Neil Derek Miller

Procognitive 5-HT6 antagonists in the rat forced swimming test: potential therapeutic utility in mood disorders associated with Alzheimer's disease.

AIMS 5-HT(6) receptor subtype is predominantly expressed in the brain, and preclinical evidence suggests its potential role in the cognitive function. Brain microdialysis studies demonstrated that 5-HT(6) antagonists enhance not only cholinergic but also monoaminergic neurotransmission, a property that may differentiate from acetylcholine esterase (AChE) inhibitors such as donepezil. In this study we compared the antidepressant-like effects of 5-HT(6) antagonists with donepezil to determine whether their different effects on monoamines are behaviorally relevant. MAIN METHODS Selective 5-HT(6) antagonists (SB-399885 and SB-271046) and donepezil were evaluated in the rat forced swimming test since this is known to identify drugs such as antidepressants which can increase brain monoamine levels. Binding assay was undertaken by using [(125)I]SB-258585 to measure brain 5-HT(6) receptor occupancy. KEY FINDINGS Systemic administration of SB-399885 (3 and 10 mg/kg, i.p.) and SB-271046 (10 and 30 mg/kg, i.p.) produced a significant reduction of immobility time in the rat forced swimming test with a similar profile in terms of 5-HT(6) receptor occupancy (62 and 96% for 3 and 10 mg/kg SB-399885 respectively; 56 and 84% for 10 and 30 mg/kg SB-271046 respectively). In contrast, donepezil (0.5 and 1 mg/kg i.p.) did not show any effects in this model. SIGNIFICANCE These data suggest that 5-HT(6) antagonists, at doses corresponding to those occupy central 5-HT(6) receptors, could have an antidepressive effect in humans. This may differentiate 5-HT(6) antagonists from AChE inhibitors with respect to the mood control in the symptomatic treatment of Alzheimers disease.

Structure–activity relationship investigations of a potent and selective benzodiazepine oxytocin antagonist

We have investigated the structure-activity relationships of the 1- and 3-substituents and replacements of the 5-phenyl group of GW405212X 1, a potent selective oxytocin antagonist. The effect of these modifications on oxytocin binding antagonism and on pharmacokinetic parameters is reported.

Discovery of GSK2795039, a Novel Small Molecule NADPH Oxidase 2 Inhibitor.

AIMS The NADPH oxidase (NOX) family of enzymes catalyzes the formation of reactive oxygen species (ROS). NOX enzymes not only have a key role in a variety of physiological processes but also contribute to oxidative stress in certain disease states. To date, while numerous small molecule inhibitors have been reported (in particular for NOX2), none have demonstrated inhibitory activity in vivo. As such, there is a need for the identification of improved NOX inhibitors to enable further evaluation of the biological functions of NOX enzymes in vivo as well as the therapeutic potential of NOX inhibition. In this study, both the in vitro and in vivo pharmacological profiles of GSK2795039, a novel NOX2 inhibitor, were characterized in comparison with other published NOX inhibitors. RESULTS GSK2795039 inhibited both the formation of ROS and the utilization of the enzyme substrates, NADPH and oxygen, in a variety of semirecombinant cell-free and cell-based NOX2 assays. It inhibited NOX2 in an NADPH competitive manner and was selective over other NOX isoforms, xanthine oxidase, and endothelial nitric oxide synthase enzymes. Following systemic administration in mice, GSK2795039 abolished the production of ROS by activated NOX2 enzyme in a paw inflammation model. Furthermore, GSK2795039 showed activity in a murine model of acute pancreatitis, reducing the levels of serum amylase triggered by systemic injection of cerulein. INNOVATION AND CONCLUSIONS GSK2795039 is a novel NOX2 inhibitor that is the first small molecule to demonstrate inhibition of the NOX2 enzyme in vivo.

Novel adenosine A2A receptor ligands: A synthetic, functional and computational investigation of selected literature adenosine A2A receptor antagonists for extending into extracellular space

Growing evidence has suggested a role in targeting the adenosine A2A receptor for the treatment of Parkinsons disease. The literature compounds KW 6002 (2) and ZM 241385 (5) were used as a starting point from which a series of novel ligands targeting the adenosine A2A receptor were synthesized and tested in a recombinant human adenosine A2A receptor functional assay. In order to further explore these molecules, we investigated the biological effects of assorted linkers attached to different positions on selected adenosine A2A receptor antagonists, and assessed their potential binding modes using molecular docking studies. The results suggest that linking from the phenolic oxygen of selected adenosine A2A receptor antagonists is relatively well tolerated due to the extension towards extracellular space, and leads to the potential of attaching further functionality from this position.

