Obinutuzumab may chart the way to improved QOL for CLL patients

Obinutuzumab recently received accelerated approval from the US Food and Drug Administration with breakthrough therapy designation for use in combination with chlorambucil in patients with untreated chronic lymphocytic leukemia (CLL). Obinutuzumab is a CD20 targeting fully humanized, type II, IgG1 antibody. CD20 is weakly expressed on the surface of CLL cells but has been demonstrated to be an effective in vivo target as shown by the activity observed with the use of rituximab and ofatumomab.2-4 Obinutuzumab binds selectively to the extracellular domain of CD20 with reduced internalization and its structural modifications explain its enhanced effectiveness. The antibody is modified in the hinge region which allows for more potent direct cytotoxicity. More importantly, afucosylation in the Fc region allows for enhanced antibody dependent cellular cytotoxicity (ADCC) through robust engagement of Fc-gamma receptor type III on effector cells. Together, these modifications translate into a higher efficacy compared with rituximab both in preclinical and clinical studies.