The discovery of azetidine-piperazine di-amides as potent, selective and reversible monoacylglycerol lipase (MAGL) inhibitors.

Monoacylglycerol lipase (MAGL) is the enzyme that is primarily responsible for hydrolyzing the endocannabinoid 2-arachidononylglycerol (2-AG) to arachidonic acid (AA). It has emerged in recent years as a potential drug target for a number of diseases. Herein, we report the discovery of compound 6g from a series of azetidine-piperazine di-amide compounds as a potent, selective, and reversible inhibitor of MAGL. Oral administration of compound 6g increased 2-AG levels in rat brain and produced full efficacy in the rat complete Freund's adjuvant (CFA) model of inflammatory pain.

The discovery of diazetidinyl diamides as potent and reversible inhibitors of monoacylglycerol lipase (MAGL).

Monoacylglycerol lipase (MAGL) has emerged as an attractive drug target because of its important role in regulating the endocannabinoid 2-arachidonoylglycerol (2-AG) and its hydrolysis product arachidonic acid (AA) in the brain. Herein, we report the discovery of a novel series of diazetidinyl diamide compounds 6 and 10 as potent reversible MAGL inhibitors. In addition to demonstrating potent MAGL inhibitory activity in the enzyme assay, the thiazole substituted diazetidinyl diamides 6d-l and compounds 10 were also effective at increasing 2-AG levels in a brain 2-AG accumulation assay in homogenized rat brain. Furthermore, selected compounds have been shown to achieve good brain penetration after oral administration in an animal study.

Pharmacologic Characterization of JNJ-42226314, [1-(4-Fluorophenyl)indol-5-yl]-[3-[4-(thiazole-2-carbonyl)piperazin-1-yl]azetidin-1-yl]methanone, a Reversible, Selective, and Potent Monoacylglycerol Lipase Inhibitor.

The serine hydrolase monoacylglycerol lipase (MAGL) is the rate-limiting enzyme responsible for the degradation of the endocannabinoid 2-arachidonoylglycerol (2-AG) into arachidonic acid and glycerol. Inhibition of 2-AG degradation leads to elevation of 2-AG, the most abundant endogenous agonist of the cannabinoid receptors (CBs) CB1 and CB2. Activation of these receptors has demonstrated beneficial effects on mood, appetite, pain, and inflammation. Therefore, MAGL inhibitors have the potential to produce therapeutic effects in a vast array of complex human diseases. The present report describes the pharmacologic characterization of [1-(4-fluorophenyl)indol-5-yl]-[3-[4-(thiazole-2-carbonyl)piperazin-1-yl]azetidin-1-yl]methanone (JNJ-42226314), a reversible and highly selective MAGL inhibitor. JNJ-42226314 inhibits MAGL in a competitive mode with respect to the 2-AG substrate. In rodent brain, the compound time- and dose-dependently bound to MAGL, indirectly led to CB1 occupancy by raising 2-AG levels, and raised norepinephrine levels in cortex. In vivo, the compound exhibited antinociceptive efficacy in both the rat complete Freund's adjuvant-induced radiant heat hypersensitivity and chronic constriction injury-induced cold hypersensitivity models of inflammatory and neuropathic pain, respectively. Though 30 mg/kg induced hippocampal synaptic depression, altered sleep onset, and decreased electroencephalogram gamma power, 3 mg/kg still provided approximately 80% enzyme occupancy, significantly increased 2-AG and norepinephrine levels, and produced neuropathic antinociception without synaptic depression or decreased gamma power. Thus, it is anticipated that the profile exhibited by this compound will allow for precise modulation of 2-AG levels in vivo, supporting potential therapeutic application in several central nervous system disorders. SIGNIFICANCE STATEMENT: Potentiation of endocannabinoid signaling activity via inhibition of the serine hydrolase monoacylglycerol lipase (MAGL) is an appealing strategy in the development of treatments for several disorders, including ones related to mood, pain, and inflammation. [1-(4-Fluorophenyl)indol-5-yl]-[3-[4-(thiazole-2-carbonyl)piperazin-1-yl]azetidin-1-yl]methanone is presented in this report to be a novel, potent, selective, and reversible noncovalent MAGL inhibitor that demonstrates dose-dependent enhancement of the major endocannabinoid 2-arachidonoylglycerol as well as efficacy in models of neuropathic and inflammatory pain.

