The main purpose of this study is to investigate the antiviral effect of S-337395 compared with placebo among nonhospitalized adult participants with high-risk factors for progression to severe RSV infection starting intervention within 72 hours of RSV symptom onset.
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.
≥ 75 years of age;
Chronic lung disease that is symptomatic and requiring chronic treatment; and
Hospitalized or expected to be hospitalized within 24 hours of screening.
Is considered by the investigator to be immunocompromised, due to an underlying medical condition or medical therapy, chemotherapy, radiation, stem cell or solid organ transplant.
Has known allergies, hypersensitivity, or intolerance to S-337395 or to any of the excipients of the S-337395 or placebo formulation.
Suspicion or known severe renal impairment.