Study closed out early due to evolving COVID-19 standard of care

The objectives of this study are to evaluate the safety, tolerability, antiviral activity and efficacy of AT-527 in adult subjects ≥18 years of age with moderate COVID-19 and risk factors for poor outcomes (such as obesity (BMI>30), hypertension, diabetes or asthma). Eligible subjects will be randomized to blinded AT-527 (nucleotide analog) tablets or matching placebo tablets to be administered orally for 5 days. Part A will evaluate an AT-527 dose of 550 mg BID and Part B will evaluate a second dose of AT-527 (1100 mg BID). Local supportive standard of care (SOC) will be allowed for all subjects. Efficacy, antiviral activity and safety observations will be compared for treatment with active AT-527 tablets vs. placebo tablets.

Key Inclusion Criteria:

• Hospitalized or in a hospital-affiliated confinement facility
• SARS-CoV-2 positive
• Initial COVID-19 symptom onset within 5 days prior to Screening
• SpO2 ≥ 93% on room air or requires ≤ 2L/min oxygen by nasal cannula or mask to maintain SpO2 ≥ 93%
• Must also have a history of at least one of the following known risk factors for poor outcomes: obesity (BMI>30), hypertension, diabetes or asthma.

Key Exclusion Criteria:

• 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).

Blinded

Principal Investigator may publish or present results pertaining to the PI's activities after the first publication of the multicentre clinical trial results, or 18 months after the clinical study database lock. Any such publications must be submitted for review by Sponsor before submission. The Sponsor may request that Confidential Information be deleted and/or the publication be postponed in order to protect the Sponsor's intellectual property rights.