Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/12—Ketones
  • A61K31/122—Ketones having the oxygen directly attached to a ring, e.g. quinones, vitamin K1, anthralin
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/13—Amines
  • A61K31/131—Amines acyclic
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/21—Esters, e.g. nitroglycerine, selenocyanates
  • A61K31/27—Esters, e.g. nitroglycerine, selenocyanates of carbamic or thiocarbamic acids, meprobamate, carbachol, neostigmine
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/33—Heterocyclic compounds
  • A61K31/335—Heterocyclic compounds having oxygen as the only ring hetero atom, e.g. fungichromin
  • A61K31/35—Heterocyclic compounds having oxygen as the only ring hetero atom, e.g. fungichromin having six-membered rings with one oxygen as the only ring hetero atom
  • A61K31/351—Heterocyclic compounds having oxygen as the only ring hetero atom, e.g. fungichromin having six-membered rings with one oxygen as the only ring hetero atom not condensed with another ring
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/33—Heterocyclic compounds
  • A61K31/335—Heterocyclic compounds having oxygen as the only ring hetero atom, e.g. fungichromin
  • A61K31/365—Lactones
  • A61K31/366—Lactones having six-membered rings, e.g. delta-lactones
  • A61K31/37—Coumarins, e.g. psoralen
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/33—Heterocyclic compounds
  • A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
  • A61K31/41—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having five-membered rings with two or more ring hetero atoms, at least one of which being nitrogen, e.g. tetrazole
  • A61K31/4164—1,3-Diazoles
  • A61K31/4178—1,3-Diazoles not condensed 1,3-diazoles and containing further heterocyclic rings, e.g. pilocarpine, nitrofurantoin
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/33—Heterocyclic compounds
  • A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
  • A61K31/435—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with one nitrogen as the only ring hetero atom
  • A61K31/44—Non condensed pyridines; Hydrogenated derivatives thereof
  • A61K31/4427—Non condensed pyridines; Hydrogenated derivatives thereof containing further heterocyclic ring systems
  • A61K31/4439—Non condensed pyridines; Hydrogenated derivatives thereof containing further heterocyclic ring systems containing a five-membered ring with nitrogen as a ring hetero atom, e.g. omeprazole
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/70—Carbohydrates; Sugars; Derivatives thereof
  • A61K31/7028—Compounds having saccharide radicals attached to non-saccharide compounds by glycosidic linkages
  • A61K31/7032—Compounds having saccharide radicals attached to non-saccharide compounds by glycosidic linkages attached to a polyol, i.e. compounds having two or more free or esterified hydroxy groups, including the hydroxy group involved in the glycosidic linkage, e.g. monoglucosyldiacylglycerides, lactobionic acid, gangliosides
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P25/00—Drugs for disorders of the nervous system
  • A61P25/30—Drugs for disorders of the nervous system for treating abuse or dependence
  • A61P25/34—Tobacco-abuse
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P35/00—Antineoplastic agents
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P43/00—Drugs for specific purposes, not provided for in groups A61P1/00-A61P41/00

Definitions

• the invention relates to methods and compositions for regulating nicotine metabolism in an individual; methods and compositions for enhancing nicotine replacement therapies; methods and compositions for diagnosing tobacco risk dependence and risk for cancers and methods for treating or preventing cancer.
• Nicotine is one of the most widely used psychoactive drugs in the world.
• the World Health Organization reports that there are currently in excess of 1 billion smokers worldwide, or roughly one-third of the global population aged 15 years and older. It is well established that smoking is associated with a higher incidence of many diseases, including various types of cancers, respiratory diseases, cardiovascular diseases, gastrointestinal disorders, as well as many other medical complications (Lee et al., Arch. Intern. Med., "Cigarette smoking, nicotine addiction, and its pharmacologic treatment," 153(1): 34-48 (1993)).
• Nicotine is the primary compound present in tobacco that is responsible for establishing and maintaining tobacco dependence (Henningfield et al., J. Pharmacol. Exp. Ther., "Abuse liability and pharmacodynamic characteristics of intravenous and inhaled nicotine,” 234(1): 1-12 (1985)). Specifically, it has been established in the art that dependent smokers adjust their smoking behaviour to maintain central nicotine levels (Mc orrow MJ, et al., "Nicotine's role in smoking: an analysis of nicotine regulation," Psychological Bulletin, 93(2):302-27 (1983); Russell MSH, "Nicotine intake and its regulation by smokers.
• CYP cytochrome P450
• Tobacco products are vehicles for the delivery of nicotine to the bloodstream which quickly carries nicotine to the bram and other organs Nicotme produces many physiological and behavioural effects, including alteration of bram chemistry and function, which leads to an mdividual's dependence on nicotme Dependent smokers adjust their smoking behaviour to regulate nicotme in the brain and body.
