Combination of Lenalidomide and Rituximab Overcomes Rituximab Resistance in Patients with Indolent B-cell and Mantle Cell Lymphomas.

PURPOSE:Lenalidomide, an immunomodulatory agent that enhances antibody-dependent cell-mediated cytotoxicity, has the potential to synergize with rituximab, an anti-CD20 mAb. We hypothesized that the addition of lenalidomide to rituximab would improve clinical outcomes in patients with B-cell lymphomas who were previously rituximab resistant, defined as no response to or progression of lymphoma within 6 months of rituximab-based therapy. EXPERIMENTAL DESIGN:We conducted a single-center, phase II trial in patients with indolent B-cell or mantle cell lymphomas who were previously rituximab resistant. Patients received 10 mg lenalidomide daily for 8 weeks, and then received four weekly doses of 375 mg/m(2) rituximab; lenalidomide continued during and after rituximab. Response to therapy was assessed after 8 weeks of lenalidomide and 12 weeks after first dose of rituximab. The primary endpoint was overall response rate (ORR) after lenalidomide and rituximab. RESULTS:Fifty patients were enrolled and 43 patients completed both response assessments. ORR after 8 weeks of lenalidomide was 30.2%; 12 weeks after the addition of rituximab to lenalidomide, ORR increased to 62.8% (N = 43). For all patients (N = 50), median progression-free survival (PFS) is 22.2 months (median follow-up, 39.2 months). PFS after lenalidomide-rituximab was significantly longer than the PFS for the antecedent regimen used to define rituximab resistance (22.2 vs. 9.13 months, P = 0.0004). CONCLUSIONS:This trial is the first to show that the combination of lenalidomide and rituximab overcomes prior rituximab resistance in patients with indolent B-cell and mantle cell lymphomas.