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  • C07D271/06—1,2,4-Oxadiazoles; Hydrogenated 1,2,4-oxadiazoles
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  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D413/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and oxygen atoms as the only ring hetero atoms
  • C07D413/02—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and oxygen atoms as the only ring hetero atoms containing two hetero rings
  • C07D413/04—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and oxygen atoms as the only ring hetero atoms containing two hetero rings directly linked by a ring-member-to-ring-member bond
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  • C07D471/02—Heterocyclic compounds containing nitrogen atoms as the only ring hetero atoms in the condensed system, at least one ring being a six-membered ring with one nitrogen atom, not provided for by groups C07D451/00 - C07D463/00 in which the condensed system contains two hetero rings
  • C07D471/04—Ortho-condensed systems

Definitions

• the invention relates to novel compounds and compositions comprising oxadiazole derivatives, and methods of using the same.
• acetylcholine exerts its biological effect via two types of cholinergic receptors, the muscarinic acetylcholine receptors (mAChR) and the nicotinic acetylcholine receptors (nAChR).
• nAChRs are pentameric assemblies of subunits surrounding a central pore that gates the flux OfNa + , K + and Ca 2+ ions. At least 16 subunit proteins, i.e. ⁇ 2- ⁇ l ⁇ , ⁇ l- ⁇ lO, ⁇ , ⁇ and ⁇ , have been identified in neuronal tissues.
• neuronal nAChR or neuronal nicotinic receptor (NNR) assemblies can be homomeric, comprising ⁇ 7 or ⁇ 8 or ⁇ 9 subunits, or heteromeric, usually with at least one subunit from the ⁇ group ( ⁇ 2, ⁇ 3, ⁇ 4, ⁇ 6) and the remainder from the ⁇ group ( ⁇ 2, ⁇ 4).
• ⁇ 4 ⁇ 2-containing NNR and ⁇ 7-containing NNR subtypes are the most widespread and mediate synaptic and, possibly, paracrine functions.
• NNRs are expressed at high levels in areas involved with learning and memory, and play key roles in modulating neurotransmission in these regions.
• Reduced cholinergic activity and dysregulation of NNRs have been correlated with disease states involving cognitive deficits, progressive dementia, and epilepsy. Accordingly, these NNRs are implicated in a range of physiological and patho-physiological functions related to cognitive function, learning and memory, reward, motor control, arousal and analgesia (reviewed in Gopalakrishnan, M. et al., Ion channels - Ligand-gated. Comprehensive Medicinal Chemistry II, Edited by Triggle D. J. et al., Major Reference Works, Elsevier. Unit 2.22, pp 877-918, 2006).
• Neuronal nicotinic receptors especially ⁇ 4 ⁇ 2 neuronal nicotinic acetylcholine receptors (nAChRs) have been targeted for pain and various central nervous system diseases.
• Antisense knockdown of the ⁇ 4 subunit was found to decrease the analgesic effect of agonists (Bitner RS, et al., Brain Res. 871 :66-74, 2000).
• Reduced antinociceptive responses to nicotine also is seen in ⁇ 4 gene knockout animals (Marubio LM, et al., Nature 398:805- 810, 1999).
• ⁇ 4 and ⁇ 2 nAChRs are responsible for mediating nicotinic analgesia at supraspinal responses and spinal sites (Decker, MW, et al., Curr Top Med Chem., 4: 369-384, 2004).
• Antinociceptive effects through ⁇ 4 ⁇ 2 nAChRs are generally attributed to stimulation of brainstem monoaminergic transmission, particularly in the raphe (Cucchiaro G, et al., J Pharmacol Exp Ther. 313:389-394, 2005).
• ⁇ 4 ⁇ 2 stimulation of GABAergic and glycinergic inhibitory transmission in the spinal cord also may contribute (Rashid MH, et al., Pain 125:125-135, 2006).
• Central ⁇ 3* nAChRs may contribute to nicotinic analgesia (Khan IM, et al., J Neurocytol. 33:543-556, 2004), but ⁇ 3 ⁇ 4 ligands are of little interest because of likely autonomic side effects. Indeed, the goal has been to avoid ⁇ 3* neuronal nicotinic receptor (NNR), as the dose-limiting emetic liability of nonselective compounds has been attributed to activation of ⁇ 3 containing nAChRs. ⁇ 3* nAChRs are expressed in the enteric nervous system as well as in other components of the peripheral and central nervous systems.
• nAChRs in the dorsal motor nucleus of the vagus and in nucleus tractus solitarius have been implicated in gastric and blood pressure responses to nicotine injected locally (Ferreira M, et al J. Pharmacol. Exp. Ther., 294:230-238, 2000).
• Compounds with varying degrees of selectivity for ⁇ 4 ⁇ 2 nAChRs over other nicotinic subtypes ⁇ 3, ⁇ 7, ⁇ l -containing
• ABT-594 (referred to as Compound A in this application) was efficacious across a number of rodent models of nociception including acute thermal, chemogenic, neuropathic, and visceral pain (Decker MW, et al., Expert Opinion on Investigational Drugs, 10:1819-1830, 2001).
• Available data suggest that ligands with selectivity for the ⁇ 4 ⁇ 2 nAChRs over ⁇ 3 ⁇ 4 efficacy is preferred for low adverse event profiles.
• the therapeutic index could be expanded by (a) reducing ⁇ 3 ⁇ 4 activity or (b) increasing ⁇ 4 ⁇ 2 efficacy without increasing ⁇ 3 ⁇ 4 activity.
• an ⁇ 4 ⁇ 2 selective positive allosteric modulator PAM
• PAM selective positive allosteric modulator
• Positive allosteric modulators can potentiate effects by enhancing the efficacy and or potency of agonists. Accordingly, an ⁇ 4 ⁇ 2 selective positive allosteric modulator can selectively enhance effects at the preferred ⁇ 4 ⁇ 2 nAChRs over other nAChR subtypes.
• Initially known positive allosteric modulators of the ⁇ 4 ⁇ 2 nAChRs have been nonselective and not very potent.
• nefiracetam has been reported to potentiate ⁇ 4 ⁇ 2 nAChR responses (Narahashi T, et al, Biol.Pharm.Bull, 27:1701-1706, 2004). More recently, subtype selective PAMs have been disclosed. Compounds like 3-(3-pyridin-3-yl- l,2,4-oxadiazol-5-yl) benzonitrile and others have been described with robust ⁇ 4 ⁇ 2 PAM effects with little modulatory activity at other subtypes such as ⁇ 3 ⁇ 4 (e.g., see WO 2006/114400, published November 2, 2006).
• Pain is an unmet medical need and the methods and possibilities for treatments of such indications are insufficient. Although continued efforts are being made to treat pain using nAChR agonists, robust efficacy in pain may be limited by the range of side effects associated with their use, albeit to differing degrees. In light of the significance of chronic pain and the limitations in their treatment, it would be beneficial to identify new methods of treating such disorders, particularly in a manner that reduces adverse ganglionic effects such as at the gastrointestinal systems (e.g. emesis). It would be particularly beneficial to identify compounds and compositions that offer an opportunity to wide the therapeutic window of nicotinic (nAChR) agonists in pain. Enhanced efficacy with nAChR ligands for the treatment of other central nervous system diseases such as cognitive and attention deficits is also desirable.
• nAChR nicotinic
• the invention relates to oxadiazole compounds, compositions comprising such compounds, and methods of using such compounds and compositions. [0009] In one aspect, the invention is directed to compounds of formula II
• Ar 1 and Ar 2 are independently optionally substituted aryl or heteroaryl, or a pharmaceutically acceptable salt thereof.
• compositions comprising compounds of the invention.
• Such compositions can be administered in accordance with a method of the invention, typically as part of a therapeutic regimen for treatment or prevention of conditions and disorders related to nAChR activity, and more particularly ⁇ 4 ⁇ 2 nAChR positive allosteric modulator activity.
• Yet another aspect of the invention relates to a method of modulating ⁇ 4 ⁇ 2 nAChR positive allosteric modulator activity.
• the method is useful for treating, preventing or both treating and preventing conditions and disorders related to ⁇ 4 ⁇ 2 nAChR positive allosteric modulator activity, particularly in mammals.
• One embodiment of this invention provides compositions that are useful for treatment of diseases or disorders related to the nicotinic acetylcholine receptor (nAChR) with enhanced efficacy and less side effects than nicotinic agents alone.
• Another embodiment of the invention relates to methods and compositions wherein the efficacy of a nicotinic (nAChR) agent is enhanced by co-dosing a nicotinic ligand with a positive allosteric modulator (PAM) of nAChR subtype ⁇ 4 ⁇ 2.
• PAM positive allosteric modulator
• Another embodiment of the invention relates to methods and compositions for treatment of individuals with nAChR- mediated diseases or disorders, and particularly for pain or CNS disorders, which involves a combination of a nicotinic ligand with an ⁇ 4 ⁇ 2 positive allosteric modulator.
• the invention relates to methods and compositions comprising (i) a nicotinic acetylcholine receptor ligand; and (ii) a nicotinic acetylcholine receptor subtype ⁇ 4 ⁇ 2 selective positive allosteric modulator, in admixture with at least one pharmaceutically acceptable excipient.
• Figures IA and IB depict responses of a representative nicotinic acetylcholine receptor ligand, 5-[(2R)-azetidin-2-ylmethoxy]-2-chloropyridine (Compound A) in the absence and presence of a nicotinic acetylcholine receptor subtype ⁇ 4 ⁇ 2 positive allosteric modulator, 3-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5-yl)benzonitrile (PAM, Compound 1), at human ⁇ 4 ⁇ 2 or ⁇ 3 ⁇ 4 nicotinic acetylcholine receptor subtypes expressed in HEK-293 cells.
• PAM nicotinic acetylcholine receptor subtype ⁇ 4 ⁇ 2 positive allosteric modulator
• PAM 3-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5-yl)benzonitrile
• FIGS. 2 A and 2B depict responses of another representative nicotinic acetylcholine receptor ligand, (3R)-l-pyridin-3-ylpyrrolidin-3-amine (Compound B), in the absence and presence of an ⁇ 4 ⁇ 2 positive allosteric modulator, 3-(3-(pyridin-3-yl)- 1,2,4- oxadiazol-5-yl)benzonitrile (PAM, Compound 1), at human ⁇ 4 ⁇ 2 or ⁇ 3 ⁇ 4 nicotinic receptor subtypes expressed in HEK-293 cells.
• 3R 3-(3-(pyridin-3-yl)- 1,2,4- oxadiazol-5-yl)benzonitrile (PAM, Compound 1)
• Figures 3 A and 3B graphically represent the effect of ⁇ 4 ⁇ 2 positive allosteric modulator in enhancing the effect of a nAChR partial agonist, such as 2-methyl-3-(2-(S)- pyrrolidinylmethoxy)pyridine (Compound C, also known as ABT-089; Reuter, L. E., et al, CNS Drug Rev., 10 (2), 167-182, 2004).
• a nAChR partial agonist such as 2-methyl-3-(2-(S)- pyrrolidinylmethoxy)pyridine
• Compound C alone does not evoke a calcium response, but when co-applied with the PAM, 3-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5- yl)benzonitrile (Compound 1), evoked robust responses at ⁇ 4 ⁇ 2 nAChRs ( Figure 3A), but not at ⁇ 3 ⁇ 4 nAChRs ( Figure 3B).
• Compound C is a representative of other nicotinic partial agonists.
• Compound D alone does not evoke a response, but when co-applied with the PAM, 3-(3- (pyridin-3-yl)-l,2,4-oxadiazol-5-yl)benzonitrile (Compound 1), evoked robust responses at ⁇ 4 ⁇ 2 nAChRs ( Figure 4A), but not at ⁇ 3 ⁇ 4 nAChRs ( Figure 4B).
• Compound D is a representative of other nicotinic partial agonists.
• Figure 5 shows correlation of potencies for activation of ⁇ 4 ⁇ 2 nAChRs by various nicotinic acetycholine receptor ligands in the presence and absence of an ⁇ 4 ⁇ 2 PAM, 3-(3- (pyridin-3-yl)-l,2,4-oxadiazol-5-yl)benzonitrile (Compound 1).
• these nicotinic ligands are found to be more potent in activating ⁇ 4 ⁇ 2 nAChRs in the presence of ⁇ 4 ⁇ 2 PAM (Compound 1).
• Figure 6A graphically represents the effect of an ⁇ 4 ⁇ 2 PAM, 3-(3-(pyridin-3-yl)- l,2,4-oxadiazol-5-yl)benzonitrile (Compound 1), on enhancing the efficacy by 5-[(2R)- azetidin-2-ylmethoxy]-2-chloropyridine (Compound A) in reversing neuropathic pain.
• Figure 6B graphically represents the dose dependent effect of an ⁇ 4 ⁇ 2 PAM, 3-(3- (pyridin-3-yl)-l,2,4-oxadiazol-5-yl)benzonitrile (Compound 1), on enhancing the neuropathic pain efficacy of 5-[(2R)-azetidin-2-ylmethoxy]-2-chloropyridine (Compound A).
• An ineffective dose of Compound A (I nmol/kg) demonstrates effect when combined with various doses of ⁇ 4 ⁇ 2 PAM (Compound 1).
• Figure 7A shows dose-dependent effects in neuropathic pain of 5-[(2R)-azetidin-2- ylmethoxy]-2-chloropyridine (Compound A) alone, ⁇ 4 ⁇ 2 PAM, 3-(3-(pyridin-3-yl)-l,2,4- oxadiazol-5-yl)benzonitrile (Compound 1), alone and a combination of Compound 1 (3.5 ⁇ mol/kg) with various doses of Compound A.
