Publications by authors named "Sonya G Lehto"

30 Publications

  • Page 1 of 1

Discovery of Selective Pituitary Adenylate Cyclase 1 Receptor (PAC1R) Antagonist Peptides Potent in a Maxadilan/PACAP38-Induced Increase in Blood Flow Pharmacodynamic Model.

J Med Chem 2021 Mar 15;64(6):3427-3438. Epub 2021 Mar 15.

Therapeutic Discovery, Amgen Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States.

Inhibition of the pituitary adenylate cyclase 1 receptor (PAC1R) is a novel mechanism that could be used for abortive treatment of acute migraine. Our research began with comparative analysis of known PAC1R ligand scaffolds, PACAP38 and Maxadilan, which resulted in the selection of des(24-42) Maxadilan, , as a starting point. C-terminal modifications of improved the peptide metabolic stability and . SAR investigations identified synergistic combinations of amino acid replacements that significantly increased the PAC1R inhibitory activity of the analogs to the pM IC range. Our modifications further enabled deletion of up to six residues without impacting potency, thus improving peptide ligand binding efficiency. Analogs and exhibited robust efficacy in the rat Maxadilan-induced increase in blood flow (MIIBF) pharmacodynamic model at 0.3 mg/kg subcutaneous dosing. The first cocrystal structure of a PAC1R antagonist peptide () with PAC1R extracellular domain is reported.
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http://dx.doi.org/10.1021/acs.jmedchem.0c01396DOI Listing
March 2021

Discovery of TRPM8 Antagonist ( S)-6-(((3-Fluoro-4-(trifluoromethoxy)phenyl)(3-fluoropyridin-2-yl)methyl)carbamoyl)nicotinic Acid (AMG 333), a Clinical Candidate for the Treatment of Migraine.

J Med Chem 2018 09 10;61(18):8186-8201. Epub 2018 Sep 10.

Transient-receptor-potential melastatin 8 (TRPM8), the predominant mammalian cold-temperature thermosensor, is a nonselective cation channel expressed in a subpopulation of sensory neurons in the peripheral nervous system, including nerve circuitry implicated in migraine pathogenesis: the trigeminal and pterygopalatine ganglia. Genomewide association studies have identified an association between TRPM8 and reduced risk of migraine. This disclosure focuses on medicinal-chemistry efforts to improve the druglike properties of initial leads, particularly removal of CYP3A4-induction liability and improvement of pharmacokinetic properties. A novel series of biarylmethanamide TRPM8 antagonists was developed, and a subset of leads were evaluated in preclinical toxicology studies to identify a clinical candidate with an acceptable preclinical safety profile leading to clinical candidate AMG 333, a potent and highly selective antagonist of TRPM8 that was evaluated in human clinical trials.
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http://dx.doi.org/10.1021/acs.jmedchem.8b00518DOI Listing
September 2018

Pharmacologic Characterization of AMG8379, a Potent and Selective Small Molecule Sulfonamide Antagonist of the Voltage-Gated Sodium Channel Na1.7.

J Pharmacol Exp Ther 2017 07 4;362(1):146-160. Epub 2017 May 4.

Department of Neuroscience (T.J.K., R.Y., S.A, C.P.I., M.J., D.J., J.H.L., S.G.L., J.Li., D.L., J.Lu., D.M., D.O., K.T., J.W., V.Y., D.X.D.Z., R.T.F., B.D.M.), Department of Medicinal Chemistry (M.M.W.), and Department of Pharmacokinetics and Drug Metabolism (X.B., V.B., J.R.), Amgen Inc., Cambridge, Massachusetts and Thousand Oaks, California

Potent and selective antagonists of the voltage-gated sodium channel Na1.7 represent a promising avenue for the development of new chronic pain therapies. We generated a small molecule atropisomer quinolone sulfonamide antagonist AMG8379 and a less active enantiomer AMG8380. Here we show that AMG8379 potently blocks human Na1.7 channels with an IC of 8.5 nM and endogenous tetrodotoxin (TTX)-sensitive sodium channels in dorsal root ganglion (DRG) neurons with an IC of 3.1 nM in whole-cell patch clamp electrophysiology assays using a voltage protocol that interrogates channels in a partially inactivated state. AMG8379 was 100- to 1000-fold selective over other Na family members, including Na1.4 expressed in muscle and Na1.5 expressed in the heart, as well as TTX-resistant Na channels in DRG neurons. Using an ex vivo mouse skin-nerve preparation, AMG8379 blocked mechanically induced action potential firing in C-fibers in both a time-dependent and dose-dependent manner. AMG8379 similarly reduced the frequency of thermally induced C-fiber spiking, whereas AMG8380 affected neither mechanical nor thermal responses. In vivo target engagement of AMG8379 in mice was evaluated in multiple Na1.7-dependent behavioral endpoints. AMG8379 dose-dependently inhibited intradermal histamine-induced scratching and intraplantar capsaicin-induced licking, and reversed UVB radiation skin burn-induced thermal hyperalgesia; notably, behavioral effects were not observed with AMG8380 at similar plasma exposure levels. AMG8379 is a potent and selective Na1.7 inhibitor that blocks sodium current in heterologous cells as well as DRG neurons, inhibits action potential firing in peripheral nerve fibers, and exhibits pharmacodynamic effects in translatable models of both itch and pain.
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http://dx.doi.org/10.1124/jpet.116.239590DOI Listing
July 2017

Development of TRPM8 Antagonists to Treat Chronic Pain and Migraine.

Pharmaceuticals (Basel) 2017 Mar 30;10(2). Epub 2017 Mar 30.

One Amgen Center Dr, Thousand Oaks, CA 91320, USA.

A review. Development of pharmaceutical antagonists of transient receptor potential melastatin 8 (TRPM8) have been pursued for the treatment of chronic pain and migraine. This review focuses on the current state of this progress.
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http://dx.doi.org/10.3390/ph10020037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5490394PMC
March 2017

The Discovery and Hit-to-Lead Optimization of Tricyclic Sulfonamides as Potent and Efficacious Potentiators of Glycine Receptors.

