A Study to Learn About the Safety and Tolerability of Sisunatovir in Infants and Children With Pneumonia, Caused by the Respiratory Syncytial Virus

An Interventional, Phase 1b, Randomized, Double-blind, Sponsor-Open, Placebo-Controlled, Multi-Center, Dose-Finding Study to Evaluate Safety, Tolerability and Pharmacokinetics of Sisunatovir in Pediatric Participants up to Age 60 Months With Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Infection (LRTI)