AMG 9810 [(E)-3-(4-t-Butylphenyl)-N-(2,3-dihydrobenzo[b][1,4] dioxin-6-yl)acrylamide], a Novel Vanilloid Receptor 1 (TRPV1) Antagonist with Antihyperalgesic Properties

Abstract

The vanilloid receptor 1 (VR1 or TRPV1) is a membrane-bound, nonselective cation channel expressed by peripheral sensory neurons. TRPV1 antagonists produce antihyperalgesic effects in animal models of inflammatory and neuropathic pain. Here, we describe the in vitro and in vivo pharmacology of a novel TRPV1 antagonist, AMG 9810,AMG 9810 is a competitive antagonist of capsaicin activation (IC 50 value for human TRPV1, 24.5 Ϯ 15.7 nM; rat TRPV1, 85.6 Ϯ 39.4 nM) and blocks all known modes of TRPV1 activation, including protons (IC 50 value for rat TRPV1, 294 Ϯ 192 nM; human TRPV1, 92.7 Ϯ 72.8 nM), heat (IC 50 value for rat TRPV1, 21 Ϯ 17 nM; human TRPV1, 15.8 Ϯ 10.8 nM), and endogenous ligands, such as anandamide, N-arachidonyl dopamine, and oleoyldopamine. AMG 9810 blocks capsaicin-evoked depolarization and calcitonin gene-related peptide release in cultures of rat dorsal root ganglion primary neurons. Screening of AMG 9810 against a panel of G protein-coupled receptors and ion channels indicated selectivity toward TRPV1. In vivo, AMG 9810 is effective at preventing capsaicin-induced eye wiping in a dose-dependent manner, and it reverses thermal and mechanical hyperalgesia in a model of inflammatory pain induced by intraplantar injection of complete Freund's adjuvant. At effective doses, AMG 9810 did not show any significant effects on motor function, as measured by open field locomotor activity and motor coordination tests. AMG 9810 is the first cinnamide TRPV1 antagonist reported to block capsaicin-induced eye wiping behavior and reverse hyperalgesia in an animal model of inflammatory pain.Activation of peripheral nociceptors in humans by capsaicin results in burning pain (Park et al., 1995). Capsaicin, and its ultrapotent analog resiniferatoxin, aided the identification and characterization of the vanilloid receptor 1 (aka VR1 and TRPV1). TRPV1 is a nonselective cation channel with high permeability to calcium (Caterina et al., 1997) and belongs to a superfamily of ion channels known as the transient receptor potential channels or TRPs (Clapham et al., 2001). In addition to activation by exogenous agonists such as capsaicin and resiniferatoxin, TRPV1 can be activated by physical stimuli, such as heat (Ͼ42°C) and protons (pH 5). Based on their structural similarity to capsaicin, several endogenous ligands have been proposed that include anandamide (AEA), 12-hydroperoxy-5,8,10,14-eicosatetraenoic acid,N-arachidonyl dopamine (NADA), N-oleoyldopamine (OLDA), and products of lipoxygenases (Hwang et al., 2000;Olah et al., 2001;Huang et al., 2002;Chu et al., 2003). TRPV1 is up-regulated during inflammation (Ji et al., 2002), and channel activity is modulated by the action of inflammaArticle, publication date, and citation information can be found at http://jpet.aspetjournals.org.doi :

TRPV1 Receptors in the CNS Play a Key Role in Broad-Spectrum Analgesia of TRPV1 Antagonists

“…However, in these animals, mechanical allodynia associated with both inflammation and nerve injury remained unchanged. In contrast to these results, several novel TRPV1 antagonists,piperazine-1-carboxamide (BCTC) (Pomonis et al, 2003), AMG 9810 [(E)-3-(4-tert-butylphenyl)-N-(2,3-dihydrobenzo[b] [1,4] dioxin-6-yl)acrylamide] (Gavva et al, 2005), and A-425619 [1-isoquinolin-5-yl-3-(4-trifluoromethyl-benzyl) -urea] Honore et al, 2005), have demonstrated efficacy in reducing thermal hyperalgesia and mechanical allodynia associated with both chronic inflammation and neuropathy in rats. Together, these studies suggest that TRPV1 plays an important role in integrating multiple pain-producing stimuli.…”

“…Several other novel selective TRPV1 antagonists (e.g., capsazepine, BCTC, and AMG 9810) have been reported to reduce mechanical allodynia associated with inflammation (Pomonis et al, 2003;Walker et al, 2003;Gavva et al, 2005). In contrast, mechanical allodynia associated with inflammation developed normally in TRPV1 knock-out mice (Caterina et al, 2000).…”

Serotonin Facilitates Peripheral Pain Sensitivity in a Manner That Depends on the Nonproton Ligand Sensing Domain of ASIC3 Channel

“…To exclude the interference by classical 5-HT receptors, we included Y-25130 (200 nM) and methysergide (40 M) in the recording solution to block 5-HT 3 and 5-HT 1,2,7 receptors (Yakushiji and Akaike, 1992; Dahlöf and Maassen Van Den Brink, 2012), respectively. We also included AMG9810 (10 M), a TRPV1 selective antagonist, to block proton-induced TRPV1 activation (Gavva et al, 2005). Under these conditions, the prevalent type of currents induced by the pH 5.0 solution among small-and medium-sized (15-30 m) WT mouse DRG neurons were ASIC-like (rapidly inactivating in response to acid; 79.4%, 27 of 34 total tested neurons) (Fig.…”

Novel Gating and Sensitizing Mechanism of Capsaicin Receptor (TRPV1)

“…Some endogenous ligands termed endovanilloids (3), including 15-hydroperoxyeicosa-5Z,8Z,11Z,13E-tetraenoic acid (15(S)-HPETE), a lipoxygenase product, also activate TRPV1 (4). Because mice genetically lacking the TRPV1 channel exhibit impaired nociception (5,6) and several TRPV1 antagonists have antinociceptive activity in vivo (7)(8)(9), TRPV1 is considered to be a key component of signal transduction pathways in the nociceptive system. Several regulatory mechanisms of TRPV1 function have been elucidated.…”