Treatment with Human Umbilical Cord-Derived Mesenchymal Stem Cells for Severe COVID-19 Patients with Lung Damage: A Randomised, Double-Blind, Placebo‑Controlled Phase 2 Trial

Background: Treatment of severe Corona Virus Disease 2019 (COVID-19) is challenging. We performed a phase 2 trial to assess the efficacy and safety of human umbilical cord-mesenchymal stem cells (UC‑MSCs) to treat patients with severe COVID-19 with lung damage, based on our phase 1 data. Methods: In this randomised, double-blind, and placebo-controlled trial, we recruited 101 eligible patients with severe COVID-19 with lung damage aged between 18–74 years from two hospitals. Enrolled patients were randomly assigned at a 2:1 ratio to receive either UC-MSCs (4 × 107 cells per infusion) or placebo on day 0, 3, and 6. We excluded patients with malignant tumours, shock, or other organ failure. The primary endpoint was an altered proportion of whole lung lesion areas from baseline to day 28, measured by chest computed tomography. Other imaging outcomes, 6-minute walk test, maximum vital capacity, diffusing capacity, plasma biomarkers, and adverse events were recorded and analysed. Primary analysis was done in the modified intention-to-treat (mITT) population and safety analysis was done in all patients who started their assigned treatment. Findings: From March 5, 2020, to March 28, 2020, 100 patients were finally enrolled and received either UC-MSCs (n = 65) or placebo (n = 35). During follow-up, the patients receiving UC-MSCs exhibited a trend of numerical improvement in whole lung lesions from baseline to day 28 compared with the placebo cases. UC-MSCs administration significantly reduced the proportions of consolidation lesions from baseline to day 28 in the treated patients compared with the placebo subjects. The 6-minute walk test showed an increased distance in patients treated with UC-MSCs. Notably, UC-MSCs delivery was well tolerated, with no serious adverse events. Interpretation: UC-MSCs treatment is a safe and potentially effective therapeutic approach for patients with severe COVID‑19. The trial suggests that UC-MSCs administration might benefit patients with COVID-19 with lung damage at the convalescent stage as well as the progression stage. Trial Registration: This trial is registered with ClinicalTrials.gov, number NCT04288102. Funding Statement: This trial was supported by The National Key RD The Innovation Groups of the National Natural Science Foundation of China (81721002); The National Science and Technology Major Project (2017YFA0105703). Declaration of Interests: All authors declare no competing interests. Ethics Approval Statement: Ethical approval was obtained from the institutional review boards of each participating hospital. Written informed consent was obtained from all the enrolled patients or their legal representatives if they were unable to provide consent.