Safety and Efficacy Study of Allogeneic Human Dental Pulp Mesenchymal Stem Cells to Treat Severe COVID-19 Patients

Inclusion Criteria:

1. Aged 18-65 years;

2. Voluntarily participate in this clinical trial and sign off "informed consent form";

3. Diagnosed with severe pneumonia of COVID: respiratory distress, RR >30 times / min;
resting oxygen saturation of 93% or less; arterial partial pressure of oxygen / oxygen
concentration 300mmHg; SARS-CoV-2 nucleic acid test was positive.

4. Chest imaging confirm COVID-19 featured lesions in lung.

Exclusion Criteria:

1. Receive any clinical trial drug treatment for COVID-2019 within 30 days before the
screening assessment;

2. Severe liver disease (e.g., Child Pugh score >=C or AST> 5 times of the upper limit);

3. Patients with known severe renal insufficiency (estimated glomerular filtration rate
<=30mL / min/1.73 m2) or patients receiving continuous renal replacement therapy,
hemodialysis, peritoneal dialysis;

4. Co-infection of HIV, hepatitis B, tuberculosis, influenza virus, adenovirus or other
respiratory infection viruses;

5. Female patients who have no sexual protection in the last 30 days prior to the
screening assessment;

6. Pregnant or lactating women or women using estrogen contraception;

7. Patients who are planning to become pregnant during the study period or within 6
months after the end of the study period;

8. Other conditions that the researchers consider not suitable for participating in this
clinical trial.