• An ⁇ 4 ⁇ 2 PAM (Compound 1) alone is ineffective.
• the dose response curve of Compound A in the Chung model of neuropathic pain shifts to the left.
• Figure 7B shows the effects on emesis in ferrets.
• the effects of 5-[(2R)-azetidin- 2-ylmethoxy]-2-chloropyridine (Compound A) alone, ⁇ 4 ⁇ 2 PAM, 3-(3-(pyridin-3-yl)- 1,2,4- oxadiazol-5-yl)benzonitrile (Compound 1), alone and a combination of Compound 1 (3.5 ⁇ mol/kg) with various doses of Compound A are shown.
• An ⁇ 4 ⁇ 2 PAM (Compound 1) alone does not cause emesis, and does not shift the dose response curve of Compound A in the ferret model of emesis.
• Figure 8 A and 8B show plasma level analysis in models of neuropathic pain and emesis.
• the efficacy of Compound A is shifted left- ward as shown in Figure 8 A, but no shift in effects on emesis are shown in Figure 8B.
• the maximal efficacy of Compound A can be realized in neuropathic pain without incidence of emesis, in presence of ⁇ 4 ⁇ 2 PAM, 3-(3- (pyridin-3-yl)-l,2,4-oxadiazol-5-yl)benzonitrile (Compound 1).
• the data demonstrates that the therapeutic window of ⁇ 4 ⁇ 2 nAChR agonists is wider in the presence of ⁇ 4 ⁇ 2 PAM.
• Figure 9 shows the efficacy of a partial agonist, Compound D, in the presence and absence of ⁇ 4 ⁇ 2 PAM, 3-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5-yl)benzonitrile (Compound 1).
• Compound D when administered alone is ineffective in relieving pain.
• Compound D When co-dosed with ⁇ 4 ⁇ 2 PAM (Compound 1), Compound D demonstrates effect, and the data demonstrate that Compound D provides significant relief of neuropathic pain in rats.
• Figure 10 is a graphical representation of specific binding to receptor sites in human brain membranes (fmoles per mg protein) as a function of the concentration of a radioligand [ 3 H]-3-(5-(pyridin-3-yl)-l,2,4-oxadiazol-3-yl)benzonitrile ([ 3 H]-POB, nM).
• C x - C y wherein x and y are integers from 1 to 10 refer to a range of carbon atoms in the hydrocarbon portion of the group which it modifies, for example, the designation "Ci - C 6 haloalkyl” refers to at least one halogen appended to the parent molecular moiety through an alkyl group having from 1 to 6 carbon atoms.
• alkenyl means a straight or branched chain hydrocarbon containing from 2 to 10 carbons and containing at least one carbon-carbon double bond formed by the removal of two hydrogens. Representative examples of alkenyl include, but are not limited to, ethenyl, 2-propenyl, 2-methyl-2-propenyl, 3-butenyl, A- pentenyl, 5-hexenyl, 2-heptenyl, 2-methyl-l-heptenyl, and 3-decenyl.
• alkoxy means an alkyl group, as defined herein, appended to the parent molecular moiety through an oxygen atom.
• Representative examples of alkoxy include, but are not limited to, methoxy, ethoxy, propoxy, 2-propoxy, butoxy, tert- butoxy, pentyloxy, and hexyloxy .
• alkoxy alkoxy means an alkoxy group, as defined herein, appended to the parent molecular moiety through another alkoxy group, as defined herein.
• Representative examples of alkoxyalkoxy include, but are not limited to, tert- butoxymethoxy, 2-ethoxyethoxy, 2-methoxyethoxy, and methoxymethoxy.
• alkoxyalkoxyalkyl as used herein, means an alkoxyalkoxy group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• alkoxyalkoxyalkyl include, but are not limited to, tert- butoxymethoxymethyl, ethoxymethoxymethyl, (2-methoxyethoxy)methyl, and 2-(2- methoxyethoxy)ethyl.
• alkoxyalkyl means an alkoxy group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• alkoxyalkyl include, but are not limited to, tert-butoxymethyl, 2- ethoxyethyl, 2-methoxyethyl, and methoxymethyl.
• alkoxycarbonyl means an alkoxy group, as defined herein, appended to the parent molecular moiety through a carbonyl group, as defined herein.
• Representative examples of alkoxycarbonyl include, but are not limited to, methoxycarbonyl, ethoxycarbonyl, and tert-butoxy carbonyl.
• alkoxycarbonylalkyl means an alkoxycarbonyl group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• Representative examples of alkoxycarbonylalkyl include, but are not limited to, 3-methoxycarbonylpropyl, 4-ethoxycarbonylbutyl, and 2-tert-butoxycarbonylethyl.
• alkoxycarbonylamino as used herein, means an alkoxycarbonyl group, as defined herein, appended to the partent molecular moiety through an amino group, as defined herein.
• alkoxycarbonyamino include, but are not limited to, t-butoxycarbonylamino and methoxycarbonylamino.
• alkoxycarbonylaminoalkyl means an alkoxycarbonylamino group, as defined herein, appended to the partent molecular moiety through an alkyl group, as defined herein.
• alkoxycarbonyaminoalkyl include, but are not limited to, t-butoxycarbonylaminomethyl and methoxycarbonylaminopropyl.
• alkoxysulfonyl means an alkoxy group, as defined herein, appended to the parent molecular moiety through a sulfonyl group, as defined herein.
• Representative examples of alkoxysulfonyl include, but are not limited to, methoxysulfonyl, ethoxy sulfonyl and propoxy sulfonyl.
• alkyl means a straight or branched chain hydrocarbon containing from 1 to 10 carbon atoms.
• Representative examples of alkyl include, but are not limited to, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n- pentyl, isopentyl, neopentyl, n-hexyl, 3-methylhexyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, n-heptyl, n-octyl, n-nonyl, and n-decyl.
• alkylamino means an alkyl group, as defined herein, appended to the parent molecular moiety through an amino group, as defined herein.
• Representative examples of alkylamino include, but are not limited to, methylamino, ethylamino, and t-butylamino.
• alkylcarbonyl means an alkyl group, as defined herein, appended to the parent molecular moiety through a carbonyl group, as defined herein.
• alkylcarbonyl include, but are not limited to, acetyl, 1-oxopropyl, 2,2-dimethyl-l-oxopropyl, 1-oxobutyl, and 1-oxopentyl.
• alkylcarbonylalkyl means an alkylcarbonyl group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• Representative examples of alkylcarbonylalkyl include, but are not limited to, 2- oxopropyl, 3,3-dimethyl-2-oxopropyl, 3-oxobutyl, and 3-oxopentyl.
• alkylcarbonyloxy means an alkylcarbonyl group, as defined herein, appended to the parent molecular moiety through an oxygen atom.
• Representative examples of alkylcarbonyloxy include, but are not limited to, acetyloxy, ethylcarbonyloxy, and tert-butylcarbonyloxy.
• alkylcarbonyloxylalkyl means an alkylcarbonyloxy group, as defined herein, appended to the parent molecular moiety through an alkyl group.
• alkylene as used herein, means a divalent group derived from a straight or branched chain hydrocarbon of from 1 to 10 carbon atoms.
• alkylene examples include, but are not limited to, -CH 2 -, -CH(CH 3 )-, -C(CH 3 ) 2 -, -CH 2 CH 2 - , -CH 2 CH 2 CH 2 -, -CH 2 CH 2 CH 2 CH 2 -, and -CH 2 CH(CH 3 )CH 2 -.
• alkylsulfinyl means an alkyl group, as defined herein, appended to the parent molecular moiety through a sulfmyl group, as defined herein.
• alkylsulfinyl include, but are not limited to, methylsulfinyl and ethylsulfmyl.
• alkylsulfinylalkyl means an alkylsulfinyl group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• Representative examples of alkylsulfinylalkyl include, but are not limited to, methylsulfmylmethyl and ethylsulfmylmethyl.
• alkylsulfonyl means an alkyl group, as defined herein, appended to the parent molecular moiety through a sulfonyl group, as defined herein.
• Representative examples of alkylsulfonyl include, but are not limited to, methylsulfonyl and ethylsulfonyl.
• alkylsulfonylalkyl means an alkylsulfonyl group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• Representative examples of alkylsulfonylalkyl include, but are not limited to, methylsulfonylmethyl and ethylsulfonylmethyl.
• alkylthio as used herein, means an alkyl group, as defined herein, appended to the parent molecular moiety through a sulfur atom.
• alkylthio include, but are not limited, methylthio, ethylthio, tert-butylthio, and hexylthio.
• alkylthioalkyl means an alkylthio group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• alkylthioalkyl include, but are not limited, methylthiomethyl and 2-(ethylthio)ethyl.
• alkynyl means a straight or branched chain hydrocarbon group containing from 2 to 10 carbon atoms and containing at least one carbon- carbon triple bond. Representative examples of alkynyl include, but are not limited, to acetylenyl, 1-propynyl, 2-propynyl, 3-butynyl, 2-pentynyl, and 1-butynyl.
• amino means a -NH 2 group.
• aminoalkyl means at least one amino group, as defined herein, is appended to the parent molecular moiety through an alkyl group, as defined herein.
• Representative examples of hydroxyalkyl include, but are not limited to, aminomethyl, 2- aminoethyl, 3-aminopropyl, and 2-ethyl-4-aminoheptyl.
• amido means an amino (H 2 N-), alkylamino (alkylN(H)-), dialkylamino (alkyl 2 N-), arylamino (arylN(H)-), arylalkylamino (arylalkylN(H)-) or another substituted amine group appended to the parent molecular moiety through a carbonyl group, as defined herein.
• Representative examples of amido include, but are not limited to, aminocarbonyl, methylaminocarbonyl, dimethylaminocarbonyl, and ethylmethylaminocarbonyl.
• aryl means phenyl, a bicyclic aryl or a tricyclic aryl.
• the bicyclic aryl is naphthyl, a phenyl fused to a cycloalkyl, or a phenyl fused to a cycloalkenyl.
• Representative examples of the bicyclic aryl include, but are not limited to, dihydroindenyl, indenyl, naphthyl, dihydronaphthalenyl, and tetrahydronaphthalenyl.
• the tricyclic aryl is anthracene or phenanthrene, or a bicyclic aryl fused to a cycloalkyl, or a bicyclic aryl fused to a cycloalkenyl, or a bicyclic aryl fused to a phenyl.
• Representative examples of tricyclic aryl ring include, but are not limited to, azulenyl, dihydroanthracenyl, fluorenyl, and tetrahydrophenanthrenyl.
• aryl groups of this invention can be substituted with 0, 1, 2, 3, 4 or 5 substituents independently selected from alkenyl, alkoxy, alkoxyalkoxy, alkoxyalkoxyalkyl, alkoxyalkyl, alkoxycarbonyl, alkoxycarbonylalkyl, alkyl, alkylcarbonyl, alkylcarbonylalkyl, alkylcarbonyloxy, alkylcarbonyloxyalkyl, alkylsulfmyl, alkylsulfinylalkyl, alkylsulfonyl, alkylsulfonylalkyl, alkylthio, alkylthioalkyl, alkynyl, arylalkyl, arylalkoxy, aryloxy, carboxy, carboxyalkyl, cyano, cyanoalkyl, formyl, formylalkyl, halogen, haloalkyl, haloalkoxy,
• arylalkoxy include, but are not limited to, 2-phenylethoxy, 3- naphth-2-ylpropoxy, and 5-phenylpentyloxy.
• arylalkyl means an aryl group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• Representative examples of arylalkyl include, but are not limited to, benzyl, 2-phenylethyl, 3- phenylpropyl, and 2-naphth-2-ylethyl.
• aryloxy means an aryl group, as defined herein, appended to the parent molecular moiety through an oxygen atom.
• Representative examples of aryloxy include, but are not limited to, phenoxy, naphthyloxy, 3-bromophenoxy, 4- chlorophenoxy, 4-methylphenoxy, and 3,5-dimethoxyphenoxy.
• carbonyl as used herein, means a -C(O)- group.
• carboxyalkyl means a carboxy group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• carboxyalkyl examples include, but are not limited to, carboxymethyl, 2- carboxyethyl, and 3-carboxypropyl.
• the term "concurrent administration” refers to administering the ⁇ 4 ⁇ 2 receptor ligand to a patient, who has been prescribed (or has consumed) at least one an ⁇ 4 ⁇ 2 PAM, at an appropriate time so that the patient's symptoms may subside. This may mean simultaneous administration of an ⁇ 4 ⁇ 2 PAM and an ⁇ 4 ⁇ 2 receptor ligand, or administration of the medications at different, but appropriate times. Establishing such a proper dosing schedule will be readily apparent to one skilled in the art, such as a physician treating various pain states.
• cyano means a -CN group.
• cyanoalkyl means a cyano group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• cyanoalkyl include, but are not limited to, cyanomethyl, 2- cyanoethyl, and 3-cyanopropyl.
• cycloalkenyl means a cyclic hydrocarbon containing from 3 to 8 carbons and containing at least one carbon-carbon double bond formed by the removal of two hydrogens.
• Representative examples of cycloalkenyl include, but are not limited to, 2-cyclohexen-l-yl, 3-cyclohexen-l-yl, 2,4-cyclohexadien-l-yl and 3-cyclopenten-
• cycloalkyl means a monocyclic, bicyclic, or tricyclic ring system.
