Study of Obeldesivir to Treat Children With Respiratory Syncytial Virus (RSV) Infection

Key Inclusion Criteria: * Participants assigned male or female at birth, from birth to \< 5 years of age who meet one of the following criteria, where permitted according to local law and approved nationally and by relevant institutional review board or independent ethics committee: * Cohort 1: Infants and children from 4 weeks postnatal age, weighing ≥ 3 kg to \< 40 kg (Part A) and ≥ 1.5 kg to \< 3 kg (Part B) * Cohort 2: Neonates, either born at term or preterm, weighing ≥ 1.5 kg to \< 6 kg * RSV infection diagnosis ≤ 3 days prior to randomization. * Negative test for influenza A/B, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 infection) ≤ 7 days prior to randomization. * Onset of RSV signs or symptoms ≤ 3 days prior to randomization. * Presence of at least 1 sign or symptom of RSV infection at screening and at randomization. Key Exclusion Criteria: * Currently requiring or expected to require hospitalization for RSV infection within 48 hours after randomization. * Not expected to survive the current RSV-related illness. * Documented previous infection and/or hospitalization for RSV during the current respiratory virus season. * Diagnosed with acute concurrent active systemic infections requiring treatment with systemic antiviral, antibacterial, antifungal, or antimycobacterial therapy, or with any documented respiratory viral infection (other than RSV), ≤ 7 days prior to randomization. * History of asthma or recurrent wheezing. * Neuromuscular di…