MSC and HSC Coinfusion in Mismatched Minitransplants

The present project aims at evaluating the capacity of MSC to improve one-year overall survival of patients transplanted with HLA-mismatched PBSC from related or unrelated donors after non-myeloablative conditioning. Co-infusion of MSC has been shown to facilitate engraftment of hematopoietic stem cell (HSC) in an immunodeficient mouse model. In addition, it has been shown that infusion of third party MSC in HSC transplantation could be successfully used as treatment for grade II-IV steroid-refractory acute graft versus host disease. One hundred and twenty patients with HLA-mismatched donors will be included over 6 years at multiple centers across Belgium through the transplant committee of the Belgian Hematological Society. The conditioning regimen will consist of fludarabine and 2 Gy TBI, followed by the infusion of donor HSC. Patients will be randomized 1/1 in double-blind fashion to receive or not MSC (1.5-.3.0 x106/kg) from third-party (either haploidentical family members or unrelated volunteer) donors on day 0. Postgrafting immunosuppression will combine tacrolimus and MMF. Except for the collection, expansion and infusion of MSC, the clinical management of the patient will not differ from that of routine NM-HCT.