Benzo[d]imidazole Transient Receptor Potential Vanilloid 1 Antagonists for the Treatment of Pain: Discovery of trans-2-(2-{2-[2-(4-Trifluoromethyl-phenyl)-vinyl]-1H-benzimidazol-5-yl}-phenyl)-propan-2-ol (Mavatrep).

Reported herein is the design, synthesis, and pharmacologic characterization of a class of TRPV1 antagonists constructed on a benzo[d]imidazole platform that evolved from a biaryl amide lead. This design composes three sections: a 2-substituted 5-phenyl headgroup attached to the benzo[d]imidazole platform, which is tethered at the two position to a phenyl tail group. Optimization of this design led to the identification of 4 (mavatrep), comprising a trifluoromethyl-phenyl-vinyl tail. In a TRPV1 functional assay, using cells expressing recombinant human TRPV1 channels, 4 antagonized capsaicin-induced Ca(2+) influx, with an IC50 value of 4.6 nM. In the complete Freund's adjuvant- and carrageenan-induced thermal hypersensitivity models, 4 exhibited full efficacy, with ED80 values of 7.8 and 0.5 mg/kg, respectively, corresponding to plasma levels of 270.8 and 9.2 ng/mL, respectively. On the basis of its superior pharmacologic and safety profile, 4 (mavatrep) was selected for clinical development for the treatment of pain.

Global deletion of MGL in mice delays lipid absorption and alters energy homeostasis and diet-induced obesity.

Monoacylglycerol lipase (MGL) is a ubiquitously expressed enzyme that catalyzes the hydrolysis of monoacylglycerols (MGs) to yield FFAs and glycerol. MGL contributes to energy homeostasis through the mobilization of fat stores and also via the degradation of the endocannabinoid 2-arachidonoyl glycerol. To further examine the role of MG metabolism in energy homeostasis, MGL(-/-) mice were fed either a 10% (kilocalories) low-fat diet (LFD) or a 45% (kilocalories) high-fat diet (HFD) for 12 weeks. Profound increases of MG species in the MGL(-/-) mice compared with WT control mice were found. Weight gain over the 12 weeks was blunted in both diet groups. MGL(-/-) mice were leaner than WT mice at both baseline and after 12 weeks of LFD feeding. Circulating lipids were decreased in HFD-fed MGL(-/-) mice, as were the levels of several plasma peptides involved in glucose homeostasis and energy balance. Interestingly, MGL(-/-) mice had markedly reduced intestinal TG secretion following an oral fat challenge, suggesting delayed lipid absorption. Overall, the results indicate that global MGL deletion leads to systemic changes that produce a leaner phenotype and an improved serum metabolic profile.

Identification of a dual δ OR antagonist/µ OR agonist as a potential therapeutic for diarrhea-predominant Irritable Bowel Syndrome (IBS-d).

A small set of acyclic analogs 5 were prepared to explore their structure-activity relationships (SARs) relative to heterocyclic core, opioid receptor (OR) agonists 4. Compound 5l was found to have very favorable OR binding affinities at the δ and µ ORs (r K(i) δ=1.3 nM; r K(i) µ=0.9 nM; h K(i) µ=1.7 nM), with less affinity for the κ OR (gp K(i) κ=55 nM). The OR functional profile for 5l varied from the previously described dual δ/µ OR agonists 4, with 5l being a potent, mixed dual δ OR antagonist/µ OR agonist [δ IC(50)=89 nM (HVD); µ EC(50)=1 nM (GPI); κ EC(50)=1.6 µM (GPC)]. Compound 5l has progressed through a clinical Phase II Proof of Concept study on 800 patients suffering from diarrhea-predominant Irritable Bowel Syndrome (IBS-d). This Phase II study was recently completed successfully, with 5l demonstrating statistically significant efficacy over placebo.

Screening and characterization of human monoglyceride lipase active site inhibitors using orthogonal binding and functional assays.

Endocannabinoids such as 2-arachidonylglycerol (2-AG) are ligands for cannabinoid receptors that contribute to the transmission and modulation of pain signals. The antinociceptive effect of exogenous 2-AG suggests that inhibition of monoglyceride lipase (MGLL), the enzyme responsible for degrading 2-AG and arresting signaling, may be a target for pain modulation. Here we describe the characterization of MGLL ligands following a high-throughput screening campaign. Ligands were discovered using ThermoFluor, a label-free affinity-based screening tool that measures ligand binding via modulation of protein thermal stability. A kinetic fluorescent assay using the substrate 4-methylcoumarin butyrate was used to counterscreen confirmed HTS positives. A comparison of results from binding and inhibition assays allowed elucidation of compound mechanism of action. We demonstrate the limit of each technology and the benefits of using orthogonal assay techniques in profiling compounds.