Investigation of novel ropinirole analogues: synthesis, pharmacological evaluation and computational analysis of dopamine D2 receptor functionalized congeners and homobivalent ligands

Herein, we report the development of novel functionalized congeners of ropinirole toward the design of pharmacological tools to probe structural requirements at the dopamine D2 receptor. Subsequently, we have used the functionalized amine congener 11 and synthesized and pharmacologically evaluated a series of homobivalent ligands of ropinirole with designated spacer lengths ranging from 14 to 30 atoms. The most potent homobivalent ligands (22-, 26- and 30-atom spacers) showed approximately 20- to 80-fold greater potency (EC50 = 3.9, 6.2 and 14 nM, respectively) than ropinirole (304 nM) in a [35S]GTPγS functional assay. Molecular modeling studies suggest that the observed increase in potency of the homobivalent ligands is possibly due to a bitopic binding mode involving the orthosteric site and an allosteric interaction at the dopamine D2 receptor protomer rather than bridging interactions at two orthosteric sites across a dopamine D2 receptor dimer. This research has the potential to advance the development of structurally related bitopic ligands, biomarkers such as radioligands and fluorescently labeled probes, and furnish new homo- and heterobivalent ligands towards a better understanding of the dopamine D2 receptor and potential novel treatment for Parkinsons disease.

Synthesis, molecular structure, NMR spectroscopic and computational analysis of a selective adenosine A2A antagonist, ZM 241385

Herein, we describe the synthesis of the adenosine A2A antagonist ZM 241385 (9) starting from commercially available 2-furanhydrazide (1) and including a comprehensive structural characterization of all the intermediates and the final product. In addition, extensive NMR analysis, including temperature and concentration-dependent experiments, are reported as well as the first single-crystal structure of the compound ZM 241385 (9) as the trihydrate. Furthermore, an extensive structural comparison of the single-crystal structure with the published protein bound X-ray structures is reported.

P4-319: 5-HT6 receptor antagonists modulate brain monoaminergic neurotransmission: Different mode of action from acetylcholinesterase (AchE) inhibitors

Background: 5-HT6 receptors are predominantly expressed in a variety of brain regions (e.g. striatum and hippocampus) associated with cognitive processing. Targeting 5-HT6 receptors with synthetic antagonists is a promising strategy for the treatment of cognitive symptoms associated with Alzheimer’s disease. Preclinical microdialysis studies have demonstrated that both 5-HT6 antagonists and the gold-standard AchE inhibitor, Donepezil enhance cholinergic neurotransmission; the proposed mechanism of action for the cognition-enhancing properties. 5-HT6 antagonists have also been shown to enhance monoaminergic neurotransmission, a property which may differentiate 5-HT6 antagonists from Donepezil in terms of its mechanism of action. Methods: In the present study, the 5-HT6-selective antagonists SB-399885 and SB-271046 were evaluated in the rat forced swimming test (FST) in comparison with Donepezil to determine whether this different mode of action on monoamines is behaviorally relevant (FST is known to identify drugs such as antidepressants which can increase brain extracellular monoamine levels). The doses of 5-HT6 antagonist and Donepezil were based on ex-vivo binding and cognition assay data. Results: Intraperitoneal (ip) injection of SB-399885 at doses of 3 and 10 mg/kg significantly reduced the immobility time of rats by 27 and 21 % respectively compared with the vehicle-treated group. Similarly, SB-271046 (10 and 30 mg/kg ip) reduced the immobility time by 27 and 29 %. In contrast, Donepezil (0.5 and 1 mg/kg ip) did not show any effect in this model. Conclusions: Therefore, these data suggest that the effect of 5-HT6 antagonists on monoaminergic neurotransmission is behaviorally relevant. The contrasting effects on brain neurochemistry may discriminate 5-HT6 antagonists from AchE inhibitors such as Donepezil with respect to the mood control in the symptomatic treatment of Alzheimer’s disease.

Tandem cobalt mediated rearrangement and Pauson–Khand reaction for the synthesis of functionalised polycyclic systems

The cobalt mediated rearrangement of enol ether complex 2 furnishes cyclic ketone 6, which undergoes an intramolecular Pauson-Khand reaction allowing access to functionalized polycyclic systems.