Stability of peptides and therapeutic success in cancer.

INTRODUCTION: Although naturally occurring peptides have been widely used as drugs, their rapid in vivo degradation by proteolysis and their interactions at multiple receptors are part of the reason for the limitation of their clinical applications. AREAS COVERED: This paper reviews peptide-metabolizing enzymes in the brain and intestinal brush-border membranes, and discusses potential strategies to improve biological activity, specificity and stability of peptides. The reader will gain, via some examples, an appreciation of the challenges involved in identifying peptides stability to improve their biological properties such as selectivity. EXPERT OPINION: Due to the metabolic process, it is crucial to follow the biodistribution of a peptide drug and/or a peptidic moiety in order to improve its biological properties such as selectivity. To these purposes, pseudopeptides and peptidomimetics preserving the biological properties of native peptides have been developed to increase their resistance to degradation and elimination, bioavailability and selectivity to become good drug candidates.