WO2007006117A1

WO2007006117A1 - Novel cyp2a6 inhibitors

Info

Publication number: WO2007006117A1
Application number: PCT/CA2005/001088
Authority: WO
Inventors: Billy R. Martin; M. Imad Damaj; William Glassco; Edward Sellers; Rachel Tyndale
Original assignee: Nicogen Inc.; Virginia Commonwealth University Intellectual Property Foundation
Priority date: 2005-07-13
Filing date: 2005-07-13
Publication date: 2007-01-18

Abstract

The present invention provides novel compounds of Formula I, compositions comprising these compounds and methods of using these compounds as inhibitors of CYP2A6. In particular, the compound of the invention are useful for treating diseases which benefit from a decrease in the metabolism of nicotine, for example smoking cessation, exposure reduction, smoking reduction and cancer.

Description

TITLE: Novel CYP2A6 Inhibitors

This invention was made with government support under NIH Grant Number 2 P50 DA05274-14. The government has certain rights in the invention.

FIELD OF THE INVENTION

The present invention relates to novel inhibitors of the enzyme CYP2A6, to pharmaceutical and diagnostic compositions containing them and to their medical use, particularly in the treatment, reduction and/or prevention of disorders associated with nicotine and tobacco dependence, and other indications for nicotine, such as diseases being treated by nicotine (i.e. Parkinson's disease). BACKGROUND OF THE INVENTION

Tobacco is an insidious chemical product as, among its numerous toxic compounds, it contains nicotine which is responsible for the dependency associated with tobacco smoking (Khuranas, S. et al., Respir. Med. 2003, 97, 295-301). According to the World Health Organization (WHO), tobacco use is the leading cause of the disease burden measured in disability adjusted life years in developed countries and one of the top 10 health risk factors even in the poorest developing regions (Ezzati, M. et al., Lancet 2003, 362, 271-280).

Nicotine is the essential component smokers seek from tobacco use. Various nicotine preparations have been developed as medication to assist in smoking cessation, and nicotine has also been evaluated in the treatment of a variety of medical disorders (Benowitz, N. L., Annu. Rev. Pharmacol. Toxicol. 1996, 36, 597-613). After entering the circulation, active nicotine is eliminated mainly by metabolism of nicotine to inactive cotinine. The main enzyme catalyzing this reaction is cytochrome P450 2A6 (CYP2A6) (Messina, E.S. et al., J Pharmacol Exp Ther 1997, 282, 1608-1614; Oscarson, M., Drug Metab. Dispos. 2001, 29, 91-95; Raunio, H. et al., Br. J Clin. Pharmacol. 2001, 52, 357-363; Sellers, E. M. et al., Drug Discovery Today 2003, 8, 487-493). Individuals having deficient CYP2A6 enzyme function, due to inactive alleles of the CYP2A6 gene, display a decreased capacity for nicotine metabolism and these individuals may be less likely to become smokers, are less prone to nicotine addiction, smoke less per day and for shorter durations than individuals with a normally functioning CYP2A6 enzyme (Kitagawa, K., Biochem. Biophys. Res. Commun. 1999, 262, 146- 151 ; Inoue, K. et al. Arch. Toxicol. 2000, 73, 532-539; Nakajima, M. et al. Clin. Pharmacol. Ther. 2000, 67, 57-69; Tyndale, R. F. et al. Ther. Drug Monit 2002, 24, 163-171). Pilot studies have found that chemical inhibition of the CYP2A6 enzyme can reduce the smoking frequency (Sellers, E.M. et al., Clin. Pharmacol. Ther. 2000, 68, 35-43; Tyndale, R. F. et al. Ther. Drug Monit. 2002, 24, 163-171 ; Sellers et al. Nicotine Tob Res 2003, 5: 891-9). There has also been reported evidence that in the Japanese population, those individuals with inactive CYP2A6 alleles are protected from developing lung cancer caused by cigarette smoking (Ando M. et al. J Epidemiol. 2003; 13: 176-81 ; Ariyoshi N. et al. Cancer Epidemiol Biomarkers Prev. 2002;11(9):890-

4; Miyamoto M. et al. Biochem. Biophys. Res. Commun. 1999, 261, 658-660).

Other than nicotine dependence as a result of tobacco use, nicotine itself is not considered hazardous, namely it is not considered to be a causative agent in cancer and heart and lung disease. It is the other products which are found in tobacco products which are considered to be harmful, including combustion products such as carbon monoxide, gases and tar.

Nicotine is routinely used in smoking cessation therapy in which nicotine is delivered to individuals in an attempt to assist that individual in abstaining from tobacco products. In current smoking cessation therapy, nicotine is administered to an individual as chewing gum, transdermal patches, or via nasal spray. To the knowledge of the inventors, oral nicotine administration is not currently commercially available for the reason that oral nicotine must first pass through the liver before entering the systemic circulation. As a result, very high degree of CYP2A6 mediated first pass metabolism occurs in the liver resulting in a small fraction of the nicotine reaching the blood and brain. Since oxidation by CYP2A6 is the rate-limiting step in nicotine inactivation, blocking this reaction by a chemical inhibitor would increase nicotine bioavailability and allow for peroral administration of nicotine (Sellers, E.M. et al. Drug Discovery Today 2003, 8, 487-493). CYP2A6 inhibitors can also be used to reduce nicotine inactivation from alternative sources of nicotine such as smoking resulting in reduced smoking or to reduce the inactivation of nicotine from non-oral nicotine replacement therapies thus increasing nicotine duration and bioavailability. In addition to nicotine inactivation, the human CYP2A6 and mouse CYP2A5 enzymes can also activate several other xenobiotics, such as many of tobacco-specific nitrosamines and other toxic compounds (Oscarson, M. Drug Metab. Dispos. 2001, 29, 91-95; Raunio, H. et al., Br. J CHn. Pharmacol. 2001, 52, 357-363; Tyndale, R.F. et al., Drug Metab. Dispos. 2001, 29, 548-552). Pilot data has demonstrated that CYP2A6 inhibitors in vivo can reduce the activation of tobacco-smoke nitrosamines, rerouting these nitrosamines to detoxified glucuronidated products (Sellers et al. Nicotine Tob Res 2003, 5; 1-9). Since nicotine is inactivated by metabolism to cotinine by the

CYP2A6 enzyme, understanding of the inhibitory structure-activity of the CYP2A6 enzyme is crucial. To the knowledge of the inventors, about 200 compounds have been tested to date for the inhibitory properties on CYP2A5 or CYP2A6 enzymes. However, there is still a need for developing potent and specific chemical inhibitors of the CYP2A enzymes, in particular the human CYP2A6 enzyme, as these inhibitors can be used to regulate nicotine metabolism in an individual. SUMMARY OF THE INVENTION

It has been found that compounds of Formula I show inhibition of the enzyme CYP2A6.

The present invention therefore provides a compound selected from a compound of Formula I, and salts, solvates and prodrugs thereof:

wherein

R¹, R², R³ and R⁴ are independently selected from the group consisting of H, Ci_-4alkyl, C^alkoxy, OH, halo, CF₃. OCF₃, CN, NH₂, NHC_1-4alkyl, N(Ci- ₄alkyl)(Ci_-4alkyl), NO₂, C_2-4alkenyl, C_3-6cycloalkyl and aryl; R⁵ is selected from the group consisting of H, Ci_-6alkyl, C_2-6alkenyl, C_2- ₆alkynyl, aryl-Ci-6alkylene, heteroaryl-d-βalkylene, C_3-6-cycloalkyl, C₃. ₆cycloalkyl-Ci.₆-alkylene, wherein aryl and heteroaryl may be unsubstituted or substituted with 1-5 substituents independently selected from the group consisting of Ci_-4alkyl, Ci_-4alkoxy, halo, OH, CF₃. OCF₃, CN, NH₂, NHCi- ₄alkyl, N(Ci_-4alkyl)(Ci_-4alkyl) and NO₂ and heteroaryl is a mono- or benzofused bicyclic aromatic ring containing from 5-10 carbon atoms in which 1-3 of which is replaced with a heteroatom selected from O, S and N; R⁶ is selected from the group consisting of H and Ci-₄alkyl; and n is 0 or 1.

