Assessment of novel anti-p185(HER-2) monoclonal antibodies for internalization-dependent therapies

Novel therapies that require internalization of effector domains may be imp roved by assessing the efficacy of postbinding receptor-mediated endocytosi s. To achieve targeted gene therapy of immunotoxin therapy, natural vector- host tropisms must be altered. Recent improvements in monoclonal antibody ( MAb) engineering have expanded the potential range of host cells that can b e targeted for therapeutic intervention. However, relatively little is know n about cellular responses after binding of a vector construct. We have tes ted the utility of four novel MAbs recognizing the extracellular domain of p185(HER-2), a membrane receptor protein, for use in internalization-depend ent therapies. All four antibodies bound to p185HER-2 in a number of immuno assays, Two antibodies recognized accessible epitopes of p185(HER-2) On via ble cells. Radioimmunoassay demonstrated that antibody-membrane receptor co mplexes formed by two antibodies were internalized and trafficked through a n endolysosomal degradative pathway. Two of the four antibodies evaluated w ere found to have favorable internalization characteristics suitable for in corporation in a targeting vector, This analytical approach could be applie d to antibodies prior to and after fusion with various vectors or toxins to determine the potential utility of the antibodies for targeted therapy.