SARS-CoV-2 virus RNA was measured by reverse-transcription polymerase chain reaction (RT-PCR) from nasopharyngeal (NP) swabs. The change from baseline was estimated from an ANCOVA model with baseline viral load as a covariate. Reported here is the adjusted mean change from baseline. A negative change from baseline indicates an improvement.

The modified ITT infected (mITTi) population was defined as all participants randomized in the study who received any amount of study drug and had at least one positive SARS-CoV-2 RT-PCR test result above or equal to the limit of quantification (LOQ) during the study, with participants grouped according to the treatment assignment at randomization.

Time to cessation of viral shedding was defined as the time between the initiation of any study treatment and the first time when a negative or below the limit of detection RT-PCR test result was obtained. RT-PCR was measured from NP swabs. Median, 25th and 75th percentiles were estimated from the Kaplan-Meier curve.

The mITTi population was defined as all participants randomized in the study who received any amount of study drug and had at least one positive SARS-CoV-2 RT-PCR test result above or equal to the limit of quantification (LOQ) during the study, with participants grouped according to the treatment assignment at randomization.

Time to sustained non-detectable SARS-CoV-2 virus RNA was defined as the time between the initiation of any study treatment and first time when a negative or below the limit of detection test result by RT-PCR is obtained after which no positive test above or equal to the limit of detection was reported. RT-PCR was measured from NP swabs. Median, 25th and 75th percentiles were estimated from the Kaplan-Meier curve.

The mITTi population was defined as all participants randomized in the study who received any amount of study drug and had at least one positive SARS-CoV-2 RT-PCR test result above or equal to the limit of quantification (LOQ) during the study, with participants grouped according to the treatment assignment at randomization.

Reported here is the percentage of participants with a positive virus RNA by RT-PCR test result above or equal to the limit of quantification (LOQ). RT-PCR was measured from NP swabs.

The mITTi population was defined as all participants randomized in the study who received any amount of study drug and had at least one positive SARS-CoV-2 RT-PCR test result above or equal to the limit of quantification (LOQ) during the study, with participants grouped according to the treatment assignment at randomization.

AUC is the amount of SARS-CoV-2 virus RNA from baseline to the last sample timepoint and was calculated using the trapezoidal method. RT-PCR was measured from NP swabs.

The mITTi population was defined as all participants randomized in the study who received any amount of study drug and had at least one positive SARS-CoV-2 RT-PCR test result above or equal to the limit of quantification (LOQ) during the study, with participants grouped according to the treatment assignment at randomization.

COVID-19 symptoms were evaluated using the first 12 items in the COVID-19 Symptom Diary, which included the following 12 items: nasal congestion or runny nose, sore throat, cough, shortness of breath, muscle or body aches, fatigue, headache, chills/sweats, feeling hot or feverish, nausea, vomiting, and diarrhea. The symptoms were scored on the 4-point Likert scale (0=none, 1=mild, 2=moderate, 3=severe).Time to alleviation or improvement is defined as the length of time taken from start of treatment to the point at which all of the following three criteria are met and maintained for a concurrent duration of at least 21.5 hours: "new" symptoms with a score of 0 or 1; "pre- existing and worsened due to COVID-19" symptoms with at least a single category improvement from baseline; "pre-existing and not worsened due to COVID-19" symptoms remaining the same or at least a single category improvement from baseline.

The mITTi population was defined as all participants randomized in the study who received any amount of study drug and had at least one positive SARS-CoV-2 RT-PCR test result above or equal to the limit of quantification (LOQ) during the study, with participants grouped according to the treatment assignment at randomization.

COVID-19 symptoms were evaluated using the first 12 items in the COVID-19 Symptom Diary, which included the following 12 items: nasal congestion or runny nose, sore throat, cough, shortness of breath, muscle or body aches, fatigue, headache, chills/sweats, feeling hot or feverish, nausea, vomiting, and diarrhea. The symptoms were scored on the 4-point Likert scale (0=none, 1=mild, 2=moderate, 3=severe). Time to alleviation or improvement is defined as the length of time taken from start of treatment to the point at which all of the following three criteria are met and maintained for a concurrent duration of at least 43 hours: "new" symptoms with a score of 0 or 1; "pre- existing and worsened due to COVID-19" symptoms with at least a single category improvement from baseline; "pre-existing and not worsened due to COVID-19" symptoms remaining the same or at least a single category improvement from baseline.

The mITTi population was defined as all participants randomized in the study who received any amount of study drug and had at least one positive SARS-CoV-2 RT-PCR test result above or equal to the limit of quantification (LOQ) during the study, with participants grouped according to the treatment assignment at randomization.

COVID-19 symptoms were evaluated using the first 12 items in the COVID-19 Symptom Diary, which included the following 12 items: nasal congestion or runny nose, sore throat, cough, shortness of breath, muscle or body aches, fatigue, headache, chills/sweats, feeling hot or feverish, nausea, vomiting, and diarrhea. The symptoms were scored on the 4-point Likert scale (0=none, 1=mild, 2=moderate, 3=severe). Time to alleviation of COVID-19 symptoms is defined as the length of time taken from start of treatment to the point at which the following criterion is met and maintained for at least 21.5 hours: Score of 0 or 1 on Items 1-12 of the COVID-19 Symptom Diary, regardless of if the symptom is pre-existing or new.

