Inclusion Criteria:  Patients whose clinical and laboratory test results have a positive diagnosis of Covid-19. Patients who are willing to participate as subjects in the study by signing the informed content. Diagnosed with severe pneumonia of COVID: respiratory distress, RR >30 times/min; resting oxygen saturation of 90% or less; arterial partial pressure of oxygen / oxygen concentration ≤300mmHg; Pulmonary infiltration more than 50% in 24 to 48 hours SARS-CoV-2 nucleic acid test was positive.  Exclusion Criteria:  History of drug reactions or allergies Pneumonia caused by bacteria, Mycoplasma, Chlamydia, Legionella, fungi, or other viruses Airway obstruction due to lung cancer or unknown factors Carcinoid syndrome History of epilepsy and long-term use of anticonvulsant drugs during the last 3 years History of long-term use of immunosuppressive drugs History of chronic respiratory illness that requires long-term oxygen therapy The patient is on blood or peritoneal dialysis Creatinine clearance <15 ml / min Moderate to severe liver disease (Child-Pugh score> 12) History of deep vein thrombosis (DVT) or pulmonary embolism over the past 3 years Being under ECMO or high-frequency oscillatory ventilation support Diagnostic of HIV, hepatitis B, and syphilis Pregnant or lactating women Lack of consciousness and inability to provide informed consent by the patient