This pivotal Phase 2b study will determine if MEDI8897 will be efficacious in reducing medically attended RSV-confirmed lower respiratory tract infections (LRTI) in healthy preterm infants entering their first RSV season. The population to be enrolled is healthy preterm infants born between 29 weeks 0 days and 34 weeks 6 days GA who would not receive RSV prophylaxis. A total of 1500 infants will be randomized 2:1 to receive either MEDI8897 or placebo. Participants will be followed for 360 days after dosing. Enrollment is planned at approximately 197 sites across the USA, Canada, Europe, and the Southern Hemisphere.

Results

The New England Journal of Medicine published the results of this clinical trial on July 30, 2020.

Results: From November 2016 through November 2017, a total of 1453 infants were randomly assigned to receive nirsevimab (969 infants) or placebo (484 infants) at the start of the RSV season. The incidence of medically attended RSV-associated lower respiratory tract infection was 70.1% lower (95% confidence interval [CI], 52.3 to 81.2) with nirsevimab prophylaxis than with placebo (2.6% [25 infants] vs. 9.5% [46 infants]; P<0.001) and the incidence of hospitalization for RSV-associated lower respiratory tract infection was 78.4% lower (95% CI, 51.9 to 90.3) with nirsevimab than with placebo (0.8% [8 infants] vs. 4.1% [20 infants]; P<0.001). These differences were consistent throughout the 150-day period after the dose was administered and across geographic locations and RSV subtypes. Adverse events were similar in the two trial groups, with no notable hypersensitivity reactions.

Conclusions: A single injection of nirsevimab resulted in fewer medically attended RSV-associated lower respiratory tract infections and hospitalizations than placebo throughout the RSV season in healthy preterm infants.