The fatty acid amide hydrolase inhibitor URB597 (cyclohexylcarbamic acid 3'-carbamoylbiphenyl-3-yl ester) reduces neuropathic pain after oral administration in mice

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.

Pharmacological profile of the selective FAAH inhibitor KDS-4103 (URB597)

In the present article, we review the pharmacological properties of KDS-4103 (URB597), a highly potent and selective inhibitor of the enzyme fatty-acid amide hydrolase (FAAH), which catalyzes the intracellular hydrolysis of the endocannabinoid anandamide. In vitro, KDS-4103 inhibits FAAH activity with median inhibitory concentrations (IC(50)) of 5 nM in rat brain membranes and 3 nM in human liver microsomes. In vivo, KDS-4103 inhibits rat brain FAAH activity after intraperitoneal (i.p.) administration with a median inhibitory dose (ID(50)) of 0.15 mg/kg. The compound does not significantly interact with other cannabinoid-related targets, including cannabinoid receptors and anandamide transport, or with a broad panel of receptors, ion channels, transporters and enzymes. By i.p. administration to rats and mice KDS-4103 elicits significant, anxiolytic-like, antidepressant-like and analgesic effects, which are prevented by treatment with CB1 receptor antagonists. By contrast, at doses that significantly inhibit FAAH activity and substantially raise brain anandamide levels, KDS-4103 does not evoke classical cannabinoid-like effects (e.g., catalepsy, hypothermia, hyperphagia), does not cause place preference, and does not produce generalization to the discriminative effects of the active ingredient of cannabis, Delta9-tetrahydrocannabinol (Delta9-THC). These findings suggest that KDS-4103 acts by enhancing the tonic actions of anandamide on a subset of CB(1) receptors, which may normally be engaged in controlling emotions and pain. KDS-4103 is orally available in rats and cynomolgus monkeys. Sub-chronic repeated dose studies (1,500 mg/kg, per os) in these two species have not demonstrated systemic toxicity. Likewise, no toxicity was noted in bacterial cytotoxicity tests in vitro and in the Ames test. Furthermore, no deficits were observed in rats on the rotarod test after acute i.p. treatment with KDS-4103 at doses up to 5 mg/kg or in a functional observation battery after oral doses up to 1,500 mg/kg. The results suggest that KDS-4103 will offer a novel approach with a favorable therapeutic window for the treatment of anxiety, depression and pain.

Pharmacological characterization of hydrolysis-resistant analogs of oleoylethanolamide with potent anorexiant properties

Oleoylethanolamide (OEA) is an endogenous lipid mediator that reduces food intake, promotes lipolysis, and decreases body weight gain in rodents by activating peroxisome proliferator-activated receptor-alpha (PPAR-alpha). The biological effects of OEA are terminated by two intracellular lipid hydrolase enzymes, fatty-acid amide hydrolase and N-acylethanolamine-hydrolyzing acid amidase. In the present study, we describe OEA analogs that resist enzymatic hydrolysis, activate PPAR-alpha with high potency in vitro, and persistently reduce feeding when administered in vivo either parenterally or orally. The most potent of these compounds, (Z)-(R)-9-octadecenamide,N-(2-hydroxyethyl,1-methyl) (KDS-5104), stimulates transcriptional activity of PPAR-alpha with a half-maximal effective concentration (EC50) of 100 +/- 21 nM (n = 11). Parenteral administration of KDS-5104 in rats produces persistent dose-dependent prolongation of feeding latency and postmeal interval (half-maximal effective dose, ED50 = 2.4 +/- 1.8 mg kg(-1) i.p.; n = 18), as well as increased and protracted tissue exposure compared with OEA. Oral administration of the compound also results in a significant tissue exposure and reduction of food intake in free-feeding rats. These results suggest that the endogenous high-affinity PPAR-alpha agonist OEA may provide a scaffold for the discovery of novel orally active PPAR-alpha ligands.