A Study to Assess the Efficacy and Safety of XC221 in Patients With Mild COVID-19

8 Russian centers will participate in this study. The trail will consist of three periods: screening (duration not more than 1 day, it may coincide with the randomization visit and beginning of drug administration), treatment period (14 full days) and follow-up period (15 ± 1 days after completion of treatment with XC221 / Placebo). The duration of participation in the study for each patient will be no more than 32 days. 274 eligible patients with confirmed COVID-19 will be randomized into two groups (Group A and Group B) in a 1:1 ratio: Group A - XC221 200 mg daily (137 patients); Group В - Placebo (137 patients). During the treatment period (14 full days), 1 tablet of XC221 / Placebo will be administered 2 times a day in addition to the standard of care (SoC) for COVID-19 according to The Temporary guidelines for the prevention, diagnosis and treatment of SARS-CoV-2 infection of the Ministry of Health of the Russian Federation (the MoH Temporary Guidelines). The follow-up period will last for 15 ± 1 days.