• Monocyclic ring systems are exemplified by a saturated cyclic hydrocarbon group containing from 3 to 8 carbon atoms. Examples of monocyclic ring systems include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl.
• Bicyclic ring systems are exemplified by a bridged monocyclic ring system in which two adjacent or non- adjacent carbon atoms of the monocyclic ring are linked by an alkylene bridge of between one and three additional carbon atoms.
• bicyclic ring systems include, but are not limited to, bicyclo[3.1.1]heptane, bicyclo[2.2.1]heptane, bicyclo[2.2.2]octane, bicyclo[3.2.2]nonane, bicyclo[3.3.1]nonane, and bicyclo[4.2.1]nonane.
• Tricyclic ring systems are exemplified by a bicyclic ring system in which two non-adjacent carbon atoms of the bicyclic ring are linked by a bond or an alkylene bridge of between one and three carbon atoms.
• tricyc lie-ring systems include, but are not limited to, tricyclo[3.3.1.0 3 ' 7 ]nonane and tricyclo[3.3.1.1 3 ' 7 ]decane (adamantane).
• the cycloalkyl groups of the invention are optionally substituted with 1, 2, 3, 4 or 5 substituents selected from the group consisting of alkenyl, alkoxy, alkoxyalkoxy, alkoxyalkyl, alkoxycarbonyl, alkoxysulfonyl, alkyl, alkylcarbonyl, alkylcarbonyloxy, alkylsulfonyl, alkylthio, alkylthioalkyl, alkynyl, carboxy, cyano, formyl, haloalkoxy, haloalkyl, halogen, hydroxy, hydroxyalkyl, mercapto, oxo, -NZ 1 Z 2 , and (NZ 3 Z 4 )carbony
• cycloalkylalkyl means a cycloalkyl group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• Representative examples of cycloalkylalkyl include, but are not limited to, cyclopropylmethyl, 2-cyclobutylethyl, cyclopentylmethyl, cyclohexylmethyl, and 4- cycloheptylbutyl.
• dialkylamino refers to two independent alkyl groups, as defined herein, appended to the parent molecular moiety through an amino group, as defined herein.
• dialkylamino include, but are not limited to, dimethylamino, diethylamino, ethylmethylamino, butylmethylamino, ethylhexylamino, and the like.
• dialkylaminoalkyl means a dialkyl group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• dialkylaminoalkyl include, but are not limited to, dimethylaminomethyl and dimethylaminoethyl.
• formyl as used herein, means a -C(O)H group.
• formylalkyl as used herein, means a formyl group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein. Representative examples of formylalkyl include, but are not limited to, formylmethyl and 2- formylethyl.
• halo or halogen
• haloalkoxy means at least one halogen, as defined herein, appended to the parent molecular moiety through an alkoxy group, as defined herein.
• Representative examples of haloalkoxy include, but are not limited to, chloromethoxy, 2- fluoroethoxy, trifluoromethoxy, and pentafluoroethoxy .
• haloalkyl means at least one halogen, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• Representative examples of haloalkyl include, but are not limited to, chloromethyl, 2- fluoroethyl, trifluoromethyl, pentafluoroethyl, and 2-chloro-3-fluoropentyl.
• haloalkylcarbonyl means a haloalkyl group, as defined herein, appended to the parent molecular moiety through a carbonyl group, as defined herein.
• haloalkylcarbonyl include, but are not limited to, trichloromethylcarbonyl and trifluoromethylcarbonyl.
• heteroaryl means a monocyclic heteroaryl or a bicyclic heteroaryl.
• the monocyclic heteroaryl is a 5 or 6 membered ring that contains at least one heteroatom selected from the group consisting of nitrogen, oxygen and sulfur.
• the 5 membered ring contains two double bonds and the 6 membered ring contains three double bonds.
• the 5 or 6 membered heteroaryl is connected to the parent molecular moiety through any carbon atom or any substitutable nitrogen atom contained within the heteroaryl, provided that proper valance is maintained.
• monocyclic heteroaryl include, but are not limited to, furyl, imidazolyl, isoxazolyl, isothiazolyl, oxadiazolyl, oxazolyl, pyridinyl, pyridazinyl, pyrimidinyl, pyrazinyl, pyrazolyl, pyrrolyl, tetrazolyl, thiadiazolyl, thiazolyl, thienyl, triazolyl, and triazinyl.
• the bicyclic heteroaryl consists of a monocyclic heteroaryl fused to a phenyl, or a monocyclic heteroaryl fused to a cycloalkyl, or a monocyclic heteroaryl fused to a cycloalkenyl, or a monocyclic heteroaryl fused to a monocyclic heteroaryl, or a monocyclic heteroaryl fused to a monocyclic heterocycle.
• the bicyclic heteroaryl is connected to the parent molecular moiety through any carbon atom or any substitutable nitrogen atom contained within the bicyclic heteroaryl, provided that proper valance is maintained.
• bicyclic heteroaryl include, but are not limited to, azaindolyl, benzimidazolyl, benzo[d][l,3]dioxolyl, benzofuranyl, benzoxadiazolyl, benzo[d]imidazolyl, benzo[d]imidazle-2(3H)-thione, benzoisoxazole, benzoisothiazole, benzooxazole, benzooxazolone, benzo[d][l,2,3]thiadiazolyl, 1,3-benzothiazolyl, benzothiophenyl, benzo[d][l,2,3]triazolyl, cinnolinyl, 2,2-difluorobenzo[d][l,3]dioxolyl, furopyridine, imidazopyridinyl, indolyl, indazolyl, isobenzofuran, isoindolyl, isoquinolin
• heteroaryl groups of the invention are optionally substituted with 1, 2, 3 or 4 substituents independently selected from the group consisting of alkenyl, alkoxy, alkoxyalkoxy, alkoxyalkyl, alkoxycarbonyl, alkoxycarbonylalkyl, alkoxysulfonyl, alkyl, alkylcarbonyl, alkylcarbonylalkyl, alkylcarbonyloxy, alkylthio, alkylthioalkyl, alkynyl, carboxy, carboxyalkyl, cyano, cyanoalkyl, formyl, haloalkoxy, haloalkyl, halogen, hydroxy, hydroxyalkyl, mercapto, nitro, -NZ 1 Z 2 , (NZ 3 Z 4 )carbonyl and oxo.
• Heteroaryl groups of the invention that are substituted with a hydroxyl group may be present as tautomers.
• heterocycle or “heterocyclic”, as used herein, means a monocyclic heterocycle, a bicyclic heterocycle or a tricyclic heterocycle.
• the monocyclic heterocycle is a 3, 4, 5, 6 or 7 membered ring containing at least one heteroatom independently selected from the group consisting of O, N, and S.
• the 3 or 4 membered ring contains 1 heteroatom selected from the group consisting of O, N and S.
• the 5 membered ring contains zero or one double bond and one, two or three heteroatoms selected from the group consisting of O, N and S.
• the 6 or 7 membered ring contains zero, one or two double bonds and one, two or three heteroatoms selected from the group consisting of O, N and S.
• the monocyclic heterocycle is connected to the parent molecular moiety through any carbon atom or any nitrogen atom contained within the monocyclic heterocycle.
• Representative examples of monocyclic heterocycle include, but are not limited to, azetidinyl, azepanyl, aziridinyl, diazepanyl, 1,3-dioxanyl, 1,3-dioxolanyl, 1,3-dithiolanyl, 1,3-dithianyl, imidazolinyl, imidazolidinyl, isothiazolinyl, isothiazolidinyl, isoxazolinyl, isoxazolidinyl, morpholinyl, oxadiazolinyl, oxadiazolidinyl, oxazolinyl, oxazolidinyl, piperazinyl, piperidinyl, pyranyl, pyrazolinyl, pyrazolidinyl, pyr
• the bicyclic heterocycle is a 5 or 6 membered monocyclic heterocycle fused to a phenyl group, or a 5 or 6 membered monocyclic heterocycle fused to a cycloalkyl, or a 5 or 6 membered monocyclic heterocycle fused to a cycloalkenyl, or a 5 or 6 membered monocyclic heterocycle fused to a monocyclic heterocycle.
• the bicyclic heterocycle is connected to the parent molecular moiety through any carbon atom or any nitrogen atom contained within the bicyclic heterocycle.
• bicyclic heterocycle include, but are not limited to, 1,3-benzodioxolyl, 1,3-benzodithiolyl, 2,3-dihydro-l,4-benzodioxinyl, benzodioxolyl, 2,3- dihydro-1-benzofuranyl, 2,3-dihydro-l-benzothienyl, chromenyl and 1,2,3,4-tetrahydroquinolinyl.
• the tricyclic heterocycle is a bicyclic heterocycle fused to a phenyl, or a bicyclic heterocycle fused to a cycloalkyl, or a bicyclic heterocycle fused to a cycloalkenyl, or a bicyclic heterocycle fused to a monocyclic heterocycle.
• the tricyclic heterocycle is connected to the parent molecular moiety through any carbon atom or any nitrogen atom contained within the tricyclic heterocycle.
• tricyclic heterocycle include, but are not limited to, 2,3,4,4a,9,9a-hexahydro-lH-carbazolyl, 5a,6,7,8,9,9a-hexahydrodibenzo[b,d]furanyl, and 5a,6,7,8,9,9a- hexahydrodibenzo[b,d]thienyl.
• heterocycles of this invention are optionally substituted with 1, 2, 3 or 4 substituents independently selected from the group consisting of alkenyl, alkoxy, alkoxyalkoxy, alkoxyalkyl, alkoxycarbonyl, alkoxycarbonylalkyl, alkoxysulfonyl, alkyl, alkylcarbonyl, alkylcarbonylalkyl, alkylcarbonyloxy, alkylthio, alkylthioalkyl, alkynyl, carboxy, carboxyalkyl, cyano, cyanoalkyl, formyl, haloalkoxy, haloalkyl, halogen, hydroxy, hydroxyalkyl, nitro, mercapto, oxo, -NZ 1 Z 2 and (NZ 3 Z 4 )carbonyl.
• substituents independently selected from the group consisting of alkenyl, alkoxy, alkoxyalkoxy, alkoxyalkyl, alkoxycarbonyl
• hydroxy means an -OH group.
• hydroxyalkyl means at least one hydroxy group, as defined herein, is appended to the parent molecular moiety through an alkyl group, as defined herein. Representative examples of hydroxyalkyl include, but are not limited to, hydroxymethyl, 2-hydroxyethyl, 3-hydroxypropyl, 2,3-dihydroxypentyl, and 2-ethyl-4- hydroxyheptyl.
• hydroxy-protecting group or "O-protecting group” means a substituent which protects hydroxyl groups against undesirable reactions during synthetic procedures.
• hydroxy-protecting groups include, but are not limited to, substituted methyl ethers, for example, methoxymethyl, benzyloxymethyl, 2-methoxyethoxymethyl, 2- (trimethylsilyl)-ethoxymethyl, benzyl, and triphenylmethyl; tetrahydropyranyl ethers; substituted ethyl ethers, for example, 2,2,2-trichloroethyl and t-butyl; silyl ethers, for example, trimethylsilyl, t-butyldimethylsilyl and t-butyldiphenylsilyl; cyclic acetals and ketals, for example, methylene acetal, acetonide and benzylidene acetal; cyclic ortho esters, for example, methoxym
• lower alkenyl is a subset of alkenyl, as defined herein, and means an alkenyl group containing from 2 to 4 carbon atoms. Examples of lower alkenyl are ethenyl, propenyl, and butenyl.
• lower alkoxy is a subset of alkoxy, as defined herein, and means a lower alkyl group, as defined herein, appended to the parent molecular moiety through an oxygen atom, as defined herein.
• Representative examples of lower alkoxy include, but are not limited to, methoxy, ethoxy, propoxy, 2-propoxy, butoxy, and tert- butoxy.
• lower alkyl is a subset of alkyl, as defined herein, and means a straight or branched chain hydrocarbon group containing from 1 to 4 carbon atoms.
• Examples of lower alkyl are methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, and tert-butyl.
• lower haloalkoxy is a subset of haloalkoxy, as defined herein, and means a straight or branched chain haloalkoxy group containing from 1 to 4 carbon atoms.
• Representative examples of lower haloalkoxy include, but are not limited to, trifluoromethoxy, trichloromethoxy, dichloromethoxy, fluoromethoxy, and pentafluoroethoxy.
• lower haloalkyl is a subset of haloalkyl, as defined herein, and means a straight or branched chain haloalkyl group containing from 1 to 4 carbon atoms.
• Representative examples of lower haloalkyl include, but are not limited to, trifluoromethyl, trichloromethyl, dichloromethyl, fluoromethyl, and pentafluoroethyl.
• the term "mammal” includes humans and animals, such as cats, dogs, swine, cattle, horses, and the like.
• methylenedioxy means a -OCH 2 O- group wherein the oxygen atoms of the methylenedioxy are attached to the parent molecular moiety through two adjacent carbon atoms.
• nitrogen protecting group means those groups intended to protect an amino group against undesirable reactions during synthetic procedures.
• Preferred nitrogen protecting groups are acetyl, benzoyl, benzyl, benzyloxycarbonyl (Cbz), formyl, phenylsulfonyl, tert-butoxycarbonyl (Boc), tert-butylacetyl, trifluoroacetyl, and triphenylmethyl (trityl).
• Z 1 Z 2 means two groups, Z 1 and Z 2 , which are appended to the parent molecular moiety through a nitrogen atom.