J Med Chem 2017 02 21;60(3):1105-1125. Epub 2016 Dec 21.

Department of Neuroscience, Amgen Inc. , One Amgen Center Drive, Thousand Oaks, California 91320, United States.

Current pain therapeutics suffer from undesirable psychotropic and sedative side effects, as well as abuse potential. Glycine receptors (GlyRs) are inhibitory ligand-gated ion channels expressed in nerves of the spinal dorsal horn, where their activation is believed to reduce transmission of painful stimuli. Herein, we describe the identification and hit-to-lead optimization of a novel class of tricyclic sulfonamides as allosteric GlyR potentiators. Initial optimization of high-throughput screening (HTS) hit 1 led to the identification of 3, which demonstrated ex vivo potentiation of glycine-activated current in mouse dorsal horn neurons from spinal cord slices. Further improvement of potency and pharmacokinetics produced in vivo proof-of-concept tool molecule 20 (AM-1488), which reversed tactile allodynia in a mouse spared-nerve injury (SNI) model. Additional structural optimization provided highly potent potentiator 32 (AM-3607), which was cocrystallized with human GlyRα3 to afford the first described potentiator-bound X-ray cocrystal structure within this class of ligand-gated ion channels (LGICs).
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http://dx.doi.org/10.1021/acs.jmedchem.6b01496DOI Listing
February 2017

Crystal structures of human glycine receptor α3 bound to a novel class of analgesic potentiators.

Nat Struct Mol Biol 2017 02 19;24(2):108-113. Epub 2016 Dec 19.

Department of Neuroscience, Amgen Inc., Cambridge, Massachusetts, USA.

Current therapies to treat persistent pain and neuropathic pain are limited by poor efficacy, side effects and risk of addiction. Here, we present a novel class of potent selective, central nervous system (CNS)-penetrant potentiators of glycine receptors (GlyRs), ligand-gated ion channels expressed in the CNS. AM-1488 increased the response to exogenous glycine in mouse spinal cord and significantly reversed mechanical allodynia induced by nerve injury in a mouse model of neuropathic pain. We obtained an X-ray crystal structure of human homopentameric GlyRα3 in complex with AM-3607, a potentiator of the same class with increased potency, and the agonist glycine, at 2.6-Å resolution. AM-3607 binds a novel allosteric site between subunits, which is adjacent to the orthosteric site where glycine binds. Our results provide new insights into the potentiation of cysteine-loop receptors by positive allosteric modulators and hold promise in structure-based design of GlyR modulators for the treatment of neuropathic pain.
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http://dx.doi.org/10.1038/nsmb.3329DOI Listing
February 2017

Selective antagonism of TRPA1 produces limited efficacy in models of inflammatory- and neuropathic-induced mechanical hypersensitivity in rats.

Mol Pain 2016 29;12. Epub 2016 Nov 29.

Department of Neuroscience, Amgen Inc, Thousand Oaks, CA, USA.

The transient receptor potential ankyrin 1 (TRPA1) channel has been implicated in pathophysiological processes that include asthma, cough, and inflammatory pain. Agonists of TRPA1 such as mustard oil and its key component allyl isothiocyanate (AITC) cause pain and neurogenic inflammation in humans and rodents, and TRPA1 antagonists have been reported to be effective in rodent models of pain. In our pursuit of TRPA1 antagonists as potential therapeutics, we generated AMG0902, a potent (IC of 300 nM against rat TRPA1), selective, brain penetrant (brain to plasma ratio of 0.2), and orally bioavailable small molecule TRPA1 antagonist. AMG0902 reduced mechanically evoked C-fiber action potential firing in a skin-nerve preparation from mice previously injected with complete Freund's adjuvant, supporting the role of TRPA1 in inflammatory mechanosensation. In vivo target coverage of TRPA1 by AMG0902 was demonstrated by the prevention of AITC-induced flinching/licking in rats. However, oral administration of AMG0902 to rats resulted in little to no efficacy in models of inflammatory, mechanically evoked hypersensitivity; and no efficacy was observed in a neuropathic pain model. Unbound plasma concentrations achieved in pain models were about 4-fold higher than the IC concentration in the AITC target coverage model, suggesting that either greater target coverage is required for efficacy in the pain models studied or TRPA1 may not contribute significantly to the underlying mechanisms.
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http://dx.doi.org/10.1177/1744806916677761DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5131813PMC
October 2017

Optimization of a Novel Quinazolinone-Based Series of Transient Receptor Potential A1 (TRPA1) Antagonists Demonstrating Potent in Vivo Activity.

J Med Chem 2016 Mar 4;59(6):2794-809. Epub 2016 Mar 4.

Departments of Medicinal Chemistry, ‡Lead Discovery, §Molecular Structure, and ∥Pharmacokinetics and Drug Metabolism, Amgen, Inc. , 360 Binney Street, Cambridge, Massachusetts 02142, United States.

There has been significant interest in developing a transient receptor potential A1 (TRPA1) antagonist for the treatment of pain due to a wealth of data implicating its role in pain pathways. Despite this, identification of a potent small molecule tool possessing pharmacokinetic properties allowing for robust in vivo target coverage has been challenging. Here we describe the optimization of a potent, selective series of quinazolinone-based TRPA1 antagonists. High-throughput screening identified 4, which possessed promising potency and selectivity. A strategy focused on optimizing potency while increasing polarity in order to improve intrinsic clearance culminated with the discovery of purinone 27 (AM-0902), which is a potent, selective antagonist of TRPA1 with pharmacokinetic properties allowing for >30-fold coverage of the rat TRPA1 IC50 in vivo. Compound 27 demonstrated dose-dependent inhibition of AITC-induced flinching in rats, validating its utility as a tool for interrogating the role of TRPA1 in in vivo pain models.
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http://dx.doi.org/10.1021/acs.jmedchem.6b00039DOI Listing
March 2016

Pharmacologic Characterization of AMG 334, a Potent and Selective Human Monoclonal Antibody against the Calcitonin Gene-Related Peptide Receptor.

