Tim Illidge, Andrei Ivanov and Yong Du

School of Cancer and Imaging Sciences, The University of Manchester, Christie Hospital NHS Foundation Trust, Wilmslow Road, Manchester M20 4BX, UK.

Abstract

B1 or Tositumomab was the first B-cell specific antibody to be discovered and it targets the CD20 antigen. The potential therapeutic importance of this discovery in targeting CD20, however remained unrealised until the mid 1990’s when Tositumomab was radiolabelled and the ¹³¹I Tositumomab radioimmunotherapy (RIT) regimen (Bexxar™) developed. The ¹³¹I Tositumomab regimen is completed within one to two weeks and consists of a tracer dose of the radioimmunoconjugate followed by the therapeutic dose 7 to 14 days later. Each infusion of ¹³¹I-tositumomab is preceded by an infusion of a pre-dose of 450 mg “cold” or unlabeled tositumomab. ¹³¹I Tositumomab has demonstrated remarkable clinical activity in patients with relapsed follicular lymphoma with high response rates and durable remission even in patients with disease that is refractory to chemotherapy and rituximab antibody therapy. Recent new data has provided new insights into the potential mechanisms of the antibody and targeted radiation effects and these as well as the safety and efficacy of this novel therapy in follicular lymphoma are reviewed.