Donald Stuart Middleton

Novel Indazole Non-Nucleoside Reverse Transcriptase Inhibitors Using Molecular Hybridization Based on Crystallographic Overlays

A major problem associated with non-nucleoside reverse transcriptase inhibitors (NNRTIs) for the treatment of HIV is their lack of resilience to mutations in the reverse transcriptase (RT) enzyme. Using structural overlays of the known inhibitors efavirenz and capravirine complexed in RT as a starting point, and structure-based drug design techniques, we have created a novel series of indazole NNRTIs that possess excellent metabolic stability and mutant resilience.

An Imidazopiperidine Series of CCR5 Antagonists for the Treatment of HIV: The Discovery of N-{(1S)-1-(3-Fluorophenyl)-3-[(3-endo)-3-(5-isobutyryl-2-methyl-4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridin-1-yl)-8-azabicyclo[3.2.1]oct-8-yl)propyl}acetamide (PF-232798)

Preventing entry of HIV into human host cells has emerged as an attractive approach to controlling viral replication. Maraviroc 1 is an approved antagonist of the human CCR5 receptor which prevents the entry of HIV. Herein, we report the design and discovery of a series of imidazopiperidine CCR5 antagonists which retain the attractive antiviral profile and window over hERG activity of maraviroc 1, combined with improved absorption profiles in rat and dog. Furthermore, this series of compounds has been shown to retain activity against a laboratory generated maraviroc-resistant HIV-1 strain, which indicates an alternative resistance profile to that of maraviroc 1. Compound 41f (PF-232798) was selected as a clinical candidate from the imidazopiperidine series and is currently in phase II clinical trials.

Inhalation by Design: Novel Tertiary Amine Muscarinic M3 Receptor Antagonists with Slow Off-Rate Binding Kinetics for Inhaled Once-Daily Treatment of Chronic Obstructive Pulmonary Disease

A novel tertiary amine series of potent muscarinic M(3) receptor antagonists are described that exhibit potential as inhaled long-acting bronchodilators for the treatment of chronic obstructive pulmonary disease. Geminal dimethyl functionality present in this series of compounds confers very long dissociative half-life (slow off-rate) from the M(3) receptor that mediates very long-lasting smooth muscle relaxation in guinea pig tracheal strips. Optimization of pharmacokinetic properties was achieved by combining rapid oxidative clearance with targeted introduction of a phenolic moiety to secure rapid glucuronidation. Together, these attributes minimize systemic exposure following inhalation, mitigate potential drug-drug interactions, and reduce systemically mediated adverse events. Compound 47 (PF-3635659) is identified as a Phase II clinical candidate from this series with in vivo duration of action studies confirming its potential for once-daily use in humans.

SILICON TETHERED TYPE II ENE CYCLISATIONS

Abstract Type II intramolecular carbonyl ene reactions of vinyl silanes 1, 4 and 5 are shown to generate methylene silacyclohexanols 3, 6 and 8 as the major products.

4-Amino-2-(aryl)-butylbenzamides and Their conformationally constrained analogues. Potent antagonists of the human neurokinin-2 (NK2) receptor

A library, evaluating a range of piperazines, piperidines and acyclic amines, as replacements for the 4-hydroxy-4-phenylpiperidine moiety in lead (1b) was prepared. These efforts identified the 4-((N)-benzimidazolone)piperidine analogue (2a) which was further optimised using classical single-compound synthesis to yield the 3-((N)-morpholino)azetidine (2j). Conformationally constrained analogues of (2j), generally offered no potency advantage in this particular series.

1-Amido-1-phenyl-3-piperidinylbutanes - CCR5 antagonists for the treatment of HIV. Part 1.

The development of a new class of CCR5 antagonist replacing the tropane core of maraviroc by piperidine with a branched N-substituent is described. Compound 15h shows good whole cell antiviral activity together with microsomal stability and only weak activity at the hERG ion channel.

Comparison of the Non‐Nucleoside Reverse Transcriptase Inhibitor Lersivirine with its Pyrazole and Imidazole Isomers

Lersivirine is a potent non‐nucleoside reverse transcriptase inhibitor with exceptional mutant resilience. Here, we compare the pharmacological and pharmacokinetic profile of lersivirine with its pyrazole and imidazole isomers and briefly explore the profile of these series. This work establishes lersivirine as the outstanding molecule in this set.

The discovery of a novel prototype small molecule TLR7 agonist for the treatment of hepatitis C virus infection

A series of heterocycle analogues of an adenine template were explored for TLR7 agonist potency and pharmacokinetics. One compound was identified with an excellent pharmacokinetic, in vitro potency and in vivo interferon induction profile in a mouse model, and was selected for further pre-clinical evaluation as a potential treatment for hepatitis C viral infection.

Stereoselective Synthesis of Silacyclohexanols by Silicon Tethered Type II Ene Cyclisation

Abstract Vinyl silane precursors for intramolecular ene reaction were prepared either by sequential organometallic substitution of appropriate silyl halides or by ring opening of oxasilacyclopentanes with 2-propenyllithium. The oxasilacyclopentane intermediates were prepared by free-radical cyclisation, intramolecular hydrosilylation, or intramolecular Diels–Alder reaction. Treatment of the ene precursors with methylaluminium dichloride resulted in the formation of silacyclohexanols with high stereoselectivity.

Cytochrome P450 metabolism and inhibition: analysis for drug discovery.

Publisher Summary The cytochrome P450 (CYP) family of enzymes is arguably the most important human drug metabolizing enzymes (DME) system. All of the CYPs considered to be important in human drug metabolism have been studied to some degree with one or all of the techniques detailed in the chapter. Information produced from these studies has been used to gain an understanding of the high-level structural requirements, which will predispose a compound to interact with a particular member of this family, be that as a substrate or an inhibitor. The structure–activity relationships for the DMEs and their substrates is an important area of research that impacts pharmacology, toxicology, and basic enzymology. Thus, the case study examples in the chapter illustrates that while the high-level requirements for CYP hold true, the broad substrate specificity of these enzymes continues to frustrate efforts to develop series-specific metabolic SARs.