Monoclonal antibody therapy in lymphoid malignancies.

The concept of targeted therapy for patients with advanced cancer has intrigued researchers for many years. The lymphoid malignancies are particularly good candidates for this therapeutic approach, due to the identification of multiple lymphocyte-specific antigens. The recent introduction of rituximab marks the beginning of a new era in the treatment of lymphoid malignancies. Rituximab is one of the most active single agents for patients with refractory indolent lymphoma, producing response rates of approximately 50%, with low toxicity and a brief duration of treatment. Additional uses of rituximab are being evaluated in ongoing clinical trials, and are briefly reviewed. As a first-line agent, responses of approximately 70% are produced in patients with indolent lymphoma, with minimal toxicity. A substantial percentage of patients can be successfully retreated with rituximab, with second remission durations longer than the first remission (14-16 months versus 12 months). Multiple combination regimens using rituximab plus chemotherapy are also being evaluated. Although the role of these combined approaches is incompletely defined, high complete response rates can be obtained, with a higher rate of molecular complete remission (i.e., eradication of detectable bcl-2 rearrangements) than has been observed in patients receiving chemotherapy alone. Rituximab is also being evaluated in other CD20(+) lymphoid malignancies including large-cell lymphoma, chronic lymphocytic leukemia, mantle cell lymphoma, and Waldenstrom's macroglobulinemia. Within the next 12 months, several additional monoclonal antibodies will be available for the treatment of lymphoid malignancies. These include the radioimmunoconjugates tositumomab (Bexxar) and ibritumomab (Zevalin), as well as Campath-1H (anti-CD52) monoclonal antibody. Early clinical data with each of these agents are also briefly reviewed.