Nirsevimab Under Review for Protection Against RSV for All Infants

Respiratory syncytial virus. Coloured transmission electron micrograph (TEM) of a respiratory syncytial virus (RSV). This pneumovirus, a type of paramyxovirus, is a major cause of human respirat- ory tract infections in temperate climates, especially in winter. The virus consists of RNA (ribonucleic acid) genetic material enclosed in a protein coat, or capsid, within a phospholipid envelope. The envelope is covered in protein spikes, seen as the yellow lines around the edge of the virus. In adults, the virus only affects the upper respiratory tract, but in infants bronchiolitis (bronchiole inflammation) or bron- chopneumonia can result. Magnification unknown.
Nirsevimab is a long-acting anti-RSV for nirsevimab for the prevention of RSV lower.

The Food and Drug Administration (FDA) has accepted for review the Biologics License Application (BLA) for nirsevimab for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in newborns and infants entering or during their first RSV season, and for children up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season.

Nirsevimab is a long-acting anti-RSV monoclonal antibody. The BLA is supported by efficacy and safety data from the nirsevimab clinical development program, which includes the phase 3 MELODY trial ( Identifier: NCT03979313), the phase 2/3 MEDLEY trial ( Identifier: NCT03959488), and a phase 2b trial.

The MELODY trial compared a single intramuscular (IM) injection of nirsevimab to placebo in 1490 healthy infants who were born at a gestational age of at least 35 weeks. Findings showed that treatment with nirsevimab was associated with a statistically significant reduction in the incidence of medically-attended RSV-associated lower respiratory tract infection (LRTI) and a lower incidence of hospitalization for RSV-associated LRTI compared with placebo. 

In the randomized, double-blind, phase 2/3 MEDLEY trial, the safety and tolerability of nirsevimab was compared with palivizumab in approximately 925 infants with congenital heart disease, chronic lung disease, and/or prematurity before entering their first RSV season. Findings showed that nirsevimab demonstrated a similar safety and tolerability profile compared with palivizumab.

A decision on the application is expected sometime in the third quarter of 2023.


Nirsevimab US regulatory submission accepted for the prevention of RSV lower respiratory tract disease in infants and children up to age 24 months. News release. AstraZeneca. Accessed January 5, 2023.