Dynamic mass redistribution as a means to measure and differentiate signaling via opioid and cannabinoid receptors.

Classically, G protein-coupled receptor activation by a ligand has been viewed as producing a defined response such as activation of a G protein, activation or inhibition of adenylyl cyclase, or stimulation of phospholipase C and/or alteration in calcium flux. Newer concepts of ligand-directed signaling recognize that different ligands, ostensibly acting at the same receptors, may induce different downstream effects, complicating the selection of a screening assay. Dynamic mass redistribution (DMR), a label-free technology that uses light to measure ligand-induced changes in the mass of cells proximate to the biosensor, provides an integrated cellular response comprising multiple pathways and cellular events. Using DMR, signals induced by opioid or cannabinoid agonists in cells transfected with these receptors were blocked by pharmacologically appropriate receptor antagonists as well as by pertussis toxin. Differences among compounds in relative potencies at DMR versus ligand-stimulated GTPγS or receptor binding endpoints, suggesting functional selectivity, were observed. Preliminary evidence indicates that inhibitors of intermediate steps in the cell signaling cascade, such as receptor recycling inhibitors, mitogen-activated protein kinase kinase/p38 mitogen-activated protein kinase inhibitors, or cytoskeletal disruptors, altered or attenuated the cannabinoid-induced response. Notable is the finding that mitogen-activated protein kinase kinase 1/2 inhibitors attenuated signaling induced by the cannabinoid type 2 receptor inverse agonist AM630 but not that stimulated by the agonist CP 55,940. Thus, DMR has the potential to not only identify ligands that activate a given G protein-coupled receptor, but also ascertain the signaling pathways engaged by a specific ligand, making DMR a useful tool in the identification of biased ligands, which may ultimately exhibit improved therapeutic profiles.

Diabetogenic effect of a series of tricyclic delta opioid agonists structurally related to cyproheptadine.

The unexpected observation of a hyperglycemic effect of some tricycle-based delta opioid receptor (DOR) agonists led to a series of studies to better understand the finding. Single administration of two novel tricyclic DOR agonists dose dependently elevated rat plasma glucose levels; 4-week toxicology studies confirmed the hyperglycemic finding and further revealed pancreatic ß-cell hypertrophy, including vacuole formation, as well as bone dysplasia and Harderian gland degeneration with regeneration. Similar diabetogenic effects were observed in dog. A review of the literature on the antiserotonergic and antihistaminergic drug cyproheptadine (CPH) and its metabolites revealed shared structural features as well as similar hyperglycemic effects to the present series of DOR agonists. To further evaluate these effects, we established an assay measuring insulin levels in the rat pancreatic ß-cell-derived RINm5F cell line, extensively used to study CPH and its metabolites. Like CPH, the initial DOR agonists studied reduced RINm5F cell insulin levels in a concentration-dependent manner. Importantly, compound DOR potency did not correlate with the insulin-reducing potency. Furthermore, the RINm5F cell insulin results correlated with the diabetogenic effect of the compounds in a 5-day mouse study. The RINm5F cell insulin assay enabled the identification of aryl-aryl-amine DOR agonists that lacked an insulin-reducing effect and did not elevate blood glucose in repeated dosing studies conducted over a suprapharmacologic dose range. Thus, not only did the RINm5F cell assay open a path for the further discovery of DOR agonists lacking diabetogenic potential but also it established a reliable, economical, and high-throughput screen for such potential, regardless of chemotype or target pharmacology. The present findings also suggest a mechanistic link between the toxicity observed here and that underlying Wolcott-Rallison Syndrome.

Ex vivo delta opioid receptor autoradiography: CNS receptor occupancy of two novel compounds over their antihyperalgesic dose range.

