This study is a monocentric prospective phase I/II clinical trial, aiming at evaluating the safety and efficacy of 3 intravenous administrations of BM-MSC in 20 patients with severe to critical COVID-19 pneumonia.~After signed informed consent, patients will receive 3 infusions of (1.5)-3.0 x106/kg BM-MSC (from the same donor) at 3-4 days interval, in addition to the standard of care for COVID-19 disease.~The trial will be open for inclusion for 2 years after initiation. Each patient will be followed for 90 days after inclusion. The total study duration will thus be 2 years and 90 days.
The overall objective of the study is to evaluate the safety and efficacy of MSC therapy combined with best supportive care in hospitalized patients with COVID-19.