The mITTi population was defined as all participants randomized in the study who received any amount of study drug and had at least one positive SARS-CoV-2 RT-PCR test result above or equal to the limit of quantification (LOQ) during the study, with participants grouped according to the treatment assignment at randomization.

COVID-19 symptoms were evaluated using the first 12 items in the COVID-19 Symptom Diary, which included the following 12 items: nasal congestion or runny nose, sore throat, cough, shortness of breath, muscle or body aches, fatigue, headache, chills/sweats, feeling hot or feverish, nausea, vomiting, and diarrhea. The symptoms were scored on the 4-point Likert scale (0=none, 1=mild, 2=moderate, 3=severe). Time to alleviation of COVID-19 symptoms is defined as the length of time taken from start of treatment to the point at which the following criterion is met and maintained for at least 43 hours: Score of 0 or 1 on Items 1-12 of the COVID-19 Symptom Diary, regardless of if the symptom is pre-existing or new.

The mITTi population was defined as all participants randomized in the study who received any amount of study drug and had at least one positive SARS-CoV-2 RT-PCR test result above or equal to the limit of quantification (LOQ) during the study, with participants grouped according to the treatment assignment at randomization.

Duration of fever was defined as the time from start of treatment to return to an afebrile state (temperature ≤ 37.5°C) maintained for at least 21.5 hours.

The modified ITT infected (mITTi) population was defined as all participants randomized in the study who received any amount of study drug and had at least one positive SARS-CoV-2 RT-PCR test result above or equal to the limit of quantification (LOQ) during the study, with participants grouped according to the treatment assignment at randomization. Only participants who had a fever (temperature > 37.5 degrees Celsius) at baseline are included.

COVID-19 related complications include death, hospitalization, radiologically confirmed pneumonia, acute respiratory failure, sepsis, coagulopathy, pericarditis, myocarditis, and cardiac failure.

The mITTi population was defined as all participants randomized in the study who received any amount of study drug and had at least one positive SARS-CoV-2 RT-PCR test result above or equal to the limit of quantification (LOQ) during the study, with participants grouped according to the treatment assignment at randomization.

The COVID-19 Symptom Diary included the following 14 items: nasal congestion or runny nose, sore throat, cough, shortness of breath, muscle or body aches, fatigue, headache, chills/sweats, feeling hot or feverish, nausea, vomiting, diarrhea, sense of smell over the past 7 days and sense of taste over the past 7 days. The severity of items 1-12 was recorded on a 4-point Likert scale (none=0, mild=1, moderate=2, severe=3). Items 13-14 were recorded on a 3-point Likert scale (same as usual=0, less than usual=1, no sense=2). Time to alleviation of an individual symptom was defined as the time taken from the start of treatment to the point at which the following criterion was met and maintained (for each individual symptom) for at least 21.5 hours: score of 0 or 1 for Items 1-12 of the COVID-19 Symptom Diary; score of 0 for Items 13 and 14 of the COVID-19 Symptom Diary.

The mITTi population was defined as all participants randomized in the study who received any amount of study drug and had at least one positive SARS-CoV-2 RT-PCR test result above or equal to the limit of quantification (LOQ) during the study, with participants grouped according to the treatment assignment at randomization. Only participants with a baseline score of > 1 for Items 1 - 12 or > 0 for Items 13 - 14 of the COVID-19 Symptom Diary were included in the analysis.

An AE is any untoward medical occurrence in a clinical investigation subject administered a pharmaceutical product, regardless of causal attribution. An AE can therefore be any of the following: any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a pharmaceutical product, whether or not considered related to the medicinal product, any new disease or exacerbation of an existing disease, recurrence of an intermittent medical condition not present at baseline or related to a protocol-mandated intervention.

Safety population consisted of all participants who received any amount of study drug and were grouped according to the treatment that the participants actually received rather than the treatment assigned at randomization.

AT-511 is the free base form of AT-527. Its major metabolites are AT-551, AT-229, and AT-273.

The pharmacokinetic-evaluable population consisted of all participants randomized into the study who had at least one post-dose drug concentration measurement at a scheduled visit timepoint.

AT-511 is the free base form of AT-527. Its major metabolites are AT-551, AT-229, and AT-273.

The pharmacokinetic-evaluable population consisted of all participants randomized into the study who had at least one post-dose drug concentration measurement at a scheduled visit timepoint.

SARS-CoV-2 virus RNA was measured by reverse-transcription polymerase chain reaction (RT-PCR) from NP swabs. The change from baseline was estimated from an ANCOVA model with baseline viral load as a covariate. Reported here is the adjusted mean change from baseline. A negative change from baseline indicates an improvement.

The modified ITT infected (mITTi) population was defined as all participants randomized in the study who received any amount of study drug and had at least one positive SARS-CoV-2 RT-PCR test result above or equal to the limit of quantification (LOQ) during the study, with participants grouped according to the treatment assignment at randomization.