J Pharmacol Exp Ther 2016 Jan 11;356(1):223-31. Epub 2015 Nov 11.

Department of Neuroscience (L.S., S.G.L., D.X.D.Z., H.S., J.Z., D.C.I., K.D.W., C.X.), Department of Global Biostatistical Science (B.P.S.), Amgen Inc., Thousand Oaks, California

Therapeutic agents that block the calcitonin gene-related peptide (CGRP) signaling pathway are a highly anticipated and promising new drug class for migraine therapy, especially after reports that small-molecule CGRP-receptor antagonists are efficacious for both acute migraine treatment and migraine prevention. Using XenoMouse technology, we successfully generated AMG 334, a fully human monoclonal antibody against the CGRP receptor. Here we show that AMG 334 competes with [(125)I]-CGRP binding to the human CGRP receptor, with a Ki of 0.02 nM. AMG 334 fully inhibited CGRP-stimulated cAMP production with an IC50 of 2.3 nM in cell-based functional assays (human CGRP receptor) and was 5000-fold more selective for the CGRP receptor than other human calcitonin family receptors, including adrenomedullin, calcitonin, and amylin receptors. The potency of AMG 334 at the cynomolgus monkey (cyno) CGRP receptor was similar to that at the human receptor, with an IC50 of 5.7 nM, but its potency at dog, rabbit, and rat receptors was significantly reduced (>5000-fold). Therefore, in vivo target coverage of AMG 334 was assessed in cynos using the capsaicin-induced increase in dermal blood flow model. AMG 334 dose-dependently prevented capsaicin-induced increases in dermal blood flow on days 2 and 4 postdosing. These results indicate AMG 334 is a potent, selective, full antagonist of the CGRP receptor and show in vivo dose-dependent target coverage in cynos. AMG 334 is currently in clinical development for the prevention of migraine.
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http://dx.doi.org/10.1124/jpet.115.227793DOI Listing
January 2016

AMG2850, a potent and selective TRPM8 antagonist, is not effective in rat models of inflammatory mechanical hypersensitivity and neuropathic tactile allodynia.

Naunyn Schmiedebergs Arch Pharmacol 2015 Apr 10;388(4):465-76. Epub 2015 Feb 10.

Department of Neuroscience, Amgen Inc, One Amgen Center Dr, Thousand Oaks, CA, 91320-1799, USA,

TRPM8 has been implicated in pain and migraine based on dorsal root- and trigeminal ganglion-enriched expression, upregulation in preclinical models of pain, knockout mouse studies, and human genetics. Here, we evaluated the therapeutic potential in pain of AMG2850 ((R)-8-(4-(trifluoromethyl)phenyl)-N-((S)-1,1,1-trifluoropropan-2-yl)-5,6-dihydro-1,7-naphthyridine-7(8H)-carboxamide), a small molecule antagonist of TRPM8 by in vitro and in vivo characterization. AMG2850 is potent in vitro at rat TRPM8 (IC90 against icilin activation of 204 ± 28 nM), highly selective (>100-fold IC90 over TRPV1 and TRPA1 channels), and orally bioavailable (F po > 40 %). When tested in a skin-nerve preparation, AMG2850 blocked menthol-induced action potentials but not mechanical activation in C fibers. AMG2850 exhibited significant target coverage in vivo in a TRPM8-mediated icilin-induced wet-dog shake (WDS) model in rats (at 10 mg/kg p.o.). However, AMG2850 did not produce a significant therapeutic effect in rat models of inflammatory mechanical hypersensitivity or neuropathic tactile allodynia at doses up to 100 mg/kg. The lack of efficacy suggests that either TRPM8 does not play a role in mediating pain in these models or that a higher level of target coverage is required. The potential of TRPM8 antagonists as migraine therapeutics is yet to be determined.
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http://dx.doi.org/10.1007/s00210-015-1090-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4359714PMC
April 2015

Voltage-gated sodium channel function and expression in injured and uninjured rat dorsal root ganglia neurons.

Int J Neurosci 2016 7;126(2):182-92. Epub 2015 Apr 7.

a Department of Neuroscience, Amgen Inc. , Thousand Oaks, CA, USA.

The nine members of the voltage-gated sodium channel (Nav) family mediate inward sodium currents that depolarize neurons and lead to action potential firing. Increased Nav expression and function in sensory ganglia may drive ectopic action potentials and result in neuropathic pain. Using patch-clamp electrophysiology and molecular biology techniques, experiments were performed to elucidate the contribution of Nav channels to sodium currents in rat dorsal root ganglion (DRG) neurons following the L5/L6 spinal nerve ligation (SNL) model of neuropathic pain. The abundance of DRG neurons with fast, tetrodotoxin sensitive (TTX-S) currents was seven-fold higher whereas the abundance of DRG neurons with slow, tetrodotoxin resistant (TTX-R) currents was nearly thirty-fold lower when comparing ipsilateral (injured) to contralateral (uninjured) neurons. TTX-S currents were elevated in larger neurons while TTX-R currents were reduced in both small and large neurons. Among Nav transcripts encoding TTX-R channels, Scn10a (Nav1.8) and Scn11a (Nav1.9) expression was twenty- to thirty-fold lower, while among Nav transcripts encoding TTX-S channels, Scn3a (Nav1.3) expression was four-fold higher in injured compared to uninjured DRG by qRT-PCR analysis. In summary, the SNL model of neuropathic pain induced a phenotypic switch in Nav expression from TTX-R to TTX-S channels in injured DRG neurons. Transcriptional reprogramming of Nav genes may drive ectopic action potential firing and contribute to neuropathic pain.
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http://dx.doi.org/10.3109/00207454.2015.1004172DOI Listing
September 2016

Development of novel azabenzofuran TRPA1 antagonists as in vivo tools.

