- Participants will receive the drugs dasatinib, fludarabine, and rituximab at the following time points through each cycle of treatment. A cycle of study treatment is 28 days. Dasatinib pills will be taken orally each day for the first 2 weeks of each cycle. Fludarabine will be give intravenously on three days of each cycle (Days 3-5 in the first cycle, days 1-3 after that). Rituximab will be given intravenously with a total dose of 375 mg/m2 each cycle (split on Days 3+4 in the first cycle and at the discretion of the treating physician after that on Days 1-3).