Study to Evaluate the Safety and Antiviral Activity of Remdesivir (GS-5734™) in Participants With Severe Coronavirus Disease (COVID-19)

Key Inclusion Criteria:

   - Willing and able to provide written informed consent, or with a legal representative
   who can provide informed consent, or enrolled under International Conference on
   Harmonization (ICH) E6(R2) 4.8.15 emergency use provisions as deemed necessary by the
   investigator (age ≥ 18), or willing and able to provide assent (age ≥ 12 to < 18,
   where locally and nationally approved) 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))

   - Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV)-2 infection confirmed by
   polymerase chain reaction (PCR) test ≤ 4 days before randomization

   - Currently hospitalized

   - Peripheral capillary oxygen saturation (SpO2) ≤ 94% or requiring supplemental oxygen
   at screening

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 is prohibited < 24 hours prior to study drug dosing

   - Evidence of multiorgan failure

   - Mechanically ventilated [including veno-venous (V-V) extracorporeal membrane
   oxygenation (ECMO)] ≥ 5 days, or any duration of veno-arterial (V-A) ECMO.

   - Alanine Aminotransferase (ALT) or aspartate aminotransferase (AST) > 5 X upper limit
   of normal (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

Note: Other protocol defined Inclusion/Exclusion criteria may apply.