Introduction: Delayed hematological recovery, graft failure, and acute graft-versus-host disease (GVHD) still remain major problems in cord blood transplantation (CBT). Mesenchymal stem cells (MSCs) are known to support bone marrow stroma and promote hematopoiesis. Additionally, MSCs possess immunomodulatory properties and are used clinically for the treatment of acute GVHD. Therefore, the use of MSCs to enhance engraftment and prevent GVHD after allogeneic hematopoietic cell transplantation has been explored. Recent clinical trials have shown the feasibility and safety of intravenous cotransplantation of MSCs with cord blood cells in pediatric patients, but not in adult patients, who are at greater risk of graft failure. As for the route of administration of MSCs, direct intrabone marrow injection of MSCs is thought to enhance the engraftment of cord blood cells more than intravenous injection. Based on these background findings, this clinical trial was designed to develop a new strategy to enhance engraftment and prevent GVHD after CBT.
Methods and analysis: This is a single-center, phase I, clinical study to evaluate the safety of CBT combined with intrabone marrow injection of ex vivo expanded MSCs from bone marrow of a third-party donor. Adult patients with hematological disorders are eligible for this study. The target sample size is 5, and the registration period is 3 years. The target dose of MSCs infused is 0.5 × 10 cells/kg of patient body weight. On the day of CBT, MSCs are injected into the intrabone marrow of the patient 4 hours before the infusion of a single cord blood unit. The conditioning regimen varies according to patient age and disease. GVHD prophylaxis consists of a combination of tacrolimus and methotrexate. The primary endpoint of this study is infusional toxicity of MSCs within 14 days after transplantation.