Therapy of Patients With Human T-Cell Lymphotrophic Virus I-Induced Adult T-Cell Leukemia With Anti-Tac, a Monoclonal Antibody to the Receptor for Interleukin-2

Human T-cell lymphotropic virus I (HTLV-I)-induced adult T-cell leukemia (ATL) cells constitutively express interleukin-2 (IL-2) receptors identified by the anti-Tac monoclonal antibody (MoAb), whereas normal resting cells do not. This observation provided the scientific basis for a trial of intravenous anti-Tac in the treatment of nine patients with ATL. The patients did not suffer untoward reactions and did not have a reduction in the normal formed elements of the blood, and only one of the nine produced antibodies to the anti-Tac MoAb. Three patients had trensient mixed, partial, or complete remissions lasting from 1 to more than 8 months after anti-Tec therapy, as assessed by routine hematologic tests, immunofluorescence enelysis of circulating cells, and molecular genetic analysis of HTLV-I provirus integration and of the T-cell receptor gene rearrangement. The precise mechanism of the entitumor effects is uncleer; however, the use of a MoAb that prevents the interaction of IL-2 with its receptor on ATL cells provides a rational epproach for the treatment of this malignancy.