Abstract
Fatty acid amide hydrolase (FAAH) is the primary catabolic regulator of several bioactive lipid amides in vivo, including the endogenous cannabinoid anandamide and the sleep-inducing substance oleamide. Inhibitors of FAAH are considered a potential therapeutic approach for the treatment of several nervous system disorders, including pain, anxiety, and insomnia. However, for FAAH inhibitors to achieve clinical utility, they must not only display efficacy in vivo but also selectivity for this enzyme relative to the numerous other serine hydrolases present in mammalian proteomes. Here, we report a general strategy for evaluating the pharmacological activity and target specificity of FAAH inhibitors and its implementation to develop the first class of selective reversible inhibitors of this enzyme that are highly efficacious in vivo. Using a series of functional proteomics, analytical chemistry, and behavioral pharmacology assays, we have identified a class of α-keto-heterocycles that show unprecedented selectivity for FAAH relative to other mammalian hydrolases, and, when administered to rodents, raise central nervous system levels of anandamide and promote cannabinoid receptor 1-dependent analgesia in several assays of pain sensation. These studies provide further evidence that FAAH may represent an attractive therapeutic target and describe a general route by which inhibitors of this enzyme can be optimized to achieve exceptional potency, selectivity, and efficacy in vivo.
Footnotes
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This work was supported by the National Institutes of Health (CA87660, DA15197, DA017259, DA005274, and DA009789), a Merck Life Science Research Foundation Fellowship (to A.S.), The Helen L. Dorris Institute for the Study of Neurological and Psychiatric Disorders of Children and Adolescents, and The Skaggs Institute for Chemical Biology.
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doi:10.1124/jpet.104.069401.
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ABBREVIATIONS: PEA, N-palmitoylethanolamine; OEA, N-oleoylethanolamine; FAAH, fatty acid amide hydrolase; CB1, central cannabinoid receptor; DMSO, dimethyl sulfoxide; FP, fluorophosphonate; PAGE, polyacrylamide gel electrophoresis; %MPE, percent maximum possible effect; TGH, triacylglycerol hydrolase; AAD, arylacetamide deacetylase; CE-1, carboxylesterase 1; LPL, lipoprotein lipase; MAGL, monoacylglycerol lipase; SR141716, N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-di-chlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride; SR144528, N-[(1S)endo-1,3,3-trimethyl bicyclo [2.2.1] heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide; OL-135, 1-oxo-1[5-(2-pyridyl)-2-yl]-7-phenylheptane; OL-92, 1-(oxazolo[4,5-b]pyridin-2-yl)-1-oxo-7-phenylheptane; CP 55,940, (1R,3R,4R)-3-[2-hydroxy-4-(1,1-dimethylheptyl) phenyl]-4-(3-hydroxypropyl)cyclohexan-1-ol; URB532, n-butylcarbamic acid 4-benzyloxyphenyl ester; URB597, cyclohexylcarbamic acid 3′carbamoylbiphenyl-3-yl ester; BMS-1, [6-(2-methyl-4,5-diphenyl-imidazol-1-yl)-hexyl]-carbamic acid 2-fluoro-phenyl ester.
- Received April 3, 2004.
- Revision received June 30, 2004.
- The American Society for Pharmacology and Experimental Therapeutics
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