- severe or critical covid-19 illness: rr ≥30, hr ≥125, spo2 <93% on room air or requires >2l/min oxygen by nasal cannula or mask to maintain spo2 ≥93%, systolic blood pressure < 90 mm hg, diastolic blood pressure < 60 mm hg or pao2/fio2 <300 - requires mechanical ventilation - lobar or segmental consolidation on chest imaging. - treatment with other drugs thought to possibly have activity against sars-cov-2 - alt or ast > 5 x upper limit of normal (uln) - female subject is pregnant or breastfeeding - has received or is expected to receive any dose of a sars-cov-2 vaccine before the day 14 visit (part b).

- severe or critical covid-19 illness: rr ≥30, hr ≥125, spo2 <93% on room air or requires >2l/min oxygen by nasal cannula or mask to maintain spo2 ≥93%, systolic blood pressure < 90 mm hg, diastolic blood pressure < 60 mm hg or pao2/fio2 <300 - requires mechanical ventilation - lobar or segmental consolidation on chest imaging. - treatment with other drugs thought to possibly have activity against sars-cov-2 - alt or ast > 5 x upper limit of normal (uln) - female subject is pregnant or breastfeeding - has received or is expected to receive any dose of a sars-cov-2 vaccine before the day 14 visit (part b).

- severe or critical covid-19 illness: rr ≥30, hr ≥125, spo2 <93% on room air or requires >2l/min oxygen by nasal cannula or mask to maintain spo2 ≥93%, systolic blood pressure < 90 mm hg, diastolic blood pressure < 60 mm hg or pao2/fio2 <300 - requires mechanical ventilation - lobar or segmental consolidation on chest imaging. - treatment with other drugs thought to possibly have activity against sars-cov-2 - alt or ast > 5 x upper limit of normal (uln) - female subject is pregnant or breastfeeding

- severe or critical covid-19 illness: rr ≥30, hr ≥125, spo2 <93% on room air or requires >2l/min oxygen by nasal cannula or mask to maintain spo2 ≥93%, systolic blood pressure < 90 mm hg, diastolic blood pressure < 60 mm hg or pao2/fio2 <300 - requires mechanical ventilation - lobar or segmental consolidation on chest imaging. - treatment with other drugs thought to possibly have activity against sars-cov-2 - alt or ast > 5 x upper limit of normal (uln) - female subject is pregnant or breastfeeding