Bioorg Med Chem Lett 2014 Aug 6;24(15):3464-8. Epub 2014 Jun 6.

Department of Medicinal Chemistry, Amgen Inc., 360 Binney St., Cambridge, MA 02142, USA.

The transient receptor potential ankyrin 1 (TRPA1) channel is activated by noxious stimuli including chemical irritants and endogenous inflammatory mediators. Antagonists of this channel are currently being investigated for use as therapeutic agents for treating pain, airway disorders, and itch. A novel azabenzofuran series was developed that demonstrated in vitro inhibition of allyl isothiocyanate (AITC)-induced (45)Ca(2+) uptake with nanomolar potencies against both human and rat TRPA1. From this series, compound 10 demonstrated in vivo target coverage in an AITC-induced flinching model in rats while providing unbound plasma concentrations up to 16-fold higher than the TRPA1 rat IC50.
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http://dx.doi.org/10.1016/j.bmcl.2014.05.069DOI Listing
August 2014

Transient receptor potential channel ankyrin-1 is not a cold sensor for autonomic thermoregulation in rodents.

J Neurosci 2014 Mar;34(13):4445-52

Systemic Inflammation Laboratory (FeverLab), Trauma Research, St. Joseph's Hospital and Medical Center, Phoenix, Arizona 85013, Department of Pathophysiology and Gerontology, Medical School, University of Pecs, Pecs, H-7624, Hungary, Department of Neuroscience, Amgen Inc., Thousand Oaks, California 91320, Department of Pharmacology and Pharmacotherapy, Medical School, University of Pecs, Pecs, H-7624, Hungary, Janos Szentagothai Research Centre, University of Pecs, Pecs, H-7624, Hungary, and Neuroscience Research, Global Pharmaceutical Research and Development, AbbVie Inc., North Chicago, Illinois 60064.

The rodent transient receptor potential ankyrin-1 (TRPA1) channel has been hypothesized to serve as a temperature sensor for thermoregulation in the cold. We tested this hypothesis by using deletion of the Trpa1 gene in mice and pharmacological blockade of the TRPA1 channel in rats. In both Trpa1(-/-) and Trpa1(+/+) mice, severe cold exposure (8°C) resulted in decreases of skin and deep body temperatures to ∼8°C and 13°C, respectively, both temperatures being below the reported 17°C threshold temperature for TRPA1 activation. Under these conditions, Trpa1(-/-) mice had the same dynamics of body temperature as Trpa1(+/+) mice and showed no weakness in the tail skin vasoconstriction response or thermogenic response to cold. In rats, the effects of pharmacological blockade were studied by using two chemically unrelated TRPA1 antagonists: the highly potent and selective compound A967079, which had been characterized earlier, and the relatively new compound 43 ((4R)-1,2,3,4-tetrahydro-4-[3-(3-methoxypropoxy)phenyl]-2-thioxo-5H-indeno[1,2-d]pyrimidin-5-one), which we further characterized in the present study and found to be highly potent (IC50 against cold of ∼8 nm) and selective. Intragastric administration of either antagonist at 30 mg/kg before severe (3°C) cold exposure did not affect the thermoregulatory responses (deep body and tail skin temperatures) of rats, even though plasma concentrations of both antagonists well exceeded their IC50 value at the end of the experiment. In the same experimental setup, blocking the melastatin-8 (TRPM8) channel with AMG2850 (30 mg/kg) attenuated cold-defense mechanisms and led to hypothermia. We conclude that TRPA1 channels do not drive autonomic thermoregulatory responses to cold in rodents.
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http://dx.doi.org/10.1523/JNEUROSCI.5387-13.2014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3965775PMC
March 2014

Optimization of potency and pharmacokinetic properties of tetrahydroisoquinoline transient receptor potential melastatin 8 (TRPM8) antagonists.

J Med Chem 2014 Apr 19;57(7):2989-3004. Epub 2014 Mar 19.

Departments of Chemistry Research and Discovery, ‡Neuroscience, and §Pharmacokinetics and Drug Metabolism, Amgen Inc. , One Amgen Center Drive, Thousand Oaks, California 91320, United States.

Transient receptor potential melastatin 8 (TRPM8) is a nonselective cation channel expressed in a subpopulation of sensory neurons in the peripheral nervous system. TRPM8 is the predominant mammalian cold temperature thermosensor and is activated by cold temperatures ranging from 8 to 25 °C and cooling compounds such as menthol or icilin. TRPM8 antagonists are being pursued as potential therapeutics for treatment of pain and bladder disorders. This manuscript outlines new developments in the SAR of a lead series of 1,2,3,4-tetrahydroisoquinoline derivatives with emphasis on strategies to improve pharmacokinetic properties and potency. Selected compounds were profiled in two TRPM8 target-specific in vivo coverage models in rats (the icilin-induced wet dog shake model and the cold pressor test). Compound 45 demonstrated robust efficacy in both pharmacodynamic models with ED90 values <3 mg/kg.
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http://dx.doi.org/10.1021/jm401955hDOI Listing
April 2014

Transient receptor potential melastatin 8 (TRPM8) channels are involved in body temperature regulation.

Mol Pain 2012 May 9;8:36. Epub 2012 May 9.

Department of Neuroscience, Amgen, One Amgen Center Drive, Thousand Oaks, CA 91320, USA.

Background: Transient receptor potential cation channel subfamily M member 8 (TRPM8) is activated by cold temperature in vitro and has been demonstrated to act as a 'cold temperature sensor' in vivo. Although it is known that agonists of this 'cold temperature sensor', such as menthol and icilin, cause a transient increase in body temperature (Tb), it is not known if TRPM8 plays a role in Tb regulation. Since TRPM8 has been considered as a potential target for chronic pain therapeutics, we have investigated the role of TRPM8 in Tb regulation.

