Receptor-mediated tumor targeting with radiolabeled peptides: there is more to it than somatostatin analogs.

In this issue of The Journal of Nuclear Medicine, Wild et al. report the binding and animal biodistribution data of [Lys(Ahx-DTPA-In)NH2]exendin-4 (Ahx is aminohexanoic acid; DTPA is diethylenetriaminepentaacetic acid), an analog of glucagonlike peptide-1 (GLP-1) (1). Their results raise high hopes of actually achieving selective and potent receptormediated targeting of tumors with a radiolabeled peptide but, at the same time, revive critical issues on the possibility of predicting the clinical success,