Clinical Trial to Evaluate the Safety, Tolerability and Efficacy of CT303 in Patients With ARDS

Inclusion Criteria: * ≥ 19 years old * Patients who meet the ARDS criteria according to the Berline definition 1. within 1 week of a known clinical insult or new or worsening respiratory symtoms 2. Bilateral opacities not fully explained by effusions, loar/lung collapse, or nodules 3. Respiratory failure not fully explained by cardiac failure or fluid overload 4. oxygenation corresponding to mild, moderate, severe * Patients requiring positive pressure ventilation using an endotracheal tube * Patients or legal representative signed Informed consent form Exclusion Criteria: * Greater than 96 hours since first meeting ARDS criteria * Patients who was previously administered mesenchymal stem cell therapy products or other cell therapy products * Patients with the following medical history or comorbid condition 1. medical history 1. Patients who had an organ transplant or bone-marrow transplantation 2. Patients who had a pneumonectomy 3. a maligant tumor within 5 years 4. a deep vein thrombosis or pulmonary embolism with in 6 months 5. a trauma within 7 days 2. comorbid condition 1. Patients with AST or ALT exceeding 5 times the upper limit of the normal range 2. eGFR ≤ 29mL/min or Patients requiring continuous renal replacement therapy 3. severe chronic respiratory disease 4. WHO functional assessment class III/IV pulmonary hypertension 5. Severe cardiac insufficiency 6. QTc \> 480msec 7. chronic underlying diseases * viral hepatitis type B or type C, or positive HIV test * Patients using extracorporeal life support devices or high-frequency oscillatory ventilation * Moribund patients expected to die within 48 hours * Patients who refuse or are likely to refuse life-sustaining treatment * Fertile women or men who disagree a continence and a contraception * Patients with a history of hypersensitivity reaction * Patients participating in clinical trials within 4 weeks * Patients determined by the investigator to be inappropriate to participate in this clinical trial