In vitro and in vivo effects of BT 563, an anti-interleukin-2 receptor monoclonal antibody.

BT 563, a murine anti-IL-2R MoAb, was found to be more potent than anti-Tac in inhibiting proliferation in the mixed lymphocyte reaction. Results obtained with 33B3.1 in these experiments were similar to those with BT 563. The anti-IL-2R MoAb 2A3 was shown to be a suitable agent for monitoring the effect of BT 563 on peripheral blood. IL-2R-positive cells were not detected in peripheral blood samples from 1 h after the first dose until 8 days after the last dose. Plasma trough levels were measured in patients receiving 5 or 10 mg daily. The administration of BT 563 to allograft recipients did not lead to clinically significant side effects.