Preparation of TH227-labeled radioimmunoconjugates, assessment of serum stability and antigen binding ability.

In this study, the feasibility of constructing radioimmunoconjugates by using the novel therapeutic candidate alpha-emitter, (227)Th, was evaluated. By use of the bifunctional chelator, p-SCN-benzyl-DOTA, (227)Th was conjugated to the two monoclonal antibodies, rituximab and trastuzumab. Their stability in 80% fetal bovine serum at 37 degrees C was measured. The immunoreactive fractions were determined by using CD20- and HER/2-positive cells, respectively. The overall labeling yield spanned from 6% to 17%. The radioimmunoconjugates demonstrated a relevant stability in serum and showed appropriate antigen-binding abilities.