1 The reversible fatty acid amide hydrolase (FAAH) inhibitor OL135 reverses mechanical allodynia in the spinal nerve ligation (SNL) and mild thermal injury (MTI) models in the rat. The purpose of this study was to investigate the role of the cannabinoid and opioid systems in mediating this analgesic effect. À/À mice. 5 OL135 given i.p. resulted in a dose-responsive reversal of mechanical allodynia in both MTI and SNL models in the rat with an ED 50 between 6 and 9 mg kg À1 . The plasma concentration at the ED 50 in both models was 0.7 mM (240 ng ml À1 ). 6 In the rat SNL model, coadministration of the selective CB 2 receptor antagonist SR144528 (5 mg kg À1 i.p.), with 20 mg kg À1 OL135 blocked the OL135-induced reversal of mechanical allodynia, but the selective CB 1 antagonist SR141716A (5 mg kg À1 i.p.) was without effect. 7 In the rat MTI model neither SR141716A or SR144528 (both at 5 mg kg À1 i.p.), or a combination of both antagonists coadministered with OL135 (20 mg kg À1) blocked reversal of mechanical allodynia assessed 30 min after dosing. 8 In both the MTI model and SNL models in rats, naloxone (1 mg kg À1 , i.p. 30 min after OL135) reversed the analgesia (to 15% of control levels in the MTI model, to zero in the SNL) produced by OL135.

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to de®ne precisely the role of 5-HT 2B receptors in normal and disease processes have been hindered by the absence of selective antagonists. To address this de®ciency, we developed a series of naphthylpyrimidines as potentially useful 5-HT 2B receptor antagonists. 2 RS-127445 (2-amino-4-(4-¯uoronaphth-1-yl)-6-isopropylpyrimidine) was found to have nanomolar a nity for the 5-HT 2B receptor (pK i =9.5+0.1) and 1,000 fold selectivity for this receptor as compared to numerous other receptor and ion channel binding sites. 3 In cells expressing human recombinant 5-HT 2B receptors, RS-127445 potently antagonized 5-HTevoked formation of inositol phosphates (pK B =9.5+0.1) and 5-HT-evoked increases in intracellular calcium (pIC 50 =10.4+0.1). RS-127445 also blocked 5-HT-evoked contraction of rat isolated stomach fundus (pA 2 =9.5+1.1) and (+)a-methyl-5-HT-mediated relaxation of the rat jugular vein (pA 2 =9.9+0.3). RS-127445 had no detectable intrinsic activity in these assays. 4 In rats, the fraction of RS-127445 that was bioavailable via the oral or intraperitoneal routes was 14 and 60% respectively. Intraperitoneal administration of RS-127445 (5 mg kg 71 ) produced plasma concentrations predicted to fully saturate accessible 5-HT 2B receptors for at least 4 h. 5 In conclusion, RS-127445 is a selective, high a nity 5-HT 2B receptor antagonist suitable for use in vivo. The therapeutic potential of this molecule is being further evaluated.

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High throughput screening using the recombinant human TRPV1 receptor was used to identify a series of pyridinylpiperazine ureas (3) as TRPV1 vanilloid receptor ligands. Exploration of the structure-activity relationships by parallel synthesis identified the essential pharmacophoric elements for antagonism that permitted further optimization via targeted synthesis to provide a potent orally bioavailable and selective TRPV1 modulator 41 active in several in vivo models.

Fatty acid amide hydrolase (FAAH) is an integral membrane enzyme within the amidase-signature family. It catalyzes the hydrolysis of several endogenous biologically active lipids, including anandamide (arachidonoyl ethanolamide), oleoyl ethanolamide, and palmitoyl ethanolamide. These endogenous FAAH substrates have been shown to be involved in a variety of physiological and pathological processes, including synaptic regulation, regulation of sleep and feeding, locomotor activity, pain and inflammation. Here we describe the biochemical and biological properties of a potent and selective FAAH inhibitor, 4-(3-phenyl-[1,2,4]thiadiazol-5-yl)-piperazine-1-carboxylic acid phenylamide (JNJ-1661010). The time-dependence of apparent IC(50) values at rat and human recombinant FAAH, dialysis and mass spectrometry data indicate that the acyl piperazinyl fragment of JNJ-1661010 forms a covalent bond with the enzyme. This bond is slowly hydrolyzed, with release of the piperazinyl fragment and recovery of enzyme activity. The lack of inhibition observed in a rat liver esterase assay suggests that JNJ-1661010 is not a general esterase inhibitor. JNJ-1661010 is >100-fold preferentially selective for FAAH-1 when compared to FAAH-2. JNJ-1661010 dose-dependently increases arachidonoyl ethanolamide, oleoyl ethanolamide, and palmitoyl ethanolamide in the rat brain. The compound attenuates tactile allodynia in the rat mild thermal injury model of acute tissue damage and in the rat spinal nerve ligation (Chung) model of neuropathic pain. JNJ-1661010 also diminishes thermal hyperalgesia in the inflammatory rat carrageenan paw model. These data suggest that FAAH inhibitors with modes of action similar to JNJ-1661010 may be useful clinically as broad-spectrum analgesics.

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The pre-clinical characterization of the aryl piperazinyl urea inhibitor of fatty acid amide hydrolase (FAAH) JNJ-42165279 is described. JNJ-42165279 covalently inactivates the FAAH enzyme, but is highly selective with regard to other enzymes, ion channels, transporters, and receptors. JNJ-42165279 exhibited excellent ADME and pharmacodynamic properties as evidenced by its ability to block FAAH in the brain and periphery of rats and thereby cause an elevation of the concentrations of anandamide (AEA), oleoyl ethanolamide (OEA), and palmitoyl ethanolamide (PEA). The compound was also efficacious in the spinal nerve ligation (SNL) model of neuropathic pain. The combination of good physical, ADME, and PD properties of JNJ-42165279 supported it entering the clinical portfolio. KEYWORDS: FAAH, covalent, ethanolamides, enzyme, anandamide T he fatty acid amide hydrolases 1,2 interrupt the actions, through degradation, of a variety of endogenous lipid signaling molecules.3 FAAH rapidly degrades several fatty acid ethanolamides, including FAAH's primary substrate, AEA (N-arachidonyl ethanolamide or anandamide), 4 PEA (N-palmitoyl ethanolamide), 5,6 and OEA (N-oleoyl ethanolamide).7 In contrast, FAAH-2 catabolizes ethanolamides less efficiently, but will hydrolyze long-chain primary amides. The likely source of AEA's analgesic pharmacology is its ability to agonize the cannabinoid receptor CB 1 .8−10 However, AEA is synthesized on demand and then rapidly broken down locally, which mitigates the side-effects observed as a result of systemic CB 1 agonism (e.g., Δ 9 THC pharmacology). As AEA is synthesized in a localized manner, one might hypothesize that inhibiting FAAH could lead to elevated concentrations of AEA in relevant tissues. Indeed, prior reports have described an increase in AEA levels in the plasma and brains 11−14 of rats and in the plasma of humans upon inhibition of FAAH.Small molecule interruption of FAAH activity has been examined in numerous laboratories (Figure 1)