Each subject must meet all of the following criteria to be eligible for study participation: Part 1: 1. Hospitalized adult male or non-pregnant, non-lactating female subjects (between 18 and 80 years), with SARS-CoV-2, previously known as novel coronavirus (2019-nCoV) infection that is documented by an authorized diagnostic PCR test. A rapid PCR test could also be used. Confirmation that subject has COVID 19 within the last 1 week prior to randomization. 2. Meeting WHO COVID 19 Clinical Improvement Ordinal Scale Criteria 3 (hospitalized, no oxygen therapy) or Criteria 4 (hospitalized, oxygen by mask or nasal prongs). 3. Having at least 1 medical risk factor, i.e. having absolute lymphocyte count <1000 cells/mm3, age >60 years, hypertension, diabetes, cardiac failure or COPD. 4. Male subjects and female subjects of childbearing potential must agree to use protocol specified methods of contraception. 5. Females subjects of childbearing potential and women of non childbearing potential (defined as at least 2 years postmenopausal or permanently sterilized women [bilateral tubal ligation, bilateral ovariectomy, or hysterectomy]) must have a negative serum pregnancy test at screening or pretreatment on Day 1. 6. The subject or a LAR has provided written informed consent. 7. The subject or the LAR is aware of the investigational nature of this study and willing to comply with protocol treatments, blood tests, and other evaluations listed in the ICF. Part 2: Same as part 1 except 1.Meeting WHO COVID 19 Clinical Improvement Ordinal Scale Criteria 5 (non-invasive mechanical ventilation or high-flow oxygen) or Criteria 6 (intubation and mechanical ventilation).

Each subject must meet all of the following criteria to be eligible for study participation: Part 1: 1. Hospitalized adult male or non-pregnant, non-lactating female subjects (between 18 and 80 years), with SARS-CoV-2, previously known as novel coronavirus (2019-nCoV) infection that is documented by an authorized diagnostic PCR test. A rapid PCR test could also be used. Confirmation that subject has COVID 19 within the last 1 week prior to randomization. 2. Meeting WHO COVID 19 Clinical Improvement Ordinal Scale Criteria 3 (hospitalized, no oxygen therapy) or Criteria 4 (hospitalized, oxygen by mask or nasal prongs). 3. Having at least 1 medical risk factor, i.e. having absolute lymphocyte count <1000 cells/mm3, age >60 years, hypertension, diabetes, cardiac failure or COPD. 4. Male subjects and female subjects of childbearing potential must agree to use protocol specified methods of contraception. 5. Females subjects of childbearing potential and women of non childbearing potential (defined as at least 2 years postmenopausal or permanently sterilized women [bilateral tubal ligation, bilateral ovariectomy, or hysterectomy]) must have a negative serum pregnancy test at screening or pretreatment on Day 1. 6. The subject or a LAR has provided written informed consent. 7. The subject or the LAR is aware of the investigational nature of this study and willing to comply with protocol treatments, blood tests, and other evaluations listed in the ICF. Part 2: Same as part 1 except 1.Meeting WHO COVID 19 Clinical Improvement Ordinal Scale Criteria 5 (non-invasive mechanical ventilation or high-flow oxygen) or Criteria 6 (intubation and mechanical ventilation).