Solid phase labeling of monoclonal antibodies with 99mTc using two bifunctional photocleavable reagents

Two photolabile heterobifunctional O-nitrobenzyl reagents were used to modify B72.3 monoclonal antibody followed by immobilization on a solid support. Antibody was labeled with 99mTc and then cleaved from the resin on irradiation with light of peak intensity at 365 nm. The antibody was restored unmodified after cleavage. The labeled product, void of any impurity or free 99mTc, exhibited compatible imaging quality and biodistribution when compared to the same product labeled using solution chemistry. This new technique offers the potential of a commercially attractive 99Tc-labeling kit. Although the method was designed from the perspective of 99mTc-labeling of monoclonal antibodies, it should be applicable to any solid phase protein modification.