At 3d interim analysis, randomization, but not follow-up, was halted by the DSMB due to low predictive probability of achieving postulated mortality benefit (pre-specified 42.5% relative mortality reduction) were the trial to complete randomization.

The mortality rate in SARS-CoV-2-related severe ARDS is high despite treatment with antivirals, glucocorticoids, immunoglobulins, and ventilation. Preclinical and clinical evidence indicate that MSCs migrate to the lung and respond to the pro-inflammatory lung environment by releasing anti-inflammatory factors reducing the proliferation of pro-inflammatory cytokines while modulating regulatory T cells and macrophages to promote resolution of inflammation. Therefore, MSCs may have the potential to increase survival in management of COVID-19 induced ARDS.

The primary objective of this phase 3 trial is to evaluate the efficacy and safety of the addition of the mesenchymal stromal cell (MSC) remestemcel-L plus standard of care compared to placebo plus standard of care in patients with acute respiratory distress syndrome (ARDS) due to SARS-CoV-2. The secondary objective is to assess the impact of MSCs on inflammatory biomarkers.

This will be a randomized (1:1 ratio), double blind, parallel design, placebo controlled trial. Randomization will be stratified by clinical center and by moderate versus severe ARDS. The study is designed to have three interim analyses for stopping accrual early for efficacy and futility when 30%, 45% and 60% of the 300 patients have reached the primary endpoint using Bayesian predictive probabilities.

Patients will be randomized in a 1:1 allocation to intravenous infusion of MSCs (remestemcel-L) plus standard of care versus placebo plus standard of care for the treatment of COVID-19 related ARDS:

• Group 1: 2x10^6 MSC/kg of body weight plus standard of care, administered twice during the first week, with the second infusion at 4 days following the first infusion (± 1 day)
• Group 2: Placebo (Plasma-Lyte) plus standard of care, administered twice during the first week, with the second infusion at 4 days following the first infusion (± 1 day) (control)

MSCs and placebo will initially be administered intravenously in the dose defined above at randomization. The rate of infusion may be tailored to the patient's respiratory status and fluid status, but the duration of infusion should not exceed 60 minutes.

Patients will be followed for 90 days post randomization, with assessment of pulmonary symptoms at 6 and 12 months.

Inclusion Criteria

• 18 years or older

• Patient has SARS-CoV-2 (COVID-19) confirmed by real-time reverse transcription polymerase chain reaction (RT-PCR) assay or other diagnostic test

• Patient requiring mechanical ventilatory support with moderate to severe ARDS as determined by the following criteria (adapted from the Berlin criteria)

  • Bilateral opacities must be present on a chest radiograph or computerized tomographic (CT) scan. These opacities are not fully explained by pleural effusions, lobar collapse, lung collapse, or pulmonary nodules.
  • Respiratory failure not fully explained by cardiac failure or fluid overload.
  • Moderate to severe impairment of oxygenation must be present, as defined by the ratio of arterial oxygen tension to fraction of inspired oxygen (PaO2/FiO2). The severity of the hypoxemia defines the severity of the ARDS:

• Moderate ARDS: PaO2/FiO2 >100 mmHg and ≤200 mmHg, on ventilator settings that include PEEP ≥5 cm H2O OR

• Severe ARDS: PaO2/FiO2 ≤100 mmHg on ventilator settings that include PEEP ≥5 cm H2O

• High sensitivity C-Reactive Protein (hs-CRP) or CRP serum level >4.0 mg/dL

• Acute Physiologic and Chronic Health Evaluation (APACHE IV) score >5

• Creatinine clearance of ≥ 30 mL/minute OR a creatinine clearance of 20-29 mL/minute with urine output of ≥0.3 mLs/kg/hour over the last 8 hours or ≥500 mLs over the last 24 hours

• The patient or his/her legally authorized representative (LAR) is able to provide informed consent

Exclusion Criteria

• Currently receiving extracorporeal membrane oxygenation (ECMO) or high frequency oscillatory ventilation (HFOV)
• Females who are pregnant or lactating
• Patients with established positive bacterial blood cultures prior to enrollment or suspicion of superimposed bacterial pneumonia
• Patients with BMI >55
• Patients with untreated HIV infection
• Patients with malignancy who are within 12 months of active treatment with any chemotherapy, radiation or immunotherapy.
• Patients who have been intubated for more than 72 hours in total at the time of randomization
• Creatinine clearance less than 20 mL/minute or receiving renal replacement therapy
• LFTs (isolated ALT or AST) > 8x upper limit of normal or > 5x upper limit of normal in the setting of other liver function abnormalities (i.e., total bilirubin ≥ 2x upper limit of normal)
• Known hypersensitivity to DMSO or to porcine or bovine proteins
• History of prior respiratory disease with requirement for supplemental oxygen
• Any end-stage organ disease which in the opinion of the investigator may possibly affect the safety of remestemcel-L treatment
• Receiving an investigational cellular therapy agent

All of the individual participant data collected during the trial, after deidentification.

De-identified study data sets must be submitted to the designated NHLBI Program Official no later than 3 years after the end of the clinical activity (final patient follow-up, etc.) or 2 years after the main paper of the trial has been published, whichever comes first. Data are prepared by the study coordinating center and sent to the designated PO for review prior to release.

Anyone who wishes to access the data.

This is a randomized clinical trial, in which the patients and investigators are masked to treatment assignment.