• Z 1 and Z 2 are each independently selected from the group consisting of hydrogen, alkyl, alkylcarbonyl, alkoxycarbonyl, aryl, arylalkyl, and formyl. In certain instances within the invention, Z 1 and Z 2 taken together with the nitrogen atom to which they are attached form a heterocyclic ring.
• NZiZ 2 include, but are not limited to, amino, methylamino, acetylamino, acetylmethylamino, phenylamino, benzylamino, azetidinyl, pyrrolidinyl and piperidinyl.
• NZ 3 Z 4 means two groups, Z 3 and Z 4 , which are appended to the parent molecular moiety through a nitrogen atom.
• Z 3 and Z 4 are each independently selected from the group consisting of hydrogen, alkyl, aryl and arylalkyl.
• Representative examples of NZ 3 Z 4 include, but are not limited to, amino, methylamino, phenylamino and benzylamino.
• pharmaceutically acceptable amide refers to those amides, which retain, upon hydrolysis of the amide bond, the biological effectiveness and properties of the carboxylic acid and are not biologically or otherwise undesirable.
• Pharmaceutically acceptable amides of the invention can be derived from ammonia, primary Ci_ 6 alkyl amines and secondary Ci_ 6 dialkyl amines. In the case of secondary amines, the amine can also be in the form of a 5- or 6-membered heterocycle containing one nitrogen atom.
• Amides derived from ammonia, Ci_3 alkyl primary amides and Ci_ 2 dialkyl secondary amides are preferred.
• Amides of the compounds of formulas (I) and (II) can be prepared according to conventional methods.
• Pharmaceutically acceptable amides can be prepared from compounds containing primary or secondary amine groups by reaction of the compound that contains the amino group with an alkyl anhydride, aryl anhydride, acyl halide, or aroyl halide.
• the pharmaceutically acceptable esters are prepared from compounds containing the carboxylic acid groups by reaction of the compound with base such as triethylamine, a dehydrating agent such as dicyclohexyl carbodiimide or carbonyl diimidazole, and an alkyl amine, dialkylamine, for example with methylamine, diethylamine, piperidine. They also can be prepared by reaction of the compound with an acid such as sulfuric acid and an alkylcarboxylic acid such as acetic acid, or with acid and an arylcarboxylic acid such as benzoic acid under dehydrating conditions as with molecular sieves added.
• base such as triethylamine
• a dehydrating agent such as dicyclohexyl carbodiimide or carbonyl diimidazole
• an alkyl amine, dialkylamine for example with methylamine, diethylamine, piperidine.
• They also can be prepared by reaction of the compound with an acid such as sulfuric
• composition can contain a compound of the invention in the form of a pharmaceutically acceptable prodrug.
• pharmaceutically acceptable prodrug or "prodrug” as used herein, represents those prodrugs of the compounds of the invention which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of humans and lower animals without undue toxicity, irritation, allergic response, and the like, commensurate with a reasonable benefit/risk ratio, and effective for their intended use.
• Prodrugs of the invention can be rapidly transformed in vivo to a parent compound of the invention, for example, by hydrolysis in blood. A thorough discussion is provided in Higuchi T., et al, Pro-drugs as Novel Delivery Systems, V. 14 of the A.C.S.
• pharmaceutically acceptable carrier means a non-toxic, solid, semi-solid or liquid filler, diluent, encapsulating material, or formulation auxiliary of any type.
• therapeutically suitable excipients include sugars; cellulose and derivatives thereof; oils; glycols; solutions; buffering, coloring, releasing, coating, sweetening, flavoring, and perfuming agents; and the like. These therapeutic compositions can be administered parenterally, intracisternally, orally, rectally, intraveneously, or intraperitoneally.
• sulfinyl means a -S(O)- group.
• sulfonamide means an amino, alkylamino, or dialkylamino group, as defined herein, appended to the parent molecular moiety through a sulfonyl group, as defined herein. Representative examples include, but are not limited to, aminosulfonyl, methylaminosulfonyl, and diethylaminosulfonyl.
• sulfonyl means a -SO 2 - group.
• tautomer means a proton shift from one atom of a compound to another atom of the same compound wherein two or more structurally distinct compounds are in equilibrium with each other.
• radioactive atoms refers to a compound in which at least one of the atoms is a radioactive atom or radioactive isotope, wherein the radioactive atom or isotope spontaneously emits gamma rays or energetic particles, for example alpha particles or beta particles, or positrons.
• radioactive atoms include, but are not limited to, H (tritium), 14 C, 11 C, 15 O, 18 F, 35 S, 123 I, and 125 I.
• Compounds suitable for the composition, method, and article of manufacture for the invention are any chemical compounds for which ⁇ 4 ⁇ 2 nicotinic receptor activity can be identified.
• treatment includes any process, action, application, therapy, or the like, wherein a subject, including human, is provided medical aid with the object of improving the subject's condition, directly or indirectly, or slowing the progression of a condition or disorder in the subject.
• nicotinic receptor ligands surprisingly can be improved by combining a nicotinic acetylcholine receptor ligand, particularly an ⁇ 4 ⁇ 2 receptor ligand (agonist, partial agonist), with a nicotinic acetylcholine receptor ⁇ 4 ⁇ 2 subtype selective positive allosteric modulator (PAM).
• PAM nicotinic acetylcholine receptor ⁇ 4 ⁇ 2 subtype selective positive allosteric modulator
• Nicotinic Acetylcholine Subtype ⁇ 4 ⁇ 2 Receptor Ligands modulate the function by altering the activity of the receptor. Suitable compounds also can be partial agonists that partially block or partially activate the ⁇ 4 ⁇ 2 receptor or agonists that activate the receptor. Nicotinic acetylcholine receptor ⁇ 4 ⁇ 2 receptor ligands suitable for the invention can include full agonists or partial agonists. Compounds modulating activity of nicotinic acetylcholine receptor ⁇ 4 ⁇ 2 subtype are suitable for the invention regardless of the manner in which they interact with the receptor.
• [00115] One manner for characterizing ⁇ 4 ⁇ 2 receptor ligands is by a binding assay.
• [ 3 H]- Cytisine binding values ("K 1 Cyt") of compounds of the invention ranged from about 0.001 nanomolar to greater than 100 micromolar.
• Preferred compounds for the composition demonstrate binding values of from about 0.001 nanomolar to 10 micromolar.
• the [ 3 H]- cytisine binding assays have been well reported; however, further details for carrying out the assays can be obtained in International Publication No. WO 99/32480; U.S. Patent Nos. 5,948,793 and 5,914,328; WO 2004/018607; U.S. Patent No. 6,809,105; WO 00/71534; and U.S. Patent No. 6,833,370.
• ⁇ 4 ⁇ 2 receptor ligands suitable for the invention can be compounds of various chemical classes.
• some examples of ⁇ 4 ⁇ 2 receptor ligands suitable for the invention include, but are not limited to heterocyclic ether derivatives (see, for example, International Publication No. WO 99/32480, published July 1, 1999; U.S. Patent No. 5,948,793, issued September 7, 1999, and U.S. Patent No 5,914,328, issued June 22, 1999); N-substituted diazabicyclic derivatives (see for examplelnternational Publication No. WO 2004/0186107, published September 23, 2004, and U.S. Patent No.
• ⁇ 4 ⁇ 2 receptor ligands suitable for the invention include, but are not limited to aryl-fused azapolycyclic compounds (see for example, International Publication No.
• ⁇ 4 ⁇ 2 ligands include, but are not limited to, TC-1734 (ispronicline), GTS-21, 4-hydroxy-GTS-21, TC-5619, TC-2696, dianicline and varenicline, which are all described in the publicly available literature.
• Specific examples of compounds contemplated for the ⁇ 4 ⁇ 2 receptor ligands include, but are not limited to,
• Positive allosteric modulators are compounds that potentiate receptor responses to acetylcholine without themselves triggering receptor activation or desensitization, or either, of the receptor.
• Steroid hormones represent a family of molecules with varying modulatory effects onnAChRs as well as other members of the LGIC superfamily.
• positive allosteric modulation of human ⁇ 4 ⁇ 2 nAChRs expressed either in Xenopus oocytes or in human embryonic kidney cells was reported with 17 ⁇ -estradiol (Curtis L, et al., Molecular Pharmacology, 61 : 127-135, 2002).
• Examples of compounds reported as selective ⁇ 4 ⁇ 2 positive allosteric modulators are oxadiazole derivatives, for example as described in WO 2006/114400.
• ⁇ 4 ⁇ 2 positive allosteric modulator is 3,5-diphenylisoxazole, which is commercially available from Sigma Aldrich, St. Louis, Missouri, USA.
• ⁇ 4 ⁇ 2 positive allosteric modulators include, but are not limited to, oxadiazole derivatives. Suitable oxadiazole derivatives can include 1,2,4- oxadiazole derivatives and 1,3,4-oxadiazole derivatives. Examples of 1,3,4-oxadiazole derivatives are described in co-pending U.S. Patent Application No. 61/000,295, filed on April 12, 2007, wherein the methods of preparation disclosed are incorporated by reference herein. Such compounds have the formula (I):
• X is a bond, O, NR 1 , S, or Ci-C 3 alkylene
• Y represents a monocyclic aryl, cycloalkyl, heterocycle, or heteroaryl group
• Ar 1 represents a monocyclic aryl or a heteroaryl group
• R 1 is hydrogen, alkyl, haloalkyl or arylalkyl.
• X is selected from a bond, O, NR 1 , S, or C1-C3 alkylene, wherein R 1 is selected from hydrogen, alkyl, haloalkyl, and arylalkyl.
• R 1 is selected from hydrogen, alkyl, haloalkyl, and arylalkyl.
• X is a bond.
• R 1 is hydrogen or alkyl.
• Y represents a monocyclic aryl, cycloalkyl, heterocycle, or heteroaryl group, which can be substituted or unsubstituted with substituents. Examples of suitable heterocycle groups can include, but are not limited to, pyrrolidine, piperidine, and the like.
• heteroaryl groups can include, but are not limited to, thienyl, furanyl, pyridinyl, pyrazinyl, and the like.
• a preferred monocyclic aryl group is substituted or unsubstituted phenyl.
• Suitable substituents for the monocyclic aryl, heterocycle, or heteroaryl group are, for example, alkyl, cycloalkyl, cycloalkylalkyl, halo, haloalkyl, hydroxyl, alkoxy, haloalkoxy, nitro, and cyano.
• Ar 1 represents a monocyclic aryl, such as substituted or unsubstituted phenyl, or heteroaryl group.
• heteroaryl groups include, but are not limited, thienyl, furanyl, pyrrolyl, pyrazolyl, thiazolyl, 1,3,4-thiadiazolyl, and pyridinyl, each of which can be unsubstituted or substituted with one, two, or three substituents selected from alkyl, cycloalkyl, cycloalkylalkyl, halo, haloalkyl, hydroxyl, alkoxy, haloalkoxy, nitro, cyano, and amino.
• suitable 2,5-disubstituted-l,3,4-oxadiazole derivatives can have the formula (I) wherein X is a bond; Y is aryl, cycloalkyl, heterocycle, or heteroaryl; and Ar 1 is monocyclic aryl or heteroaryl.
• suitable 2,5-disubstituted-l,3,4-oxadiazole derivatives can have the formula (I) wherein X is a bond; Y is monocyclic cycloalkyl, phenyl, thienyl, furyl, pyridinyl, pyrazinyl, pyrrolidinyl, or piperidinyl optionally substituted with one or more of the substituents selected from the group consisting of alkyl, halogen, haloalkyl, hydroxy, alkoxy, haloalkoxy, nitro and cyano; and Ar 1 is phenyl, thienyl, furyl, pyrrolyl, pyrazolyl, thiazolyl, 1,3,4-thiadiazolyl, pyrimidinyl, pyrazinyl, or pyridinyl optionally substituted with one or more of the substituents selectected from the group consisting of alkyl, alkylcarbon
• the suitable 2,5-disubstituted-l,3,4-oxadiazole derivatives can have the formula (I) wherein X is a bond; Y is pyridyl; and Ar 1 is phenyl, pyrimidinyl, pyrazinyl, or pyridinyl optionally substituted with one or more of the substituents selected from the group consisting of alkyl, halogen, haloalkyl, hydroxy, alkoxy, haloalkoxy, nitro, cyano, and NZ 1 Z 2 , wherein Z 1 and Z 2 are hydrogen, alkyl, alkylcarbonyl, alkoxycarbonyl, aryl, arylalkyl, or formyl.
• ⁇ 4 ⁇ 2 positive allosteric modulators include, but are not limited to, compounds of the formula (II):
• Ar 2 is aryl or heteroaryl, wherein the aryl or heteroaryl is substituted or unsubstituted, and, when substituted, the aryl or heteroaryl is substituted with 0, 1, 2, 3, or 4 substituents selected from halo, Ci-C 6 haloalkyl, C 6 -CiO aryl, C4-C7 cycloalkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C5-C10 heteroaryl, C4-C10 heterocycle, Ci-C 6 alkyl, -(Ci-C 6 alkyl)NHC(O)O-(Ci-C 6 alkyl), Ci-C 6 hydroxyalkyl, Ci-C 6 alkylcarbonyl, amino, hydroxyl, haloalkyl-C(O)-, haloalkyl-SO 2 -, alkyl-SO 2 -, -SO 2 NH 2 , -SO 2 , -
• Ar 3 is aryl or heteroaryl, wherein the aryl or heteroaryl is optionally substituted, and, when substituted, the aryl or heteroaryl is substituted with a substituent selected from halo, Ci-C 6 haloalkyl, C 6 -Ci 0 aryl, C 4 -C 7 cycloalkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 5 -Ci 0 heteroaryl, Ci-C 6 alkyl, Ci-C 6 hydroxyalkyl, amino, hydroxyl, haloalkyl-SO 2 -, cyano, nitro, Ci-C 6 acylamino, Ci-C 6 alkoxy, -N(Ci-C 6 alkyl) 2 , and carboxy.
