Inclusion Criteria:  Availability of the Informed Consent Form of the Patient Information Leaflet (PIL) signed and dated by patient. Men and women aged 18 to 80 years inclusive at the time of signing the Informed Consent Form in PIL. Confirmed case of COVID-19 at the time of screening based on SARS-CoV-2 RNA test using nucleic acid amplification (NAA) method. It is acceptable to include a patient with a presumptive COVID-19 diagnosis prior to receiving the results of SARS-CoV-2 RNA test made at the screening stage. Hospital admission due to COVID-19.  Moderate severity infection with SARS-CoV-2:  Clinical signs: Mandatory: CT pattern typical of a viral lesion (lesion volume is minimal or moderate; CT 1-2). Additional (at least 1 of the following criteria): body temperature > 38 °C; RR > 22/min; shortness of breath on exertion; SpO2 < 95%; Serum CRP > 10 mg/L. Patient's consent to use reliable contraceptive methods throughout the study and within 1 month for women and 3 months for men after its completion. Reliable means of contraception are: sexual abstinence, use of condom in combination with spermicide.  For men (optional): Consent to avoid sexual contact with pregnant women for the duration of the study and for 3 months after its completion.  Women incapable of childbearing may also participate in the study (with past history of: hysterectomy, tubal ligation, infertility, menopause for more than 2 years), as well as men with infertility or a history of vasectomy.  Exclusion Criteria:  Hypersensitivity to favipiravir, remdesivir and/or other components of the study drug. Impossibility of CT procedure (for example, gypsum dressing or metal structures in the field of imaging). History of vaccination against COVID-19. History of presumptive or confirmed COVID-19 case of moderate, severe and extremely severe course of the disease. Use of favipiravir or remdesivir within 10 days prior to screening. The need to use drugs from the list of prohibited therapy. Meeting the criteria for severe and extremely severe course of the disease. Need for treatment in the intensive care unit. Impaired liver function (AST and/or ALT ≥ 2 UNL and/or total bilirubin ≥ 1.5 UNL) at the time of screening. Renal impairment (GFR < 60 ml/min) at the time of screening. History of gout. Positive testing for HIV, syphilis, hepatitis B and/or C. Chronic heart failure FC III-IV according to New York Heart Association (NYHA) functional classification (see Appendix 2). Malignancies in the past medical history. Alcohol, pharmacological and/or drug addiction in the past medical history and/or at the time of screening. Schizophrenia, schizoaffective disorder, bipolar disorder, or other history of mental pathology or suspicion of their presence at the time of screening. Severe, decompensated or unstable somatic diseases (any disease or condition that threaten the patient's life or impair the patient's prognosis, and also make it impossible for him/her to participate in the clinical study). Any history data that the investigating physician believes could lead to complication in the interpretation of the study results or create an additional risk to the patient as a result of his/her participation in the study. Patient's unwillingness or inability to comply with procedures of the Study Protocol (in the opinion of physician investigator). Pregnant or nursing women or women planning pregnancy. Participation in another clinical study for 3 months prior to inclusion in the study. Other conditions that, according to the physician investigator, prevent the patient from being included in the study.