H-Tyr-Lys-OH

Reaction of the dipeptide KY with diethylenetriaminepentaacetic (DTPA) cyclic anhydride yielded monovalent and bivalent haptens. In vitro, the antibody conjugate (which was prepared by coupling F(ab’)2 or Fab’ fragments of an antibody specific for the human high molecular weight melanoma associated antigen to Fab’ fragments of an antibody specific for In-DTPA complexes) mediated binding of the ¹¹¹In-labeled haptens to melanoma cells. In vivo, it allowed specific localization of the haptens in A375 tumors. The bivalent hapten exhibited much higher efficiency at targeting ¹¹¹In onto cells, both in vitro and in vivo.