First clinical use of ofatumumab, a novel fully human anti-CD20 monoclonal antibody in relapsed or refractory follicular lymphoma: results of a phase 1/2 trial

Ofatumumab is a unique monoclonal antibody that targets a distinct small loop epitope on the CD20 molecule. Preclinical data show that ofatumumab is active against B-cell lymphoma/chronic lymphocytic leukemia cells with low CD20-antigen density and high expression of complement inhibitory molecules. In a phase 1/2 trial evaluating safety and efficacy of ofatumumab in relapsed or refractory follicular non-Hodgkin lymphoma (FL) grade 1 or 2, 4 dose groups of 10 patients received 4 weekly infusions of 300, 500, 700, or 1000 mg. Patients had a median of 2 prior FL therapies and 13% had elevated lactate dehydrogenase. No safety concerns or maximum tolerated dose was identified. A total of 274 adverse events were reported; 190 were judged related to ofatumumab, most occurring on the first infusion day with Common Terminology Criteria grade 1 or 2. Eight related events were grade 3. Treatment caused immediate and profound B-cell depletion, and 65% of patients reverted to negative BCL2 status. Clinical response rates ranged from 20% to 63%. Median time to progression for all patients/ responders was 8.8/ 32.6 months, and median duration of response was 29.9 months at a median/ maximum follow-up of 9.2/38.6 months. Ofatumumab is currently being evaluated in patients with rituximab-refractory FL. This trial was registered at www. clinicaltrials.gov as #NCT00092274.