Oral Presentation 9th Modern Solid Phase Peptide Synthesis & Its Applications Symposium 2023

Developing simplified insulin-like peptide 5 (INSL5) analogues as colon motility regulators (96809)

Hongkang Wu 1 , Ruslan V Pustovit 1 , Thomas NG Handley 1 , Chaitra Chandrashekar 1 , Ross AD Bathgate 1 2 , John B Furness 1 3 , M. Akhter Hossain 1 4
  1. The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, MELBOURNE, Victoria, Australia
  2. Department of Biochemistry and Pharmacology, The University of Melbourne, MELBOURNE, Victoria, Australia
  3. Department of Anatomy and Physiology, The University of Melbourne, MELBOURNE, Victoria, Australia
  4. School of Chemistry, The University of Melbourne, MELBOURNE, Victoria, Australia

Constipation is an unappreciated but common gastrointestinal motility disorder that affects the general population, with a high prevalence in senior people and those with neurological disorders1. Current therapies are inefficient and have adverse side effects. Therefore, there is an urgent need to develop new pharmacological drug leads for the treatment of constipation.

Our laboratory has recently discovered that human insulin-like peptide 5 (INSL5) is a promising therapeutic candidate in treating constipation2, 3. INSL5 is a gut hormone exclusively produced by colonic L-cells, and its colonic propulsion is mediated by the target GPCR, relaxin family peptide receptor 4, RXFP44. INSL5 consists of two peptide chains (A- and B-) cross-linked by one intra-A-chain and two inter-chain disulphide bonds. The chemical or recombinant assembly of INSL5 is very challenging and time-consuming, due to the aggregative nature of both chains and the multi-step synthesis protocol5.

We previously generated biologically active novel INSL5 analogues by shortening both the INSL5 A- and B- chains and deleting the intra-A-chain disulphide bond. While the simplified peptide ligands are easier to synthesise (yield ~14%) compared with native INSL5 (yield 0.8%), they still possess a complex two-chain and two-disulphide-bond structure6-8. Previous structure-activity data suggest that B-chain of INSL5 contains all the key residues for RXFP4 binding and activity. Therefore, we hypothesise that it is possible to generate B-chain-specific bioactive INSL5 analogues.

Here I present new designs and chemical approaches to produce B-chain-specific biologically active INSL5 analogues. One of the analogues was high yielding (41%) that exhibited high affinity and cAMP potency (~100 nM) at RXFP4 in vitro. Importantly, this single B-chain analogue was shown to reverse opioid-induced constipation in mice with similar efficacy to the currently available two-chain lead peptide, INSL5-A13. This new compound, therefore, is an important research tool and drug template for the potential treatment of constipation.