According to another aspect of the present invention, there is provided a pharmaceutical composition comprising a compound of the invention and a pharmaceutically acceptable carrier or diluent. Also within the scope of the present invention is a method of treating conditions which benefit from an inhibition of CYP2A6 comprising administering an effective amount of a compound of the invention to a subject in need thereof.

The present invention also relates to a use of a compound of the invention to treat conditions which benefit from an inhibition of CYP2A6. Further, the present invention relates to the use of a compound of the invention to prepare a medicament to treat conditions which benefit from an inhibition of CYP2A6. In embodiments of the invention a condition which benefits from an inhibition of CYP2A6 is one which benefits from decrease in the metabolism of nicotine, for example, preventing, reducing or treating smoking, or is one which benefits from decrease in the in vivo formation of carcinogens, for example prevention or treatment of cancer.

The present invention also relates to a method of enhancing oral nicotine replacement therapy comprising administering an effective amount of a compound of the invention to a subject in need thereof. The invention also relates to a use of a compound of the invention to enhance oral nicotine replacement therapy and a use of a compound of the invention to prepare a medicament to enhance oral nicotine replacement therapy. In an embodiment of the invention, the compound of the invention is administered contemporaneously with nicotine. Moreover, the present invention relates to a method of reducing cardiovascular or pulmonary disease risk comprising administering an effective amount of a compound of the invention to a subject in need thereof.

Other features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples while indicating preferred embodiments of the invention are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. DETAILED DESCRIPTION OF THE INVENTION Novel compounds showing inhibition of the enzyme CYP2A6 have been identified. As such, the compounds of the invention are useful for treating diseases which benefit from a decrease in the metabolism of nicotine and precarcinogens, for example smoking cessation, exposure reduction, smoking reduction and cancer. Accordingly, the present invention provides a compound selected from a compound of Formula I, and salts, solvates and prodrugs thereof:

wherein R¹, R², R³ and R⁴ are independently selected from the group consisting of H, Ci_-4alkyl, Ci_-4alkoxy, OH, halo, CF₃. OCF₃, CN, NH₂, NHCi_-4alkyl, N(Ci- ₄alkyl)(Ci_-4alkyl), NO₂, C₂-₄alkenyl, C_3-6cycloalkyl and aryl; R⁵ is selected from the group consisting of H, Ci_-6alkyl, C₂-₆alkenyl, C_2- βalkynyl, aryl-d-βalkylene, heteroaryl-Ci-6alkylene, C_3-6-cycloalkyl, C_3- ecycloalkyl-Ci-β-alkylene, wherein aryl and heteroaryl may be unsubstituted or substituted with 1-5 substituents independently selected from the group consisting of C_1-4alkyl, Ci_-4alkoxy, halo, OH, CF₃. OCF₃, CN, NH₂, NHCi- ₄alkyl, N(Ci_-4alkyl)(Ci_-4alkyl) and NO₂ and heteroaryl is a mono- or benzofused bicyclic aromatic ring containing from 5-10 carbon atoms in which 1-3 of which is replaced with a heteroatom selected from O, S and N; R⁶ is selected from the group consisting of H and Ci_-4alkyl; and n is O or 1.

The present invention includes compounds of Formula I, wherein R¹, R², R³ and R⁴ are independently selected from the group consisting of H, Ci_-4alkyl, Ci_-4alkoxy, OH, halo, CF₃. OCF₃, CN, NH₂, NHCi- ₄alkyl, N(Ci-₄alkyl)(Ci-₄alkyl), NO₂, C_2-4alkenyl, C_3-6cycloalkyl and aryl. In embodiment of the invention, only one of R¹, R², R³ and R⁴ is selected from the group consisting of Ci_-4alkyl, Ci_-4alkoxy, OH, halo, CF₃. OCF₃, CN, NH₂, NHCi_-4alkyl, N(Ci_-4alkyl)(Ci_-4alkyl), NO₂, C₂.₄alkenyl, C_3-6cycloalkyl and aryl, while the remaining are all H. In further embodiments of the invention, R¹, R², R³ and R⁴ are independently selected from the group consisting of H, CH₃, CH₃O, OH, halo, CF₃. OCF₃, CN, NH₂, NHCH₃, N(CH₃)₂ and NO₂. In still further embodiments of the invention, R¹, R², R³ and R⁴ are all H. Also included within the scope of the present invention are compounds of Formula I, where R⁵ is selected from the group consisting of H, Ci_-6alkyl, C₂-6alkenyl, C_2-6alkynyl, aryl-C-i-βalkylene, heteroaryl-Ci_-6alkylene, C₃-6-cycloalkyl, Cs-ecycloalkyl-d-β-alkylene, wherein aryl and heteroaryl may be unsubstituted or substituted with 1-5 substituents independently selected from the group consisting of Ci_-4alkyl, Ci_-4alkoxy, halo, OH, CF₃. OCF₃, CN, NH₂, NHCi-4alkyl, N(Ci.4alkyl)(Ci.₄alkyl) and NO₂ and heteroaryl is a mono- or benzofused bicyclic aromatic ring containing from 5-10 carbon atoms in which 1-3 of which is replaced with a heteroatom selected from O, S and N. In embodiments of the invention, R⁵ is selected from the group consisting of H, CH₃, ethyl, CH₂Cf,CH, Ph-CH₂, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclopropyl-CH₂, cyclobuty-CH₂, cyclopentyl-CH₂, cyclohexyl-CH₂, wherein Ph may be unsubstituted or substituted with 1-3 substituents independently selected from the group consisting of CH₃, CH₃O, OH, halo, CF₃. OCF₃, CN, NH₂, NHCH₃, N(CH₃)₂ and NO₂. In a further embodiment of the invention R⁵ is selected from the group consisting of H, CH₃ and PhCH₂, specifically H and CH₃.

The present invention includes compounds of Formula I wherein R⁶ is selected from the group consisting of H and C-i^alkyl. In embodiments of the invention, R⁶ is selected from H and CH₃. In further embodiments, R⁶ is H.

The compounds of Formula I include those in which n is 0 or 1. In embodiments of the invention n is 0.

In an embodiment of the invention the compound of Formula I is selected from:

3-Methyl-1-(pyridin-3-yl)-3-azabicyclo[3.1.0]hexane; 3-Benzyl-1-(pyridin-3-yl)-3-aza-bicyclo[3.1.0]hexane; and 1 -(Pyridin-3-yl)-3-azabicyclo[3.1.0]hexane.

In a further embodiment of the invention the compound of Formula I is selected from:

3-Methyl-1 -(pyridin-3-yl)-3-azabicyclo[3.1.0]hexane; and 1 -(Pyridin-3-yl)-3-azabicyclo[3.1.0]hexane. The term "Ci_-4alkyl" as used herein means straight and/or branched chain alkyl radicals containing from one to four carbon atoms and includes methyl, ethyl, propyl, isopropyl, t-butyl and the like.

The term "Ci^alkoxy" as used herein means straight and/or branched chain alkoxy radicals containing from one to four carbon atoms and includes methoxy, ethoxy, propyoxyl, isopropyloxy, t-butoxy and the like.

The term "Ci-₆alkyl" as used herein means straight and/or branched chain alkyl radicals containing from one to six carbon atoms and includes methyl, ethyl, propyl, isopropyl, t-butyl, pentyl, hexyl and the like. The term "aryl" as used herein means unsubstituted or substituted mono- or bicyclic aromatic radicals containing from 6 to 10 carbon atoms and includes phenyl and naphthyl and the like.

The term "heteroaryl" as used herein means unsubstituted or substituted mono- or benzofused bicyclic heteroaromatic radicals containing from 5 to 10 atoms, of which 1-3 atoms may be a heteroatom selected from the group consisting of S, O and N, and includes furanyl, thienyl, pyrrolo, pyridyl, indolo, benzofuranyl and the like.

The term "halo" as used herein means halogen and includes chloro, flouro, bromo, iodo and the like. The term "C₂-₆alkenyl" as used herein means straight and/or branched chain alkenyl groups containing from two to six carbon atoms and at least one double bond, provided that the double bond is not located at the carbon adjacent to a nitrogen atom, and includes allyl, isoprenyl and the like.

The term "C₂-₆alkynyl" as used herein means straight and/or branched chain alkynyl groups containing from two to six carbon atoms and at least one triple bond, provided that the triple bond is not located at the carbon adjacent to a nitrogen atom, and includes -CHbCfCH, -CH₂CΞCCH3 and the like.

