Differential chemical behavior of Humanized Monoclonal Antibodies in the radiolabeled with99mTc

摘要

The purpose of this work consisted in the comparison of the chemical behavior ofrnimmunoglobulins of different origin. The immunoglobulins were the human-IgG, the R3 and T1rnhumanized monoclonal antibodies, and the ior t3 murine monoclonal antibody. The immunoglobulinsrnwere reduced with sodium metabisulfite at a molar relation SMB: IgG of 950:1 for 45 minutes beforernradiolabeling with 99mTc. The formation of fragments and aggregates, and the immunoreactivity of thernmonoclonal antibodies were studied once concluded the reduction process. Also, comparative studiesrnof the radiochemical stability and challenges were carried out after radiolabeled. Our results indicatedrndifferences in the chemical behavior among the immunoglobulins after their reduction with sodiumrnmetabisulfite. The first difference observed was a higher generation of fragments in the humanizedrnmonoclonal antibodies, the second one was a higher formation of free sulphydryl groups and the thirdrnone was an increased percentage of dissociation when the radiolabeled humanized antibodies werernchallenged with cysteine. These results demonstrated that the humanized antibodies were morernsensitive to the reduction process, and once radiolabeled presented lower radiochemical parametersrnthan the murine antibody and the human IgG. This work demonstrated that the origin of thernimmunoglobulin is an important element in its chemical and radiochemical behavior when sodiumrnmetabisulfite was used as a reducing agent for radiolabeling with 99mTc.