Mesenchymal Stem Cells for The Treatment of Acute Respiratory Distress Syndrome (ARDS)

Inclusion Criteria: * Subjects of age ≥ 20 years and ≤ 85 years. * Subject has a diagnosis of moderate ARDS according to the Berlin definition of ARDS: 1. No clinical evidence of left atrial hypertension for bilateral pulmonary infiltrates. 2. Bilateral infiltrates consistent with pulmonary edema on frontal chest radiograph. 3. Hypoxemia: PaO2/ FiO2 \> 100 mmHg to ≤ 200 mmHg with PEEP ≥ 5 cm H2O. 4. The time of onset of ARDS is when all of the specified ARDS criteria (2a-c) are met. * Patient is intubated and mechanically ventilated. * Subjects who had an onset of ARDS within 72 to 120 hours before start of treatment. * Subjects with body weight between 40 to 90 kg. * No decompensated heart failure. * Subject is willing to provide written informed consent to participate in the study after reading the informed consent form and the information provided. * Women of child-bearing potential should have a negative serum pregnancy test prior to administration of investigational product., UNLESS they meet the following criteria: 1. Post-menopausal: 12 months of natural (spontaneous) amenorrhea or 6 months of spontaneous amenorrhea with serum Follicle Stimulating Hormone (FSH) levels \> 40 mIU/ml, OR; 2. 6 weeks post-surgical bilateral oophorectomy with or without hysterectomy. Exclusion Criteria: * Greater than 72 hours since first meeting ARDS criteria per the Berlin definition. * No intent/unwillingness to follow lung protective ventilation strategy or fluid management protocol. * Expected life \< 3 months from other cause than the respiratory failure. * Subject is receiving extra-corporeal membrane oxygenation, high-frequency oscillatory ventilation or any form of extra-corporeal lung support. * Subjects with history of any type of malignancy. * Major trauma in the prior 5 days. * Subjects with major surgery (body organs that require anesthesia, such as tumor removal, open chest, heart surgery, abdominal surgery, intracranial surgery, or normal surgery for more than 3 hours, etc.) within previous 14 days. * Subjects who are pregnant (or plan to become pregnant within 3 months of investigational product treatment) or lactating. * Subjects who have a significant concomitant illness as judged by principal investigator (PI). * Subjects who have significant abnormal laboratory tests at screening: 1. \>5 × upper limit of normal for alanine aminotransferase (ALT) or aspartate aminotransferase (AST). 2. \>3 × upper limit of normal for total bilirubin. 3. \>2 × upper limit of normal for serum creatinine. * Subjects with known human immunodeficiency virus infection or who are immune compromised. * Subjects who are unable to return for follow-up visits for clinical evaluation, laboratory studies, or imaging evaluation. * Subjects with a history of severe allergic or anaphylactic reactions. * Subjects with known allergy or hypersensitivity to any component of the formulation (normal saline and human serum albumin). * Subjects who have participated in another clinical study of new investigational therapies or have received an investigational therapy within the 12 weeks before study drug administration.