What is a Peptide?
Peptides are naturally-occurring substances that form when two or more singe amino acids join together via peptide bonds to form a short chain.
Therapeutic peptides which have a long history represent a unique class of compounds positioned between small molecules and proteins. The FDA defines a peptide therapeutic as a chain of amino acids (the building blocks of proteins) containing 40 amino acids or less, and regulates them as small molecules.
Therapeutic peptides are designed by rational methods with high specificity to bind and modulate a protein interaction of interest.
THE PEPTIDE COMEBACK
Now viewed as a promising and a novel approach to treat many diseases this renewed interest has led to a number of highly successful ‘blockbuster’ peptide drugs such as (e.g. Copaxone®, Victoza® or Lupron®). As of 2018, more than 100 approved peptide therapeutics for various clinical indications were commercially available in the global market. Additionally, a robust clinical pipeline currently has more than 100 type of therapeutics in late stage of clinical development with more than 200 types of therapeutics in pre-clinical stage.
Therapeutic peptides have several important advantages over proteins or antibodies: they are small in size, easy to synthesise and have the ability to penetrate the cell membranes. They also have high activity, specificity and affinity; minimal drug-drug interaction; and biological and chemical diversity. An added benefit of using peptides as a treatment is that they do not accumulate in specific organs (e.g. kidney or liver), which can help to minimise any toxic side effects. A considerable benefit to patients.
In the case of cancer, peptides can be used in a variety of ways, including carrying cytotoxic drugs, vaccines, hormones and radionuclides
Despite revolutionising diabetes treatment, and their known benefits, the appetite for the development of therapeutic peptides was held back by challenges such as short plasma half-life and limited oral bioavailability and took a back-seat to small molecules in modern drug development.
The tide is now turning and the industry has renewed its interest in the development of therapeutic peptides recognising the benefit they can bring to the treatment of a wide range of conditions.
Diversifying from its original focus the genomic era has allowed for the identification and molecular characterisation for many endogenous peptide hormones and, as such, novel peptidic ligands for these receptors are being pursued.