A Trial to Treat Patients With ITP Who Do Not Achieve a Durable Response to Rituxan Alone

The purpose of this research study is to compare the efficacy and safety of higher doses of rituximab to a combination of standard doses of Rituxan + CVP (Cyclophosphamide, Vincristine, and Prednisone) in patients with chronic Idiopathic Thrombocytopenic Purpura (ITP who did not respond to or relapsed after standard doses of rituximab.

Primary Objectives 1. Efficacy: The primary objective (primary endpoint) is to determine the rate of response (partial or complete response) at week 16 (± 2) post-treatment in both pilot arms: the high dose Rituximab (or HDR) group (750 mg/m2 x 4) and the group treated with a regimen combining standard doses of Rituximab with CVP (R-CVP.) A complete response (CR) will be a platelet count increase ³ 150,000/mL on two consecutive occasions one week apart, without any other therapy. A partial response will be considered if the platelet count increases between 50 and 150,000/mL. 2. Safety: To assess and compare the incidence of moderate and severe adverse-events including the number and type of infections in both arms of the study using Genentech standard safety monitoring and serious adverse event (SAE) reporting. Secondary Objectives 1. To compare the response rate in the 2 treatment arms in the "Rituximab non-responders" sub group (see 4.1 for definition) 2. To compare the response rate in the 2 treatment arms in the " Rituximab relapsers" subgroup 3. To assess the mean duration of response (PR or CR) in the 2 treatment arms. 4. To evaluate the duration of very low to absent peripheral blood B cells in the two treatment arms. 5. To assess the incidence of hypogammaglobulinemia (IgG and/or IgM level \< ½ of lower limit of normal for age) and white blood counts in the two arms.