The study consists of 3 phases: screening phase, treatment phase (Day 1 to Day 5/6 \[depending on timing of loading dose\]), and follow-up phase of 28 days post randomization. Participants will have assessments at Days 7, 10, 14, and 28 to evaluate safety, efficacy, and pharmacokinetics (PK). The primary hypothesis of study is a positive dose-response relationship of active treatment on average hMPV viral load area under concentration versus time curve (AUC) over 7 days, meaning that either average AUC on pooled active treatments is lower than on placebo, or average AUC on high active dose is lower than average AUC on placebo using multiple contrast testing. Based on review of PK, efficacy and safety data, Independent Data Monitoring Committee (IDMC) may recommend modifications to study design that is changes in dose and treatment duration.