The term "Ca-ecycloalkyl" as used herein means a saturated carbocylic group containing from three to six carbon atoms and includes cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl. The term "compound(s) of the invention" as used herein means compound(s) of Formula I, enantiomers thereof and/or pharmaceutically acceptable salts, solvates and/or prodrugs thereof.

It is to be clear that the present invention includes pharmaceutically acceptable salts, solvates and prodrugs of compounds of the invention and mixtures comprising two or more of compounds of Formula I, pharmaceutically acceptable salts of the compounds of Formula I₁ pharmaceutically acceptable solvates of compounds of Formula I and prodrugs of compounds of Formula I. The compounds of the invention may have at least one asymmetric ^, centre. Where the compounds according to the invention possess more than one asymmetric centre, they may exist as diastereomers. It is to be understood that all such isomers and mixtures thereof in any proportion are encompassed within the scope of the present invention. It is to be understood that while the stereochemistry of the compounds of the invention may be as provided for in any given compound listed herein, such compounds of the invention may also contain certain amounts (e.g. less than 20%, preferably less than 10%, more preferably less than 5%) of compounds of the invention having alternate stereochemistry. The term "pharmaceutically acceptable" means compatible with the treatment of animals, in particular, humans.

The term "pharmaceutically acceptable salt" means an acid addition salt which is suitable for or compatible with the treatment of patients. The term "pharmaceutically acceptable acid addition salt" as used herein means any non-toxic organic or inorganic salt of any base compound of the invention, or any of its intermediates. Illustrative inorganic acids which form suitable salts include hydrochloric, hydrobromic, sulfuric and phosphoric acids, as well as metal salts such as sodium monohydrogen orthophosphate and potassium hydrogen sulfate. Illustrative organic acids that form suitable salts include mono-, di-, and tricarboxylic acids such as glycolic, lactic, pyruvic, malonic, succinic, glutaric, fumaric, malic, tartaric, citric, ascorbic, maleic, benzoic, phenylacetic, cinnamic and salicylic acids, as well as sulfonic acids such as p-toluene sulfonic and methanesulfonic acids. Either the mono or di-acid salts can be formed, and such salts may exist in either a hydrated, solvated or substantially anhydrous form. In general, the acid addition salts of the compounds of the formula I are more soluble in water and various hydrophilic organic solvents, and generally demonstrate higher melting points in comparison to their free base forms. The selection of the appropriate salt will be known to one skilled in the art. Other non- pharmaceutically acceptable salts, e.g. oxalates, may be used, for example, in the isolation of the compounds of the formula I, for laboratory use, or for subsequent conversion to a pharmaceutically acceptable acid addition salt. In embodiments of the invention, the pharmaceutically acceptable acid addition salt is the hydrochloride salt.

The formation of a desired compound salt is achieved using standard techniques. For example, the neutral compound is treated with an acid or base in a suitable solvent and the formed salt is isolated by filtration, extraction or any other suitable method.

The term "solvate" as used herein means a compound of the formula I or a pharmaceutically acceptable salt of a compound of the formula I, wherein molecules of a suitable solvent are incorporated in the crystal lattice. A suitable solvent is physiologically tolerable at the dosage administered. Examples of suitable solvents are ethanol, water and the like. When water is the solvent, the molecule is referred to as a "hydrate". The formation of solvates of the compounds of the invention will vary depending on the compound and the solvate. In general, solvates are formed by dissolving the compound in the appropriate solvent and isolating the solvate by cooling or using an antisolvent. The solvate is typically dried or azeotroped under ambient conditions.

Compounds of the formula I includes prodrugs. In general, such prodrugs will be functional derivatives of a compound of the formula I which are readily convertible in vivo into the compound from which it is notionally derived. Prodrugs of the compounds of the formula I may be conventional esters formed with available hydroxy, or amino group. For example, an available OH or nitrogen in a compound of the formula I may be acylated using an activated acid in the presence of a base, and optionally, in inert solvent (e.g. an acid chloride in pyridine). Some common esters which have been utilized as prodrugs are phenyl esters, aliphatic (C₈-C₂₄) esters, acyloxymethyl esters, carbamates and amino acid esters. In certain instances, the prodrugs of the compounds of the formula I are those in which one or more of the hydroxy groups in the compounds is masked as groups which can be converted to hydroxy groups in vivo. Conventional procedures for the selection and preparation of suitable prodrugs are described, for example, in "Design of Prodrugs" ed. H. Bundgaard, Elsevier, 1985.

Compounds of the formula I includes radiolabeled forms, for example, compounds of the formula I labeled by incorporation within the structure ³H or ¹⁴C or a radioactive halogen such as ¹²⁵I. A radiolabeled compound of the formula I may be prepared using standard methods known in the art. For example, tritium may be incorporated into a compound of the formula I using standard techniques, for example by hydrogenation of a suitable precursor to a compound of the formula I using tritium gas and a catalyst. Alternatively, a compound of the formula I containing radioactive iodo may be prepared from the corresponding trialkyltin (suitably trimethyltin) derivative using standard iodination conditions, such as [¹²⁵I] sodium iodide in the presence of chloramine-T in a suitable solvent, such as dimethylformamide. The trialkyltin compound may be prepared from the corresponding non-radioactive halo, suitably iodo, compound using standard palladium-catalyzed stannylation conditions, for example hexamethylditin in the presence of tetrakis(triphenylphosphine) palladium (0) in an inert solvent, such as dioxane, and at elevated temperatures, suitably 50-100⁰C.

In accordance with another aspect of the present invention, the compounds of Formula can be prepared using the methods described herein. Accordingly, the present invention also includes a method of preparing a compound of Formula I comprising reacting a compound of Formula II:

wherein R¹-R⁶ and n are as defined in Formula I, under standard Mitsonubu reaction conditions, for example in the presence of triphenylphosphine and carbon tetrachloride in an inert solvent at ambient or elevated (i.e. around 30- 50 ⁰C) temperatures. For the case where R⁵ is H, it is an embodiment of the invention that, for the reaction, the group R⁵ is replaced with a protecting group, for example benzyl, which is compatible with the Mitsonubu reaction conditions, yet can be removed after the reaction is complete. The present invention further includes a method for preparing a compound of Formula Il comprising reacting a compound of Formula III:

wherein R¹-R⁴, R⁶ and n are as defined in Formula I, with a compound of Formula IV:

R⁵-NH₂ IV

wherein R⁵ is as defined in Formula I, in the presence of a base, for example a non-nucleophilic organic base such as triethylamine, followed by reduction under standard conditions, for example standard hydride reduction conditions.

Compounds of Formula III may be prepared using procedures known in the art, for example as described in Examples 1(a) - 1(c) hereinbelow. In some cases the chemistries outlined above may have to be modified, for instance by use of protective groups, to prevent side reactions due to reactive groups, such as reactive groups attached as substituents. This may be achieved by means of conventional protecting groups, for example as described in "Protective Groups in Organic Chemistry" McOmie, J.F.W. Ed., Plenum Press, 1973 and in Greene, T.W. and Wuts, P.G.M., "Protective Groups in Organic Synthesis", John Wiley & Sons, 3^rd Edition, 1999.

As hereinbefore mentioned, novel compounds of the Formula I have been prepared. Accordingly, the present invention includes all uses of the compounds of the invention including their use in therapeutic methods and compositions for inhibiting CYP2A6, their use in diagnostic assays and their use as research tools. In particular, the present invention includes the use of a compound of the invention as a medicament, The present invention includes a method of treating conditions which benefit from an inhibition of CYP2A6 comprising administering an effective amount of a compound of the invention to a subject in need thereof.

The present invention also relates to a use of a compound of the invention to treat conditions which benefit from an inhibition of CYP2A6. Further, the present invention relates to the use of a compound of the invention to prepare a medicament to treat conditions which benefit from an inhibition of CYP2A6.

