This is a Phase 1, open label, dose escalation, multi-center clinical trial of Allogeneic Bone Marrow-Derived Human Mesenchymal Stem Cells (hMSCs) for the treatment of Acute Respiratory Distress Syndrome (ARDS). The purpose of this study is to assess the safety of hMSCs in patients with ARDS.

The primary objective of this study is to assess the safety of intravenous infusion of Allogeneic Bone Marrow-Derived Human Mesenchymal Stem Cells (hMSCs) in patients with ARDS.

Inclusion Criteria:

Patients will be eligible for inclusion if they meet all of the below criteria. Criteria 1-3 must all be present within a 24-hour time period and at the time of enrollment:

Acute onset (defined below) of:

1. A need for positive pressure ventilation by an endotracheal or tracheal tube with a PaO2/FiO2 ratio < 200 with at least 8 cm H2O positive end-expiratory airway pressure (PEEP)
2. Bilateral infiltrates consistent with pulmonary edema on frontal chest radiograph
3. No clinical evidence of left atrial hypertension for bilateral pulmonary infiltrates.

In addition to meeting inclusion criteria, enrollment must occur within 96-hours of first meeting ARDS criteria per the Berlin definition of ARDS.

Exclusion Criteria:

1. Age less than 18 years
2. Greater than 96 hours since first meeting ARDS criteria per the Berlin definition of ARDS
3. Pregnant or breast-feeding
4. Prisoner
5. Presence of any active malignancy (other than non-melanoma skin cancer) that required treatment within the last 2 years
6. Any other irreversible disease or condition for which 6-month mortality is estimated to be greater than 50%
7. Moderate to severe liver failure (Childs-Pugh Score > 12)
8. Severe chronic respiratory disease with a PaCO2 > 50 mm Hg or the use of home oxygen
9. Patient, surrogate, or physician not committed to full support (exception: a patient will not be excluded if he/she would receive all supportive care except for attempts at resuscitation from cardiac arrest).
10. Major trauma in the prior 5 days
11. Lung transplant patient
12. No consent/inability to obtain consent
13. Moribund patient not expected to survive 24 hours
14. WHO Class III or IV pulmonary hypertension
15. Documented deep venous thrombosis or pulmonary embolism within past 3 months
16. No arterial line/no intent to place an arterial line
17. No intent/unwillingness to follow lung protective ventilation strategy or fluid management protocol
18. Currently receiving extracorporeal life support (ECLS) or high-frequency oscillatory ventilation (HFOV)

1 year