The Fatty Acid Amide Hydrolase Inhibitor URB597 (Cyclohexylcarbamic Acid 3′-Carbamoylbiphenyl-3-yl Ester) Reduces Neuropathic Pain after Oral Administration in Mice

Roberto Russo,Andrea Duranti,Antonio Calignano,Timothy R Compton,Jesse Loverme,Giorgio Tarzia,Jeff Parrott,Giovanna La Rana,Andrea Tontini,Daniele Piomelli,Marco Mor

doi:10.1124/jpet.107.119941

Abstract

Fatty acid amide hydrolase (FAAH) is an intracellular serine hydrolase that catalyzes the cleavage of bioactive fatty acid ethanolamides, such as the endogenous cannabinoid agonist anandamide. Genetic deletion of the faah gene in mice elevates brain anandamide levels and amplifies the antinociceptive effects of this compound. Likewise, pharmacological blockade of FAAH activity reduces nocifensive behavior in animal models of acute and inflammatory pain. In the present study, we investigated the effects of the selective FAAH inhibitor URB597 (KDS-4103, cyclohexylcarbamic acid 3'-carbamoylbiphenyl-3-yl ester) in the mouse chronic constriction injury (CCI) model of neuropathic pain. Oral administration of URB597 (1-50 mg/kg, once daily) for 4 days produced a dose-dependent reduction in nocifensive responses to thermal and mechanical stimuli, which was prevented by a single i.p. administration of the cannabinoid CB(1) receptor antagonist rimonabant (1 mg/kg). The antihyperalgesic effects of URB597 were accompanied by a reduction in plasma extravasation induced by CCI, which was prevented by rimonabant (1 mg/kg i.p.) and attenuated by the CB(2) antagonist SR144528 (1 mg/kg i.p.). Oral dosing with URB597 achieved significant, albeit transient, drug levels in plasma, inhibited brain FAAH activity, and elevated spinal cord anandamide content. The results provide new evidence for a role of the endocannabinoid system in pain modulation and reinforce the proposed role of FAAH as a target for analgesic drug development.

Highlights

The results indicate that URB597 is systemically absorbed and inhibits brain fatty acid amide hydrolase (FAAH) activity after oral administration
These effects are accompanied by an increase in spinal cord anandamide levels, are prevented by the cannabinoid receptor type I (CB1) antagonist rimonabant, and are reduced by the cannabinoid receptor type II (CB2) antagonist SR144528 when the stimuli are thermal or tactile, suggesting that they are caused by anandamide-mediated activation of both CB1 and CB2 receptors
It is noteworthy that the analgesic actions of URB597 are associated with a marked reduction in plasma extravasation, a finding that supports a role for anandamide in the modulation of neurogenic inflammation (Richardson et al, 1998)

Summary

Introduction

U.S patent 7176201 on this work was filed by the University of California and is licensed to Kadmus Pharmaceuticals, Inc. to be produced in a stimulus-dependent manner by activation of phospholipase D or phospholipase C activities (Okamoto et al, 2004; Liu et al, 2006). After release from cells, anandamide may be eliminated via a two-step process consisting of high-affinity transport into cells (Di Marzo et al, 1994; Beltramo et al, 1997) followed by intracellular degradation, catalyzed by fatty acid amide hydrolase (FAAH) (McKinney and Cravatt, 2005). On the other hand, saturated and monounsaturated FAEs, such as PEA, are poor substrates for the anandamide transport system, and their deactivation may be primarily mediated by intracellular hydrolysis catalyzed by FAAH and/or a distinct N-acylethanolamine acid amidase (Sun et al, 2005). Mutant mice lacking the gene encoding for FAAH (faah) display reduced FAE hydrolysis and elevated brain levels of ABBREVIATIONS: PEA, palmitoylethanolamide; FAE, fatty acid ethanolamide; FAAH, fatty-acid amide hydrolase; CB1, cannabinoid receptor type I; URB597 (KDS-4103), cyclohexylcarbamic acid 3Ј-carbamoylbiphenyl-3-yl ester; CCI, chronic constriction injury; 2-AG, 2-arachidonoylglycerol; SR144528, N-[(1S)-endo-1,3,3-trimethylbicyclo[2.2.1]heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)pyrazole-3-carboxamide; SR141716, rimonabant, 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-N-1-piperidinyl-1H-pyrazole-3-carboxamide; LC, liquid chromatography; MS, mass spectrometry; OEA, oleoylethanolamide; AUC, area under the curve; CB2, cannabinoid receptor type II

Methods

Results

Conclusion