To "inhibit" or "suppress" or "reduce" a function or activity, such as CYP2A6 activity, is to reduce the function or activity when compared to otherwise same conditions except for a condition or parameter of interest, or alternatively, as compared to another condition. The terms "inhibitor" and "inhibition", in the context of the present invention, are intended to have a broad meaning and encompass compounds of the invention which directly or indirectly (e.g., via reactive intermediates, metabolites and the like) act on CYP2A6 to inhibit or otherwise regulate the ability of CYP2A6 to catalyze metabolism of a nicotine to cotinine. The term an "effective amount" or a "sufficient amount " of an compound as used herein is that amount sufficient to effect beneficial or desired results, including clinical results, and, as such, an "effective amount" depends upon the context in which it is being applied. For example, in the context of administering an agent that inhibits CYP2A6, an effective amount of an agent is, for example, an amount sufficient to achieve such an inhibition in CYP2A6 activity as compared to the response obtained without administration of the agent.

As used herein, and as well understood in the art, "treatment" is an approach for obtaining beneficial or desired results, including clinical results. Beneficial or desired clinical results can include, but are not limited to, alleviation or amelioration of one or more symptoms or conditions, diminishment of extent of disease, stabilized (i.e. not worsening) state of disease, preventing spread of disease, delay or slowing of disease progression, amelioration or palliation of the disease state, diminishment of the reoccurrence of disease, and remission (whether partial or total), whether detectable or undetectable. "Treatment" can also mean prolonging survival as compared to expected survival if not receiving treatment.

"Palliating" a disease or disorder means that the extent and/or undesirable clinical manifestations of a disorder or a disease state are lessened and/or time course of the progression is slowed or lengthened, as compared to not treating the disorder.

The term "subject" as used herein includes all members of the animal kingdom including human. The subject is preferably a human. In embodiments of the invention a condition which benefits from an inhibition of CYP2A6 is one which benefits from decrease in the metabolism of nicotine, for example, preventing, reducing or treating smoking, or is one which benefits from decrease in the in vivo formation of carcinogens, for example prevention or treatment of cancer, for example colorectal cancer. As mentioned previously, the present invention relates to methods for the treatment of conditions requiring a reduction in the activity the CYP2A6 enzyme. In particular, the therapeutic aspect of the present invention relates to treatment, reduction and prevention of smoking, in vivo carcinogen formation and cancer in an individual. Each of this involves administration to a subject a CYP2A6 inhibitor.

In one aspect, the present invention provides a method of preventing, treating or regulating smoking in subject in need thereof comprising administering an effective amount of a compound of the invention. Also included is a use of a compound of the invention to prevent, treat or regulate smoking and a use of a compound of the invention to prepare a medicament to prevent, treat or regulate smoking. As used throughout this specification, the terms "smoking prevention" and "preventing smoking", are intended to mean that the likelihood of the onset of smoking (i.e., the progression from a cigarette to regular smoking) in a current non-smoking individual (i.e., a person who has never smoked or is a ex-smoker) and the return to smoking of a previous smoker (i.e. relapse prevention) is substantially mitigated. "

The terms "smoking regulation" and "regulating smoking", as used throughout this specification, are intended to mean that the amount smoked by a current smoking individual is reduced or, at least, fails to increase. The terms "smoking treatment" or "treatment of smoking" means the stopping of all smoking or the reduction in amount of smoking as reflected in less use of tobacco products, a decrease in pattern of use or a decrease in tobacco smoke exposure, and reduction of the amount of smoking leading to cessation. The measure of tobacco smoke exposure can be measured by analyzing breath carbon monoxide.

An oral nicotine replacement therapy containing nicotine alone would be ineffective due to the extensive metabolism of nicotine in the liver which significantly decreases the systemic availability of the nicotine. However, administering the nicotine with a CYP2A6 inhibitor would increase the bioavailability and the effectiveness of the oral nicotine therapy.

Accordingly, the present invention also relates to a method of enhancing oral nicotine replacement therapy comprising administering an effective amount of a compound of the invention to a subject in need thereof. The invention also relates to a use of a compound of the invention to enhance oral nicotine replacement therapy and a use of a compound of the invention to prepare a medicament to enhance oral nicotine replacement therapy. In an embodiment of the invention, the compound of the invention is administered contemporaneously with nicotine.

As used herein, "administered contemporaneously" means that the two substances are administered to a subject such that they are both biologically active in the subject at the same time. The exact details of the administration will depend on the pharmacokinetics of the two substances in the presence of each other, and can include administering one substance within 24 hours of administration of the other, if the pharmacokinetics are suitable. Design of suitable dosing regimens are routine for one skilled in the art. In particular embodiments, two substances will be administered substantially simultaneously, i.e. within minutes of each other, or in a single composition that comprises both substances.

The present invention further relates to a method of treating a condition requiring inhibition of nicotine metabolism to cotinine comprising administering an effective amount of a compound of the invention to a subject in need thereof. The invention also relates to a use of a compound of the invention to treat a condition requiring inhibition of nicotine metabolism to cotinine and a use of a compound of the invention to prepare a medicament to treat a condition requiring inhibition of nicotine metabolism to cotinine.

Conditions requiring inhibition of nicotine metabolism to cotinine include nicotine use disorders - i.e. dependent and non-dependent tobacco use, and nicotine-induced disorders - i.e. withdrawal. The conditions may develop with the use of all forms of tobacco (e.g. cigarettes, chewing tobacco, snuff, pipes and cigars) and with prescription medications (e.g. nicotine gum, nicotine patch, spray, pulmonary inhalation or other forms). In particular, the compounds, pharmaceutical compositions and treatment methods of the invention may be used to diminish a subject's desire to smoke and thereby alter smoking behaviour. The inhibitor and nicotine combination can be used for the treatment of other neurological syndromes. The inhibitor alone or combined with nicotine can also be used for reducing smoking behaviours to reduce cardiovascular and/or pulmonary disease risk.

The compounds, compositions and treatment methods of the present invention by regulating nicotine metabolism in an individual are highly effective. The methods and compositions maintain the behavioural components of smoking and modify them by reducing nicotine metabolism to cotinine. An individual with reduced nicotine metabolism following administration of a compound or composition of the present invention, will alter smoking behaviour and smoke exposure because of modification of nicotine requirements. The methods and compositions of the invention show patterns of reduction, more sustained abstinence, and lower tobacco smoke exposure than obtained with prior art methods in particular those using nicotine deprivation. The behavioural component of smoking is particularly important in some groups of individuals, and thus the methods, compounds and compositions of the invention, in modifying and maintaining behavioural components, may be particularly useful in reducing smoking in those individuals. For example, it has been found that behavioural components are significant in tobacco use by women. The present invention permits the development of behavioural learning on an individual/or group basis.

The compounds, compositions and treatment methods of the invention are also particularly suited to regulate nicotine metabolism in individuals or populations having high levels of CYP2A6. For example, Caucasians in North America have high levels of CYP2A6. An individual or population having a high level of CYP2A6 can be identified using our methods for measuring CYP2A6.

The compounds, compositions and methods of the invention also have the advantage of individualization and flexibility in treatment duration. The compositions and treatment methods are particularly suitable for severely dependent individuals, previous treatment failures, individuals unable to accept the current approach of complete cessation, treatment/prevention of relapse, or concurrent treatment with other methods such as the nicotine patch. It is expected that the compositions and treatments of the invention will decrease the doses of nicotine patch and all other forms of nicotine replacement therapies that are needed and will prolong the duration of action of the therapy and/or enforce their effectiveness in the treatment of tobacco dependence.

The compounds, methods and compositions of the invention in treating individuals with nicotine use disorders and nicotine-induced disorders are also useful in the treatment and prophylaxis of diseases or conditions, including nicotine-related disorders such as opioid related disorders; proliferative diseases; cognitive, neurological or mental disorders; pulmonary or cardiovascular diseases; and other drug dependencies in the individuals. Examples of such underlying diseases or conditions include malignant disease, psychosis, schizophrenia, Parkinson's disease, anxiety, depression, alcoholism, opiate dependence, memory deficits, ulcerative colitis, cholinergic deficits, and the like.

