Design of Inhibitors of Protein Tyrosine Phosphatase-1B

Abstract

According to World Health Organisation statistics, more than 171 million people and at least 400 million people worldwide suffer from diabetes and obesity, respectively. PTP1B knock-out mouse experiments launched PTP1B as a novel druggable target for type II diabetes mellitus and diet-induced obesity. It was observed that mice lacking PTP1B were more capable of resisting weight gain and lowering glucose levels in the fed state as compared with wildtype mice, thus confirming that PTP1B is involved in the pathogenesis of type II diabetes mellitus and diet-induced obesity. However, the highly charged environment of the PTP1B catalytic site hinders the development of inhibitors with sufficient oral bioavailability. Moreover, PTP1B shares a common motif in its active pocket with all protein tyrosine phosphatases, which brings about a problem of low selectivity and thus potential toxicity. Therefore, the main challenge of our research was to develop lead-like molecules that are capable of inhibiting PTP1B with sufficient potency and improved cell permeability; then, in the lead optimisation stage, try to maximise their selectivity towards PTP1B against other similar PTPs using key structural differences.To achieve this, a receptor-based virtual screening approach against the PTP1B catalytic site was validated and performed in this project for a large ligand library of more than 300,000 compounds. Using the same ligand library, a ligand-based virtual screening approach was conducted using known PTP1B inhibitors for targeting the PTP1B allosteric site. From both screenings, around 200 compounds were selected for experimental testing using biochemical enzyme assays against BTP1B. Many compounds supplied by the external vendors (NCI and Timtec) showed inhibitory activity ranging from the low micromolar to the high micromolar level (the best inhibitor had an IC50 value of 6.8 µM). Subsequently, the most promising candidates were evaluated using different biophysical and analytical techniques in order to verify the identity and purity of the samples. Mass spectrometry and NMR analysis indicated that some of the tested compounds supplied by the external vendors were either impure and/or did not contained expected inhibitors in sufficient quantities to be confidently identified. However, several hits with sufficient inhibition potency have been successfully verified by both mass spectrometry and NMR spectroscopy. These structurally identified inhibitors exhibited novel scaffolds, neutral net charge and low molecular weight. Furthermore, the identified hits functioning on the PTP1B catalytic site featured two types of novel neutral phosphate isosteres, which is highly beneficial for further improvement of cellular permeability.Hence, these lead-like inhibitors discovered and validated in this research provide a good starting point and a step forward in the development of potential therapeutic agents for the treatment of type II diabetes mellitus and diet-induced obesity.

Date of Award	1 Aug 2011
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Elena Bichenkova (Supervisor) & Richard Bryce (Supervisor)