Removal of marrow T cells with OKT3-OKT11 monoclonal antibodies and complement to prevent acute graft-versus-host disease. A pilot study in ten patients.

We studied the feasibility of T cell depletion of bone marrow for transplantation in preventing acute graft-versus-host disease GVHD in patients having a high risk of acute GVHD. We report our preliminary clinical experience of the ex-vivo treatment of allogeneic marrow using a pan-T monoclonal antibody combination (OKT3-OKT11) plus baby rabbit complement. Ten patients received allografts from HLA-identical sibling donors. All patients had malignant hematological disease with poor prognosis (6 acute leukemia, 3 chronic granulocytic leukemia, and 1 multiple myeloma). Nine patients were at high risk of acute GVHD (older than 30 years for 4 patients, chronic granulocytic leukemia in acute or accelerated phase for 3, and acute leukemia in relapse for 2). Posttransplant management with methotrexate was maintained until day 100 in the first four patients and stopped at day 11 for the six others. The ex-vivo treatment with the OKT combination and complement removed 88.3% +/- 11.8 of the T lymphocytes. The myeloid progenitors recovered at the end of the procedure showed a moderate effect of monoclonal antibodies and complement (75.8% +/- 12.2). Engraftment was achieved in all patients: 23.3 days +/- 5.10 to reach 0.5 X 10(9) granulocytes per liter and 31.5 days +/- 12.2 to reach 50 X 10(9) platelets per liter. No acute GVHD was observed in this group of patients. Of the 10 patients, 7 are alive and well and have been in continuous remission from 2-10 months. Three patients have relapsed.