Peptidomimetics are used for overcoming problems arising in the pharmacokinetic issues of therapeutic proteins and peptides. Peptidomimetics are molecules that are designed to mimic the structure of a bioactive protein or peptide and show acceptable pharmacokinetic properties while retaining the desired biological activity.
All peptidomimetics are divided into 4 classes. Classes A and B mimetics are peptides with various alterations to the peptide side chains and backbone.  However, there are a lot of restrictions in therapeutic applications involving peptides, due to lack of oral bioavailability and to proteolytic degradation. This results in generally very short biological half-lives.
Class C mimetics consist of highly modified structures that completely replace the entire peptide backbone with small molecule character. The central scaffold displays the substituents in comparison to the orientation of the key residues in the bioactive conformation of the antecedent peptide. The replacement of the entire peptide backbone leads to the improvement of oral bioavailability and pharmacokinetic properties.
Class D mimetics are small-molecule drugs used in the classical medicinal chemistry that mimic the mode of action of a bioactive peptide without a direct link to its side chain functionalities. The small-molecule drugs bind either into the active site of a protein or at an allosteric position. Such molecules can be generated by affinity optimization of a class C molecule or they can be identified in screenings of compound libraries or by in silico screening of virtual libraries. 
Peptidomimetics are designed for a broad range of targets preferably in cancer diagnostics and therapeutics. Their applicability has been tested on different protein model systems that include apoptosis regulators, transmembrane receptors, small GTPases and transcriptional regulators.
 L. Mabonga and A. P. Kappo, “Peptidomimetics: A Synthetic Tool for Inhibiting Protein–Protein Interactions in Cancer,” International Journal of Peptide Research and Therapeutics, vol. 26, no. 1. Springer, pp. 225–241, Mar. 01, 2020, doi: 10.1007/s10989-019-09831-5.
 M. Pelay-Gimeno, A. Glas, O. Koch, and T. N. Grossmann, “Structure-Based Design of Inhibitors of Protein-Protein Interactions: Mimicking Peptide Binding Epitopes,” Angew. Chemie – Int. Ed., vol. 54, no. 31, pp. 8896–8927, 2015, doi: 10.1002/anie.201412070.