Study to Evaluate the Efficacy and Safety of Suptavumab (REGN2222) for the Prevention of Medically Attended RSV (Respiratory Syncytial Virus) Infection in Preterm Infants

This study occurred in two parts: Part A and Part B. Part A of the study was an open-label, PK evaluation of intramuscular (IM) administered suptavumab in preterm infants for whom palivizumab was not recommended to enable the selection of dosing regimens for Part B. Part B of the study was randomized, double-blind, and placebo-controlled, designed to evaluate efficacy, safety, serum concentration and immunogenicity of IM administration of suptavumab in preterm infants for whom palivizumab was not recommended. The total duration of Part B was up to 265 days (includes a 28-day screening period, 57-day treatment period and 180-day follow-up period). Up to 1515 subjects were planned to be included in Part B of the study. Participants were randomly assigned to 1 of 3 different groups, each with 505 infants; one group received one dose of suptavumab and one dose of placebo, the second group received two doses of suptavumab, and the third group received two doses of placebo. There was a separate genetic testing sub study.