This research examined the synthesis of Trastuzumab-PEI-OG, PEI-OG, Trastuzumab-OG, 149Pm-DOTA-PEI-Trastuzumab and subsequent in vitro studies with Her2/neu expressed on human breast adenocarcinoma SkBr-3 cells. This evidence concerns the gene ERBB2 and breast adenocarcinoma.