A Phase 2b, Multicenter, Randomized, Double-blind, Placebo-controlled, Parallel-group Study to Evaluate the Safety, Tolerability, and Efficacy of S-337395 in Symptomatic Nonhospitalized Adults With Respiratory Syncytial Virus Who Are at High Risk of Progression to Severe Disease

Key Inclusion Criteria: * Participants who have new onset or worsening (if present chronically) of at least 1 of the following signs and/or symptoms consistent with a viral acute respiratory infection within 72 hours prior to randomization: fever, nasal congestion, nasal discharge, sore throat, cough, sputum production, shortness of breath, or wheezing. * Participants diagnosed with RSV infection preferably using a rapid polymerase chain reaction (PCR) or other molecular-based diagnostic assay. * Has at least 1 of the following risk factors for severe RSV disease: 1. ≥ 75 years of age; 2…