Clinical Study for Subjects With COVID-19 Using Allogeneic Adipose Tissue-Derived Mesenchymal Stem Cells

Inclusion Criteria: * Age above 18 years. * Male and female * Must understand and voluntarily sign an Informed Consent for study participation obtained prior to undergoing any study-specific procedures * Diagnosed as COVID-19 based upon SARS-CoV-2 RT-PCR test positive * Clinical diagnosis meets severe and/or critical parameters * Male participants must be willing to ensure their partners do not become pregnant either by practicing abstinence or the use of condoms during sexual activity Exclusion Criteria: * Participation in another clinical study (with use of another Investigational Medical Product) within 3 months prior to study treatment start * Unwillingness or inability to comply with study procedures * Patients with serious basic diseases that affect survival, including blood diseases, cachexia, active bleeding, severe malnutrition, etc. * Clinically active malignant disease * Subjects who are receiving ECMO and CRRT currently * History of known pulmonary embolism or known secondary anti-phospholipid syndrome * Known or suspected hypersensitivity to any components used to culture the AdMSCs, e.g. BSA and sulfur containing products (e.g., DMSO) * Known or suspected allergic to diphenhydramine. * Major trauma or surgery within 14 days of study treatment start * Mental condition rendering the subject (or the subject's legally acceptable representative\[s\]) unable to understand the nature, scope and possible consequences of the study * Alcohol, drug, or medication abuse within one year prior to study treatment start * Any condition that, in the Investigator's opinion, is likely to interfere with evaluation of the AdMSC therapy or satisfactory conduct of the study * Irreversible severe end organ failure, such as heart failure/attack, stroke, liver and renal failure due to other disease conditions * Patients or family history with hypercoagulable status, such as protein C/protein S deficiency, factor V Leiden, prothrombin gene mutation, dysfibrinogenemia, etc. * History of long-term use of immunosuppressive agents * Organ transplants in the past 6 months * Pregnant, breastfeeding, or desire to become pregnant or unwilling to practice birth control during participation in the study duration, unless surgically sterilized or postmenopausal during the study. * Patients with previous pulmonary obstructive pneumonia, severe pulmonary interstitial fibrosis, alveolar proteinosis, allergic alveolitis, and other known viral pneumonia or bacterial pneumonia before COVID-19 infection. The pulmonary imaging revealed the interstitial damage of lungs before the COVID-19 confirmed. * QT interval shows greater than 450 ms in males and 470 ms in females in the medical histories or during screen EKG test. * Subjects are not medically unstable at time of infusion including but not limiting unstable hypertension, pulse, oximetry, etc.