Ofatumumab: A Novel Anti-CD20 Monoclonal Antibody for Treatment of Refractory Chronic Lymphocytic Leukemia

OBJECTIVE: To present the current clinical evidence on ofatumumab for use in refractory chronic lymphocytic leukemia (CLL). DATA SOURCES: A literature search was performed using MEDLINE and PubMed (both 1966-May 2011), as well as the American Society of Hematology abstracts (2000-May 2011), using the primary search terms ofatumumab and HuMax-CD20. STUDY SELECTION AND DATA EXTRACTION: Clinical studies and abstracts available in the English language, describing the pharmacology, pharmacokinetics, clinical activity, and safety of ofatumumab in CLL were included in this review. DATA SYNTHESIS: Ofatumumab is a human immunoglobulin monoclonal antibody that binds to B-lymphocytes expressing CD-20 cell surface antigens. Ofatumumab was granted accelerated approval by the Food and Drug Administration in October 2009 for the treatment of CLL refractory to fludarabine and alemtuzumab. A Phase 1/2 trial has established the safety and tolerability of single-agent ofatumumab at an initial dose of 300 mg intravenously on week 1, followed by 2000 mg once weekly for 7 doses (weeks 2-8), followed by 2000 mg once every 4 weeks for 4 doses (weeks 9-12), for a total of 12 doses. The final analysis of a pivotal international multicenter trial has shown promising activity in patients with CLL refractory to fludarabine and alemtuzumab, demonstrating overall response rates of 44-51%, with prolonged progression-free and overall survival. Ofatumumab activity has also been shown in a variety of other malignant and nonmalignant conditions, including non-Hodgkin lymphoma, rheumatoid arthritis, and multiple sclerosis. The most common adverse effect is grade 1 and 2 infusion reactions. Other adverse effects include infection, neutropenia, anemia, rash, fever, and diarrhea. CONCLUSIONS: Clinical evidence suggests that ofatumumab is an effective agent in patients with CLL refractory to fludarabine and alemtuzumab. Data are awaited comparing ofatumumab to other salvage regimens. Until results of head-to-head trials are conducted comparing ofatumumab to existing regimens, it cannot be said whether ofatumumab is more efficacious or tolerable than currently available therapies.