• a substituent selected from halo, Ci-C 6 haloalkyl, C 6 -Ci 0 aryl, C 4 -C 7 cycloalkyl
• suitable 3,5-disubstituted-l,2,4-oxadiazole derivatives can have the formula (I) wherein Ar 2 is substituted monocyclic aryl or monocyclic heteroaryl, which can be substituted or unsubstituted, and Ar 3 is substituted monocyclic aryl or heteroaryl, which can be substituted or unsubstituted.
• the substituent is selected from halo, Ci-C 6 haloalkyl, C 6 -Ci 0 aryl, C 4 -C 7 cycloalkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, Cs-Ci 0 heteroaryl, C 4 -Ci 0 heterocycle, Ci-C 6 alkyl, -(Ci-C 6 alkyl)NHC(O)O-(Ci-C 6 alkyl), Ci-C 6 hydroxyalkyl, Ci-C 6 alkylcarbonyl, amino, hydroxyl, haloalkyl-C(O)-, haloalkyl-SO 2 -, alkyl-SO 2 -, -SO 2 NH 2 , -SO 2 NH(Ci-C 6 alkyl), - SO 2 N(Ci-C 6 alkyl) 2 , cyano, nitro,
• the substituent is selected from halo, Ci-C 6 haloalkyl, C 6 -Ci 0 aryl, C 4 -C 7 cycloalkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, Cs-Ci 0 heteroaryl, Ci-C 6 alkyl, Ci-C 6 hydroxyalkyl, amino, hydroxyl, haloalkyl-SO 2 - , cyano, nitro, Ci-C 6 acylamino, Ci-C 6 alkoxy, -N(Ci-C 6 alkyl) 2 , and carboxy.
• Preferred for monocyclic heteroaryl are pyridine-3-yl, pyridine-4-yl, and pyridine-2(lH)-one.
• suitable 3,5-disubstituted-l,2,4-oxadiazole derivatives can have the formula (II) wherein wherein Ar 2 is pyridinyl, which can be substituted or unsubstituted, or substituted phenyl; and Ar 3 is pyridinyl, which can be substituted or unsubstituted, or substituted phenyl.
• the pyridinyl group when substituted, is substituted with fluoro.
• the phenyl group is substituted with cyano or halo. It is preferred that the pyridinyl group for Ar 2 or Ar 3 is pyridin-3-yl.
• ⁇ 4 ⁇ 2 positive allosteric modulators are, for example, 3,5- disubstituted-l,2,4-oxadiazole derivatives, such as:
• FIG. 1 A block diagram illustrating an exemplary embodiment of the invention.
• FIG. 1 A block diagram illustrating an exemplary embodiment of the invention.
• FIG. 1 A block diagram illustrating an exemplary embodiment of the invention.
• FIG. 1 A block diagram illustrating an exemplary embodiment of the invention.
• FIG. 1 A block diagram illustrating an exemplary embodiment of the invention.
• FIG. 1 A block diagram illustrating an exemplary embodiment of the invention.
• Another embodiment of the invention is a compound of formula (II), wherein Ar 2 is optionally substituted pyridinyl or pyrimidinyl.
• Another embodiment of the invention is a compound of formula (II), wherein Ar 2 is optionally substituted bicyclic heteroaryl.
• Another embodiment of the invention is a compound of formula (II), wherein Ar 3 is optionally substituted pyridinyl, pyrimidinyl or pyridazinyl.
• Another embodiment of the invention is a compound of formula (II), wherein Ar 3 is optionally substituted bicyclic heteroaryl.
• Another embodiment of the invention is a compound of formula (II), wherein Ar 2 and Ar 3 are independently, optionally substituted monocyclic or bicycliic heteroaryl, wherein the monocyclic heteroaryl is six-membered heterocycle, provided that when one of Ar 2 and
• Ar 3 is pyridinyl, the other is not pyridinyl, and when Ar 3 is pyridinyl, Ar 2 is not pyrazinyl.
• Another embodiment of the invention is a compound of formula (II), wherein Ar 2 and Ar are independently, optionally substituted pyrazinyl, pyridazinyl, pyridinyl, pyrimidinyl, triazinyl, or a bicyclic heteroaryl.
• Another embodiment of the invention is a compound of formula (II), wherein Ar 2 and Ar 3 are independently, optionally substituted phenyl, pyridazinyl, pyridinyl, pyrimidinyl, or bicyclic heteroaryl.
• Another embodiment of the invention is a compound of formula (II), wherein one of Ar 2 and Ar 3 is optionally substituted bicyclic heteroaryl.
• Another embodiment of the invention is a compound of formula (II), wherein one of Ar 2 and Ar 3 is optionally substituted bicyclic heteroaryl selected from the group consisting of benzimidazolyl, benzo[d][l,3]dioxolyl, benzofuranyl, benzo[d]imidazolyl, benzooxazole, benzo[d][l,2,3]thiadiazolyl, 1,3-benzothiazolyl, benzo[d][l,2,3]triazolyl, 2,2- difluorobenzo[d][l,3]dioxolyl, imidazopyridinyl, indolyl, indazolyl, pyrazolopyrimidinyl, pyrrolopyridinyl, and [l,2,4]triazolopyridinyl.
• benzimidazolyl benzo[d][l,3]dioxolyl
• benzofuranyl benzo[d]
• Another embodiment of the invention is a compound of formula (II), selected from the group of compounds exemplified in Examples 79-134 described below.
• Another embodiment of the invention is a compound of formula (II), selected from the group of compounds exemplified in Examples 79-105 described below.
• Another embodiment of the invention is a compound of formula (II), selected from the group of compounds exemplified in Examples 79-82, 85-89, 101, and 103-105 described below.
• Another embodiment of the invention is a compound of formula (II), selected from the group of compounds exemplified in Examples 90 and 102 described below.
• Another embodiment of the invention is a compound of formula (II), selected from the group of compounds exemplified in Examples 83-84 and 92-100 described below.
• Another embodiment of the invention is a compound of formula (II), selected from the group of compounds exemplified in Examples 90-91 described below.
• Another embodiment of the invention is a compound of formula (II), selected from the group of compounds exemplified in Examples 106-134 described below.
• Another embodiment of the invention is a compound of formula (II), selected from the group of compounds exemplified in Examples 106-118, 123-131 and 134described below.
• Another embodiment of the invention is a compound of formula (II), selected from the group of compounds exemplified in Examples 119-122 and 132-133 described below.
• Another embodiment of the invention is 5-(2,3-difluorophenyl)-3-(pyrimidin-5-yl)-
• Another embodiment of the invention is 5-(pyridin-3-yl)-3-(pyrimidin-5-yl)-l,2,4- oxadiazole.
• Another embodiment of the invention is 2-fluoro- ⁇ /,N-dimethyl-4-(3-(pyrimidin-5- yl)-l,2,4-oxadiazol-5-yl)aniline.
• Another embodiment of the invention is 3-(3-(pyrimidin-5-yl)-l,2,4-oxadiazol-5- yl)benzonitrile. [00356] Another embodiment of the invention is 5-(3,4-difluorophenyl)-3-(pyridazin-4-yl)-
• Another embodiment of the invention is 3-(pyridazin-4-yl)-5-(pyridin-3-yl)- 1,2,4- oxadiazole.
• Another embodiment of the invention is ⁇ /, ⁇ /-dimethyl-N'-(4-(3-(pyrimidin-5-yl)- 1 ,2,4-oxadiazol-5-yl)phenylsulfonyl)-formimidamide.
• Another embodiment of the invention is 5-(4-fluorophenyl)-3-(pyrimidin-5-yl)-
• Another embodiment of the invention is 5-(3-fluorophenyl)-3-(pyrimidin-5-yl)-
• Another embodiment of the invention is 3-(pyrimidin-5-yl)-5-(3,4,5- triluorophenyl)-l,2,4-oxadiazole.
• Another embodiment of the invention is 5-(2-chloropyridin-4-yl)-3-(pyrimidin-5- yl)-l,2,4-oxadiazole.
• Another embodiment of the invention is 3-(3-(pyridazin-4-yl)-l,2,4-oxadiazol-5- yl)benzonitrile.
• Another embodiment of the invention is 5-(3-fluorophenyl)-3-(pyridazin-4-yl)-
• Another embodiment of the invention is 3-(pyridazin-4-yl)-5-(3,4,5- trifluorophenyl)- 1 ,2,4-oxadiazole.
• Another embodiment of the invention is 5-(3,5-difluorophenyl)-3-(pyridazin-4-yl)-
• Another embodiment of the invention is 5-(4-fluorophenyl)-3-(pyridazin-4-yl)-
• Another embodiment of the invention is 3-(pyridazin-4-yl)-5-(2,3,6- trifluorophenyl)- 1 ,2,4-oxadiazole.
• Another embodiment of the invention is 3-(pyridazin-4-yl)-5-(2,3,4- trifluorophenyl)- 1 ,2,4-oxadiazole.
• Another embodiment of the invention is ⁇ /, ⁇ /-dimethyl-N'-(4-(3-(pyridazin-4-yl)- l,2,4-oxadiazol-5-yl)phenylsulfonyl)formimidamide.
• Another embodiment of the invention is 5-(3,4-difluorophenyl)-3-(pyrimidin-5-yl)-
• Another embodiment of the invention is 3-(pyrimidin-5-yl)-5-(2,3,4- trifluorophenyl)- 1 ,2,4-oxadiazole.
• Another embodiment of the invention is 3-(pyrimidin-5-yl)-5-(2,3,6- trifluorophenyl)- 1 ,2,4-oxadiazole.
• Another embodiment of the invention is 3-(pyrimidin-5-yl)-5-(2, 3,4,5- tetrafluorophenyl)- 1 ,2,4-oxadiazole. [00377] Another embodiment of the invention is 3-(pyrimidin-5-yl)-5-(2,3,6- trifluorophenyl)- 1 ,2,4-oxadiazole.
• Another embodiment of the invention is 3-(pyrimidin-5-yl)-5-(2, 3,4,5- tetrafluorophenyl)- 1 ,2,4-oxadiazole. [00379] Another embodiment of the invention is 5-(imidazo[l,5-a]pyridin-6-yl)-3-(pyridin-
• Another embodiment of the invention is 5-(lH-indol-6-yl)-3-(pyridin-3-yl)-l,2,4- oxadiazole.
• Another embodiment of the invention is 5-(2,7-dimethylpyrazolo[l,5-a]pyrimidin- 6-yl)-3-(pyridin-3-yl)-l ,2,4-oxadiazole.
• Another embodiment of the invention is 5-(2,2-difluorobenzo[d][l,3]dioxol-5-yl)-
• Another embodiment of the invention is 5-(2-methylbenzofuran-5-yl)-3-(pyridin-3- yl)-l,2,4-oxadiazole.
• Another embodiment of the invention is 5-(benzo[d][l,2,3]thiadiazol-5-yl)-3-
• Another embodiment of the invention is 5-(lH-benzo[d]imidazol-5-yl)-3-(pyridin-
• Another embodiment of the invention is 5-(lH-benzo[d][l,2,3]triazol-5-yl)-3- (pyridin-3-yl)-l,2,4-oxadiazole.
• Another embodiment of the invention is 5-(benzo[d]thiazol-5-yl)-3-(pyridin-3-yl)-
• Another embodiment of the invention is 3-(pyridin-3-yl)-5-(l ⁇ -pyrrolo[2,3- b]pyridin-5-yl)-l,2,4-oxadiazole. [00389] Another embodiment of the invention is 5-(lH-indol-5-yl)-3-(pyridin-3-yl)-l,2,4- oxadiazole.
• Another embodiment of the invention is 5-(benzofuran-5-yl)-3-(pyridin-3-yl)-
• Another embodiment of the invention is 5-(l-methyl-l ⁇ -benzo[d]imidazol-5-yl)- 3-(pyridin-3-yl)-l,2,4-oxadiazole.
• Another embodiment of the invention is 3-(imidazo[l,2-a]pyridin-6-yl)-5-(pyridin-
• Another embodiment of the invention is 5-(6-chloropyridin-3-yl)-3-(imidazo[l,2- a]pyridin-6-yl)- 1 ,2,4-oxadiazole.
• Another embodiment of the invention is 5-(6-fluropyridin-3-yl)-3-(imidazo[l,2- a]pyridin-6-yl)- 1 ,2,4-oxadiazole.
• Another embodiment of the invention is 5-(5-fluropyridin-3-yl)-3-(imidazo[l,2- a]pyridin-6-yl)- 1 ,2,4-oxadiazole.
• Another embodiment of the invention is 5-(lH-indazol-5-yl)-3-(pyridin-3-yl)-
• Another embodiment of the invention is 5-([l,2,4]triazolo[4,3-a]pyridin-6-yl)-3- (pyridin-3-yl)-l,2,4-oxadiazole.
• Another embodiment of the invention is 5-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5- yl)benzo [d]oxazol-2(3H)-one .
• Another embodiment of the invention is 5-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5-yl)- l ⁇ -benzo[d]imidazole-2(3 ⁇ )-thione.
• Another embodiment of the invention is l,3-dimethyl-5-(3-(pyridin-3-yl)- 1,2,4- oxadiazol-5-yl)-lH-benzo[d]imidazol-2(3H)-one.
