Background: The combination of bendamustine and rituximab is effective in the treatment of low grade NHL. Lenalidomide shows significant synergy when combined with rituximab and rituximab-containing chemotherapy. The primary aim of this phase 1 study was to establish a maximum tolerated dose (MTD) of bendamustine, rituximab and lenalidomide. Secondary endpoints included toxicity, overall response and progression-free survival. Methods: Eligible patients (pts) had relapsed or refractory low grade NHL, treated with at least 1 prior regimen. A 3+3 phase was used. Dose levels are shown in the Table. Bendamustine was given on day 1 and 2, rituximab on day 1 and lenalidomide orally, daily, days 1-10 of 28-day cycle for up to 6 cycles. Pegfilgrastin was given on day 3 of the cycle. Results: 15 patients were enrolled. The median age was 58 years (47-71), 5/15 patients were female, 12/15 patients had stage 4 disease. The histological subtypes were: follicular lymphoma grade 1 and 2 (6/15 pts), marginal zone lymphoma (5/15 pts) and lymphoplasmacytic lymphoma (4/15 pts). No dose-limiting toxicity was seen. Dose escalation beyond 25 mg daily of lenalidomide was not performed, since 25 mg is considered a biologically effective dose. The most common toxicity was hematological, with 2/15 pts experiencing grade 3 neutropenia. The overall response was 100% (Table). Only 1/15 pts experienced grade 3 or more non-hematological toxicity (grade 3 urticaria). All patients remain alive with median follow up of 17 months (6-28) and only 1 pt disease progression at 12 months. Conclusions: Lenalidomide at 25 mg/day, days 1-10 of a 28-day cycle can be safely combined with the standard dose bendamustine rituximab regimen and is well tolerated. The encouraging response rates in a relapsed setting warrant further evaluation of this combination in larger trials. Support: U10CA180821, U10CA180882, CA025224 Clinical trial information: NCT01429025