Single-Dose Nirsevimab for Prevention of RSV in Preterm Infants

Area of Science:

• Pediatrics
• Infectious Diseases
• Immunology

Background:

• Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections in infants.
• There is a critical need for effective RSV prevention strategies in healthy infants.
• Nirsevimab, an extended half-life monoclonal antibody, is under development for single-dose RSV protection.

Purpose of the Study:

• To evaluate the efficacy of nirsevimab for preventing RSV-associated lower respiratory tract infection in healthy preterm infants.
• To assess the impact of nirsevimab on medically attended RSV-associated lower respiratory tract infections and hospitalizations.

Main Methods:

• A randomized, placebo-controlled trial involving healthy preterm infants (29 0/7 to 34 6/7 weeks gestation).
• Infants received a single intramuscular dose of nirsevimab (50 mg) or placebo at the start of the RSV season.
• Primary endpoint: medically attended RSV-associated lower respiratory tract infection through 150 days post-administration. Secondary endpoint: hospitalization for RSV-associated lower respiratory tract infection.

Main Results:

• Nirsevimab prophylaxis reduced medically attended RSV-associated lower respiratory tract infection by 70.1% compared to placebo (2.6% vs. 9.5%).
• Hospitalization for RSV-associated lower respiratory tract infection was reduced by 78.4% with nirsevimab (0.8% vs. 4.1%).
• These benefits were observed consistently across the 150-day period, geographic locations, and RSV subtypes, with similar adverse event profiles.

Conclusions:

• A single intramuscular dose of nirsevimab effectively prevented medically attended RSV-associated lower respiratory tract infections and hospitalizations in healthy preterm infants.
• Nirsevimab offers a promising new option for season-long RSV protection in this vulnerable population.