• Another embodiment of the invention is 6-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5- yl)benzo [d]oxazol-2(3H)-one .
• Another embodiment of the invention is 5-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5-yl)- lH-benzo[d]imidazol-2(3H)-one.
• Another embodiment of the invention is 6-(3-(Pyridin-3-yl)-l,2,4-oxadiazol-5- yl)benzo[d]oxazol-2-amine.
• Another embodiment of the invention is 6-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5- yl)benzo[d]oxazole. [00405] Another embodiment of the invention is 5-(5-(pyridin-3-yl)-l,2,4-oxadiazol-3- yl)benzo [d]oxazol-2(3H)-one .
• Another embodiment of the invention is 5-(5-(6-chloropyridin-3-yl)- 1,2,4- oxadiazol-3-yl)benzo[d]oxazol-2(3 ⁇ )-one.
• Another embodiment of the invention is 5-(benzo[d][l,3]dioxol-5-yl)-3-(pyridin-3- yl)-l,2,4-oxadiazole.
• Another embodiment of the invention is 3-(Pyridin-3-yl)-5-(pyrimidin-5-yl)- 1 ,2,4- oxadiazole.
• Another embodiment of the invention is 5-(Pyridazin-4-yl)-3-(pyridin-3-yl)- 1,2,4- oxadiazole.
• Another embodiment of the invention is 3-(3,4-difluorophenyl)-5-(pyrimidin-5-yl)- 1,2,4-oxadiazole.
• Geometric isomers can exist in the present compounds. The invention contemplates the various geometric isomers and mixtures thereof resulting from the disposition of substituents around a carbon-carbon double bond, a carbon nitrogen double bond, a cycloalkyl group, or a heterocycloalkyl group.
• Preparation of compounds suitable for the composition of the invention can be understood in connection with the following synthetic schemes and examples, which illustrate a means by which the compounds can be prepared.
• Methods for preparing suitable nicotinic acetylcholine receptor ligands and suitable nicotinic acetylcholine subtype ⁇ 4 ⁇ 2 allosteric modulators are readily available in the literature.
• Suitable compounds can be prepared by conventional methods for chemical synthesis with readily available starting materials. Nicotinic acetylcholine receptor ligands and nicotinic acetylcholine subtype ⁇ 4 ⁇ 2 allosteric modulators also may be commercially available.
• Oxadiazole derivatives suitable for the composition of the invention can be prepared according to conventional methods. Some suitable methods for preparing such oxadiazole derivatives are provided in the Schemes and Examples below. However, such further illustration is intended only for reference and is not intended in any way to limit the scope of the invention.
• compounds of formula (4) can be reacted with compounds of formula (5) in POCl 3 at temperatures from 40-100 0 C over 1-24 hours to provide compounds of formula (6); wherein R 3 is Ar 1 and R 4 is Y, or R 3 is Y and R 4 is Ar 1 .
• compounds of formula (4) can be reacted with compounds of formula (5) in the presence of triphenylphosphine, which may optionally be polymer bound, and trichloroacetonitrile in acetonitrile.
• the mixture may be heated in a microwave oven at 100- 175 0 C for 5-30 minutes as described by Wang, Y.; Sauer, D. R.; Djuric, S. W. Tetrahedron.
• Another alternative includes combining compounds of formula (4) and compounds of formula (5) in a solvent such as methylene chloride in the presence of 2- chloro-l,3-dimethylimidazolinium chloride and a base such as triethylamine at 15-35 0 C for 10-120 hours as described by Isobe, T.; Ishikawa, T. J. Org. Chem. 1999, 64, 6989-6992.
• compounds of formula (1) can be reacted with urea (7) in a solvent such as dichloromethane in the presence of a base such as triethylamine at 25-40 0 C for 1-12 hours to provide compounds of formula (8) as described in Sobol, E.; Bialer, M.; Yagen, B. J. Med. Chem. 2004, 47, 4316-4326.
• compounds of formula (1) and (7) may be combined in pyridine at 20-110 0 C for 1-24 hours to provide compounds of formula (8).
• Compounds of formula (8) can be treated with POCl 3 at 25-100 0 C for 1-24 hours to provide compounds of formula (9).
• compounds of formula (II) can also be prepared by heating a mixture of compounds of formula (2) and compound of formula (1) which can be obtained from either a commercial source or by the treatment of compound of formula (10) with a chlorinating agent, such as oxalyl chloride or thionyl chloride, in a solvent such as but not limited to pyridine or THF at 60-110 0 C.
• a chlorinating agent such as oxalyl chloride or thionyl chloride
• the compounds of formula (15) reacts with compounds of formula (13) in the presence a base, such as but not limited to triethylamine, Na 2 CO 3 and K 2 CO 3 , in a solvent, such as toluene, at temperature ranging 80- 110 0 C over 10-40 hours to provide compounds of formula (16) as described by Humphrey, G. R.; Wright, S. H. B. in J. Heterocyclic Chem. (1989, 26, 23-24).
• a base such as but not limited to triethylamine, Na 2 CO 3 and K 2 CO 3
• Compounds of formula (16) can be reacted with compounds of formula (20) in the presence of a palladium catalyst, such as, but not limited to Pd(OAc) 2 , PdCl 2 (PPh 3 ) 2 , Pd(PPh 3 ) 4 , PdCl 2 (dppf), Pd 2 (dba) 3 , and a base, such as but not limited to CsF, Na 2 CO 3 , K 2 CO 3 and K 3 PO 4 , will provide compounds of formula (III).
• a palladium catalyst such as, but not limited to Pd(OAc) 2 , PdCl 2 (PPh 3 ) 2 , Pd(PPh 3 ) 4 , PdCl 2 (dppf), Pd 2 (dba) 3
• a base such as but not limited to CsF, Na 2 CO 3 , K 2 CO 3 and K 3 PO 4
• compounds of formula (16) when treated with organoboranes of formula (18) or ditin compounds of formulas (19), such as bis(pinacolato)diboron or hexmethlyditin, respectively, in the presence of a palladium catalyst provide organotin compounds, organoboronic acids or organoboronic esters compounds of formula (23), wherein M is -Sn- (R n ) 3 or -B(0R m ) 2 .
• Compounds of formula (23) can also be prepared by the initial treatment of compounds of formula (16) with 5-BuLi at temperature ranging from -90 0 C to -60 0 C and then reaction with a boronic ester of formula (21) or an organotin compound of formula (22).
• Compounds of formula (23) can be reacted with compounds of formula (17) in the presence of a palladium catalyst, such as, but not limited to Pd(OAc) 2 , PdCl 2 (PPh 3 ) 2 , Pd(PPh 3 ) 4 , PdCl 2 (dppf), Pd 2 (dba) 3 , and a base, such as but not limited to CsF, Na 2 CO 3 , K 2 CO 3 and K 3 PO 4 to provide compounds of formula (III).
• a palladium catalyst such as, but not limited to Pd(OAc) 2 , PdCl 2 (PPh 3 ) 2 , Pd(PPh 3 ) 4 , PdCl 2 (dppf), Pd 2 (dba) 3
• a base such as but not limited to CsF, Na 2 CO 3 , K 2 CO 3 and K 3 PO 4 to provide compounds of formula (III).
• compounds of formula (II) and (III), wherein at least one of Ar 1 and Ar 2 is a N-containing heteroaryl can be converted to compounds with N + -O " by treatment with an oxidizing agent.
• the oxidizing agent include, but are not limited to aqueous hydrogen peroxide and m-chloroperbenzoic acid.
• the reaction is generally performed in a solvent such as, but not limited to acetonitrile, water, dichloromethane, acetone or a mixture thereof, preferably a mixture of acetonitrile and water, at a temperature from about 0° C to about 80 0 C, for a period of about 1 hour to about 4 days.
• the compounds and intermediates of the invention may be isolated and purified by methods well-known to those skilled in the art of organic synthesis.
• Examples of conventional methods for isolating and purifying compounds can include, but are not limited to, chromatography on solid supports such as silica gel, alumina, or silica derivatized with alkylsilane groups, by recrystallization at high or low temperature with an optional pretreatment with activated carbon, thin-layer chromatography, distillation at various pressures, sublimation under vacuum, and trituration, as described for instance in "Vogel's Textbook of Practical Organic Chemistry", 5th edition (1989), by Furniss et al.,, pub. Longman Scientific & Technical, Essex CM20 2JE, England.
• Suitable 2,5-disubstituted-l,3,4-oxadiazole derivatives were prepared using readily available starting materials.
• International Publication WO 02/100826 published December 19, 2002, describes the preparation of some oxadiazole derivatives.
• Compounds of formula (I) also can be prepared according to the following general methods.
• Method B A Smith Process vial (0.5-2 ml) was charged with a stir bar. To the vessel were added a carboxylic acid (0.1 mmol), nicotinic hydrazide (Aldrich, 13.7 mg, 0.1 mmol), PS-PPh 3 (Fluka, 2.2 mmol/g, 136 mg, 0.3 mmol) and Acetonitrile (anhydrous,
• Fractions were collected based upon UV signal threshold, and selected fractions were subsequently analyzed by flow injection analysis mass spectrometry using positive APCI ionization on a Finnigan LCQ using 70:30 methanol: 10 mM NH4 ⁇ H(aq) at a flow rate of 0.8 mL/minute.]. Some mixtures were purified by an alternative preparative HPLC method [Waters, column: Sunfire OBD C8 5 ⁇ m (30 mm x 75 mm); solvent: acetonitrile/ 10 mM aqueous ammonium acetate, 10/90 to 100/0; flow rate of 50 mL/minute]. Fractions were collected based upon target mass signal threshold, and selected fractions were subsequently analyzed by flow injection analysis mass spectrometry using the previously described method.
• Suitable 2,5-disubstitued- 1 ,2,4-oxadiazole derivatives were prepared using readily available starting materials.
• International Publication WO 02/100826 published December 19, 2002, describes the preparation of some oxadiazole derivatives.
• compounds of formula (II) and (III) also can be prepared according to the following general methods.
• Method C To a solution of an aryl or heteroaryl carboxylic acid (1.0 mmol) in dimethylformamide (anhydrous, 5 mL) was added N-(3-dimethylaminopropyl)-N'- ethylcarbodiimide hydrochloride (EDC) (Aldrich, 192 mg, 1.00 mmol) and 1- hydroxybenzotriazole (HOBt) hydrate (Fluka, 153 mg, 1.00 mmol). The mixture was stirred at ambient temperature for 20 minutes.
• EDC N-(3-dimethylaminopropyl)-N'- ethylcarbodiimide hydrochloride
• HOBt 1- hydroxybenzotriazole
• Method D To a solution of ⁇ f'-Hydroxy aryl or heteroaryl carboximidamide (1.0 mmol) in pyridine (5 mL) was added an aryl or heteroaryl carbonyl chloride (1.0 mmol). The mixture was then stirred at the temperature ranging from 80-100 0 C for 2-10 hours. The reaction was cooled to ambient temperature and triturated with water (10 mL). The precipitate was filtered and dried under vacuum to give the titled compound. When the reaction mixture failed to give a precipitate, the reaction mixture was extracted with EtOAc (3 x 30 mL).
• Example 7 3-(3-(6-methylpyridin-3-vD- 1 ,2,4-oxadiazol-5-yl)benzonitrile
• Example 7A 3-(3-(6-methylpyridin-3-vD- 1 ,2,4-oxadiazol-5-yl)benzonitrile
• Example 10 5-(3,4-difluorophenvD-3-(pyridin-3-vD-l,2,4-oxadiazole [00456] The title compound was prepared according to the procedure of Example 8 using ⁇ /'-hydroxynicotinimidamide (Aldrich) and 3,4-difluorobenzoic acid (Aldrich).
• Example 17 5-(4-chloro-2,5-difluorophenyl)-3-(pyridin-3-vD-l,2,4-oxadiazole [00463]
• the title compound was prepared according to the procedure of Example 8 using N-hydroxynicotinimidamide (Aldrich) and 4-chloro-2,5-difluorobenzoic acid (Aldrich).
• Example 21 2-fluoro-5-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5-yl)phenol [00467] The title compound was prepared according to the procedure of Example 8 using N'-hydroxynicotinimidamide (Aldrich) and 4-fluoro-3-hydroxybenzoic acid (Aldrich).
• Example 43 3-(3-(pyridin-3-vD-l,2,4-oxadiazol-5-yl)benzamide [00493] A solution of the product of Example 1 (248 mg, 1 mmol) in THF (10 ml) was stirred with potassium trimethylsilanolate (257 mg, 2.000 mmol) at 65 0 C for 10 hours. It was then quenched with water (20 mL) and stirred at ambient temperature for 2 hours. The precipitate was filtered and dried under vacuum to give the title compound.
• Example 44 4-(5-(pyridin-3-yl)-l ,2,4-oxadiazol-3-yl)pyridin-2(lH)-one hydrochloric acid [00494]
• a solution of the product of Example 42 (100 mg, 0.39 mmol) in concentrated hydrochloric acid (Aldrich, 36.5%, 3.0 mL) was heated in an EmryTM Creator microwave to 150 0 C at 300 watts for 60 minutes. It was then concentrated. The residue was stirred in ethanol/ethyl acetate (v. 1/1, 5 mL) at ambient temperature for 1 hour. The title compound was collected by filtration and dried.
• N'-Hydroxynicotinimidamide (274 mg, 2.00 mmol) was coupled with 3-(tert- butoxycarbonyl)benzoic acid (Aldrich) according to the procedure described in Example 8.
• 1 H NMR 300 MHz, CD 3 OD
• Example 64 l-(3-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5-yl)phenyl)pyrrolidin-2-one [00519]
• a solution of the product of Example 63 (200mg, 0.66 mmol) and pyrrolidin-2-one (Aldrich, 85 mg, 0.99 mmol) in toluene (anhydrous 10 mL) was degassed and purged with nitrogen three times, cesium carbonate (Aldrich, 324 mg, 0.993 mmol) and tris(dibenzylideneacetone)dipalladium(0) (Aldrich, 12.1 mg, 0.013 mmol), 4,5- bis(diphenylphosphino)-9,9-dimethylxanthene (Aldrich, 23.0 mg, 0.040 mmol, xantphos) were added, degassed and purged with nitrogen three times.
• Example 4B The title compound was prepared according to the procedure of Example 4B using 3-cyano-N'-hydroxybenzimidamide (Example 4A) and 6-chloronicotinoyl chloride (Aldrich).
• Example 79A Pvrimidine-5 -carboxamide [00536] A solution of ethyl pyrimidine-5-carboxylate (6.10 g, 40.0 mmol) in methanol (40 niL) was stirred with ammonium hydroxide (4.30 mL, 110 mmol) in a sealed tube at 50 °C for 10 hours. The reaction mixture was then concentrated and the residue was stirred in ethanol/ethyl acetate (v/v 1/4, 50 mL) at ambient temperature for 2 hours. The white precipitate was collected by filtration and dried to give the titled compound.
• Example 83B pyridazine-4-carboxamide [00544] The title compound was prepared according to the procedure of Example 79A using the product of Example 83 A and ammonium hydroxide (Aldrich).
• Example 95 5-(3,5-difluorophenyl)-3-(pyridazin-4-yl)-l,2,4-oxadiazole [00560]
• the titled compound was prepared according to the procedure of Method D using the product of Example 83D and 3,5-difluorobenzoyl chloride (Aldrich).
• the titled compound was prepared according to the procedure of Method D using 3,4-difluoro-N'-hydroxybenzimidamide (Tyger) and pyrimidine-5-carbonyl chloride.
• the pyrimidine-5-carbonyl chloride was prepared by the reaction of pyrimidine-5-carboxylic acid (Maybridge, 138 mg, 1.0 mmol) with oxalyl chloride (Aldrich, 2 M, in CH 2 Cl 2 , 1.0 mL, 2.0 mmol) and a drop of dimethylformamide at room temperature over 1 hour with subsequent removal of volatiles under reduced pressure.
• Suitable pharmaceutically acceptable basic addition salts include, but are not limited to cations based on alkali metals or alkaline earth metals such as lithium, sodium, potassium, calcium, magnesium and aluminum salts and the like and nontoxic quaternary ammonia and amine cations including ammonium, tetramethylammonium, tetraethylammonium, methylamine, dimethylamine, trimethylamine, triethylamine, diethylamine, ethylamine and the like.
• Other representative organic amines useful for the formation of base addition salts include ethylenediamine, ethanolamine, diethanolamine, piperidine, piperazine and the like.
• esters include pharmaceutically acceptable amides and esters.
• esters are typically formed from the corresponding carboxylic acid and an alcohol.
• ester formation can be accomplished via conventional synthetic techniques. (See, e.g., March Advanced Organic Chemistry, 3rd Ed., John Wiley & Sons, New York p. 1157 (1985) and references cited therein, and Mark et al. Encyclopedia of Chemical Technology, John Wiley & Sons, New York (1980), both of which are hereby incorporated by reference.
• the alcohol component of the ester will generally comprise (i) a C2 -C 12 aliphatic alcohol that can or can not contain one or more double bonds and can or can not contain branched carbons or (ii) a C7 -C 12 aromatic or heteroaromatic alcohols.
• This invention also contemplates the use of those compositions, which are both esters as described herein, and at the same time are the pharmaceutically acceptable salts thereof.
• These amides are typically formed from the corresponding carboxylic acid and an amine.
• amide formation can be accomplished via conventional synthetic techniques.
• This invention also contemplates the use of those compositions, which are amides, as described herein, and at the same time are the pharmaceutically acceptable salts thereof.
• the compounds can be generated in vivo by administration of a drug precursor which, following administration, releases the drug in vivo via a chemical or physiological process (e.g., a parent compound on being brought to the physiological pH or through enzyme action is converted to the desired drug form).
• a chemical or physiological process e.g., a parent compound on being brought to the physiological pH or through enzyme action is converted to the desired drug form.
• the specific dosage will be chosen by the patient's physician taking into account the particular compounds chosen, the severity of the patient's illness, any other medical conditions or diseases the patient is suffering from, other drugs the patient is taking and their potential to cause an interaction or adverse event, the patient's previous response to medication, and other factors.
• Suitable dosage ranges for the ⁇ 4 ⁇ 2 PAM are from about 0.0001 mg/kg to 100 mg/kg of body weight.
• Suitable dosage ranges for the ⁇ 4 ⁇ 2 receptor ligand are from about 0.0001 mg/kg to 100 mg/kg of body weight.
• the ⁇ 4 ⁇ 2 PAM and an ⁇ 4 ⁇ 2 receptor ligand should be administered concurrently in amounts that are effective to treat the patient's pain, cognitive disorder, or related condition. In more general terms, one would create a combination of the present invention by choosing a dosage of an ⁇ 4 ⁇ 2 PAM and an ⁇ 4 ⁇ 2 receptor ligand according to the spirit of the guidelines presented above.
• the invention also is carried out by administering an ⁇ 4 ⁇ 2PAM together with an ⁇ 4 ⁇ 2receptor ligand in any manner which provides effective levels of the compounds in the body at the same time. Typically, the combination will be administered orally.
• the invention is not limited to oral administration. The invention should be construed to cover any route of administration that is appropriate for the medications involved and for the patient. For example, transdermal administration may be very desirable for patients who are forgetful or petulant about taking oral medicine. Injections may be appropriate for patients refusing their medication.
• One of the drugs may be administered by one route, such as oral, and the others may be administered by the transdermal, percutaneous, intravenous, intramuscular, intranasal, or intrarectal route, in particular circumstances.
• the route of administration may be varied in any way, limited by the physical properties of the drugs and the convenience of the patient and the caregiver.
• Analgesics can be broadly categorized as non-opioid analgesics (acetaminophen and non-steroidal antiinflammatory drugs (NSAIDs)), opioid analgesics (morphine) and adjuvant analgesics or co- analgesics (antiepileptic drugs and antidepressants).
• NSAIDs non-opioid analgesics
• opioid analgesics morphine
• adjuvant analgesics or co- analgesics antiepileptic drugs and antidepressants
• non-opioid analgesics are mostly used to relieve mild to moderate nociceptive pain
• adjuvant analgesics (gabapentin, pregabalin) are used to relieve neuropathic pain
• opioid analgesics are used to treat severe pain of all origins, depending on the dose prescribed.
• Nicotinic acetylcholine receptor ligands act at multiple locations throughout the pain pathway to relieve pain. Nicotinic acetylcholine receptor ligands are found on primary sensory neurons (periphery) where nociceptive information is initiated, in the cell body regions of these neurons (i.e.
• the dorsal root ganglion or DRG the dorsal spinal cord where the first pain synapse is located, in the brainstem cell body regions that control descending innervation, as well as in the higher brain regions that integrate and perceive sensory information such as the thalamus and the cortex.
• the current theory supported by evidence from multiple sources is that anti-nociceptive effects of nAChR ligands are mediated by activation of brain stem nuclei with descending inhibitory inputs to the spinal cord. Additional pathways may also mediate analgesic effects of nAChR agonists in persistent or neuropathic pain.
• Another aspect of the invention is the potential to enhance efficacy of other medications used for treating pain when combined with an ⁇ 4 ⁇ 2 PAM.
• examples of currently used drugs include opioids, gabapentin, pregabalin, duloxetine and others. Novel mechanisms such as cannabinoids, vanilloid receptor antagonists, calcium channel blockers and sodium channel blockers are also being developed for the treatment of pain. For many of these mechanisms, it is emerging that a component of efficacy may be driven by activation of descending inhibitory inputs.
• opioid analgesics can block pain transmission, in part by increasing descending inhibitory pathways to modulate pain transmission at the spinal level (Pasternack, G. W., Clin Neuropaharmcol.
• nAChR-mediated diseases or disorders also can benefit from such concurrent administration.
• the combination of ⁇ 4 ⁇ 2 nAChR ligands and ⁇ 4 ⁇ 2 selective PAMs can be used for treatment of diseases or disorders related to the cholinergic system of the central nervous system, the peripheral nervous system, diseases or disorders related to smooth muscle contraction, endocrine diseases or disorders, diseases or disorders related to neuro-degeneration, diseases or disorders related to inflammation, and withdrawal symptoms caused by the termination of abuse of chemical substances, in for example nicotine, as well as pain.
• the combination is useful for conditions and disorders related to attention deficit disorder, attention deficit hyperactivity disorder (ADHD),
• AD Alzheimer's disease
• AAMI age-associated memory impairment
• senile dementia AIDS dementia, Pick's Disease, dementia associated with Lewy bodies, dementia associated with Down's syndrome, schizophrenia, smoking cessation, substance abuse, amyotrophic lateral sclerosis, Huntington's disease, diminished CNS function associated with traumatic brain injury, acute pain, post-surgical pain, chronic pain, inflammatory pain, neuropathic pain, infertility, lack of circulation, need for new blood vessel growth associated with wound healing, more particularly circulation around a vascular occlusion, need for new blood vessel growth associated with vascularization of skin grafts, ischemia, inflammation, sepsis, wound healing, and other complications associated with diabetes, among other systemic and neuroimmunomodulatory activities.
• the method is useful for conditions and disorders related to conditions and disorders characterized by neuropsychological and cognitive dysfunction, for example in Alzheimer's disease, bipolar disorder, schizophrenia, schizoaffective disorder, and other related disorders characterized by neuropsychological and cognitive dysfunction
• one embodiment relates to a method of use for treating or preventing a condition or disorder characterized by attention or cognitive dysfunction, such as Alzhimer's disease and ADHD, among other condition and disorders.
• the method comprises the step of administering a therapeutically effective amount of a nicotinic acetylcholine receptor subtype ⁇ 4 ⁇ 2 positive allosteric modulator to a subject in need thereof in combination with a drug that improves cholinergic function.
• a drug that improves cholinergic function examples of such drugs are nicotinic acetylcholine receptor ligands and acetylcholinesterase inhibitors.
• Another method of use relates to treating or preventing a condition or disorder characterized by neuropsychological dysfunction, for example scizhophrenia, wherein the method comprises the step of administering a therapeutically effective amount of a nicotinic acetylcholine receptor subtype ⁇ 4 ⁇ 2 positive allosteric modulator to a subject in need thereof in combination with an antipsychotic agent.
• a condition or disorder characterized by neuropsychological dysfunction for example scizhophrenia
• the method comprises the step of administering a therapeutically effective amount of a nicotinic acetylcholine receptor subtype ⁇ 4 ⁇ 2 positive allosteric modulator to a subject in need thereof in combination with an antipsychotic agent.
• Example A ⁇ 4 ⁇ 2 Positive allosteric modulator enhances the effects of nicotinic agonists.
• HEK Human embryonic kidney
• HEK 293 cells stably expressing human ⁇ 4 ⁇ 2 or ⁇ 3 ⁇ 4 combinations are grown to confluency in 162 cm 2 tissue culture flasks in DMEM media supplemented with 10% FBS and 25 ⁇ g/ml zeocin and 200 ⁇ g/ml hygromycin B.
• IMR-32 neuroblastoma cells (ATCC) are grown to confluency in 162 cm 2 tissue culture flasks in minimum essential media supplemented with 10% FBS and 1 mM sodium pyruvate, 1 % non-essential amino acids and 1% antibiotic-antimycotic.
• the cells are then dissociated using cell dissociation buffer and 100-150 ⁇ l per well of 3.5 x 10 ⁇ cells/ml cell suspension (-50,000 -100,000 cells/well) was plated into 96-well black plates (poly-D- lysine precoated) with clear bottom and maintained for 24-48 hours in a tissue culture incubator at 37 0 C under an atmosphere of 5% CO 2 : 95% air.
• Other clonal cell lines or primary cell cultures that express endogenous ⁇ 4* nicotinic receptors may also be used in this assay.
• Calcium flux was measured using calcium-3 assay kit (Molecular Devices, Sunnyvale, CA) or fluo-4 (Invitrogen).
• a stock solution of the dye was prepared by dissolving each vial supplied by the vendor in Hank's balanced salt solution buffer (HBSS) or 150 mM NMDG, 20 mM CaCl 2 containing 10 mM HEPES, The stock solution was diluted 1 :20 using the same buffer before use.
• the growth media was removed from the cells.
• the cells were loaded with 100 ⁇ l of the dye per well and incubated at room temperature for up to one hour for HEK 293 clonal stable cell lines or 30 minutes - 45 minutes at 37 0 C for IMR-32 cells Fluorescence measurements were read simultaneously from all the wells by a
• Fluorometic Imaging Plate Reader FLIPR
• FLIPR Fluorometic Imaging Plate Reader
• Baseline fluorescence was measured for the first 6 seconds at which 3X concentrations of modulator/test compounds were added to the cell plate at 50 ⁇ l and incubated for five minutes. The fluorescence intensity was captured every second for the first 1 minute followed by every 5 seconds for an additional 4 minutes. This procedure was followed by 50 ⁇ l of 4X concentration of agonist and readings were taken for a period of 3-5 minutes as described above. Data was normalized to maximal responses and plotted as a function of concentration. The concentration dependence of changes fluorescence responses was fitted by nonlinear regression analysis (GraphPad Prism, San Diego, CA) to obtain EC50 values.
• the potentiating effect of an ⁇ 4 ⁇ 2modulator on ⁇ 4 ⁇ 2receptor can also be illustrated by concentration responses to ⁇ 4 ⁇ 2 agonists, for example 5-[(2R)-azetidin-2-ylmethoxy]-2- chloropyridine (Compound A) and (3R)-l-pyridin-3-ylpyrrolidin-3-amine (Compound B), in presence of a fixed concentration of PAM.
• concentration responses to ⁇ 4 ⁇ 2 agonists for example 5-[(2R)-azetidin-2-ylmethoxy]-2- chloropyridine (Compound A) and (3R)-l-pyridin-3-ylpyrrolidin-3-amine (Compound B), in presence of a fixed concentration of PAM.
• ⁇ 4 ⁇ 2PAM for example, 3-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5-yl)benzonitrile (Compound 1) at 10 ⁇ M
• concentration-responses to ⁇ 4 ⁇ 2agonists for example 5-[(2R)- azetidin-2-ylmethoxy]-2-chloropyridine (Compound A) and (3R)-l-pyridin-3-ylpyrrolidin-3- amine (Compound B)
• 1 - 2 log units (10- 100-fold) to the left resulting in more potent EC50 values to agonists.
• Table 1 lists the results for the compounds of the present invention.
• the activity (allosteric effects - potentiation of fluorescence responses) ranges are defined as follows; “a” denotes as activity range from 200 - 400%, “b” denotes an activity range from 150-200%, “c” denotes an activity range from 120-150% and “d” denotes an activity range 90-120%.
• Example B ⁇ 4 ⁇ 2Positive allosteric modulator enhances the effects of nicotinic ligands with very low intrinsic agonist efficacy.
• HEK-293 cells stably expressing human ⁇ 4 ⁇ 2 or ⁇ 3 ⁇ 4 are to confluency in 162 cm 2 tissue culture flasks in DMEM media supplemented with 10% FBS and 25 ⁇ g/ml zeocin and 200 ⁇ g/ml hygromycin B.
• IMR-32 neuroblastoma cells are grown to confluency in 162 cm 2 tissue culture flasks in minimum essential media supplemented with 10% FBS and 1 mM sodium pyruvate, 1 % non-essential amino acids and 1% antibiotic-antimycotic.
• the cells are then dissociated using cell dissociation buffer and 100-150 ⁇ l per well of 3.5 x 105 cells/ml cell suspension (-50,000 -100,000 cells/well) was plated into 96-well black plates (poly-D-lysine precoated) with clear bottom and maintained for 24-48 hours in a tissue culture incubator at 37 0 C under an atmosphere of 5% CO 2 : 95% air.
• Other clonal cell lines or dissociated primary cortical neurons that express endogenous ⁇ 4* nicotinic receptors may also be used in this assay.
• Calcium flux was measured using calcium-3 assay kit (Molecular Devices, Sunnyvale, CA) or fluo-4 (Invitrogen).
• a stock solution of the dye was prepared by dissolving each vial supplied by the vendor in Hank's balanced salt solution buffer (HBSS) or 150 mM NMDG, 20 mM CaCl 2 containing 10 niM HEPES. The stock solution was diluted 1 :20 using the same buffer before use. The growth media was removed from the cells. The cells were loaded with 100 ⁇ l of the dye per well and incubated at room temperature for up to one hour for HEK 293 clonal stable cell lines or 30 minutes - 45 minutes at 37 0 C for IMR-32 cells.
• HBSS Hank's balanced salt solution buffer
• Fluorescence measurements were read simultaneously from all the wells by a Fluorometic Imaging Plate Reader (FLIPR) at an excitation wavelength of 480 nm and an emission wavelength of 520 nm. Baseline fluorescence was measured for the first 6 seconds at which 3X concentrations of modulator/test compounds were added to the cell plate at 50 ⁇ l and incubated for five minutes. The fluorescence intensity was captured every second for the first 1 minute followed by every 5 seconds for an additional 4 minutes. This procedure was followed by 50 ⁇ l of 4X concentration of agonist and readings were taken for a period of 3-5 minutes as described above. Data was normalized to maximal responses and plotted as a function of concentration.
• FLIPR Fluorometic Imaging Plate Reader
• ⁇ 4 ⁇ 2 PAMs can also enhance the efficacy of partial agonists (compounds that bind, but activate ⁇ 4 ⁇ 2 nAChRs with low intrinsic efficacy leading to otherwise barely detectable effects on calcium responses).
• partial agonists compounds that bind, but activate ⁇ 4 ⁇ 2 nAChRs with low intrinsic efficacy leading to otherwise barely detectable effects on calcium responses.
• Compound C responses to 2-methyl-3-(2-(S)- pyrrolidinylmethoxy)pyridine (Compound C) in the presence and absence of PAM is shown in Figure 3.
• Figure 5 shows a comparison of EC50 values from calcium fluorescence (FLIPR) assays using ⁇ 4 ⁇ 2 nAChRs of several nicotinic agonists including varenicline and ispronicline in the presence and absence of positive allosteric modulator.
• the potency (EC50 values) of the nicotinic agonists increase in the presence of the positive allosteric modulator.
• Example C ⁇ 4 ⁇ 2 PAM enhances the effiacy of Compound A in an in vivo model of neuropathic pain.
• Compound 1 3-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5-yl)benzonitrile, was prepared in 30% hydroxybetacyclodextrin and injected in solution in a volume of 4 ml/kg body weight immediately before Compound A.
• the doses tested ranged from 0.3 - 30 ⁇ mol/kg i.p.
• Tactile allodynia was measured using calibrated (force; g) von Frey filaments (Stoelting, Wood Dale, IL). Briefly, rats were placed into individual plexiglass containers and allowed to acclimate for 15-20 minutes before testing. Withdrawal threshold was determined by increasing and decreasing stimulus intensity and estimated using a Dixon non- parametric test (Chaplan et al, 1994; Chaplan SR, Bach FW, Pogrel JW, Chung JM and Yaksh TL (1994) J Neurosci Methods 53:55-63). Only rats with threshold scores ⁇ 4.5 g were considered allodynic and utilized in further testing.
• a percent of maximal possible effect (% M.P.E.) of the tested compounds was calculated according to the formula: ([post- drug threshold] -[baseline threshold])/([maximum threshold] -[baseline threshold]) x 100%, where maximum threshold was equal to 15 g.
• Compound A + 3-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5-yl)benzonitrile (Compound 1, PAM) produced a pronounced reversal of nerve injury-induced mechanical allodynia (PWT: 12.1 ⁇ 0.5g) that was significantly different from vehicle (P less than 0.001), but also from Compound A alone (P less than 0.001) and 3-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5- yl)benzonitrile, Compound 1, alone (P less than 0.001).
• PWT nerve injury-induced mechanical allodynia
• Figure 6B shows that the effects of PAM (3-(3-(pyridin-3-yl)-l,2,4-oxadiazol-5- yl)benzonitrile, Compound 1) are dose-dependent.
• An ineffective dose of Compound A (1 nmol/kg) when combined with varying doses of PAM (3-(3-(pyridin-3-yl)-l,2,4-oxadiazol- 5-yl)benzonitrile, Compound 1) results in dose-dependent increase in efficacy, approaching at least that of gabapentin, a drug clinically used for the treatment of neuropathic pain.
• Figure 7A shows dose dependent effects in neuropathic pain of 5-[(2R)-azetidin-2- ylmethoxy]-2-chloropyridine (Compound A) alone, ⁇ 4 ⁇ 2 PAM (3-(3-(pyridin-3-yl)-l,2,4- oxadiazol-5-yl)benzonitrile, Compound 1) alone and a combination of Compound 1 (3.5 ⁇ mol/kg) with various doses of Compound A.
• ⁇ 4 ⁇ 2 PAM Compound 1 alone is ineffective, but is capable of left-shifting the dose response curve of Compound A in the Chung model of neuropathic pain.
• Example D Analysis of compound effects on emesis in ferrets.
• Fasted male ferrets Marshall BioResources, North Rose, NY
• Compound A was administered at various doses.
• the animals were observed for emesis and behaviors characteristic of nausea for a period of 90 minutes. The percentage of animals that experienced emesis at a given dose was recorded.
• Figure 7B shows effects on emesis. Shown are effects of 5-[(2R)-azetidin-2- ylmethoxy]-2-chloropyridine (Compound A) alone, ⁇ 4 ⁇ 2 PAM (Compound 1) alone and a combination of Compound 1 (3.5 ⁇ mol/kg) with various doses of compound A. ⁇ 4 ⁇ 2 PAM (Compound 1) alone does not cause emesis, and does not shift the dose response curve of Compound A in the ferret model of emesis.
• Figures 8 A and 8B show plasma level analysis in models of neuropathic pain and emesis. Note the left ward shift in efficacy of Compound A in Figure 8 A, but no shift in effects on emesis in Figure 8B. In other words, maximal efficacy of Compound A can be realized in neuropathic pain without incidence of emesis, in presence of ⁇ 4 ⁇ 2 PAM (Compound 1), thus widening the therapeutic window of ⁇ 4 ⁇ 2 nAChR agonists
• Example E ⁇ 4 ⁇ 2 Partial agonists can be effective in reversing neuropathic pain in the presence of ⁇ 4 ⁇ 2 positive allosteric modulators
• [00600] [ 3 H]-POB ([ 3 H]-3-(5-(pyridin-3-yl)-l,2,4-oxadiazol-3-yl)benzonitrile) binding to a ⁇ 4 ⁇ 2nAChR modulator site was determined using membrane enriched fractions from human cortex (ABS Inc., Wilmington, DE). Pellets were thawed at 4 0 C, washed and resuspended with a Polytron at a setting of 7 in 30 volumes of BSS-Tris buffer (120 mM NaCl, 5 mM KCl, 2 mM CaCl 2 , 2 mM MgCl 2 , and 50 mM Tris-Cl, pH 7.4, 4 0 C).
• BSS-Tris buffer 120 mM NaCl, 5 mM KCl, 2 mM CaCl 2 , 2 mM MgCl 2 , and 50 mM Tris-Cl, pH 7.4, 4 0 C).
• Membrane preparations from other species and from clonal or transfected cell lines that express ⁇ 4 ⁇ 2 nAChRs cloned from various species may also be used in this binding assay.
• concentration-inhibition assays seven log-dilution concentrations of test compounds containing 100-200 ⁇ g of protein, and 50 nM [ 3 H]-POB (16.4 Ci/mmol) were incubated in a final volume of 500 ⁇ L for 75 minutes at 4 0 C in duplicate. Non-specific binding was determined in the presence of 30 ⁇ M 3-(5-(pyridin-3-yl)-l,2,4-oxadiazol-3- yl)benzonitrile.
• Example 135B r 3 Hl-3-(5-(pyridin-3-vn-1.2.4-oxadiazol-3-vnbenzonitrile ([ 3 Hl-POB) [00604]
• the compound of Example 135 A was dissolved in a mixture of dichloromethane, triethylamine, and 5% palladium on carbon.
• the reaction solution was then saturated with tritium gas (1.2 Ci).
• the reaction mixture was stirred at room temperure for 3.5 hours, the catalyst was removed by filtration, ant the filtrate was concentrated to yield crude tritiated product.
• Ar 2 is aryl or heteroaryl, wherein the aryl or heteroaryl is substituted or unsubstituted, and, when substituted, the aryl or heteroaryl is substituted with 1, 2, 3, or 4 substituents selected from halo, Ci-C 6 haloalkyl, C 6 -CiO aryl, C4-C7 cycloalkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C5-C10 heteroaryl, C4-C10 heterocycle, Ci-C 6 alkyl, -(Ci-C 6 alkyl)NHC(O)O-(Ci-C 6 alkyl), C 1 -C 6 hydroxyalkyl, C 1 -C 6 alkylcarbonyl, amino, hydroxyl, haloalkyl-C(O)-, haloalkyl-SO 2 -, alkyl-SO 2 -, -SO 2 NH 2 , -SO 2
• a particular radiolabeled compound of formula (II*) is [ 3 H]-3-(5-(pyridin-3- yl)-l,2,4-oxadiazol-3-yl)benzonitrile.
• Such compounds are suitable for use in determining the binding affinity of nicotinic acetylcholine receptor subtype ⁇ 4 ⁇ 2 positive allosteric modulators.
• Another embodiment of the invention is a radiolabeled compound of formula (II*), wherein Ar 2 and Ar 3 are independently phenyl, pyrazinyl, pyridinyl, pyrimidinyl, pyridazine, triazinyl, or a bicyclic heteroaryl, substituted independently with 0, 1, 2, 3, or 4 substitutents selected from the group consisting of alkoxy, alkoxycarbonyl, alkoxycarbonylamino, alkoxycarbonylaminoalkyl, alkyl, alkylamino, alkylcarbonyl, alkylsulfonyl, amido, amino, aminoalkyl, carboxy, dialkylamino, dialkylaminoalkyl, halo, haloalkyl, haloalkylcarbonyl, heteroaryl, heterocycle, hydroxy, hydroxyalkyl, cyano, nitro, sulfonamide and dialkylsulfonylformimid

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