Results: We characterized five chemically distinct compounds (AMG0635, AMG2850, AMG8788, AMG9678, and Compound 496) as potent and selective antagonists of TRPM8 and tested their effects on Tb in rats and mice implanted with radiotelemetry probes. All five antagonists used in the study caused a transient decrease in Tb (maximum decrease of 0.98°C). Since thermoregulation is a homeostatic process that maintains Tb about 37°C, we further evaluated whether repeated administration of an antagonist attenuated the decrease in Tb. Indeed, repeated daily administration of AMG9678 for four consecutive days showed a reduction in the magnitude of the Tb decrease Day 2 onwards.

Conclusions: The data reported here demonstrate that TRPM8 channels play a role in Tb regulation. Further, a reduction of magnitude in Tb decrease after repeated dosing of an antagonist suggests that TRPM8's role in Tb maintenance may not pose an issue for developing TRPM8 antagonists as therapeutics.
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http://dx.doi.org/10.1186/1744-8069-8-36DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3489569PMC
May 2012

Fused piperidines as a novel class of potent and orally available transient receptor potential melastatin type 8 (TRPM8) antagonists.

J Med Chem 2012 Feb 13;55(4):1593-611. Epub 2012 Feb 13.

Department of Chemistry Research and Discovery, Amgen Inc., One Amgen Center Drive, Thousand Oaks, California 91320-1799, United States.

The transient receptor potential melastatin type 8 (TRPM8) is a nonselective cation channel primarily expressed in a subpopulation of sensory neurons that can be activated by a wide range of stimuli, including menthol, icilin, and cold temperatures (<25 °C). Antagonism of TRPM8 is currently under investigation as a new approach for the treatment of pain. As a result of our screening efforts, we identified tetrahydrothienopyridine 4 as an inhibitor of icilin-induced calcium influx in CHO cells expressing recombinant rat TRPM8. Exploration of the structure-activity relationships of 4 led to the identification of a potent and orally bioavailable TRPM8 antagonist, tetrahydroisoquinoline 87. Compound 87 demonstrated target coverage in vivo after oral administration in a rat pharmacodynamic model measuring the prevention of icilin-induced wet-dog shakes (WDS).
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http://dx.doi.org/10.1021/jm2013634DOI Listing
February 2012

Chromenones as potent bradykinin B1 antagonists.

Bioorg Med Chem Lett 2012 Jan 28;22(1):619-22. Epub 2011 Oct 28.

Department of Chemistry Research and Discovery, Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA 91320, USA.

A series of fused 6,6-bicyclic chromenones was investigated for activity against the bradykinin B1 receptor. SAR studies based on a pharmacophore model revealed compounds with high affinity for both human and rabbit B1. These compounds demonstrated favorable pharmacokinetic properties and 5-chlorochromenone 15 was efficacious in a carrageenan-induced mechanical hyperalgesia model for chronic pain.
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http://dx.doi.org/10.1016/j.bmcl.2011.10.068DOI Listing
January 2012

Discovery of potent, orally bioavailable phthalazinone bradykinin B1 receptor antagonists.

J Med Chem 2011 Oct 26;54(20):7232-46. Epub 2011 Sep 26.

Department of Chemistry Research and Discovery, Amgen Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States.

The bradykinin B1 receptor is rapidly induced upon tissue injury and inflammation, stimulating the production of inflammatory mediators resulting in plasma extravasation, leukocyte trafficking, edema, and pain. We have previously reported on sulfonamide and sulfone-based B1 antagonists containing a privileged bicyclic amine moiety leading to potent series of 2-oxopiperazines. The suboptimal pharmacokinetics and physicochemical properties of the oxopiperazine sulfonamides led us to seek B1 antagonists with improved druglike properties. Using a pharmacophore model containing a bicyclic amine as anchor, we designed a series of amide antagonists with targeted physicochemical properties. This approach led to a novel series of potent phthalazinone B1 antagonists, where we successfully replaced a sulfonamide acceptor with a cyclic carbonyl unit. SAR studies revealed compounds with subnanomolar B1 binding affinity. These compounds demonstrate excellent cross-species PK properties with high oral bioavailability and potent activity in a rabbit biochemical challenge pharmacodynamic study.
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http://dx.doi.org/10.1021/jm200808vDOI Listing
October 2011

A review of current animal models of osteoarthritis pain.

Curr Pharm Biotechnol 2011 Oct;12(10):1596-612

Department of Neuroscience, Amgen, Inc, Thousand Oaks, CA 91320, USA.

Osteoarthritis (OA) is a complex disease plagued by a significant unmet need for treatment. To date, no disease- modifying OA drugs (DMOADs) exist and the available symptom-modifying OA drugs (SMOADs) have limitations. Although a complete understanding of the mechanisms of OA pain in humans is lacking, animal models have helped provide insight into the multifaceted origin and manifestation of OA pain. Success in discovering new therapeutics will likely require reliance on good animal models. This review summarizes the animal models available for studying pain associated with OA.
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http://dx.doi.org/10.2174/138920111798357320DOI Listing
October 2011

Pharmacological effects of nonselective and subtype-selective nicotinic acetylcholine receptor agonists in animal models of persistent pain.

Pain 2010 Apr 18;149(1):33-49. Epub 2010 Feb 18.

Department of Neuroscience, Amgen, Inc., 360 Binney Street, Cambridge MA 02142, USA Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks CA 91320, USA Department of Protein Sciences, Amgen, Inc., One Amgen Center Drive, Thousand Oaks CA 91320, USA Department of Lead Discovery, Amgen, Inc., Josef-Engert-St. 11, D-93053 Regensburg, Germany Department of Inflammation, Amgen, Inc., One Amgen Center Drive, Thousand Oaks CA 91320, USA Department of Pharmacokinetics and Drug Metabolism, Amgen, Inc., 360 Binney Street, Cambridge MA 02142, USA Department of Chemistry Research and Development, Amgen, Inc., 360 Binney Street, Cambridge MA 02142, USA.