Discovered as part of an effort to identify delta opioid (DOPr or DOR) agonist analgesics, JNJ-20788560 and JNJ-39204880 exhibited high DOR affinity, with K(i) values of 1.7 and 2.0nM, respectively, and were selective for DOR over the mu opioid receptor (MOPr or MOR), with 596- and 122-fold selectivity, respectively. Both compounds stimulated DOR but not MOR induced GTPgammaS binding and were effective antihyperalgesic agents in the complete Freund's adjuvant model of thermal hyperalgesia in the rat, with oral ED(50) values of 13.5 and 35mg/kg, corresponding to plasma levels of 1 and 9microM, respectively. Autoradiographic analysis of DOR and MOR occupancy in sections of brain (striatum) and lumbar spinal cord (L4-L6) was determined ex vivo, using radiolabeled naltrindole or DAMGO. Quantitative image analysis resulted in striatal DOR ED(50) values of 6.9 and 10.7mg/kg, for JNJ-20788560 and JNJ-39204880 respectively, and spinal cord values of 6.4 and 3.2mg/kg, respectively. Neither compound dose-dependently occupied MOR within the dose range studied. Thus, this study confirmed the DOR selectively over MOR of both compounds following their oral administration, and further demonstrated dose-dependent DOR occupancy by each compound across its antihyperalgesic dose range. Importantly, these in vitro, in vivo, and ex vivo data revealed that the greater in vitro potency of JNJ-20788560 was paralleled by its greater in vivo potency, although JNJ-39204880 achieved higher plasma levels following its oral administration. The receptor occupancy levels observed at the pharmacologic ED(50) doses of these compounds suggest the need for greater target engagement by JNJ-39204880 than by JNJ-20788560 to elicit a similar therapeutic response.

Targeted disruption of the voltage-dependent calcium channel alpha2/delta-1-subunit.

Cardiac L-type voltage-dependent Ca(2+) channels are heteromultimeric polypeptide complexes of alpha(1)-, alpha(2)/delta-, and beta-subunits. The alpha(2)/delta-1-subunit possesses a stereoselective, high-affinity binding site for gabapentin, widely used to treat epilepsy and postherpetic neuralgic pain as well as sleep disorders. Mutations in alpha(2)/delta-subunits of voltage-dependent Ca(2+) channels have been associated with different diseases, including epilepsy. Multiple heterologous coexpression systems have been used to study the effects of the deletion of the alpha(2)/delta-1-subunit, but attempts at a conventional knockout animal model have been ineffective. We report the development of a viable conventional knockout mouse using a construct targeting exon 2 of alpha(2)/delta-1. While the deletion of the subunit is not lethal, these animals lack high-affinity gabapentin binding sites and demonstrate a significantly decreased basal myocardial contractility and relaxation and a decreased L-type Ca(2+) current peak current amplitude. This is a novel model for studying the function of the alpha(2)/delta-1-subunit and will be of importance in the development of new pharmacological therapies.

JNJ-20788560 [9-(8-azabicyclo[3.2.1]oct-3-ylidene)-9H-xanthene-3-carboxylic acid diethylamide], a selective delta opioid receptor agonist, is a potent and efficacious antihyperalgesic agent that does not produce respiratory depression, pharmacologic tolerance, or physical dependence.

Mu-opioid analgesics are a mainstay in the treatment of acute and chronic pain of multiple origins, but their side effects, such as constipation, respiratory depression, and abuse liability, adversely affect patients. The recent demonstration of the up-regulation and membrane targeting of the delta-opioid receptor (DOR) following inflammation and the consequent enhanced therapeutic effect of delta-opioid agonists have enlivened the search for delta-opioid analgesic agents. JNJ-20788560 [9-(8-azabicyclo-[3.2.1]oct-3-ylidene)-9H-xanthene-3-carboxylic acid diethylamide] had an affinity of 2.0 nM for DOR (rat brain cortex binding assay) and a naltrindole sensitive DOR potency of 5.6 nM (5'-O-(3-[(35)S]thio)triphosphate assay). The compound had a potency of 7.6 mg/kg p.o. in a rat zymosan radiant heat test and of 13.5 mg/kg p.o. in a rat Complete Freund's adjuvant RH test but was virtually inactive in an uninflamed radiant heat test. In limited studies, tolerance was not observed to the antihyperalgesic or antinociceptive effects of the compound. Unlike ibuprofen, JNJ-20788560 did not produce gastrointestinal (GI) erosion. Although morphine reduced GI motility at all doses tested and reached nearly full effect at the highest dose, JNJ-20788560 did not retard transit at the lowest dose and reached only 11% reduction at the highest dose administered. Unlike morphine, JNJ-20788560 did not exhibit respiratory depression (blood gas analysis), and no withdrawal signs were precipitated by the administration of opioid (mu or delta) antagonists. Coupled with the previously published lack of self-administration behavior of the compound by alfentanil-trained primates, these findings strongly recommend delta-opioid agonists such as JNJ-20788560 for the relief of inflammatory hyperalgesia.

Discovery of piperidine carboxamide TRPV1 antagonists.

