A Phase I/II Study of Lenalidomide in Combination with Rituximab in Relapsed/Refractory Mantle Cell Lymphoma.

Rituximab directly targets CD20 positive lymphoma cells while lenalidomide targets the microenvironment. This combination was proven effective in vitro and in vivo in mantle cell lymphoma (Wu et al, Clin Cancer Res 2008; Zhang et al, Am J Hematol 2009). Clinically, lenalidomide (Habermann et al, Br J Haematol 2009) and rituximab have single-agent activity in mantle cell lymphoma (MCL) and may be an effective combination. The goal of our study was to determine the maximum tolerated dose (MTD) in phase 1 and evaluate the efficacy and safety of lenalidomide plus rituximab in patients with relapsed/refractory MCL in phase 2.

Patients with relapsed/refractory MCL received lenalidomide on days 1–21 of every 28-day cycle, and rituximab (375 mg/m²) weekly during cycle 1. Dose escalation was used to determine the MTD with lenalidomide (10 mg, 15 mg, 20 mg, and 25 mg). Dose-limiting toxicity (DLT) was defined as grade 3 or 4 non-hematologic, or grade 4 hematologic adverse events in cycle 1. Phase 2 has reached targeted enrolment with 45 patients treated at MTD. Kaplan-Meier method was used to estimate progression free survival rate and response duration. Median time to event in months with 95% confidence interval was calculated. Of 45 patients treated at the MTD, the median age was 66 (46–85), 91% were males. All patients had received prior rituximab and were enrolled regardless of prior rituximab sensitivity or resistance.

The median follow-up time for the censored observations was 11.4 months. Two DLTs occurred at 25 mg in phase 1 (hypercalcemia, non-neutropenic fever); therefore, the MTD was 20 mg. The grade 3–4 non-hematologic events included elevated AST, elevated ALT, fatigue, myalgia, tremors, ataxia, cough, deep vein thrombosis, dyspnea, edema (facial), infection, neuropathy sensory, rash, and respiratory failure. Grade 3–4 hematologic adverse events included neutropenia (37 events), neutropenic fever (4 events), and thrombocytopenia (16 events). There were no responses in patients treated at 10 mg or 15 mg. Thirty six patients (36) were evaluable for response. Nine (9) patients are too early in their treatment and are not yet eligible for response evaluation. Among the 36 evaluable patients, 11 (31%) patients achieved CR, 8 (22%) patients achieved PR, 3 (8%) patients had minor response, 6 (17%) patients had stable disease and 8 (22%) patients had progressive mantle cell lymphoma. The overall response rate (CR + PR) was 53%. Seventy eight (78%) patients achieved stable disease or better and benefited from oral Lenalidomide plus 4 doses of rituximab. The median time to response was 2 months (2–8), and the median duration of response for the 19 patients with CR or PR was 18 months (95% CI: 10.6, NA) (range1–30 months). The median progression free survival for all patients on phase 2 was 14 months (95% CI: 9.8, NA) (ranging from 1–32 months).

Oral lenalidomide plus rituximab resulted in durable responses in relapsed/refractory MCL with a favourable toxicity profile.

Wang:Celgene: Honoraria, Research Funding. Hagemeister:Celgene Corporation: Consultancy. Samaniego:Celgene Corporation: Research Funding. Yi:Celgene Corporation: Research Funding. Shah:Celgene Corporation: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Elan: Consultancy; Millennium: Research Funding, Speakers Bureau. Bell:Celgene Corporation: Employment, Equity Ownership. Knight:Celgene Corporation: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Zeldis:Celgene: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees.