Publications by authors named "Karl R Gibson"

Class B G-protein-coupled receptors (GPCRs) remain an underexploited target for drug development. The calcitonin receptor (CTR) family is particularly challenging, as its receptors are heteromers comprising two distinct components: the calcitonin receptor-like receptor (CLR) or calcitonin receptor (CTR) together with one of three accessory proteins known as receptor activity-modifying proteins (RAMPs). CLR/RAMP1 forms a CGRP receptor, CLR/RAMP2 forms an adrenomedullin-1 (AM) receptor, and CLR/RAMP3 forms an adrenomedullin-2 (AM) receptor.

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DNA damage repair (DDR) mechanisms have been implicated in a number of neurodegenerative diseases (both genetically determined and sporadic). Consistent with this, recent genome-wide association studies in Huntington's disease (HD) and other trinucleotide repeat expansion diseases have highlighted genes involved in DDR mechanisms as modifiers for age of onset, rate of progression and somatic instability. At least some clinical genetic modifiers have been shown to have a role in modulating trinucleotide repeat expansion biology and could therefore provide new disease-modifying therapeutic targets.

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The hormone adrenomedullin has both physiological and pathological roles in biology. As a potent vasodilator, adrenomedullin is critically important in the regulation of blood pressure, but it also has several roles in disease, of which its actions in cancer are becoming recognized to have clinical importance. Reduced circulating adrenomedullin causes increased blood pressure but also reduces tumor progression, so drugs blocking all effects of adrenomedullin would be unacceptable clinically.

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The design, optimization, and evaluation of a series of novel imidazopyridazine-based subtype-selective positive allosteric modulators (PAMs) for the GABA ligand-gated ion channel are described. From a set of initial hits multiple subseries were designed and evaluated based on binding affinity and functional activity. As designing in the desired level of functional selectivity proved difficult, a probability-based assessment was performed to focus the project's efforts on a single subseries that had the greatest odds of delivering the target profile.

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Introduction: Few treatments are available for men with premature ejaculation (PE); oxytocin (OT) receptor antagonism in the central nervous system (CNS) is a potential new approach.

Aim: To determine if cligosiban selectively inhibits human OT receptors, penetrates the CNS, shows pharmacology in the CNS, and effects ejaculatory physiology in pre-clinical systems.

Methods: Experiments complied with United Kingdom legislation and were subject to local ethical review.

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The neurotrophin family of growth factors, comprised of nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), neurotrophin 3 (NT3), and neurotrophin 4 (NT4), is implicated in the physiology of chronic pain. Given the clinical efficacy of anti-NGF monoclonal antibody (mAb) therapies, there is significant interest in the development of small molecule modulators of neurotrophin activity. Neurotrophins signal through the tropomyosin related kinase (Trk) family of tyrosine kinase receptors, hence Trk kinase inhibition represents a potentially "druggable" point of intervention.

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Deubiquitinating enzymes play an important role in a plethora of therapeutically relevant processes and are emerging as pioneering drug targets. Herein, we present a novel probe, Ubiquitin Specific Protease (USP) inhibitor, alongside an alkyne-tagged activity-based probe analogue. Activity-based proteome profiling identified 12 USPs, including USP4, USP16, and USP33, as inhibitor targets using submicromolar probe concentrations.

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Visceral leishmaniasis is a severe parasitic disease that is one of the most neglected tropical diseases. Treatment options are limited, and there is an urgent need for new therapeutic agents. Following an HTS campaign and hit optimization, a novel series of amino-pyrazole ureas has been identified with potent in vitro antileishmanial activity.

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Voltage-gated sodium channels, in particular Nav1.8, can be targeted for the treatment of neuropathic and inflammatory pain. Herein, we described the optimization of Nav1.

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Drug discovery faces economic and scientific imperatives to deliver lead molecules rapidly and efficiently. Using traditional paradigms the molecular design, synthesis, and screening loops enforce a significant time delay leading to inefficient use of data in the iterative molecular design process. Here, we report the application of a flow technology platform integrating the key elements of structure-activity relationship (SAR) generation to the discovery of novel Abl kinase inhibitors.

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There is considerable ongoing investment in the research and development of selective progesterone receptor (PR) modulators for the treatment of gynecological conditions such as endometriosis. Here, we provide the first report on the clinical evaluation of a nonsteroidal progesterone receptor antagonist 4-[3-cyclopropyl-1-(mesylmethyl)-5-methyl-1H-pyrazol-4-yl]oxy,-2,6-dimethylbenzonitrile (PF-02413873) in healthy female subjects. In in vitro assays, PF-02413873 behaved as a selective and fully competitive PR antagonist, blocking progesterone binding and PR nuclear translocation.

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The recently discovered selective nonsteroidal progesterone receptor (PR) antagonist 4-[3-cyclopropyl-1-(methylsulfonylmethyl)-5-methyl-1H-pyrazol-4-yl]oxy-2,6-dimethylbenzonitrile (PF-02413873) was characterized in metabolism studies in vitro, in preclinical pharmacokinetics in rat and dog, and in an initial pharmacokinetic study in human volunteers. Clearance (CL) of PF-02413873 was found to be high in rat (84 ml · min(-1) · kg(-1)) and low in dog (3.8 ml · min(-1) · kg(-1)), consistent with metabolic stability determined in liver microsomes and hepatocytes in these species.

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The SAR of a series of novel pyrido[3,4-d]pyramid-4-ylamine mGluR1 antagonists is described. The multiple of the unbound K(i) in cerebrospinal fluid necessary to give morphine like analgesic effects in an electromyograph pinch model in rodents is determined and the effect of structure on CNS penetration examined.

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An asymmetric total synthesis of (+)-cis-sylvaticin is described. Key steps include the use of permanganate-mediated oxidative cyclization of 1,5-dienes to synthesize the two major fragments 2 and 3 and a catalytically efficient tethered RCM to unite these THF-containing fragments. In addition, t-BuP 4 base was found to reliably promote rapid alkylation of the butenolide precursor fragment 4.

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Previously, chemistry effort on the gem-cyclohexane series of gamma-secretase inhibitors has focused on the 4-position of the cyclohexane ring. Recently chemistry has been directed towards the 3-position and substitution here has also provided compounds with high gamma-secretase activity.

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Stereocontrolled syntheses of the C16-C28 CD-spiroacetal subunit of altohyrtin A/spongistatin 1 , relying on kinetic and thermodynamic control of the spiroacetal formation, are described. The kinetic control approach resulted in a slight preference (60 : 40) for the desired spiroacetal isomer. The thermodynamic approach allowed ready access to the desired spiroacetal by acid-promoted equilibration, chromatographic separation of the C23 epimers and resubjection of the undesired isomer to the equilibration conditions.

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A series of tricyclic pyridones has been evaluated as benzodiazepine site ligands with functional selectivity for the alpha(3) over the alpha(1) containing subtype of the human GABA(A) receptor ion channel. This investigation led to the identification of a high affinity, functionally selective, orally bioavailable benzodiazepine site ligand that demonstrated activity in rodent anxiolysis models and reduced sedation relative to diazepam.

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A new synthetic approach to tricyclic pyridones bearing a fused seven-membered ring is described. These compounds exhibit atropisomerism and exist in enantiomeric forms. Chiral HPLC separation of the enantiomers has allowed the rates of racemization to be measured and hence the free energy barrier for flipping the seven-membered ring to be deduced.

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As an exceptionally potent antimitotic macrolide, altohyrtin A/spongistatin 1 shows great promise in cancer chemotherapy but its extreme scarcity in the natural sponges has halted its further preclinical development. A highly stereocontrolled total synthesis, which exploits boron-mediated aldol bond constructions, has been realized to provide, for the first time, a useful amount of synthetic material.

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