Nicotinic acetylcholine receptors (nAChRs) are longstanding targets for a next generation of pain therapeutics, but the nAChR subtypes that govern analgesia remain unknown. We tested a series of nicotinic agonists, including many molecules used or tried clinically, on a panel of cloned neuronal nAChRs for potency and selectivity using patch-clamp electrophysiology and a live cell-based fluorescence assay. Nonselective nicotinic agonists as well as compounds selective either for alpha4beta2 or for alpha7 nAChRs were then tested in the formalin and complete Freund's adjuvant models of pain. Nonselective nAChR agonists ABT-594 and varenicline were effective analgesics. By contrast, the selective alpha4beta2 agonist ispronicline and a novel alpha4beta2-selective potentiator did not appear to produce analgesia in either model. alpha7-selective agonists reduced the pain-related endpoint, but the effect could be ascribed to nonspecific reduction of movement rather than to analgesia. Neither selective nor nonselective alpha7 nicotinic agonists affected the release of pro-inflammatory cytokines in response to antigen challenge. Electrophysiological recordings from spinal cord slice showed a strong nicotine-induced increase in inhibitory synaptic transmission that was mediated partially by alpha4beta2 and only minimally by alpha7 subtypes. Taken with previous studies, the results suggest that agonism of alpha4beta2 nAChRs is necessary but not sufficient to produce analgesia, and that the spinal cord is a key site where the molecular action of nAChRs produces analgesia.
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http://dx.doi.org/10.1016/j.pain.2010.01.007DOI Listing
April 2010

Antihyperalgesic effects of (R,E)-N-(2-hydroxy-2,3-dihydro-1H-inden-4-yl)-3-(2-(piperidin-1-yl)-4-(trifluoromethyl)phenyl)-acrylamide (AMG8562), a novel transient receptor potential vanilloid type 1 modulator that does not cause hyperthermia in rats.

J Pharmacol Exp Ther 2008 Jul 17;326(1):218-29. Epub 2008 Apr 17.

Department of Neuroscience, One Amgen Center Dr., Thousand Oaks, CA 91320-1799, USA.

Antagonists of the vanilloid receptor TRPV1 (transient receptor potential vanilloid type 1) have been reported to produce antihyperalgesic effects in animal models of pain. These antagonists, however, also caused concomitant hyperthermia in rodents, dogs, monkeys, and humans. Antagonist-induced hyperthermia was not observed in TRPV1 knockout mice, suggesting that the hyperthermic effect is exclusively mediated through TRPV1. Since antagonist-induced hyperthermia is considered a hurdle for developing TRPV1 antagonists as therapeutics, we investigated the possibility of eliminating hyperthermia while maintaining antihyperalgesia. Here, we report four potent and selective TRPV1 modulators with unique in vitro pharmacology profiles (profiles A through D) and their respective effects on body temperature. We found that profile C modulator, (R,E)-N-(2-hydroxy-2,3-dihydro-1H-inden-4-yl)-3-(2-(piperidin-1-yl)-4-(trifluoromethyl)phenyl)acrylamide (AMG8562), blocks capsaicin activation of TRPV1, does not affect heat activation of TRPV1, potentiates pH 5 activation of TRPV1 in vitro, and does not cause hyperthermia in vivo in rats. We further profiled AMG8562 in an on-target (agonist) challenge model, rodent pain models, and tested for its side effects. We show that AMG8562 significantly blocks capsaicin-induced flinching behavior, produces statistically significant efficacy in complete Freund's adjuvant- and skin incision-induced thermal hyperalgesia, and acetic acid-induced writhing models, with no profound effects on locomotor activity. Based on the data shown here, we conclude that it is feasible to modulate TRPV1 in a manner that does not cause hyperthermia while maintaining efficacy in rodent pain models.
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http://dx.doi.org/10.1124/jpet.107.132233DOI Listing
July 2008

Central pituitary adenylate cyclase 1 receptors modulate nociceptive behaviors in both inflammatory and neuropathic pain states.

J Pain 2008 May 12;9(5):449-56. Epub 2008 Mar 12.

Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois 60064, USA.

Unlabelled: The pituitary adenylate cyclase-activating polypeptide type 1 receptor (PAC(1)-R) is a member of the 7-transmembrane domain, group 2 G-protein coupled receptor family. PAC(1)-Rs modulate neurotransmission and neurotrophic actions and have been implicated in both pronociception and antinociception. To better understand the role of PAC(1)-Rs in pain, PACAP 6-38, a PAC(1)-R antagonist, was evaluated in several inflammatory and neuropathic pain models after intrathecal (i.t.) administration. PACAP 6-38 potently reduced mechanical allodynia in a neuropathic spinal nerve ligation model (77% +/- 15% maximal effect at 12 nmol, P < .01) and was also effective in reducing thermal hyperalgesia in the carrageenan model of inflammatory pain (89% +/- 17% maximal effect at 12 nmol, P < .01). Although nociceptive responses were also attenuated with PACAP 6-38 in a dose-dependent manner in models of chronic inflammatory and persistent pain, no effects on motor performance were observed at analgesic doses. Taken together, these data demonstrate that blockade of the PAC(1)-R/PACAP complex by PACAP 6-38 can effectively attenuate thermal hyperalgesia and mechanical allodynia associated with inflammatory and neuropathic pain states. These results further emphasize that at the level of the spinal cord, PAC(1)-R activation is pronociceptive.

Perspective: This article presents the analgesic profile generated by the blockade, at the spinal cord level, of the PAC-1 receptor by a potent peptide antagonist. This comprehensive data set demonstrates that if small molecule PAC-1 receptor antagonists could be identified, they would potentially produce broad-spectrum analgesia in both inflammatory and neuropathic pain states.
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http://dx.doi.org/10.1016/j.jpain.2008.01.329DOI Listing
May 2008

Analgesic activity of metabotropic glutamate receptor 1 antagonists on spontaneous post-operative pain in rats.

