Hu-Mik-beta1 to Treat T-Cell Large Granular Lymphocytic Leukemia

Background: * T cell large granular lymphocyte (T-LGL) leukemia is a chronic lymphoproliferative disorder associated with granulocytopenia, anemia and/or thrombocytopenia. * Although agents such as cyclosporine and methotrexate have shown activity in T-LGL, treatment of T-LGL has remained largely undefined and symptomatic. * The shared IL-2R/Il-15R Beta receptor (CD122) is over expressed on T-LGL cells and may stimulate growth T-LGL cells through its interaction with IL-15. * Hu-Mik-Beta1 is a humanized monoclonal antibody that binds to IL-2R/IL-15R Beta * Hu-Mik-Beta1 may inhibit the growth and exert cytotoxic activity against T-LGL cells. Objectives: * To determine the dose-limiting toxicity (DLT) and the maximum tolerated dose (MTD) of Hu-Mik-Beta1 when administered to patients with T-LGL. * To determine the dose of Hu-Mik-Beta1 required to saturate IL-2R/IL-15R Beta (CD122) on -T-LGL cells in the peripheral blood. * To determine the pharmacokinetics and serum die-away curve of Hu-Mik-Beta1. * To provide preliminary information on the clinical response following single dose administration of Hu-MiK-Beta1 in patients with CD122 expressing T-LGL leukemia. Eligibility: --T cell large granular lymphocyte leukemia (T-LGL). Patients must have a granulocyte count of less than 1000/microL, or hemoglobin less than 10 gm/dL, or be transfusion dependent, or platelets less than 100,000/ microL, or any combination of these unless receiving a hematopoietic growth factor. * T-LGL cell count greater than or equal to 1000/microL (CD3 plus/CD8 plus/usually CD57 plus) by flow cytometry. * Patients may be receiving a stable dose of a hematopoietic growth factor. Design: * Cohorts of 3 patients each will be treated with a single intravenous dose of Hu-Mik-Beta1 at 0.5, 1.0 or 1.5 mg/kg. * Patients will be observed for adverse events for 6-weeks. * Detailed pharmacokinetic studies and determination of CD122 receptor saturation will be performed. * Response will be evaluated using hematological, flow cytometry, molecular and clinical evaluations. * An additional 3 patients will be accrued at the highest dose or MTD to aid in design of a Phase II trial. * Patients participating in Phase I will also be eligible to participate in Phase II.