Clinical Study To Evaluate The Performance And Safety Of Favipiravir in COVID-19

Inclusion Criteria: 1. Voluntarily participating in the clinical study; fully understanding and being fully informed of the study and having signed the Informed Consent Form (ICF); willingness and capability to complete all the study procedures; 2. Age 18-75 years (inclusive) at the time of signing ICF; 3. Being confirmed with COVID-19-Moderate type according to Competent Authority and Italian Ministry of Health guidelines and to the recommendations reported in Appendix 1 to the present protocol. Based on comprehensive analysis and judgement taking into account both the epidemiological history and clinical manifestations, the diagnosis is to be confirmed for suspected cases/clinically diagnosed cases with all of the following etiological evidences: * Positivity in RT-PCR 2019-nCov test on respiratory tract specimens; * High homology with known gene sequence of 2019-nCov in viral gene sequencing on respiratory tract specimens; Note: The above criterion would be subject to any update of the Competent Authority and Italian Ministry of Health guidelines and to the recommendations reported in Appendix 1 to the present protocol. In case any new etiologically detection methods/criteria or any new detectable specimens become available after confirmed diagnosis, the new methods or new specimens may or may not be used at the discretion of the investigator. Note: Sputum specimen is preferred for RT-PCR test of 2019-nCov nucleic acid; the specific type of respiratory tract specimen (e.g., nasopharyngeal swabs, sputum, lower respiratory tract secretions) is to be selected based on the conditions of the local laboratory. The type of specimen and detection method for 2019-nCov should remain consistent for the same subject receiving study treatment. 4. Chest imaging (CT as first option or X-ray if CT not possible)-documented pneumonia; if CT cannot be performed, Pneumonia confirmed by X-ray may be used. The method of chest imaging pneumonia diagnosis must be consistent all through the study period. 5. Patients with pyrexia (axillary ≥37℃ or oral ≥37.5℃, or axillary or rectal≥38℃) or either respiratory rate \>24/min and \<30/min or cough; For not hospitalized patients, the Investigator should maintain the detection method consistent all through the study period. In addition, the Investigator should maintain the data collection and quality compliant with GCP requirements. 6. The interval between symptoms onset and randomization is no more than 10 days; symptoms onset is primarily based on pyrexia, and can be based on cough or other related symptoms for patients without experiencing pyrexia following onset; 7. For female subjects: evidence of post-menopause, or, for pre-menopause subjects, negative pre-treatment serum or urine pregnancy test. Menopause is defined as amenorrhea for at least 12 months without other medical cause, with the following age-specific requirements: * For female subjects aged \<50 years: menopause for at least 12 months following withdrawal of exogenous hormonal therapy, with LH or FSH within the post-menopausal ranges, or having undergone any contraceptive surgery (bilateral oophorectomy or hysterectomy); * For female subjects aged ≥50 years: menopause for at least 12 months following withdrawal of exogenous hormonal therapy, or having undergone radiotherapy-induced oophorectomy with amenorrhea\>1 year, or having undergone chemotherapy-induced menopause with amenorrhea\>1 year, or having undergone any contraceptive surgery (bilateral oophorectomy or hysterectomy). 8. Eligible subjects of child-bearing age (male or female) must agree to take effective contraceptive measures (including hormonal contraception, barrier methods or abstinence) with his/her partner during the study period and for at least 7 days following the last study treatment; 9. Not participating in any other interventional drug clinical studies before completion of the present study. Exclusion Criteria: 1. Where, in the opinion of the investigator, participation in this study will not be in the best interest of the subject, or any other circumstances that prevent the subject from participating in the study safely; 2. Refractory nausea, vomiting, or chronic gastrointestinal disorders, inability to swallow the study drug or having undergone extensive bowel resection which may affect adequate absorption of Favipiravir; 3. Severe liver disease: underlying liver cirrhosis or alanine aminotransferase (ALT)/aspartate aminotransferase (AST) elevated over 5 times the ULN; 4. Gout/history of gout or hyperuricemia (above the ULN); 5. Oxygen saturation (SPO2)≤93% or arterial oxygen partial pressure (PaO2)/ fraction of inspired O2 (FiO2)≤300 mmHg; 6. Known allergy or hypersensitivity to Favipiravir; 7. Known severe renal impairment \[creatinine clearance (CcCl) \<30 mL/min\] or having received continuous renal replacement therapy, hemodialysis or peritoneal dialysis; CcCl is to be calculated by the following Cockcroft-Gault formula only when the serum creatinine is\>1.5×ULN 8. Possibility of the subject being transferred to a non-study hospital within 72h; 9. Pregnant or lactating women; 10. Having used Favipiravir or participated in any other interventional drug clinical study within 30 days prior to first dose of study drug. Note: Considering that COVID-19 requires immediate treatment, absence of severe hepatic/renal disorders (e.g., cirrhosis, long-term dialysis) in the medical record can be used as an evidence for eligibility determination. It is recommended that hepatic function and creatinine be examined whenever possible.