Fatty acid amide hydrolase (FAAH) is an integral membrane enzyme that degrades the fatty acid amide family of signaling lipids, including the endocannabinoid anandamide. Genetic or pharmacological inactivation of FAAH leads to analgesic, anti-inflammatory, anxiolytic, and antidepressant phenotypes in rodents without showing the undesirable side effects observed with direct cannabinoid receptor agonists, indicating that FAAH may represent an attractive therapeutic target for treatment of pain, inflammation, and other central nervous system disorders. However, the FAAH inhibitors reported to date lack druglike pharmacokinetic properties and/or selectivity. Herein we describe piperidine/piperazine ureas represented by and N-phenyl-4-(quinolin-2-ylmethyl)piperazine-1-carboxamide (PF-622) as a novel mechanistic class of FAAH inhibitors. PF-750 and PF-622 show higher in vitro potencies than previously established classes of FAAH inhibitors. Rather unexpectedly based on the high chemical stability of the urea functional group, PF-750 and PF-622 were found to inhibit FAAH in a time-dependent manner by covalently modifying the enzyme's active site serine nucleophile. Activity-based proteomic profiling revealed that PF-750 and PF-622 were completely selective for FAAH relative to other mammalian serine hydrolases. We hypothesize that this remarkable specificity derives, at least in part, from FAAH's special ability to function as a C(O)-N bond hydrolase, which distinguishes it from the vast majority of metabolic serine hydrolases in mammals that are restricted to hydrolyzing esters and/or thioesters. The piperidine/piperazine urea may thus represent a privileged chemical scaffold for the synthesis of FAAH inhibitors that display an unprecedented combination of potency and selectivity for use as potential analgesic and anxiolytic/antidepressant agents.Fatty acid amide hydrolase (FAAH 1 ) is an integral membrane enzyme (1, 2) that regulates the fatty acid amide family of lipid transmitters, which includes the endogenous cannabinoid N-arachidonyl ethanolamine (anandamide) (3), the anti-inflammatory factor N-palmitoyl ethanolamine (PEA) (4), the sleep-inducing substance 9(Z)-octadecenamide (oleamide) (5), and the satiating signal N-oleoyl ethanolamine (OEA) (6).FAAH inactivation by either genetic deletion of the FAAH gene in mice (7) or by chemical inhibitors (8) leads to elevated endogenous levels of fatty acid amides with concomitant analgesic (9-13), anxiolytic (8), antidepressant (14, 15), sleep-enhancing (16), and anti-inflammatory (9,17,18) phenotypes. Notably the behavioral phenotypes observed in FAAH knockout (-/-) mice (7, 9) or in rodents treated with FAAH inhibitors (8,(11)(12)(13)(14)18) occur in the absence of alterations in motility, weight gain, or body temperature that are typically observed with direct cannabinoid receptor 1 (CB1) agonists. These findings suggest that FAAH may represent an attractive therapeutic target for treatment of pain, inflammation, and other central nervous system (CNS) diso...

The integral membrane enzyme fatty acid amide hydrolase (FAAH) hydrolyzes the endocannabinoid anandamide and related amidated signaling lipids. Genetic or pharmacological inactivation of FAAH produces analgesic, anxiolytic, and antiinflammatory phenotypes but not the undesirable side effects of direct cannabinoid receptor agonists, indicating that FAAH may be a promising therapeutic target. Structure-based inhibitor design has, however, been hampered by difficulties in expressing the human FAAH enzyme. Here, we address this problem by interconverting the active sites of rat and human FAAH using site-directed mutagenesis. The resulting humanized rat (h/r) FAAH protein exhibits the inhibitor sensitivity profiles of human FAAH but maintains the high-expression yield of the rat enzyme. We report a 2.75-Å crystal structure of h/rFAAH complexed with an inhibitor, N-phenyl-4-(quinolin-3-ylmethyl)piperidine-1-carboxamide (PF-750), that shows strong preference for human FAAH. This structure offers compelling insights to explain the species selectivity of FAAH inhibitors, which should guide future drug design programs.anandamide ͉ crystal structure ͉ endocannabinoid ͉ fatty acid amides ͉ hydrolase F atty acid amide hydrolase (FAAH) is an integral membrane enzyme that hydrolyzes the fatty acid amide class of lipid transmitters (1, 2). FAAH substrates include the endogenous cannabinoid N-arachidonoyl ethanolamine (anandamide) (3), the antiinflammatory factor N-palmitoyl ethanolamine (PEA) (4), the sleep-inducing substance 9(Z)-octadecenamide (oleamide) (5), and the satiating signal N-oleoyl ethanolamine (OEA) (6). FAAH inactivation by either chemical inhibition or genetic deletion of the FAAH gene leads to elevated endogenous levels of fatty acid amides and a range of behavioral effects that include analgesia (7-12), anxiolytic (8,13,14), antidepressant (13, 15), sleep-enhancing (16), and antiinflammatory (17-19) phenotypes. Importantly, these behavioral phenotypes occur in the absence of alterations in motility, weight gain, or body temperature that are typically observed with direct cannabinoid receptor 1 (CB1) agonists. Inhibition of FAAH thus may offer an attractive way to produce the therapeutically beneficial phenotypes of activating the endocannabinoid system without the undesirable side effects that are observed with direct CB1 agonists.FAAH is a member of a large class of enzymes termed the amidase signature class (20). These enzymes, which span all kingdoms of life, use an unusual Ser-Ser-Lys catalytic triad (21, 22) to hydrolyze amide bonds on a wide range of small-molecule substrates. Despite their atypical catalytic mechanism, amidase signature enzymes are inactivated by general classes of serine hydrolase inhibitors [e.g., trifluoromethyl ketones (23, 24), fluorophosphonates (25), ␣-ketoheterocycles (26), carbamates (8, 27)]. First-generation FAAH inhibitors, such as methyl arachidonyl fluorophosphonate (MAFP) (25), were substrate-derived in structure and therefore lack selectivity for FAAH relative to other l...

Abnormal proliferation mediated by disruption of the normal cell cycle mechanisms is a hallmark of virtually all cancer cells. Compounds targeting complexes between cyclin-dependent kinases (CDK) and cyclins, such as CDK2/cyclin A and CDK2/cyclin E, and inhibiting their kinase activity are regarded as promising antitumor agents to complement the existing therapies. From a high-throughput screening effort, we identified a new class of CDK2/cyclin A/E inhibitors. The hit-to-lead expansion of this class is described. X-ray crystallographic data of early compounds in this series, as well as in vitro testing funneled for rapidly achieving in vivo efficacy, led to a nanomolar inhibitor of CDK2/cyclin A (N-(5-cyclopropyl-1H-pyrazol-3-yl)-2-(2-naphthyl)acetamide (41), PNU-292137, IC50 = 37 nM) with in vivo antitumor activity (TGI > 50%) in a mouse xenograft model at a dose devoid of toxic effects.

Novel pyridine-and pyrimidine-based allosteric inhibitors are reported that achieve PDE4D subtype selectivity through recognition of a single amino acid difference on a key regulatory domain, known as UCR2, that opens and closes over the catalytic site for cAMP hydrolysis. The design and optimization of lead compounds was based on iterative analysis of X-ray crystal structures combined with metabolite identification. Selectivity for the activated, dimeric form of PDE4D provided potent memory enhancing effects in a mouse model of novel object recognition with improved tolerability and reduced vascular toxicity over earlier PDE4 inhibitors that lack subtype selectivity. The lead compound, 28 (BPN14770), has entered midstage, human phase 2 clinical trials for the treatment of Fragile X Syndrome.