Safety and Efficacy of I(131) Tositumomab in the Treatment of non-Hodgkin's Lymphoma

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 T) 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.