Sequential ofatumumab and lenalidomide for the treatment of relapsed and refractory chronic lymphocytic leukemia and small lymphocytic lymphoma

Ofatumumab is a fully human anti-CD20 monoclonal antibody with enhanced antibody dependent and complement dependent cytotoxicity. Lenalidomide induces T cell and natural killer (NK) cell activation and in vitro enhances clearance of chronic lymphocytic leukemia (CLL) cells by monoclonal antibodies. We performed a multi-center, phase 2 trial of sequential treatment with ofatumumab and lenalidomide in patients with advanced, relapsed and refractory (R/R) CLL, consisting of ofatumumab 2000 mg intravenously on day 1 and lenalidomide 10 mg on days 8-28, for up to six cycles. Twenty-one subjects were included with median age of 63 years and two prior lines of therapy. The overall response rate was 47.6% and 23.8% had stable disease. Median overall survival was 21.5 months. Neutropenia and thrombocytopenia were the most frequent adverse events. Tumor flare reaction occurred in 43% of subjects. Intracycle sequential ofatumumab plus lenalidomide is active in high-risk R/R CLL and well tolerated except for frequent cytopenias.