A Experimental Study and Clinical Result of Prophylaxis aGVHD with Humanized Anti-CD25 Monoclonal Antibody in Haploidentical BMT.

Between February 1999 and March 2004, eighty-seven patients with high risk leukemia, age 3–50 (median 19 year), who needed urgent transplant but no HLA-matched or single HLA-antigen mismatched donors available, received unmanipulated HLA haploidentical BMT. The 87 patients were classified as follows AML 27 (CR1 in 7, CR2 in 15 and 5 in relapse), All 38 (CR1 in 4, CR2 in 30 and 4 in relapse) , CML 22 ( 4 in CP, 12 in AP and 6 in BP). All donors were HLA-haploidentical relatives who had at least two major histocompatibility complex antigen mismatched with the recipients. 87 patients underwent haplo-BMT with G-CSF primed BM as stem cells. All patients received a same conditioning regimen including high dose Ara-C, Cyclophosphamide, antithymocyte globulin and total body irradiation to provide both immunosuppression and myeloablation. GVHD prophylaxis consisted of anti-thymocyte globulin, cyclosporin A, methotrexate and mycofenolate mofitel. 72 patients underwent the transplants with the addition of CD25 mAb (Basiliximab Novartis) for GVHD prophylaxis designated as CD25 mAb group. Basiliximab 20mg each by 30min intravenous infusion on 2 hours before transplantion and day 4 after transplantaion. The other 15 patients without Basiliximab for GVHD prophylaxis were as the control group. The two group of patients were comparable in disease status, HLA-disparity and median age of patients. Immunophenotyping, limited dilution assay and colony forming assays were used to measure the effect of Basiliximab on the subsets of lymphocytes, cytotoxic T lymphocyte precursors (CTLp) and hematopoietic cells. All donors were primed with G-CSF at 3-5ug/kg/d for 7 days and the marrow cells were harvested on the eighth day. G-CSF donor priming significantly increased CD34⁺ and colony forming progenitors in the marrow grafts. More importantly, it significantly reduced lymphocytes and reversed CD4⁺/CD8⁺ lymphocyte ratio in the grafts. Both of group who were treated with and without Basiliximab had similar marrow graft contents. All patients established trilineage engraftments.The median time to achieve an absolute neutrophil count 0.5x10⁹/L was 19 days (range, 13 to 24 days). The median time to achieve platelets above 20x10⁹/L was 22 days (range, 16 to 32 days). Between the two groups were no differences in engraftment. Incidence of grades II–IV acute GVHD were 13.9% with GVHD-related deaths 6.9% in Basiliximab group and 33.3% with 20% GVHD-related deaths in control group. There were a significant difference between the anti-CD25 mAb treated Vs non-treated group.Forty-nine patients who survived over 12 months were eligible for the evaluation of cGVHD. 12 patients developed extensive cGVHD, one in control group and eleven in Basiliximab group. 49 were alive in CR during a median follow-up of 30 months (range3–64 months), 42 in Basiliximab group and 7 in control group. Basiliximab significantly decreased alloreactive CTLp by 10–100 fold in limiting dilution assays. It had no effect on hematopoietic stem and progenitor cells as determined by in vitro colony-forming assays.The addition of basiliximab as aGVHD prophylaxis effectively reduced severe lethal aGVHD in haplo-BMT. It is possible to selectively eliminate or reduce the number of alloreactive T cells with anti CD25 antibody, which results in prevention of or a reduction in the severity of GVHD.