"Efesovir" (FS-1) for COVID-19, Phase 2

Clinical Response Rate is calculated as the number of trial subjects with effective treatment over the total number of subjects multiplied by 100. It is calculated in each study group.

Measured in percents. The outcome is estimated among randomized subjects completed clinical study with the protocol requirements (per protocol population (PPP)).

Clinical response is evaluated as effective treatment if: all signs and symptoms of COVID19 are resolved or improved with no worsening or appearance of new signs and symptoms; there is no requirement for additional antiviral of antibacterial therapy; chest roentgenograms (CT scans) are improved. The outcome is assessed in day 21 from the start of Study Drug treatment (visits 13).

Early clinical response rate defined as complete resolution or significant improvement of at least 2 of 4 leading baseline signs and symptoms within 72 hours after the start of Study (Referent) Drug treatment. It is estimated in the Intent to Treat (ITT) population. The outcome is measured in percents.

The outcome is estimated in patients with pneumonia due to coronavirus infection (modified ITT population). It is defined as complete resolution or significant improvement of at least 2 of 4 main clinical symptoms of pneumonia (cough, shortness of breath, chest pain, sputum) within 72 hours after the start of Study (or Referent) Drug treatment. The outcome is measured in percents. The percentage of subjects with an early clinical response to pneumonia in the compared groups is statistically estimated.

Percentage of patients at Day 3 who are clinically stable.

Clinical stability defined as:

• Blood oxygen saturation >= 93%
• Temperature <=38.0°C
• Heart rate <=100 beats per minute
• Respiratory rate <=25 per minute
• Systolic blood pressure ≥90 mm Hg
• Ability to maintain oral intake
• Normal mental status (oriented to person, place or time) A patient is considered to be clinically stable if all stability criteria are met. The outcome is assessed in ITT population. The difference between groups in the percentage of clinically stable patients from the total number of study subjects in the group is statistically evaluated.

Percentage of participants surviving at day 21. The indicator is calculated as the number of live subjects at the last visit (day 21) divided by the total number of study subjects in the group multiplied by 100.

The outcome is estimated among subjects who completed the study in compliance with the protocol (per protocol population (PPP)).

The clinical status is determined by the ordinal scale:

• Not hospitalized, no limitations on activities
• Not hospitalized, limitation on activities and/or requiring home oxygen
• Hospitalized, not requiring supplemental oxygen - no longer requires ongoing medical care
• Hospitalized, not requiring supplemental oxygen - requiring ongoing medical care
• Hospitalized, requiring supplemental oxygen
• Hospitalized, on non-invasive ventilation or high flow oxygen devices
• Hospitalized, on invasive mechanical ventilation or Extracorporeal Membrane Oxygenation
• Death

Clinical status is assessed in ITT population. The outcome is recorded at all visits, starting from the day of randomization. A decrease in points indicates the effectiveness of treatment. When the indicator changes during the day, the worst score of the day is recorded. Statistical analysis is performed on the Day 7 from the start Study Drug treatment, comparing with the score at randomization.

The safety of Study Drug (Referent Drug) will be assessed by adverse event and serious adverse event monitoring.

Changes in laboratory parameters of thyroid gland function (hormones) at the last visit in comparison with the baseline data (thyroid stimulating hormone (TSH), free triiodothyronine (FT3)).