Stuart Norman Lile Bennett

Mass spectrometric characterization of circulating covalent protein adducts derived from a drug acyl glucuronide metabolite: multiple albumin adductions in diclofenac patients.

Covalent protein modifications by electrophilic acyl glucuronide (AG) metabolites are hypothetical causes of hypersensitivity reactions associated with certain carboxylate drugs. The complex rearrangements and reactivities of drug AG have been defined in great detail, and protein adducts of carboxylate drugs, such as diclofenac, have been found in liver and plasma of experimental animals and humans. However, in the absence of definitive molecular characterization, and specifically, identification of signature glycation conjugates retaining the glucuronyl and carboxyl residues, it cannot be assumed any of these adducts is derived uniquely or even fractionally from AG metabolites. We have therefore undertaken targeted mass spectrometric analyses of human serum albumin (HSA) isolated from diclofenac patients to characterize drug-derived structures and, thereby, for the first time, have deconstructed conclusively the pathways of adduct formation from a drug AG and its isomeric rearrangement products in vivo. These analyses were informed by a thorough understanding of the reactions of HSA with diclofenac AG in vitro. HSA from six patients without drug-related hypersensitivities had either a single drug-derived adduct or one of five combinations of 2–8 adducts from among seven diclofenac N-acylations and three AG glycations on seven of the protein’s 59 lysines. Only acylations were found in every patient. We present evidence that HSA modifications by diclofenac in vivo are complicated and variable, that at least a fraction of these modifications are derived from the drug’s AG metabolite, and that albumin adduction is not inevitably a causation of hypersensitivity to carboxylate drugs or a coincidental association.

Free-Wilson and Structural Approaches to Co-optimizing Human and Rodent Isoform Potency for 11β-Hydroxysteroid Dehydrogenase Type 1 (11β-HSD1) Inhibitors

11β-Hydroxysteroid dehydrogenase 1 (11β-HSD1) has been a target of intensive research efforts across the pharmaceutical industry, due to its potential for the treatment of type II diabetes and other elements of the metabolic syndrome. To demonstrate the value of 11β-HSD1 in preclinical models, we required inhibitors with good potency against both human and rodent isoforms. Herein, we describe our efforts to understand how to co-optimize human and murine potency within the (5-hydroxy-2-adamantyl)-pyrimidine-5-carboxamide series. Two approaches are described-a data-driven (Free-Wilson) analysis and a structure-based design approach. The conclusions from these approaches were used to inform an efficient campaign to design compounds with consistently good human/murine potency within a logD(7.4) range of 1-3. Compounds 20 and 26 demonstrated good rodent PK, which allowed us to demonstrate a PK/PD relationship in rat and mouse. We then evaluated 26 against glycemic and body weight end points in murine disease models, where it demonstrated glucose and body weight efficacy at 300 mg/kg/day but only body weight efficacy at 50 mg/kg/day, despite providing >90% target engagement in the liver.

Discovery of a series of 2-(pyridinyl)pyrimidines as potent antagonists of GPR40

A series of 2-(pyridinyl)pyrimidines were identified as potent GPR40 antagonists. Despite significant challenges related to improving the combination of potency and lipophilicity within the series, the compounds were optimised to identify a suitable in vivo probe compound, which was confirmed to exhibit pharmacology consistent with GPR40 antagonism.

Matched triplicate design sets in the optimisation of glucokinase activators – maximising medicinal chemistry information content

Successful lead optimisation requires the identification of the best compound within the chemical space explored during an optimisation campaign. This can be a costly and inefficient process leading to the synthesis of many sub-optimal compounds. In this paper, a method for carrying out this exercise more effectively is outlined. This relies on the generation of robust datasets on which to build predictive models in a paradigm termed “matched triplicate design sets”. The practical implementation of this approach is exemplified in the optimisation of a new series of glucokinase activators.

Optimising pharmacokinetics of glucokinase activators with matched triplicate design sets – the discovery of AZD3651 and AZD9485

The matched triplicate approach to lead optimisation offers a means of generating more robust quantitative structure activity relationship data and this rigour leads to better quality decision making and greater ability to predict optimal compounds within a series. One of the ultimate aims of this approach is to use the data generated to build more accurate predictive models to identify the best compounds within the exemplified chemical space in an efficient manner. This paper describes the continued application of this approach to the optimisation of a series of glucokinase activators. This second phase focussed primarily on the rational solution to plasma instability observed with the previous compounds and, hence, achieved acceptable oral exposure in the series. The campaign was completed by using the predictive power of Free-Wilson analysis based on the matched triplicate datasets to enable a focussed, matrix based endgame culminating in the identification of two development candidates, AZD3651 and AZD9485.

Design and synthesis of a novel series of cyclohexyloxy-pyridyl derivatives as inhibitors of diacylglycerol acyl transferase 1

A novel series of potent diacylglycerol acyl transferase 1 inhibitors was developed from the clinical candidate AZD3988. Replacement of the phenyl cyclohexyl-ethanoate side chain with substituted oxy-linked side chains to introduce changes in shape and polarity, reduce lipophilicity and mask the hydrogen bond donors with internal hydrogen bond acceptors led to improvements in solubility, unbound clearance and excellent selectivity over the related enzyme acyl-coenzyme A:cholesterol acyltransferase 1. A comparison of the small molecule crystal structures of compound 4 and compound 28 is described. Compounds in this series have good ADMET properties and provide an exposure-dependent decrease in circulating plasma triglyceride levels in a rat oral lipid tolerance test.

Reduction of acyl glucuronidation in a series of acidic 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) inhibitors: the discovery of AZD6925

Inhibition of 11β-HSD1 is viewed as a potential target for the treatment of obesity and other elements of the metabolic syndrome. We report here the optimisation of a carboxylic acid class of inhibitors from AZD4017 (1) to the development candidate AZD6925 (11). A central aim of this optimisation campaign was the modulation of clearance mechanism to reduce the extent of acyl glucuronidation. This was achieved by modulation of the acid substructure together with a redistribution of lipophilicity in order to achieve the desired profile.

Discovery of a series of indan carboxylic acid glycogen phosphorylase inhibitors

A series of carboxylic acid glycogen phosphorylase inhibitors, which have potential as oral antidiabetic agents, is described. Defining and applying simple physicochemical design criteria was used to assess the opportunity and to focus synthetic efforts on compounds with the greatest probability of success. The study led to compound 17, which exhibits a good balance of properties including potent inhibition of recombinant human liver glycogen phosphorylase in vitro, a good DMPK profile including excellent bioavailability and low clearance and good in vivo activity in a glucagon challenge model of diabetes in Zucker rats.