Pharmacokinetic analysis of Hu-Mikβ1 was performed after administration of 0.5, 1.0, and 1.5 mg/kg of Hu-Mikβ1 Ab to patients with T-LGL leukemia. After administration of 0.5 (○), 1.0 (■), and 1.5 (▾) mg/kg of Hu-Mikβ1, the serum concentration of the Ab was quantitated at subsequent time points in patients with T-LGL leukemia. Hu-Mikβ1 was not demonstrable in the serum after the 2-week time point after 0.5 mg/kg administration, but was still present in the circulation at day 22 at concentrations of 160, 400, and 2530 pg/mL in the 3 patients receiving 1.5 mg/kg of Hu-Mikβ1.