The compounds, methods and compositions of the invention may also be used in the prophylaxis and treatment of individuals having a condition which requires an inhibition of CYP2A6. For example, CYP2A6 is known to metabolize several procarcinogens such as NNK (Crespi CL, et al., "A tobacco smoke-derived nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1- butanone, is activated by multiple human cytochrome P450s including the polymorphic human cytochrome P4502D6," Carcinogenesis, 12(7): 1197-201 (1991)), aflaxtoxin B1 (Yun CH, et al., "Purification and characterization of human liver microsomal cytochrome P 450 2A6," Molec. Pharmacol., 40(5):679-85 (1991)); hexamethylphosphoramide (Ding X, et al., "Mossbauer studies on the metal-thiolate cluster formation in Fe(ll)-metallothionein," Eur. J Biochem., 171(3):711-4 (1988)), and nitrosodimethylamine (Davies RL, et al., "Development of a human cell line by selection and drug-metabolizing gene transfection with increased capacity to activate promutagens," Carcinogenesis, 10:885-891 (1989); Femandez-Salguero, et al. Am J Hum Genet, 57:651-60 (1995); Fernandez-Salguero, et al. Pharmacogenetics, 5:S123-8 (1995)). Therefore, inhibitors of CYP2A6 may be useful in the prophylaxis (e.g., inhibition of CYP2A6 substrates thereby decreasing gehotoxicity, cytotoxicity and/or mutagenicity) and treatment of malignant diseases, and, without limitation, the above-mentioned conditions and diseases. Altered CYP2A6 genotypes have also been associated with a decrease risk for developing colorectal cancer (Sweeney, et al. Toxicology 181-182: 83-87 (2002); Sachse, et al. Carcinogenesis, 23:1839-1849 (2002); Nowell, et al. Mutation Research, 506-507:175-178 (2002); Nowell et al. Cancer Epidemiology, Biomarkers and Prevention, 11 :377-383 (2002)). Accordingly, inhibition of CYP2A6 can also be used for the treatment and/or prevention of colorectal cancer.

Therefore, in another aspect, the present invention includes a method of regulating the formation of a carcinogen in subject in need thereof comprising administering an effective amount a compound of the invention. Also included is a use of a compound of the invention to regulate the formulation of a carcinogen and a use of a compound of the invention to prepare a medicament to regulating the formulation of a carcinogen.

The terms "carcinogen formation regulation" and "regulating formation of a carcinogen", as used throughout this specification, are intended to mean that the occurrence of carcinogen formation in an individual is reduced. This may be achieved, for example, by using CYP2A6 inhibition to inhibit activation of procarcinogens present in the individual. As used throughout this specification, the term "procarcinogen" is meant to encompass any substance which is at least one of procytotoxic, promutagenic and progenotoxic ("pro" means the metabolite is more active that the parent compound).

In a further aspect, the present invention provides a method of preventing or treating cancer in a subject in need thereof comprising administering an effective amount of a compound of the invention. Also included is a use of a compound of the invention to prevent or treat cancer and a use of a compound of the invention to prepare a medicament to prevent or treat cancer. The terms "cancer prevention or treatment" and "preventing or treating cancer", as used throughout this specification, are intended to mean that the likelihood of the onset of cancer in a current cancer-free individual (i.e., a person who has never had cancer or whose cancer is in remission) is substantially mitigated. They also mean that the reduction of carcinogen activation can prevent the reoccurrence of the cancer in patients. In embodiment of the invention, the cancer is colorectal cancer. The compounds of the invention may be tested for their ability to inhibit CYP2A6 using known methods, for example as described in PCT Patent Application WO 99/27919. The compounds of the invention are suitably formulated into pharmaceutical compositions for administration to human subjects in a biologically compatible form suitable for administration in vivo. Accordingly, the present invention further includes a pharmaceutical composition for treating conditions which benefit from an inhibition of CYP2A6 comprising a compound of the invention and a pharmaceutically acceptable carrier and/or diluent.

The compositions containing the compounds of the invention can be prepared by known methods for the preparation of pharmaceutically acceptable compositions which can be administered to subjects, such that an effective quantity of the active substance is combined in a mixture with a pharmaceutically acceptable vehicle. Suitable vehicles are described, for example, in Remington's Pharmaceutical Sciences (2003 - 20th edition) and in The United States Pharmacopeia: The National Formulary (USP 24 NF19) published in 1999). On this basis, the compositions include, albeit not exclusively, solutions of the substances in association with one or more pharmaceutically acceptable vehicles or diluents, and contained in buffered solutions with a suitable pH and iso-osmotic with the physiological fluids.

The compounds of the formula I may be used in the form of the free base, in the form of salts and/or solvates. All forms are within the scope of the invention.

In accordance with the methods of the invention, the described compounds, salts or solvates thereof may be administered to a patient in a variety of forms depending on the selected route of administration, as will be understood by those skilled in the art. The compositions of the invention may be administered, for example, by oral, parenteral, buccal, sublingual, nasal, rectal, patch, pump or transdermal (topical) administration and the pharmaceutical compositions formulated accordingly. Parenteral administration includes intravenous, intraperitoneal, subcutaneous, intramuscular, transepithelial, nasal, intrapulmonary, intrathecal, rectal and topical modes of administration. Parenteral administration may be by continuous infusion over a selected period of time. A compound of the invention may be orally administered, for example, with an inert diluent or with an assimilable edible carrier, or it may be enclosed in hard or soft shell gelatin capsules, or it may be compressed into tablets, or it may be incorporated directly with the food of the diet. For oral therapeutic administration, the compound of the invention may be incorporated with excipient and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers, and the like.

A compound of the invention may also be administered parenterally. Solutions of a compound of the invention can be prepared in water suitably mixed with a surfactant such as hydroxypropylcellulose. Dispersions can also be prepared in glycerol, liquid polyethylene glycols, DMSO and mixtures thereof with or without alcohol, and in oils. Under ordinary conditions of storage and use, these preparations contain a preservative to prevent the growth of microorganisms. A person skilled in the art would know how to prepare suitable formulations. Conventional procedures and ingredients for the selection and preparation of suitable formulations are described, for example, in Remington's Pharmaceutical Sciences (2003 - 20th edition) and in The United States Pharmacopeia: The National Formulary (USP 24 NF19) published in 1999.

The pharmaceutical forms suitable for injectable use include sterile aqueous solutions or dispersion and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersions. In all cases the form must be sterile and must be fluid to the extent that easy syringability exists. Ampoules are convenient unit dosages.

Compositions for nasal administration may conveniently be formulated as aerosols, drops, gels and powders. Aerosol formulations typically comprise a solution or fine suspension of the active substance in a physiologically acceptable aqueous or non-aqueous solvent and are usually presented in single or multidose quantities in sterile form in a sealed container, which can take the form of a cartridge or refill for use with an atomizing device. Alternatively, the sealed container may be a unitary dispensing device such as a single dose nasal inhaler or an aerosol dispenser fitted with a metering valve which is intended for disposal after use. Where the dosage form comprises an aerosol dispenser, it will contain a propellant which can be a compressed gas such as compressed air or an organic propellant such as fluorochlorohydrocarbon. The aerosol dosage forms can also take the form of a pump-atomizer.

Compositions suitable for buccal or sublingual administration include tablets, lozenges, and pastilles, wherein the active ingredient is formulated with a carrier such as sugar, acacia, tragacanth, or gelatin and glycerine. Compositions for rectal administration are conveniently in the form of suppositories containing a conventional suppository base such as cocoa butter.

Compositions for topical administration may include, for example, propylene glycol, isopropyl alcohol, mineral oil and glycerin. Preparations suitable for topical administration include liquid or semi-liquid preparations such as liniments, lotions, applicants, oil-in-water or water-in-oil emulsions such as creams, ointments or pastes; or solutions or suspensions such as drops. In addition to the aforementioned ingredients, the topical preparations may include one or more additional ingredients such as diluents, buffers, flavouring agents, binders, surface active agents, thickeners, lubricants, preservatives, e.g. methyl hydroxybenzoate (including antioxidants), emulsifying agents and the like. Sustained or direct release compositions can be formulated, e.g. liposomes or those wherein the active compound is protected with differentially degradable coatings, such as by microencapsulation, multiple coatings, etc. It is also possible to freeze-dry the compounds of the formula I and use the lypolizates obtained, for example, for the preparation of products for injection.

The dosage administered will vary depending on the use and known factors such as the pharmacodynamic characteristics of the particular substance, and its mode and route of administration; age, health, and weight of the individual recipient; nature and extent of symptoms, kind of concurrent treatment, frequency of treatment, and the effect desired.

