Key Inclusion Criteria:

• Willing and able to provide written informed consent (participants ≥ 18 years of age) or assent (participants ≥ 12 and < 18 years of age, where locally and nationally approved) prior to performing study procedures.   For participants ≥ 12 and < 18 years of age, a parent or legal guardian willing and able to provide written informed consent prior to performing study procedures.
• Aged ≥ 18 years (at all sites), or aged ≥ 12 and < 18 years of age weighing ≥ 40 kg (where permitted according to local law and approved nationally and by the relevant institutional review board [IRB] or independent ethics committee [IEC]).
• SARS-CoV-2 infection confirmed by PCR test ≤ 4 days before randomization.
• Currently hospitalized.
• SpO2 ≤ 94% on room air or requiring supplemental oxygen at screening.
• Radiographic evidence of pulmonary infiltrates.
• Men and women of childbearing potential who engage in heterosexual intercourse must agree to use protocol specified method(s) of contraception

Key Exclusion Criteria:

• Participation in any other clinical trial of an experimental treatment for COVID-19.
• Concurrent treatment with other agents with actual or possible direct acting antiviral activity against SARS-CoV-2 < 24 hours prior to study drug dosing.
• Evidence of multiorgan failure.
• Mechanically ventilated (including V-V ECMO) ≥ 5 days, or any duration of V-A ECMO.
• ALT or AST > 5 x ULN.
• Creatinine clearance < 50 mL/min using the Cockcroft-Gault formula for participants ≥ 18 years of age {Cockcroft 1976} and Schwartz Formula for participants < 18 years of age.
• Positive pregnancy test.
• Breastfeeding woman.
• Known hypersensitivity to the study drug, the metabolites, or formulation excipient.