Eur J Pharmacol 2008 Feb 13;580(3):314-21. Epub 2007 Nov 13.

Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60064-3500, USA.

Activation of metabotropic glutamate (mGlu) receptors has previously been shown to play a role in inflammatory or neuropathic pain states. However, the role of mGlu type 1 receptors in post-operative pain remains to be investigated. In the present study, effects of potent and selective mGlu1 receptor antagonists A-841720, A-794282, A-794278, and A-850002 were evaluated in a skin incision-induced post-operative pain model in rats. Post-operative pain was examined 2 h following surgery using weight-bearing difference between injured and uninjured paws as a measure of spontaneous pain. In this model, A-841720, A-794282, A-794278, and A-850002 induced significant attenuation of spontaneous post-operative pain behavior, with ED50s of 10, 50, 50, and 65 micromol/kg i.p., respectively. Depending on the compound, significant motor side effects were also observed at 3 to 10 fold higher doses. These results support the notion that mGlu1 receptor activation plays a significant role in nociceptive transmission in post-operative pain, though motor impairment may be a limiting factor in developing mGlu1 receptor antagonists as novel analgesics.
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http://dx.doi.org/10.1016/j.ejphar.2007.09.047DOI Listing
February 2008

Repeated administration of vanilloid receptor TRPV1 antagonists attenuates hyperthermia elicited by TRPV1 blockade.

J Pharmacol Exp Ther 2007 Oct 25;323(1):128-37. Epub 2007 Jul 25.

Department of Neuroscience, MS-29-2-B, One Amgen Center Dr., Thousand Oaks, CA 91320-1799, USA.

Capsaicin, the active ingredient in some pain-relieving creams, is an agonist of a nonselective cation channel known as the transient receptor potential vanilloid type 1 (TRPV1). The pain-relieving mechanism of capsaicin includes desensitization of the channel, suggesting that TRPV1 antagonism may be a viable pain therapy approach. In agreement with the above notion, several TRPV1 antagonists have been reported to act as antihyperalgesics. Here, we report the in vitro and in vivo characterization of a novel and selective TRPV1 antagonist, N-(4-[6-(4-trifluoromethyl-phenyl)-pyrimidin-4-yloxy]-benzothiazol-2-yl)-acetamide I (AMG 517), and compare its pharmacology with that of a closely related analog, tert-butyl-2-(6-([2-(acetylamino)-1,3-benzothiazol-4-yl]oxy)pyrimidin-4-yl)-5-(trifluoromethyl)phenylcarbamate (AMG8163). Both AMG 517 and AMG8163 potently and completely antagonized capsaicin, proton, and heat activation of TRPV1 in vitro and blocked capsaicin-induced flinch in rats in vivo. To support initial clinical investigations, AMG 517 was evaluated in a comprehensive panel of toxicology studies that included in vivo assessments in rodents, dogs, and monkeys. The toxicology studies indicated that AMG 517 was generally well tolerated; however, transient increases in body temperature (hyperthermia) were observed in all species after AMG 517 dosing. To further investigate this effect, we tested and showed that the antipyretic, acetaminophen, suppressed the hyperthermia caused by TRPV1 blockade. We also showed that repeated administration of TRPV1 antagonists attenuated the hyperthermia response, whereas the efficacy in capsaicin-induced flinch model was maintained. In conclusion, these studies suggest that the transient hyperthermia elicited by TRPV1 blockade may be manageable in the development of TRPV1 antagonists as therapeutic agents. However, the impact of TRPV1 antagonist-induced hyperthermia on their clinical utility is still unknown.
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http://dx.doi.org/10.1124/jpet.107.125674DOI Listing
October 2007

The vanilloid receptor TRPV1 is tonically activated in vivo and involved in body temperature regulation.

J Neurosci 2007 Mar;27(13):3366-74

Department of Neuroscience, Amgen, Thousand Oaks, California 91320-1799, USA.

The vanilloid receptor TRPV1 (transient receptor potential vanilloid 1) is a cation channel that serves as a polymodal detector of pain-producing stimuli such as capsaicin, protons (pH <5.7), and heat. TRPV1 antagonists block pain behaviors in rodent models of inflammatory, neuropathic, and cancer pain, suggesting their utility as analgesics. Here, we report that TRPV1 antagonists representing various chemotypes cause an increase in body temperature (hyperthermia), identifying a potential issue for their clinical development. Peripheral restriction of antagonists did not eliminate hyperthermia, suggesting that the site of action is predominantly outside of the blood-brain barrier. Antagonists that are ineffective against proton activation also caused hyperthermia, indicating that blocking capsaicin and heat activation of TRPV1 is sufficient to produce hyperthermia. All TRPV1 antagonists evaluated here caused hyperthermia, suggesting that TRPV1 is tonically activated in vivo and that TRPV1 antagonism and hyperthermia are not separable. TRPV1 antagonists caused hyperthermia in multiple species (rats, dogs, and monkeys), demonstrating that TRPV1 function in thermoregulation is conserved from rodents to primates. Together, these results indicate that tonic TRPV1 activation regulates body temperature.
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http://dx.doi.org/10.1523/JNEUROSCI.4833-06.2007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6672109PMC
March 2007

Correlation between brain/plasma ratios and efficacy in neuropathic pain models of selective metabotropic glutamate receptor 1 antagonists.

Bioorg Med Chem Lett 2006 Sep 30;16(18):4936-40. Epub 2006 Jun 30.

Neuroscience Research, Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60064-6115, USA.