In some instances, instead of increasing the dosage of a compound, the kinetics of inhibition created by certain chemical compounds can be altered or enhanced by adding to the treatment protocol a second inhibitor to a substance (e.g., enzyme) that is capable of inhibiting the metabolism of the CYP2A6 inhibitor. By adding such a second inhibitor, the quantity of the CYP2A6 inhibitor will be maintained thus prolonging the beneficial effect of maintaining an elevated plasma concentration of nicotine. The use of such a second inhibitor is very beneficial since it facilitates treatment of individuals by maintaining substantially constant nicotine levels and acting locally on the kinetics of the CYP2A6 inhibitor. By using this approach, large dosages of centrally active compounds can be avoided.

Similarly, preexposure of an individual to an inhibitory substance sometimes can result in an inhibitory effect that will outlast the presence of the drug in the plasma or that will have a persistent effect in the individual despite the inhibitor's half life in the plasma. This phenomenon caused by preincubation or preexposure of an inhibitory substance can help increase the dose interval at which a dosage of the substance must be administered, decrease the chronic dose or enhance CYP2A6 inhibition. Furthermore, preexposure of an individual to one inhibitory substance can subsequently decrease the needed dose of a second inhibitor. The appropriate dosage of a substance which inhibits CYP2A6 is dependent upon the amount of CYP2A6 that is present in an individual's body. This amount is in turn dependent upon whether the individual contains two variant alleles, one variant allele or no variant alleles at the CYP2A6 gene locus. A method for determining the CYP2A6 activity in an individual containing two variant alleles, one variant allele or no variant alleles at a gene locus for the CYP2A6 gene, is described in PCT Patent Application WO 99/27919.

The individual subject may be any type of mammal, but is preferably a human. Generally, the subject is an individual having a CYP2A6 genotype associated with an active form of the enzyme. The CYP2A6 genotype of an individual and the existence of an active CYP2A6 enzyme in an individual may be determined using procedures described in PCT Patent Application WO 99/27919. For example, coumarin 7 hydroxylation has been used to measure CYP2A6 activity (Cholerton, et al. (1992); and Rautio, et al., (1992)). As discussed above, in an embodiment of the invention, the methods and compositions of the invention may be used in individuals or populations having high levels of CYP2A6, or in individuals where the behavioural components of smoking are significant. For use in the treatment of conditions requiring regulation of nicotine metabolism to cotinine, by way of general guidance, a daily oral dosage of compound of the invention can be about 0.01 to 80 mg/kg of body weight, specifically 0.01 to 20, more specifically 0.05 to 3 mg/kg of body weight. Ordinarily a dose of 0.03 to 50 mg/kg of a compound of the invention per day in divided doses one to multiple times a day, specifically up to four times per day, or in sustained release form is effective to obtain the desired results. In accordance with a particular regimen, a compound of the invention is administered once to four times daily for as long as necessary. While standard interval dose administration may be used the compositions of the invention may be administered intermittently prior to high risk smoking times, e.g., early in the day and before the end of a working day. More than one compound of the invention may be used to regulate metabolism of nicotine to cotinine. In such cases the substances can be administered by any conventional means available for the use in conjunction with pharmaceuticals, either as individual separate dosage units administered simultaneously or concurrently, or in a physical combination of each component therapeutic agent in a single or combined dosage unit. The active agents can be administered alone, but are generally administered with a pharmaceutical carrier selected on the basis of the chosen route of administration and standard pharmaceutical practice as described herein. The compounds of the invention may be administered alone or contemporaneously with nicotine and/or other inhibitors of CYP2A6 or other compounds which affect the metabolism of nicotine. In an embodiment of the invention, the compounds are administered contemporaneously with nicotine and/or inhibitors of CYP2B6. Inhibitors of CYP2B6 are described, for example in PCT Patent Application WO 99/27919. The pharmaceutical compositions and treatment methods may also be used together with other centrally active pharmaceutical compositions that modify smoking behaviour (e.g. bupropion, a.k.a. Wellbutrin™, in its various formulations) to decrease the dose of the centrally active composition or to increase its effectiveness in the treatment of tobacco dependence.

The following non-limiting examples are illustrative of the present invention:

EXAMPLES Example 1 : Synthesis of 3-Methyl-1 -(3-pyridin-3-yl)-3-azabicyclo[3.1.OJhexane hydrobromide

(a) i-Cyano^-hydroxymethyl-i-fpyridin-S-yOcyclopropane. Sodium hydride (3.75 gm., 60% dispersion, 93.8 mmol) was added to 75 ml_ of anhydrous tetrahydrofuran (THF) under nitrogen and cooled to 0° C. 3- Pyridylacetonitirile (5.0 gm., 42.2 mmol., in 50 ml_ of anhydrous THF) was added dropwise with stirring, maintaining reaction temperature below 10° C. Stirring was continued for an additional 4 h at 0° C. Epichlorohydrin (3.97 gm., 42.9 mmol., in 50 ml_ of anhydrous THF) was added dropwise over a 15 min. period to the cooled solution, and then the reaction was left to stir and gradually warm to room temperature in the ice bath overnight. The melted ice in the ice bath was replaced with fresh ice and salt, and the reaction was re- cooled to 0° C. Diethyl ether (Et₂O, 100 ml_) were added, followed by cautious introduction of 50 ml_ of ice/water and 50 ml_ of 15% aqueous potassium carbonate (15% K₂CO₃ (aq)). The organic layer was removed and the aqueous layer was washed with Et₂O (50 ml_) and methylene chloride (CH₂CI₂, 2 x 50 ml_). The combined organics were dried, filtered and concentrated to yield 8.0 gm. of a brown oil.

Crystallization from Et₂O-acetone yielded 1.9 gm. of an off-white solid, mp: 88°- 90° C (26%). EIMS m/z 174 (10), 173 (12), 145 (18), 133 (100).

(b) 1-(Pyridin-3-yl)-3-oxabicycIo[3.1.0] hexan-2-one. 1-Cyano-3- hydroxymethyl-1-(pyridin-3-yl)cyclopropane (1.0 gm., 5.74 mmol.) was dissolved in 5 ml_ of ethyl alcohol (EtOH) and added to 2.5 ml_ of 1.0 N potassium hydroxide (KOH, 2.5 mmol.). The solution was stirred and heated at reflux overnight. The resulting solution was cooled to 0° C and concentrated hydrochloric acid (cone. HCI) was added dropwise until the pH was 1. The resulting mixture was concentrated in vacuo, the residue was partitioned between ethyl acetate (EtOAc) and water, and 15% K₂CO_{3 (aq)} was added until the aqueous layer was basic. The EtOAc was separated and the aqueous layer was washed with 2 x 15 ml_ of EtOAc. The combined EtOAc layers were dried and concentrated in vacuo to yield a brown oil. The oil was redissolved in 5 ml_ of methanol (MeOH) and then extracted with 4 x 2.5 ml_ of petroleum ether. The combined petroleum ether layers were further washed with 2.5 ml_ of MeOH. The combined MeOH layers were chilled in the freezer (^~ 10° C) and any additional petroleum ether that separated out was removed. The combined MeOH layers were then concentrated in vacuo, and kugelrohr distilled (bp: 138° C @ 0.01 mm Hg) to yield 0.40 gm. (40%) of a colorless oil which crystallized in the freezer. EIMS m/z 175 (100), 145 (75), 130 (98), 117 (86), 104 (54).

(c) 2-Hydroxy-1-(pyridin-3-yl)-3-oxabicyclo[3.1.0]hexane. 1 -(PyridJn-3-yl)-

3-oxa-bicyclo[3.1.0] hexan-2-one (0.48 gm., 2.7 mmol.) was dissolved in 20 ml_ of anhydrous toluene and cooled to ~ 78° C under a nitrogen atmosphere. To this solution was added, slowly, 4.25 ml_ of Dibal-H (1.0 M in toluene, 4.25 mmol), and the resulting reaction was stirred for 2 h. at to ^~~ 78° C. MeOH (0.5 ml_) was cautiously added, and the reaction was then allowed to warm gradually to room temperature. The reaction was diluted with 10 mL of Et₂O and 10 mL of brine containing 3 drops of 8.0 N aqueous potassium hydroxide (KOH), shaken, allowed to separate, and the organic layer removed. The aqueous layer was washed with Et₂O and CH₂CI₂, and the combined organic washes were dried and concentrated in vacuo. EIMS m/z 177 (5), 176 (1), 130 (100).

