APPROACHES TO IMPROVED ANTIBODY-MEDIATED AND PEPTIDE-MEDIATED TARGETING FOR IMAGING AND THERAPY OF CANCER

Antibodies with their ability to selectivity bind antigens have been o f great interest in targeting radiation, drugs and toxins to tumors. L imited success in delivery of radioactivity has been enjoyed with conv entional attachment to antibodies. This is due to slow tumor targeting processes and slow disappearance from blood and variable uptake and d isappearance from the excretory organs, liver and kidney. Preliminary studies in animal models and patients have shown promise in increasing the tumor to blood exposure ratio by pretargeting antibody followed b y small molecule delivery of radioactivity using a molecular capture s ystem. Efficient capture of the small molecule radioactivity carrier b y tumor localized antibody and rapid clearance and excretion of the un targeted radioactivity decreases the background problem for imaging an d lowers marrow toxicity for radioimmunotherapy. Small peptide ligands that bind to receptor bearing tumors offer similar advantages.