EAPB0203 inhibited growth of HTLV-I–positive and –negative human T cell lines, and fresh ATL cells, but not normal resting and activated T lymphocytes. (A) Effects of EAPB0203 treatment on the growth of HTLV-I–positive (HuT-102, C91-PL, and MT-2) and HTLV-I–negative (CEM, Jurkat, Molt, and HuT-78) human T-cell lines, and normal resting or PHA-activated peripheral blood mononuclear cells (PBMCs). Activated normal PBMCs were supplemented with 2% PHA. EAPB0203 was added at the indicated concentrations in mol/L for 24 to 96 hours. Cells growth was assayed in triplicate wells with the CellTiter 96 nonradioactive cell proliferation kit. The results are expressed as percentage of control (0.1% DMSO) and represent the means of the results obtained in at least 3 independent experiments. (B) Effects of EAPB0203 treatment on the growth of freshly isolated leukemic cells from one patient with acute ATL and one patient with chronic ATL. EAPB0203 was added at the indicated concentrations in mol/L for 24 to 72 hours. Cells growth was assayed in triplicate wells with the CellTiter 96 nonradioactive cell proliferation kit. The results are expressed as percentage of day 0 control (0.1% DMSO) from one single experiment.