Phase II Study of Lenalidomide in Combination with Rituximab for Patients with CD5+/CD20+ Hematologic Malignancies Who Relapse or Progress After Rituximab. Interim Analysis.

Patients with relapsed or refractory CLL/SLL and patients with mantle cell lymphoma (McL) have a poor prognosis. Overall response rate (ORR) to salvage therapy for refractory patients is approximately 10-30%, and survival benefit with current treatment approaches is limited. Phase II studies of single agent lenalidomide in patients with relapsed or refractory CLL revealed an ORR of 32-58% (7-17% CR), depending on treatment dose, scheduled used and duration of treatment with lenalidomide. In patients with refractory or relapsed McL, lenalidomide treatment resulted in an ORR of 53% (CR 20%, PR 33%), and a 14-month median duration of response (Habermann et al 2009). Recent in vitro studies have shown that lenalidomide enhances the rituximab-induced killing of NHL cell lines and B-CLL cells via ADCC by restoring the defective T-cell and NK-cell mediated ability to form immune synapses to exert tumor cell cytotoxicity.

Patients with relapsed or refractory CLL/SLL or McL received oral lenalidomide via dose escalation as follows, 2.5 mg on days 1-7, 5mg on day 8-14 and 10mg on day 15-21 followed by 7 days of rest in 28-day cycle; for cycle 2 and beyond 20mg was given on day 1-21 on a 28 day cycle. Rituximab was dosed at 375mg/m2 IV weekly for 4 weeks starting on day 15 of cycle 1. Treatment was continued until disease progression or toxicity. All patients were given allopurinol 300mg orally twice per day starting 3 days prior to first dose of lenalidomide. CT scans, and bone marrow biopsies were done every 2 months to assess for response. Primary objectives were overall response rate (CR+PR) and safety and tolerability of the combination regimen.

17 patients were enrolled on study (13 patients with CLL/SLL and 4 patients with McL). Median number of prior chemotherapies was 3 (range 1-5). Median age was 64 years (range 42-80). Among patients with CLL, the most common cytogenetic abnormalities were trisomy 12 (isolated n=3, associated with other abnormalities n=4), del11q (isolated n=1, with others n=3), isolated del13q (n=1), complex cytogenetics with 3 or more abnormalities (n=4 including 1 patient with del 17p). Responses were assessed every 2 months after initiation of therapy. Response rate for 13 evaluable patients (10 with CLL and 3 with McL) relative to months on treatment with lenalidomide are summarized in the table. Although all responses were PR, the rate of PR improved with continued therapy suggesting increased responses with a longer duration of treatment with lenalidomide. Currently, 7 patients are still receiving active treatment on study, all with CLL (3 achieved a PR and 4 have SD). Of the 4 patients with McL enrolled on study, 1 achieved a PR after 2 months of therapy; 1 achieved SD after 2 months of therapy with a sustained SD after 6 months; 1 patient achieved SD after 2 months, but progressed after 6 months on treatment.

The regimen was well tolerated. Most common (>5%) toxicities include neutropenia (35% grade 3, 6% grade 4), fatigue (17% grade 1-2, 6% grade 3), tumor flare (12% grade 2, 12% grade 3), acute renal insufficiency (6% grade 1, 12% grade 3), rituximab related infusion reactions (6% grade 2, 6% grade 3), flu-like symptoms (6% grade 2, 6% grade 3), venous thromboembolic disease (6% grade 2, 6% grade 3), infections (11% including 1 patient with fatal endocarditis), and hypercalcemia (11% grade 4). Correlative studies are ongoing.

The combination of lenalidomide with Rituximab is a promising combination regimen in CLL patients with very poor prognosis who have undergone multiple lines of therapy. This treatment combination appears tolerable with observed events consistent with the use of these two agents in other studies. Further investigation is warranted, possibly in the front line setting and in combination with other agents.

Lancet:Celgene: Research Funding.