Ofatumumab for the treatment of chronic lymphocytic leukemia.

Ofatumumab is a humanized second-generation monoclonal antibody with the affinity to a transmembrane protein CD20. In in vitro studies, it exhibits higher efficacy towards chronic lymphocytic leukemia (CLL) cells compared to rituximab, and it can be explained by the fact that its epitope on the target CD20 protein is different as it includes a short as well as a long extracellular loop. Ofatumumab is especially effective in the lysis of CD20 low-expressing lymphocytes that are often observed in CLL. Currently, this agent is approved for the treatment of fludarabine- and alemtuzumab-refractory CLL. There are also promising preliminary results of the studies that indicate benefits of ofatumumab not only in patients with bulky/fludarabine-refractory CLL but also in treatment-naive patients with CLL with contraindications to fludarabine and in maintenance treatment.