Glucose homeostasis is a vital and complex process, and its disruption can cause hyperglycaemia and type II diabetes mellitus. Glucokinase (GK), a key enzyme that regulates glucose homeostasis, converts glucose to glucose-6-phosphate in pancreatic β-cells, liver hepatocytes, specific hypothalamic neurons, and gut enterocytes. In hepatocytes, GK regulates glucose uptake and glycogen synthesis, suppresses glucose production, and is subject to the endogenous inhibitor GK regulatory protein (GKRP). During fasting, GKRP binds, inactivates and sequesters GK in the nucleus, which removes GK from the gluconeogenic process and prevents a futile cycle of glucose phosphorylation. Compounds that directly hyperactivate GK (GK activators) lower blood glucose levels and are being evaluated clinically as potential therapeutics for the treatment of type II diabetes mellitus. However, initial reports indicate that an increased risk of hypoglycaemia is associated with some GK activators. To mitigate the risk of hypoglycaemia, we sought to increase GK activity by blocking GKRP. Here we describe the identification of two potent small-molecule GK-GKRP disruptors (AMG-1694 and AMG-3969) that normalized blood glucose levels in several rodent models of diabetes. These compounds potently reversed the inhibitory effect of GKRP on GK activity and promoted GK translocation both in vitro (isolated hepatocytes) and in vivo (liver). A co-crystal structure of full-length human GKRP in complex with AMG-1694 revealed a previously unknown binding pocket in GKRP distinct from that of the phosphofructose-binding site. Furthermore, with AMG-1694 and AMG-3969 (but not GK activators), blood glucose lowering was restricted to diabetic and not normoglycaemic animals. These findings exploit a new cellular mechanism for lowering blood glucose levels with reduced potential for hypoglycaemic risk in patients with type II diabetes mellitus.

In the past few decades, drug metabolism research has played an ever increasing role in the design of drugs. 1−3 In vitro metabolism assays 4 have become an integral part of the routine profiling of compounds made in drug discovery. 5 The data from these assays have allowed medicinal chemists to focus their efforts on compounds with improved metabolic stability. 6 Detailed metabolite identification studies are also done more routinely, which provide information on how to strategically replace or block metabolically labile sites. 7 Additionally, in vivo PK studies are regularly conducted in drug discovery, which helps to build in vitro−in vivo PK relationships. 4 The positive influence that these advances in PKDM sciences have had on drug discovery is reflected in the fact that fewer drug candidates fail in the clinic for PKDM related issues. 8 This suggests that medicinal chemists are successfully integrating the data generated by their PKDM colleagues into the design of compounds with fewer metabolic liabilities.Extensive data from metabolism studies have allowed medicinal chemists to develop general principles for reducing compound metabolism. These methods include, but are not limited to, reducing lipophilicity, altering sterics and electronics, introducing a conformational constraint, and altering the stereochemistry of their compounds. While no single method is able to solve every metabolic problem, these principles do give medicinal chemists guidance on how to improve the metabolic liabilities of their compounds. If the specific site of metabolism is known, medicinal chemists block the site, typically with a fluorine, or replace the metabolically labile group with a bioisostere. 9 While several authors have reviewed these techniques for reducing metabolism, 5,10,11 there is no review that summarizes different approaches to improving the metabolic stability of heterocycles. In this review, we summarize examples where changes were made at or near the heterocycle to improve metabolic stability. By summarizing these examples, we hope to provide a useful guide to medicinal chemists as they attempt to improve the metabolic profile of their own heterocyclic compounds.The majority of the examples that are included in this review came from searching the online open access database CHEMBL. 12 In addition to having pharmacology data on compounds from the medicinal chemistry literature, CHEMBL has over 120 000 points of data on the ADMET properties of compounds. With the help of the visualization software Spotfire, we were able to cull examples from the CHEMBL ADMET data that focused on heterocycles. We also identified examples from papers that cite leading reviews in the drug metabolism field 13−18 and were present in other recent reviews on drug metabolism. 19−22 The main criteria that we placed on the examples selected for this review was that the change made to improve metabolism had to occur at or near the heterocycle and nowhere else on the molecule. This allowed us to eliminate examples where a change made t...

Using fragment-based screening of a focused fragment library, 2-aminoquinoline 1 was identified as an initial hit for BACE1. Further SAR development was supported by X-ray structures of BACE1 cocrystallized with various ligands and molecular modeling studies to expedite the discovery of potent compounds. These strategies enabled us to integrate the C-3 side chain on 2-aminoquinoline 1 extending deep into the P2' binding pocket of BACE1 and enhancing the ligand's potency. We were able to improve the BACE1 potency to subnanomolar range, over 10(6)-fold more potent than the initial hit (900 μM). Further elaboration of the physical properties of the lead compounds to those more consistent with good blood-brain barrier permeability led to inhibitors with greatly improved cellular activity and permeability. Compound 59 showed an IC(50) value of 11 nM on BACE1 and cellular activity of 80 nM. This compound was advanced into rat pharmacokinetic and pharmacodynamic studies and demonstrated significant reduction of Aβ levels in cerebrospinal fluid (CSF).

Small molecule activators of glucokinase have shown robust efficacy in both preclinical models and humans. However, overactivation of glucokinase (GK) can cause excessive glucose turnover, leading to hypoglycemia. To circumvent this adverse side effect, we chose to modulate GK activity by targeting the endogenous inhibitor of GK, glucokinase regulatory protein (GKRP). Disrupting the GK-GKRP complex results in an increase in the amount of unbound cytosolic GK without altering the inherent kinetics of the enzyme. Herein we report the identification of compounds that efficiently disrupt the GK-GKRP interaction via a previously unknown binding pocket. Using a structure-based approach, the potency of the initial hit was improved to provide 25 (AMG-1694). When dosed in ZDF rats, 25 showed both a robust pharmacodynamic effect as well as a statistically significant reduction in glucose. Additionally, hypoglycemia was not observed in either the hyperglycemic or normal rats.

Thiazolones with an exo-norbornylamine at the 2-position and an isopropyl group on the 5-position are potent 11beta-HSD1 inhibitors. However, the C-5 center was prone to epimerization in vitro and in vivo, forming a less potent diastereomer. A methyl group was added to the C-5 position to eliminate epimerization, leading to the discovery of (S)-2-((1S,2S,4R)-bicyclo[2.2.1]heptan-2-ylamino)-5-isopropyl-5-methylthiazol-4(5H)-one (AMG 221). This compound decreased fed blood glucose and insulin levels and reduced body weight in diet-induced obesity mice.