Peptides in Drug Discovery
Peptide research on drug design and drug discovery is one of the most promising fields in the development of the new drugs. Peptide sequences are constituents of larger proteins, where they are responsible for molecular recognition and biological activities. Inhibition of protein-protein interactions by peptides and the evolution of peptide ligands to small molecule mimetics is a major goal of the field, with several notable successes. Peptides would therefore seem to be ideal drug leads. However, peptides are limited in that they are metabolically unstable due to the protease cleavage of the peptide backbone and have poor bioavailability, in part due to low membrane transport characteristics of the peptide is amide backbone structure.
The starting point for a peptide mimetics research is the identification of a peptide or peptide sequence within a protein context that is activ in the relevant assay. The process involves deconstructing the original peptide and reassembling the essential features on a new, mimetic scaffold that retains the ability to interact with the biological target, but circumvents the problems associated with a natural peptide. The deconstruction process begins by developing structure-activity relationships, then designing analogs to define a minimal active sequence and to identify the key residues and portions of the backbone in the peptide that are responsible for the biological effect. The structural constraints are added to check the effectivity of these features.
The interaction of a peptide with a biological target may occur via a direct binding of a linear sequence in any number of conformations accessible to a peptide. The modern peptide mimetics approach incorporates a production of small molecules which mimic peptides in order to overcome their ineffectiveness as drugs when administered orally. The small molecules mimetics retain the desired biological properties of the peptide lead, but are metabolically stable, have unlimited diversity, and can be designed to provide the new drugs.
By this process, the peptide has been reduced to its information content, the basis for a pharmacophore model that defines the critical features and their arrangement in space. This model supports the re-assembly of the critical elements and non-peptide variants on a modified scaffold that presents the optimized pharmacophore to the receptor. The optimized peptide-hybrid may be valuable as a first drug candidate, in addition to its role as a tool for further evolution to a mimetic. Mimetic scaffolds are designed to be resistant to the proteases that would destroy a natural peptide, and would have pharmaceutical properties consistent with a drug candidate.
It is possible to represent the biologically active sites of the peptides in the form of orally administered small-molecule mimietics that take all the advantages of evolutionally designed peptides on the one hand and have good drug properties, are stable, bioavailable, inexpensive in manufacture and convenient in use, on the other hand. There is no way to get involved in modern drug discovery and drug design without peptide and their small molecule mimetics research.