IMP 243 is a symmetric di-HSG (histamine-succinyl-glycine) bivalent hapten containing a Tscg-Cys ligand and two HSG groups. IMP 243 can be radiolabeled with 99m Tc-pertechnetate. IMP 243 can be conjugated to other peptides to design bispecific antibodies (bsMAbs) for cancer research.