(d) 2-Hydroxymethyl-1-(N-methylamino)methyl-1-(pyridin-3-yl)cyclo- propane. The crude oil (0.7 gm.) from the previous step was taken up in 5 mL of MeOH, and a large excess (1.0 gm, 14.8 mmol) of methylamine hydrochloride was added, followed by addition of triethylamine (3.0 gm, 2 equivalents). The mixture was stirred in a capped flask for 24 h, concentrated in vacuo, and then partitioned between 15% K₂CO_{3 (aq)} and Et₂θ. The Et₂O extracts were dried and concentrated in vacuo, and then redissolved in 5 mL of MeOH, to which 0.5 gm of sodium cyanoborohydride (7.95 mmol) were added, and the reaction was stirred at room temperature with the slow addition of methanolic 2.0 N HCI to maintain a pH around 6. After 2 h the excess sodium cyanoborohydride was decomposed by the cautious addition of excess methanolic 2.0 N HCI, while stirring in an ice-salt bath, and the reaction was then concentrated in vacuo to a watery slurry. Water (approximately 10 mL) and Et₂O (15 mL) were added, and then the two-phase solution was stirred in ice-salt while 8.0 N KOH was added dropwise until pH was > 11. The Et₂O layer was removed, and the aqueous layer was washed with Et₂O (10 mL) and CH₂CI₂ (2 x 10 mL). The combined organics were dried, filtered, and the filtrate concentrated in vacuo to yield 0.47 gm. of an oil.

CH₂Cl₂-CH₃CN

(f) 3-Methyl-1-(pyridin-3-yl)-3-azabicyclo[3.1.0]hexane hydrobromide. The oil from the previous step was dissolved in 100 ml_ of CH₂CI₂, 1 ml_ of triethylamine (7.21 mmol) was added, and the resulting mixture was added to a premixed solution of 1.95 gm of triphenyl phosphine (7.43 mmol) and 10.0 mL of carbon tetrachloride (104 mmol) in 210 ml_ of acetonitrile (stirred for 0.5 h before addition of oil from previous step). The reaction was stirred under nitrogen for 4 days. The reaction was concentrated in vacuo, and the residue was washed with 3 x 30 mL of 1.0 N aqueous HCI. The combined acidic aqueous washes were washed with Et₂O, an additional 40 mL of Et₂O were added, and the two-phase system was stirred and cooled in ice-salt while 8.0 N KOH was added until the pH was > 11. The Et₂O layer was removed, and the basic aqueous layer was washed with 3 x 40 mL of Et₂O. The combined Et₂O layers were dried, concentrated in vacuo, and the residue was chromatographed on a 4 mm Chromatotron plate using CH₂CI₂: MeOH: NH₄OH (90:9:1) as eluent. The product was concentrated, redissolved in 10 mL of 2-propanol (2-PrOH), and 10 mL of 2-PrOH with 5 mL of 30% hydrobromic acid in acetic acid (30% HBr) were added dropwise with stirring. The mixture was concentrated in vacuo, additional 2-PrOH (10-20 mL) were added, and the mixture was reconcentrated in vacuo. The last step was repeated 3 times before a consistent solid was attained. This was partially redissolved in 3 mL of MeOH, with stirring, and then filtered and the precipitate washed with 5 x 2 mL of 2-PrOH. The precipitate was dried under vacuum to yield 0.223 gm of an off-white solid, mp: 221°-223° C (dec.) EIMS m/z 174 (58), 159 (20), 145 (13), 130 (100). Anal. Calcd. for C₁₁Hi₆N₂Br₂: C, 39.31 ; H, 4.80; N, 8.34. Found: C, 39.21 ; H, 4.89; N, 8.22. Example 2: Synthesis of 1-(Pyridin-3-yl)-3-azabicyclo[3.1.0]hexane oxalate.

(a) 1-(N-Benzylamino)methyl-2-hydroxymethyl-1-(pyridin-3-yl)cyclo- propane, (from 2-hydroxy-1-(pyridin-3-yl)-3-oxabicyclo[3.1.0]hexane): The crude oil (1.50 gm, 8.0 mmol) was dissolved in 20 ml_ of MeOH, 1.1 gm of benzylamine (10.3 mmol) were added, and the capped flask was stirred overnight at room temperature. Sodium cyanoborohydride (1.5 gm, 23.8 mmol) was added, with stirring, and 8 ml_ of methanolic 2.0 M HCI were slowly added dropwise to maintain pH around 6. The reaction was stirred for 2 h, and then the unreacted reagent was decomposed with cautious addition of excess methanolic 2.0 M HCI. The resulting mixture was concentrated in vacuo until only water remained, 50 mL of water and 25 ml_ of Et₂θ were added, and the biphasic solution was stirred in an ice-salt bath while 8.0 N KOH was added until the pH was >11. The basic aqueous solution was washed with 2 x 40 mL of Et2θ and 40 mL of CH2CI2, and the combined organics were dried, filtered, and the filtrate was concentrated to a colorless oil, weighing 2.28 gm. EIMS m/z 268 (0.3), 250 (47), 159 (38), 130 (33), 91 (100).

(b) 3-Benzyl-1-(pyridin-3-yl)-3-azabicyclo[3.1.0]hexane. The crude oil from the previous step was dissolved in 350 ml_ of CH₂CI₂, 3.5 ml_ of triethylamine (25.2 mmol) were added, and the resulting solution was added to a premixed solution of 6.76 gm of triphenylphosphine (25.8 mmol), 35 ml_ of carbon tetrachloride (363 mmol) in 730 ml_ of acetonitrile (stirred for 0.5 h beforehand). The combined reaction was stirred at room temperature for 5 days. The reaction was concentrated in vacuo, redissolved in 100 mL of Et₂O and washed with 3 x 100 mL of 1.0 M aqueous HCI. The combined acidic aqueous washes were cooled in ice-salt, made basic with added 8.0 N KOH (to pH> 11) and washed with 3 x 100 mL of Et₂O and 100 mL of chloroform (CHCb). The residue was chromatographed on silica gel, using CH₂CI₂: MeOH: NH₄OH (90:9:1) as eluent, and the product fractions were concentrated in vacuo to yield 0.66 gm of product as an oil. EIMS m/z 250 (38), 159 (33), 132 (20), 130 (31), 91 (100).

(c) 1-(Pyridin-3-yl)-3-azabicyclo[3.1.0]hexane oxalate. The oil from the previous step was dissolved in 30 mL of MeOH, 2.6 mL of 2.0N methanolic HCI (2.6 mmol) were added, 0.41 gm of palladium on carbon (5%) were added, and the mixture was hydrogenated under 25 psig of hydrogen atmoshphere overnight. The catalyst was removed by filtration, and the filtrate concentrated in vacuo. The residue was chromatographed on silica gel, using CH₂CI₂: MeOH: NH₄OH (90:9:1) as eluent, and the product fractions concentrated in vacuo to yield 0.18 gm as an oil. This was dissolved in 5 ml_ of Ethyl alcohol (EtOH) and added to 0.28 gm of oxalic acid (2.5 equivalents), predissolved in 5 ml_ of EtOH, and the combined solution was concentrated to approximately one half original volume on a hot plate. On cooling, a precipitate formed, which was collected and dried under vacuum, to yield 121 mg of product as the oxalate salt, mp: 152° - 154° C. EIMS m/z 160 (45), 145 (15), 130 (100). Anal. Calcd for Ci₀H₁₂N₂O₄₅H₄₅O₉: C, 48.69; H, 4.58; N, 7.97. Found: C, 48.44; H, 4.69; N, 7.90. Example 3: The compounds of the invention were tested for their ability to inhibit CYP2A6 in vitro. The compound of Example 1 showed an inhibition constant, Ki, of around 0.5 μM in expressed human CYP2A6. This assay was performed, for example, as described in Zhang, et a/. Drug. Metab. Dispos. 29(6), 897-902, 2001 and Zhang et al. Drug Metab. Dispos. 30(3), 314-318, 2002. While the present invention has been described with reference to what are presently considered to be the preferred examples, it is to be understood that the invention is not limited to the disclosed examples. To the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. All publications, patents and patent applications are herein incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety. Where a term in the present application is found to be defined differently in a document incorporated herein by reference, the definition provided herein is to serve as the definition for the term.

