ANTI-LFA1 MONOCLONAL-ANTIBODY (25.3) FOR TREATMENT OF STEROID-RESISTANT GRADE III-IV ACUTE GRAFT-VERSUS-HOST DISEASE

The in vivo efficacy of 25.3 monoclonal antibody (mAb) directed against human LFA1 molecule was assessed in ten patients with steroid-resistant grade III-IV acute graft-versus-host disease (AGVHD). These patients received non-T-cell-depleted allogenic bone marrow transplantation for aplastic anemia in two cases and hematologic malignancies in eight cases. Five grafts were fully matched, three were one antigen-mismatched, and two were two antigen-mismatched. Despite GVHD prophylaxis with cyclosporin A and short-term methotrexate, AGVHD occurred after a median of 24 days and clearly progressed under prednisone (median 2 mg/kg), given for a median of 12 days. 25.3 mAb was given at a dosage of 0.1 mg/kg in a 4-h perfusion for five daily doses without any clinical or biological side effects. Thirty percent of the patients experienced a reduction in the overall grading with two complete responses. Partial response in at least one involved organ (mostly skin) occurred in 80% of the patients. However, seven out of the eight responding patients experienced a new episode of AGVHD. This observation, which confirms that inhibiting a functional molecule is as efficient as a cytolytic therapy, offers an alternative strategy to antithymocyte globulin (ATG) and cytotoxic mAb in controlling steroid-resistant GVHD.