A library of peptideswas prepared with a major focus on the bioisosteric replacement ofthe original methionine residue due to its susceptibility to oxidation.The peptides were characterized for their binding behavior to nectin-4,and radiopharmacological characterization of selected radioligandswas performed using urothelial carcinoma cell lines and tumor xenograftmodels derived thereof. Here, NECTIN4 is linked to neoplasm.