In a prospective, phase I/II, randomized clinical trial, the umbilical cord-mesenchymal stromal cells (UC-MSCs) treatment demonstrated beneficial effects for patient recovery in the short term by preventing more severe complications and reducing postacute sequelae in the long term. Investigators undertook this study to investigate safety and long-term effectiveness of UC-MSCs as adjunctive treatment in recovery and postacute sequelae reduction.

This single-center, placebo-controlled, double-blind study included invasive mechanical ventilation-critically ill people and coronavirus-infected people who needed intensive care surveillance (n=17).

Participants were intravenously infused with 3 doses of 5 × 105 cells/kg mesenchymal stromal cells, with a dosing interval of 48 hours (n = 11) or placebo (n = 6).

The major endpoint was the safety of UC-MSC infusion. Other outcomes incorporated participant recovery illustrated through viral load, peripheral blood mononuclear cell determination of T cell populations, blood tests and plasma levels of inflammatory cytokines, and postacute sequelae decrease assessed by computed tomography scan and biochemical markers.

A decline in the levels of ferritin, monocyte chemoattractant protein-1 (MCP1-CCL2), and interleukin-6 on the 14th day was noted in the UC-MSC group. Furthermore, a drop in the levels of D-dimer, neutrophils, and reactive C-protein, and a rise in the numbers of T lymphocytes (CD3, CD4) and natural killer lymphocytes were witnessed in the 2nd month. In the 4th month, a reduction in extension of lung damage was noted.

Until the end of participant follow-up, an improvement in all the evaluated parameters was found to be maintained. The favorable long-term safety and efficacy results suggest that mesenchymal stromal cells can play a significant role as adjunctive therapy in critically ill people infected with SARS-CoV-2.