Reduced Myelotoxicity with Sustained Tumor Concentration of Radioimmunoconjugates in Rats after Extracorporeal Depletion

The aim of this studywas to evaluate the possibility of decreasing the myelotoxicity associated with radioimmunotherapy (RIT) by extracorporeal depletion of radioimmunoconjugates (RIC) from the circulation. The optimal combination of radionuclide and the time interval between injection of the RIC and the subsequent extracorporeal depletion procedure was assessed in immuno-competent rats, with respect to both myelotoxicity and tumor concentration of RIC. Methods: Rats were injected with 177Lu-or 90Y-labeled antibody conjugate (mAb-DOTA-biotin) (mAb is monoclonal antibody; DOTA is 1,4,7,10-tetraazacyclodode-cane-N,N9,N$,N%-tetraacetic acid) and subjected to removal of the conjugate from the circulation by extracorporeal affinity ad-sorption treatment (ECAT) 12, 24, or 48 h after injection. Myelo-toxicity was assessed by analysis of blood parameters for 10 wk. The effect of ECAT on the tumor concentration of RIC wa