Age>=18 years at time of signing Informed Consent Form Positive SARS-CoV-2 diagnostic test (RT-PCR or rapid antigen test) at screening Has symptoms consistent with mild or moderate COVID-19, as determined by the investigator, with onset <=5 days prior to randomization For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use adequate contraception, during the treatment period and for 30 days after the final dose of AT-527.

Age>=18 years at time of signing Informed Consent Form Positive SARS-CoV-2 diagnostic test (RT-PCR or rapid antigen test) at screening Has symptoms consistent with mild or moderate COVID-19, as determined by the investigator, with onset <=5 days prior to randomization For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use adequate contraception, during the treatment period and for 30 days after the final dose of AT-527.

Age>=18 years at time of signing Informed Consent Form Positive SARS-CoV-2 diagnostic test (RT-PCR or rapid antigen test) at screening Has symptoms consistent with mild or moderate COVID-19, as determined by the investigator, with onset <=5 days prior to randomization For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use adequate contraception, during the treatment period and for 30 days after the final dose of study drug.

Age>=18 years at time of signing Informed Consent Form Positive SARS-CoV-2 diagnostic test (RT-PCR or rapid antigen test) at screening Has symptoms consistent with mild or moderate COVID-19, as determined by the investigator, with onset <=5 days prior to randomization For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use adequate contraception, during the treatment period and for 30 days after the final dose of study drug.

Age>=18 years at time of signing Informed Consent Form Positive SARS-CoV-2 diagnostic test (RT-PCR or rapid antigen test) at screening Has symptoms consistent with mild or moderate COVID-19, as determined by the investigator, with onset <=5 days prior to randomization For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use adequate contraception, during the treatment period and for 30 days after the final dose of AT-527.

Age>=18 years at time of signing Informed Consent Form Positive SARS-CoV-2 diagnostic test (RT-PCR or rapid antigen test) at screening Has symptoms consistent with mild or moderate COVID-19, as determined by the investigator, with onset <=5 days prior to randomization For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use adequate contraception, during the treatment period and for 30 days after the final dose of AT-527.