Claims

WE CLAIM:

1. A compound selected from a compound of Formula I, and salts, solvates and prodrugs thereof:

wherein

R¹, R², R³ and R⁴ are independently selected from the group consisting of H,

Ci_-4alkyl, C_1-4alkoxy, OH, halo, CF₃. OCF₃, CN, NH₂, NHC_1-4alkyl, N(Ci- ₄alkyl)(Ci_-4alkyl), NO₂, C_2-4alkenyl, C_3-6cycloalkyl and aryl;

R⁵ is selected from the group consisting of H₁ C_halky!, C^alkenyl, C_2- ₆alkynyl, aryl-d-βalkylene, heteroaryl-Ci_-6alkylene, C_3-6-cycloalkyl, C₃. ₆cycloalkyl-Ci-₆-alkylene, wherein aryl and heteroaryl may be unsubstituted or substituted with 1-5 substituents independently selected from the group consisting of Ci_-4alkyl, Ci_-4alkoxy, halo, OH, CF₃. OCF₃, CN, NH₂, NHC-i. ₄alkyl, N(Ci_-4alkyl)(Ci_-4alkyl) and NO₂ and heteroaryl is a mono- or benzofused bicyclic aromatic ring containing from 5-10 carbon atoms in which 1-3 of which is replaced with a heteroatom selected from O, S and N; R⁶ is selected from the group consisting of H and Ci-₄alkyl; and n is O or l

2. The compound according to claim 1 , wherein one of R¹, R², R³ and R⁴ is selected from the group consisting of Ci_-4alkyl, Ci_-4alkoxy, OH, halo, CF₃. OCF₃, CN, NH₂, NHC_1-4alkyl, N(Ci_-4alkyl)(Ci-₄alkyl), NO_2, C_2-4alkenyl, C₃. βcycloalkyl and aryl, and the others are all H.

3. The compound according to claim 1 , wherein R¹, R², R³ and R⁴ are independently selected from the group consisting of H, CH₃, CH₃O, OH, halo, CF₃. OCF₃, CN, NH₂, NHCH₃, N(CH₃)₂ and NO₂.

4. The compound according to claim 1 , R¹, R², R³ and R⁴ are all H.

5. The compound according to any one of claims 1-4, wherein, R⁵ is selected from the group consisting of H, CH₃, ethyl, CH₂C^CH, Ph-CH₂, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclopropyl-CH₂, cyclobuty- CH₂, cyclopentyl-CH_2> cyclohexyl-CH₂, wherein Ph may be unsubstituted or substituted with 1-3 substituents independently selected from the group consisting of CH₃, CH₃O, OH, halo, CF₃. OCF₃, CN, NH₂, NHCH₃, N(CH₃)₂ and NO₂.

6. The compound according to claim 5, wherein R⁵ is selected from the group consisting of H, CH₃ and PhCH₂.

7. The compound according to claim 6, wherein R⁵ is selected from the group consisting of H and CH₃.

8. The compound according to any one of claims 1-7, wherein R⁶ is selected from the group consisting of H and CH₃.

9. The compound according to claim 8, wherein R⁶ is H.

10. The compound according to anyone of claims 1-9, wherein n is 0.

11. The compound according to claim 1 selected from: 3-Methyl-1-(pyridin-3-yl)-3-azabicyclo[3.1.0]hexane; 3-Benzyl-1-(pyridin-3-yl)-3-aza-bicyclo[3.1.0]hexane; and 1 -(Pyridin-3-yl)-3-azabicyclo[3.1.0]hexane.

12. A pharmaceutical composition comprising a compound according to any one of claims 1-11 and a pharmaceutically acceptable carrier and/or diluent.

13. A method of preventing or treating conditions which benefit from an inhibition of CYP2A6 comprising administering an effective amount of a compound according to any one of claims 1-11 to a subject in need thereof.

14. The method according to claim 13, wherein the condition which benefits from an inhibition of CYP2A6 is selected from one or more of smoking, and in vivo formation of carcinogens.

15. A method of preventing, treating or regulating smoking in subject in need thereof comprising administering an effective amount of a compound according to any one of claims 1-11 to a subject in need thereof.

16. A method of enhancing oral nicotine replacement therapy comprising administering an effective amount of a compound according to any one of claims 1-11 to a subject in need thereof.

17. The method according to claim 16, wherein the compound is administered contemporaneously with nicotine.

18. A method of treating a condition requiring inhibition of nicotine metabolism to cotinine comprising administering an effective amount of a compound according to any one of claims 1-11 to a subject in need thereof.

19. The method according to claim 18, wherein the condition requiring inhibition of nicotine metabolism to cotinine is selected from one or more of opioid related disorders; proliferative diseases; cognitive, neurological or mental disorders; and other drug dependencies in the individuals.

20. The method according to claim 18 wherein the condition requiring inhibition of nicotine metabolism to cotinine is selected from one or more of malignant disease, psychosis, schizophrenia, Parkinson's disease, anxiety, depression, alcoholism, opiate dependence, memory deficits, ulcerative colitis and cholinergic deficits,

21. A method of regulating the formation of a carcinogen in subject in need thereof comprising administering an effective amount a compound according to any one of claims 1-11.

22. A method of preventing or treating cancer comprising administering an effective amount of a compound according to any one of claims 1-11 to a subject in need thereof.

23. The method according to claim 22, wherein the cancer is colorectal cancer.

24. A method of reducing cardiovascular or pulmonary disease risk comprising administering an effective amount of a compound according to any one of claims 1-11 to a subject in need thereof.

25. The method according to claim 24, wherein the compound is administered contemporaneously with nicotine.

26. A use of a compound according to any one of claims 1-11 as a medicament.

27. A use of a compound according to any one of claims 1-11 to prepare a medicament to prevent or treat conditions which benefit from an inhibition of CYP2A6.

28. The use according to claim 27, wherein the condition which benefits from an inhibition of CYP2A6 is selected from one or more of smoking, and in vivo formation of carcinogens.

29. A use of a compound according to any one of claims 1-11 to prepare a medicament to prevent, treat or regulate smoking,

30. A use of a compound according to any one of claims 1-11 to prepare a medicament to enhance oral nicotine replacement therapy.

31. The use according to claim 30, wherein the compound is used contemporaneously with nicotine.

32. A use of a compound according to any one of claims 1-11 to prepare a medicament to treat a condition requiring inhibition of nicotine metabolism to cotinine.

33. The use according to claim 32, wherein the condition requiring inhibition of nicotine metabolism to cotinine is selected from one or more of opioid related disorders; proliferative diseases; cognitive, neurological or mental disorders; and other drug dependencies.

34. The use according to claim 32 wherein the condition requiring inhibition of nicotine metabolism to cotinine is selected from one or more of malignant disease, psychosis, schizophrenia, Parkinson's disease, anxiety, depression, alcoholism, opiate dependence, memory deficits, ulcerative colitis and cholinergic deficits,

35. A use of a compound according to any one of claims 1-11 to prepare a medicament to regulate the formation of a carcinogen.

36. A use of a compound according to any one of claims 1-11 to prepare a _\ medicament to prevent or treat cancer.

I, The use according to claim 36, wherein the cancer is colorectal cancer.

38. A use of a compound according to any one of claims 1-11 to prepare a medicament to reduce cardiovascular or pulmonary disease risk.

39. The use according to claim 38, wherein the compound is administered contemporaneously with nicotine.

40. A method of preparing a compound of Formula I comprising reacting a compound of Formula II:

wherein R¹-R⁶ and n are as defined in claim 1 , under standard Mitsonubu reaction conditions,

41. The method according to claim 40, wherein the standard Mitsonubu conditions comprise reacting a compound of Formula Il the presence of triphenylphosphine and carbon tetrachloride in an inert solvent at ambient or elevated temperatures.

42. A method for preparing a compound of Formula Il comprising reacting a compound of Formula III:

Ml wherein R¹-R⁴, R⁶ and n are as defined in claim 1, with a compound of Formula IV:

R⁵-NH₂ IV

wherein R⁵ is as defined in claim 1 , in the presence of a base, followed by reduction.