during their first RSV season in Canada, the US, and Europe. Additionally, Nirsevimab is also approved in Canada and the US for use in infants up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season. These infants include, but are not limited to, those with chronic lung disease of prematurity, hemodynamically significant congenital heart disease, immunocompromised states, Down syndrome, cystic fibrosis, neuromuscular disease, and congenital airway anomalies.