From peptides to small molecules and from binding to proteolysis. Peptides as lead molecules for the development of anti-inflammatory agents.

Peptides have both advantages and disadvantages when designing new drug molecules. They can cover a large surface area, but are often not orally bioavailable. They can bid with high affinity to their target, but are often rapidly degraded. They are good starting points for the development of more "drug-like" molecules, but it is difficult to go from a peptide to small molecule. Pharmaceutical companies, traditionally averse to peptides, have woken to their potential and there are many programmes across the world looking to convert these exceptional molecules into drug entities, with some clinical successes coming to the fore. Our vision is to develop a smooth process from peptides to small molecules with biological activity. In this project, we will demonstrate three approaches to new molecules from peptides:

i) We will show that cell-penetrating peptides can be turned into proteolysis activating chimeras, or PROTACs.

ii) We will take a peptide and turn it into a small molecule with biological activity and then to a PROTACs

iii) We will turn a small cyclic peptide into a biologically active molecule through medicinal chemistry design.

Chronic inflammatory diseases are debilitating and life threatening. The protein Nrf2 is a key player in the resolution of inflammation and is controlled by another protein called Keap1. We have shown that the interaction between Nrf2 and Keap1 can be perturbed with a peptide that is designed to enter the cell (a "cell-penetrating peptide") and that the resulting activation of Nrf2 can dampen inflammation. Molecules that activate a process called proteolysis have also been developed. These are compounds that utilise the cell's own machinery to destroy a target protein and have been termed PROTACs. Our hypothesis is that by combining peptides that target Keap1 with a proteolysis activating moiety, we can generate PROTACs that will have a profound effect on inflammation.

We have made a small cyclic peptide that binds with very high affinity to Keap1 and stops it binding to Nrf2, although we have only been able to see these effects in vitro as our small peptide can't enter the cell. It is possible to further manipulate this cyclic peptide structure to make the molecule penetrate the cell using medicinal chemistry techniques combined with structural information. Our hypothesis is that we can adjust the structure of the peptide to attach a proteolysis activating moiety and generate another PROTACs structure.

Getting from a peptide to a small molecule is also very difficult, but we have developed a new approach to convert peptides to small molecules that we call peptide-directed ligand design. We intend to apply this approach to the peptide that we know binds to Nrf2 and identify new small molecule entities that can bind with high affinity. These will then be converted to PROTACs and assessed for their biological activity.

There are several potential general outcomes for this research. Our cell penetrating peptide is already sold to other researchers, so there is the potential to make more research tools. More importantly, we have the ability to generate molecules with therapeutic potential, that can be used in the treatment of chronic inflammatory diseases. Finally, we will demonstrate the smooth path from a target binding peptide to a molecule that can be used in the clinic, either a peptide or a small molecule.