Optimization of 2-piperidin-4-yl-acetamides as melanin-concentrating hormone receptor 1 (MCH-R1) antagonists: Designing out hERG inhibition

GZ-793A inhibits the neurochemical effects of methamphetamine via a selective interaction with the vesicular monoamine transporter-2

Lobeline and lobelane inhibit the behavioral and neurochemical effects of methamphetamine via an interaction with the vesicular monoamine transporter-2 (VMAT2). However, lobeline has high affinity for nicotinic receptors, and tolerance develops to the behavioral effects of lobelane. A water-soluble analog of lobelane, R-N-(1,2-dihydroxypropyl)-2,6-cis-di-(4-methoxyphenethyl)piperidine hydrochloride (GZ-793A), also interacts selectively with VMAT2 to inhibit the effects of methamphetamine, but does not produce behavioral tolerance. The current study further evaluated the mechanism underlying the GZ-793A-mediated inhibition of the neurochemical effects of methamphetamine. In contrast to lobeline, GZ-793A does not interact with the agonist recognition site on α4β2^* and α7^* nicotinic receptors. GZ-793A (0.3-100µM) inhibited methamphetamine (5µM)-evoked fractional dopamine release from rat striatal slices, and did not evoke dopamine release in the absence of methamphetamine. Furthermore, GZ-793A (1-100µM) inhibited neither nicotine (30µM)-evoked nor electrical field-stimulation-evoked (100Hz/1min) fractional dopamine release. Unfortunately, GZ-793A inhibited [³H]dofetilide binding to human-ether-a-go-go related gene channels expressed on human embryonic kidney cells, and further, prolonged action potentials in rabbit cardiac Purkinje fibers, suggesting the potential for GZ-793A to induce ventricular arrhythmias. Thus, GZ-793A selectively inhibits the neurochemical effects of methamphetamine and lacks nicotinic receptor interactions; however, development as a pharmacotherapy for methamphetamine use disorders will not be pursued due to its potential cardiac liabilities.

Discovery of (3-(4-(2-Oxa-6-azaspiro[3.3]heptan-6-ylmethyl)phenoxy)azetidin-1-yl)(5-(4-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methanone (AZD1979), a Melanin Concentrating Hormone Receptor 1 (MCHr1) Antagonist with Favorable Physicochemical Properties

A novel series of melanin concentrating hormone receptor 1 (MCHr1) antagonists were the starting point for a drug discovery program that culminated in the discovery of 103 (AZD1979). The lead optimization program was conducted with a focus on reducing lipophilicity and understanding the physicochemical properties governing CNS exposure and undesired off-target pharmacology such as hERG interactions. An integrated approach was taken where the key assay was ex vivo receptor occupancy in mice. The candidate compound 103 displayed appropriate lipophilicity for a CNS indication and showed excellent permeability with no efflux. Preclinical GLP toxicology and safety pharmacology studies were without major findings and 103 was taken into clinical trials.

Central control of thermogenesis

In mammals and birds, conservation of body heat at around 37 °C is vital to life. Thermogenesis is the production of this heat which can be obligatory, as in basal metabolic rate, or it can be facultative such as the response to cold. A complex regulatory system has evolved which senses environmental or core temperature and integrates this information in hypothalamic regions such as the preoptic area and dorsomedial hypothalamus. These areas then send the appropriate signals to generate and conserve heat (or dissipate it). In this review, the importance of the sympathetic nervous system is discussed in relation to its role in basal metabolic rate and adaptive thermogenesis with a particular emphasis to human obesity. The efferent sympathetic pathway does not uniformly act on all tissues; different tissues can receive different levels of sympathetic drive at the same time. This is an important concept in the discussion of the pharmacotherapy of obesity. Despite decades of work the medicine chest contains only one pill for the long term treatment of obesity, orlistat, a lipase inhibitor that prevents the absorption of lipid from the gut and is itself not systemically absorbed. The central controlling system for thermogenesis has many potential intervention points. Several drugs, previously marketed, awaiting approval or in the earlier stages of development may have a thermogenic effect via activation of the sympathetic nervous system at some point in the thermoregulatory circuit and are discussed in this review. If the balance is weighted to the "wrong" side there is the burden of increased cardiovascular risk while a shift to the "right" side, if possible, will afford a thermogenic benefit that is conducive to weight loss maintenance. This article is part of a Special Issue entitled 'Central Control Food Intake'