Targeting of Radio-Isotopes for Cancer Therapy

Treatment of patients with therapeutic monoclonal antibodies (mAbs) such as rituximab (Rituxan), an anti-CD20 mAb, or trastuzumab (Herceptin), an anti-HER2 mAb, have shown efficacy in clinical trials and have gained approval from the Food and Drug Administration (FDA). Mylotarg, an anti-CD33 mAb conjugated with the antibiotic calicheamicin has proven efficacious in the treatment of patients with acute myeloid leukemia and has also received FDA approval. However, the use of radionuclides to either augment inherent activity or to exploit the specific targeting properties has been a major development in mAb therapeutics. Radionuclide- bearing mAbs have recently been approved by the FDA; Zevalin, an anti-CD20 mAb armed with 90Y and Bexxar, an anti-CD20 mAb armed with 131I. This overview presents some background and some of the strategies pertaining to radiolabeled monoclonal antibody therapies with a focus on experiences reported for radiolabeled mAbs as evaluated in clinical trials.