The primary efficacy endpoint in the study is the responder rate at Day 10 in each treatment group. The state “Responder”/ “Non-Responder” to be evaluated by the composite outcome criteria as follows. Subject will be defined as “Responder” at the time point of evaluation in case one of the three outcome criteria below is fulfilled: 1) No further worsening of respiratory function as defined below: a) Improvement of oxygen saturation >3 percentage points or >10%, with stable FiO2 or b) with a possibility to reduce FiO2 to maintain adequate saturation with 100 points. 2) Significant reduction in number of viral replicas detected: as below 5% of baseline in the case of quantitative PCR was performed, or the PCR test is turned out negative at Ct18 sensitivity limit in case of qualitative PCR test performed at baseline. 3) Change in clinical state assessed by a 6-point ordinal scale (6-POC). Clinical Improvement since start of treatment, defined as a decrease of at least 1 point from baseline on a six-point ordinal scale: If none of the above three criteria is fulfilled, then the subject will be considered as “Non-Responder” at the time point of evaluation.

The primary efficacy endpoint in the study is the responder rate at Day 10 in each treatment group. The state “Responder”/ “Non-Responder” to be evaluated by the composite outcome criteria as follows. Subject will be defined as “Responder” at the time point of evaluation in case one of the three outcome criteria below is fulfilled: 1) No further worsening of respiratory function as defined below: a) Improvement of oxygen saturation >3 percentage points or >10%, with stable FiO2 or b) with a possibility to reduce FiO2 to maintain adequate saturation with 100 points. 2) Significant reduction in number of viral replicas detected: as below 5% of baseline in the case of quantitative PCR was performed, or the PCR test is turned out negative at Ct18 sensitivity limit in case of qualitative PCR test performed at baseline. 3) Change in clinical state assessed by a 6-point ordinal scale (6-POC). Clinical Improvement since start of treatment, defined as a decrease of at least 1 point from baseline on a six-point ordinal scale: If none of the above three criteria is fulfilled, then the subject will be considered as “Non-Responder” at the time point of evaluation.