We have discovered a novel, potent, and selective triazafluorenone series of metabotropic glutamate receptor 1 (mGluR1) antagonists with efficacy in various rat pain models. Pharmacokinetic and pharmacodynamic profiles of these triazafluorenone analogs revealed that brain/plasma ratios of these mGluR1 antagonists were important to achieve efficacy in neuropathic pain models. This correlation could be used to guide our in vivo SAR (structure-activity relationship) modification. For example, compound 4a has a brain/plasma ratio of 0.34, demonstrating only moderate efficacy in neuropathic pain models. On the other hand, antagonist 4b with a brain/plasma ratio of 2.70 was fully efficacious in neuropathic pain models.
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http://dx.doi.org/10.1016/j.bmcl.2006.06.053DOI Listing
September 2006

Influence of genotype, dose and sex on pruritogen-induced scratching behavior in the mouse.

Pain 2006 Sep 11;124(1-2):50-8. Epub 2006 May 11.

Department of Psychology and Centre for Research on Pain, McGill University, Montreal, Que., Canada H3A 1B1.

Itch features considerable interindividual variability in humans, and initial studies using animal models have demonstrated a likely role of genetic factors in mediating such variability. In an attempt to systematically study genetic mediation of itch in the mouse such that gene identification by linkage mapping might be achieved, we examined scratching behavior induced by histamine and chloroquine in mice of 11 inbred mouse strains. Multiple chloroquine drug doses were used, revealing the existence of inverted-U dose-response relationships in every strain, allowing us to determine strain-dependent peak scratching behavior over the entire dose range. Peak chloroquine-induced scratching varied by 2.5-fold in this set of strains; scratching behavior shows moderate heritability in the mouse. The present data also reveal, for the first time, significant sex differences in pruritogen-induced scratching behavior, with female mice scratching an average of 23% more than males. Finally, a comparison of the strain means obtained here with previously collected data using nociceptive assays revealed a suggestive negative genetic correlation between chloroquine-induced itch and thermal pain, such that strains sensitive to pain are resistant to itch and vice versa. This finding may have implications both for our understanding of itch pathophysiology and for the identification of itch-related genes.
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http://dx.doi.org/10.1016/j.pain.2006.03.023DOI Listing
September 2006

Structure-activity relationship of triazafluorenone derivatives as potent and selective mGluR1 antagonists.

J Med Chem 2005 Nov;48(23):7374-88

Neuroscience Research, Abbott Laboratories, 100 Abbott Park Road, Abbott Park, Illinois 60064-6115, USA.

SAR (structure-activity relationship) studies of triazafluorenone derivatives as potent mGluR1 antagonists are described. The triazafluorenone derivatives are non-amino acid derivatives and noncompetitive mGluR1 antagonists that bind at a putative allosteric recognition site located within the seven-transmembrane domain of the receptor. These triazafluorenone derivatives are potent, selective, and systemically active mGluR1 antagonists. Compound 1n, for example, was a very potent mGluR1 antagonist (IC50 = 3 nM) and demonstrated full efficacy in various in vivo animal pain models.
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http://dx.doi.org/10.1021/jm0504407DOI Listing
November 2005

Variable sensitivity to noxious heat is mediated by differential expression of the CGRP gene.

Proc Natl Acad Sci U S A 2005 Sep 23;102(36):12938-43. Epub 2005 Aug 23.

Department of Psychology and Centre for Research on Pain, McGill University, Montreal, QC, Canada H3A 1B1.

Heat sensitivity shows considerable functional variability in humans and laboratory animals, and is fundamental to inflammatory and possibly neuropathic pain. In the mouse, at least, much of this variability is genetic because inbred strains differ robustly in their behavioral sensitivity to noxious heat. These strain differences are shown here to reflect differential responsiveness of primary afferent thermal nociceptors to heat stimuli. We further present convergent behavioral and electrophysiological evidence that the variable responses to noxious heat are due to strain-dependence of CGRP expression and sensitivity. Strain differences in behavioral response to noxious heat could be abolished by peripheral injection of CGRP, blockade of cutaneous and spinal CGRP receptors, or long-term inactivation of CGRP with a CGRP-binding Spiegelmer. Linkage mapping supports the contention that the genetic variant determining variable heat pain sensitivity across mouse strains affects the expression of the Calca gene that codes for CGRPalpha.
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http://dx.doi.org/10.1073/pnas.0503264102DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1200271PMC
September 2005

Electrophysiological and in vivo characterization of A-317567, a novel blocker of acid sensing ion channels.

Pain 2005 Sep;117(1-2):88-96

Abbott Laboratories, Neuroscience Research, Building AP9A-Dept. R4ND,Abbott Park, IL 60064-6118, USA.

Acid Sensing Ion Channels (ASICs) are a group of sodium-selective ion channels that are activated by low extracellular pH. The role of ASIC in disease states remains unclear partly due to the lack of selective pharmacological agents. In this report, we describe the effects of A-317567, a novel non-amiloride blocker, on three distinct types of native ASIC currents evoked in acutely dissociated adult rat dorsal root ganglion (DRG) neurons. A-317567 produced concentration-dependent inhibition of all pH 4.5-evoked ASIC currents with an IC50 ranging between 2 and 30muM, depending upon the type of ASIC current activated. Unlike amiloride, A-317567 equipotently blocked the sustained phase of ASIC3-like current, a biphasic current akin to cloned ASIC3, which is predominant in DRG. When evaluated in the rat Complete Freud's Adjuvant (CFA)-induced inflammatory thermal hyperalgesia model, A-317567 was fully efficacious at a dose 10-fold lower than amiloride. A-317567 was also potent and fully efficacious when tested in the skin incision model of post-operative pain. A-317567 was entirely devoid of any diuresis or natriuresis activity and showed minimal brain penetration. In summary, A-317567 is the first reported small molecule non-amiloride blocker of ASIC that is peripherally active and is more potent than amiloride in vitro and in vivo pain models. The discovery of A-317567 will greatly help to enhance our understanding of the physiological and pathophysiological role of ASICs.
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http://dx.doi.org/10.1016/j.pain.2005.05.021DOI Listing
September 2005