A 2-STEP DELIVERY SYSTEM UTILIZING A BI-SPECIFIC MONOCLONAL-ANTIBODY FOR RADIOIMMUNOTHERAPY

This paper examines the use of a bi-specific monoclonal antibody capab le of binding both the carcinoembryonic antigen and a small, synthetic , non-immunogenic hapten that can carry a radionuclide for radioimmuno therapy. Variations in antibody dose, hapten dose, and length of time between administration of antibody and hapten were examined utilizing a murine model of human colon cancer, Tissue distribution, serum pharm acokinetics, effects on tumor growth, and tumor and whole body dosimet ry measurements are reported. We observed a two-fold enhancement in th erapeutic index with this two step system compared to standard direct label radioimmunotherapy. Serum half life of hapten, and therefore who le body radiation dose, was dependent on the serum content of bi-speci fic antibody at the time of hapten administration.