Abstract
Chronic lymphocytic leukemia (CLL) is a hematologic malignancy derived from a clonal population of mature B-lymphocytes characterized by relatively low CD20 antigen expression. Although the disease often takes an indolent course, the majority of patients will eventually require therapy. Standard treatment for medically fit patients includes purine analogs and/or alkylating agents in addition to the type I anti-CD20 monoclonal antibody, rituximab. This therapy is inherently myelosuppressive and can result in significant morbidity and even mortality in patients with impaired performance status due to age and/or medical comorbidities. Historically, treatment options for the elderly or frail patient population were limited to mono-therapy with the oral alkylating agent, chlorambucil, rituximab, or another type I anti-CD20 monoclonal antibody ofatumumab. Recently, a newer-generation anti-CD20 monoclonal antibody, obinutuzumab, was developed for patients with CLL. Obinutuzumab is a humanized type II monoclonal antibody that appears to have more direct antibody-dependent cell-mediated cytotoxicity (ADCC) and possibly more direct cytotoxicity in vitro than previously available type I antibodies. A large Phase III prospective randomized clinical trial for older patients with impaired renal function and/or significant medical comorbidities demonstrated that when compared to conventionally-dosed rituximab and chlorambucil, the combination of chlorambucil and obinutuzumab administered at a dose and schedule involving early loading doses improved response rates and progression-free survival without significantly increasing toxicity. Results of this pivotal trial led to the FDA (US Food and Drug Administration) approval of obinutuzumab in combination with chlorambucil for frontline treatment of CLL. Obinutuzumab expands the armamentarium of active and less-toxic targeted agents in the evolving treatment landscape of CLL, providing physicians and patients with an additional therapeutic option.