Extracorporeal adsorption (ECAT) reduces toxicity in radiosensitive organs by removing excess of biotinylated and radiolabeled MAb from unseparated blood in an avidin-agarose column.
Aim: To investigate the influence of biotinylation on pharmacokinetics and biodistribution of humanized MAb (111)In-MN14 and to validate the effect of subsequent ECAT on activity reduction in the whole body, in blood, and in various organs after i.v. administration of biotinylated (111)In-hMN14 in rats.
Methods: Humanized MAb MN14 recognizes the carcinoembryonic antigen. Ninety-three rats were used. (111)In-hMN14-DOTA was biotinylated using NHS-biotin or Sulfo-NHS-biotin enabling antibodies to be absorbed on the avidin-agarose column. Eight rats underwent ECAT, which implied that three blood volumes were passed through the column during 2.5 h. Whole body counts and blood activity were monitored. At dissections, organs of interest were removed and measured for activity-content.
Results: HPLC showed signs of fragmentation at a low ratio of NHS-biotin/mg of MAb. No fragmentation or aggregation was observed using sulfo-NHS-biotin. When ECAT started at 6 h p.i., whole body and blood activity were reduced by 64% and 98%, respectively. The uptake in organs sensitive to radiation was also reduced, varying between 39% for the liver and 84% for the lungs and bone marrow.
Conclusions: (111)In-hMN14 can be safely biotinylated using sulfo-NHS-biotin without significantly affecting antigenicity and biodistribution of the antibody. ECAT based on avidin-biotin concept effectively removed biotinylated (111)In-hMN14 from blood circulation and reduced activity in radiosensitive organs.