A series of piperidine carboxamides were developed as potent antagonists of the transient receptor potential vanilloid-1 (TRPV1), an emerging target for the treatment of pain. A focused library of polar head groups led to the identification of a benzoxazinone amide that afforded good potency in cell-based assays. Synthesis and a QSAR model will be presented.

N-pyridin-3-yl- and N-quinolin-3-yl-benzamides: modulators of human vanilloid receptor 1 (TRPV1).

High throughput screening of our compound library revealed a series of N-pyridyl-3-benzamides as low micromolar agonists of the human TRPV1 receptor. Synthesis of analogs in this series led to the discovery of a series of N-quinolin-3-yl-benzamides as low nanomolar antagonists of human TRPV1.

Heteroaryl beta-tetralin ureas as novel antagonists of human TRPV1.

We report on a series of alpha-substituted-beta-tetralin-derived and related phenethyl-based isoquinolinyl and hydroxynaphthyl ureas as potent antagonists of the human TRPV1 receptor. The synthesis and Structure-activity relationships (SAR) of the series are described.

High-throughput screening for N-type calcium channel blockers using a scintillation proximity assay.

N-type calcium channels located on presynaptic nerve terminals regulate neurotransmitter release, including that from the spinal terminations of primary afferent nociceptors. Accordingly, N-type calcium channel blockers may have clinical utility as analgesic drugs. A selective N-type calcium channel inhibitor, ziconotide (Prialt), is a neuroactive peptide recently marketed as a novel nonopioid treatment for severe chronic pain. To develop a small-molecule N-type calcium channel blocker, the authors developed a 96-well plate high-throughput screening scintillation proximity assay (SPA) for N-type calcium channel blockers using [125I]-labeled omega-conotoxin GVIA as a channel-specific ligand. Assay reagents were handled using Caliper's Allegro automation system, and bound ligands were detected using a PerkinElmer TopCount. Using this assay, more than 150,000 compounds were screened at 10 microM and approximately 340 compounds were identified as hits, exhibiting at least 40% inhibition of [125I]GVIA binding. This is the 1st demonstration of the use of [125I]-labeled peptides with SPA beads to provide a binding assay for the evaluation of ligand binding to calcium channels. This assay could be a useful tool for drug discovery.

Identification of potent phenyl imidazoles as opioid receptor agonists.

Using previously reported opioid receptor (OR) agonist analogs 4a-c as starting points, the structure-activity relationship (SAR) for their related series has been further refined. This SAR study has led to the identification of 2,6-di-Me-Tyr (DMT) analogs 4h and 4j as the most potent OR agonist within the series. In addition, it was discovered that 4-(aminocarbonyl)-2,6-dimethyl-Phe is a reasonable bioisostere surrogate for the DMT moiety, as supported by the OR activities of compounds 4x and 4y.

Cloning, expression, and functional characterization of human cyclooxygenase-1 splicing variants: evidence for intron 1 retention.

Recently, a splicing variant of cyclooxygenase (COX)-1, arising via the retention of its intron 1, was identified in canine. It was called COX-3 and was reported to be differentially sensitive to inhibition by various nonsteroidal anti-inflammatory drugs (NSAIDs) as well as acetaminophen (Chandrasekharan et al., 2002). However, the existence of an orthologous splicing variant in human tissues has been questioned due to a reading frame shift and premature termination. In this study, we first confirmed the existence of intron 1-retained COX-1 in certain human tissues at both the mRNA and protein levels. Molecular biology studies revealed that three distinct COX-1 splicing variants exist in human tissues. The most prevalent of these variants, called COX-1b1, arises via retention of the entire 94 base pair (bp) of intron 1, leading to a shift in the reading frame and termination at bp 249. However, the other two variant types, called COX-1b2 and COX-1b3, retain entire intron 1, but they are missing a nucleotide in one of two different positions, thereby encoding predicted full-length and likely COX-active proteins. Functional studies revealed that the COX-1b2 is able to catalyze the synthesis of prostaglandin F2alpha from arachidonic acid with Km and Vmax values of 0.54 microM and 3.07 pmol/mg/min, respectively. However, no significant differential selectivity for inhibition by selected NSAIDs was observed. Accordingly, we conclude that intron 1-retained human COX-1 is not likely to be the therapeutic target of acetaminophen or a candidate of COX-3.

Identification and biological evaluation of 4-(3-trifluoromethylpyridin-2-yl)piperazine-1-carboxylic acid (5-trifluoromethylpyridin-2-yl)amide, a high affinity TRPV1 (VR1) vanilloid receptor antagonist.

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.