This is a phase II single arm, open-label, multicenter study evaluating the efficacy and safety of the combination of induction chemoimmunotherapy with bendamustine and rituximab followed by maintenance therapy with rituximab and lenalidomide in subjects with CLL or SLL who have not received any prior cytotoxic chemotherapy for their disease (i.e., prior single-agent rituximab is permitted). The study will be carried out at the University of Wisconsin Carbone Cancer Center (UWCCC).

The subject participation will include a screening period, treatment period, and a follow-up period. The treatment period will extend from the first dose of study drug treatment (day 1, cycle 1 of induction chemoimmunotherapy) until any of the following: completion of the entire course of induction and maintenance therapy; progressive disease (PD); an unacceptable adverse event (AE); the initiation of alternate anti-neoplastic therapy; or a decision by the subject or by the investigator to discontinue treatment; or death. The induction chemoimmunotherapy regimen consists of bendamustine and rituximab for 6 cycles, followed by initiation of maintenance therapy with rituximab and lenalidomide among subjects achieving an objective response to induction therapy (i.e., complete or partial response; stable disease with objective evidence of tumor shrinkage). Subjects with objective response after 4 cycles of bendamustine + rituximab (BR) are eligible to proceed to maintenance therapy if toxicities are limiting further BR induction therapy, or if the treating physician determines that further BR induction therapy would be associated with excessive risk for additional toxicities.

To minimize toxicity with induction chemotherapy, we have chosen a dose of bendamustine at 90 mg/m2/day on days 1 \& 2 every 28 days for a total of 6 cycles. Rituximab will be administered at a dose of 500 mg/m2 IV on day 1 of each cycle of induction chemoimmunotherapy (375 mg/m2 cycle 1 only); however, patients at high-risk for cytokine release syndrome may receive rituximab on day 2 of induction therapy. In select circumstances in subjects at high risk for cytokine release syndrome and/or tumor lysis syndrome, rituximab may be administered as late as day 5 of cycle 1 (this alternative dosing of rituximab applies to cycle 1 of induction therapy only). Lenalidomide and rituximab maintenance will be initiated 6-12 weeks after the 6th cycle of chemotherapy, and continued for a total of 24 cycles. Maintenance therapy will continue for a maximum of 24 cycles or until unacceptable toxicity or progression of disease.

Maintenance therapy will begin once there has been adequate hematologic recovery (ANC ≥1000/µL and platelets ≥50,000/µL) and other criteria as outlined in Section 7.5 have been met. Rituximab will be administered at a dose of 375 mg/m2 IV on day 1 of every odd-numbered 28 day cycle (cycles 1,3,5,7,9,11,13,15,17,19,21,23) for a maximum of 12 doses during the maintenance phase. Subjects will receive concurrent lenalidomide 5 mg orally daily on days 1-21 of cycles 1-24 (28 day cycles). If subjects do not experience adverse effects from lenalidomide, dose escalation up to 10 mg orally daily on days 1-21 of each 28 day cycle will be allowed at the start of cycle 2 or at the start of any subsequent cycle (see Section 9.2.3 and 9.2.5 for criteria required to escalate the dose of lenalidomide to 10 mg/day on days 1-21). Lenalidomide dose escalation is only allowed at the start of a new cycle to a maximum dose of 10 mg/day on days 1-21. Subjects entering maintenance with reduced renal function (i.e., creatinine clearance ≥40 but \<60 mL/min) will start lenalidomide at a dose of 5 mg every other day. There is no dose modification of rituximab based on reduced renal function. Among subjects without excessive toxicity or evidence of progression, treatment with lenalidomide will continue for up to 24 cycles (cycle 1-24) and treatment with rituximab will continue for up to 12 doses (administered every odd-numbered cycle during cycles 1,3,5,7,9,11,13,15,17,19,21,23). If subjects have excessive toxicity from lenalidomide, ongoing maintenance therapy with rituximab alone is permitted after lenalidomide is discontinued. After completing 24 cycles of maintenance therapy, subjects will then be observed for evidence of PD with clinical assessments every 3 months for at least 2 years.