• Evidence m cludes increased smoking if nicotme content in cigarettes is decreased (Benowitz 1988), mcreased smoking if nicotme excretion is increased by reiterate acidification (Benowitz 1983), and decreased smokmg with concurrent I V or patch nicotme (Benowitz, et al 1994, Benowitz NL, et al 1990)
• 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 replacement therapies are used to deliver nicotine to individuals in an attempt to assist an individual in abstaining from tobacco products. Recently, in a United Nations Conference on Trade and Development, entitled “Roundtable on Social and Economic Aspects of Reduction of Tobacco Smoking by Use of Alternative Nicotine Delivery Systems", September 22-24, 1997, in an attempt to reduce tobacco-related morbidity and mortality, it was recommended that nicotine replacement therapies be made more easily available than tobacco.
• Smoking tobacco products amount to a rapid delivery mechanism of nicotine to the bloodstream since almost all of the nicotine absorbed from tobacco smoke reaches systemic circulation without the need to initially pass through liver. For this reason, conventional nicotine replacement therapies have been based on the use of a delivery system (e.g., transdermal, etc.) which will systemically deliver nicotine.
• a delivery system e.g., transdermal, etc.
• transdermal NRT's are relatively inconvenient to use and administer, and are not liked by many patients.
• transdermal e.g., transdermal, chewing gum, etc.
• NRT's are associated with occasional skin irritation and chewing gum (and other buccal delivery systems) NRT's are perceived as having a bad taste.
• transdermal and chewing gum NRT's are plagued by the delivery of inconsistent nicotine levels to the patient.
• alternative delivery NRT systems such as inhalers and nasal sprays have failed to achieve patient acceptability.
• an oral nicotine replacement therapy is not currently commercially available. While not wishing to be bound by any particular theory or mode of action, the reason for this is believed to be as follows. Oral nicotine must first pass through the liver before entering the systemic circulation. As a result, extensive metabolism of nicotine occurs. In particular, oral nicotine is about 60-85 % metabolized from nicotine to continue by the liver so only 15-40% of oral nicotine reaches the systemic circulation (Benowitz, et al., "Stable isotope studies of nicotine kinetics and bioavailability," Clin. Pharmacol. Ther. , 49(3):270-7 (1991); Svensson, "Clinical pharmacokinetics of nicotine," Clin.
• CYP2A6 has been shown to be the major nicotine metabolizing enzyme in human livers.
• Coumarin a specific CYP2A6 substrate, was found to specifically and selectively inhibit nicotine metabolism to cotinine by 84% ⁇ 11% in test livers, and addition of orphenadrine (a CYP2B6 inhibitor) enhanced the inhibition.
• Methoxsalen and tranylcypromine have also been found to be potent inhibitors of CYP2A6 and thus of nicotine to cotinine metabolism.
• the present invention relates to the diagnosis, prophylaxis and treatment of conditions requiring a reduction in the activity of a human cytochrome P450 enzyme CYP2A (referred to as "CYP2A" for brevity).
• CYP2A as used herein means all isoforms of CYP2A including but not limited to CYP2A(CYP1), CYP2A6, CYP2A7, CYP2A12, CYP2A13 and CYP2A16.
• the enzyme is CYP2A6.
• CYP2A6 human cytochrome P450 enzyme
• this invention provides a diagnostic method for tobacco dependence risk and for cancers related to CYP2A6 substrates in an individual by analysing a DNA-contammg bodily sample from the mdividual for the presence of a mutant allele of human cytochrome P450 enzyme CYP2A6
• this method comprises genotype assaying the bodily sample, which may be genomic DNA isolated from peripheral leukocytes m the bodily sample Alternatively the method comprises phenotype assaymg the bodily sample, which may be a fluid, such as a blood sample or blood plasma
• This invention also provides diagnostic kits for use in the analysis
• the mvention also provides a diagnostic method for tobacco dependence risk and for cancers related to human cytochrome P450 enzyme CYP2A6 substrates m an mdividual by admmistermg a dose of a CYP2A6 substrate to the individual and determining in a bodily sample from the mdividual the level of said CYP2A6 substrate
• the invention specifically demonstrates that individuals who are carry CYP2A6 deficient alleles are less likely to become smokers and will smoke less cigarettes if tobacco-dependent
• CYP2A6 is known to activate procarcmogens, such as those found m tobacco-smoke
• the diagnostic aspect of the invention will be useful for identifymg the contribution of this polymorphic locus to the genetic risk of an mdividual for cancer
• the present diagnostic method and kit is predictive of an mdividual who (l) has an increased risk of becoming a smoker, (n) will smoke more if he/she becomes dependent, and /or (in) may be at relatively higher risk for cancer due to both decreased smoke exposure and decreased enzyme mediated activation of procarcmogens
• he/she may be treated prophylactively with effective quantities of CYP2A6 inhibitors described m detail in copendmg International patent application Ser No PCT/CA97/00506 (filed July 17, 1997) and United States provisional patent application Ser No 60/067,021 (filed on December 1, 1997), which lead to other aspects of the present mvention
• the mvention also provides a smokmg prevention composition or a smokmg regulation composition comp ⁇ smg a CYP2A6 inhibitor, together with a carrier therefor, along with methods for preventmg or regulating smokmg by admmistermg a CYP2A6 inhibitor to an mdividual Likewise, this mvention provides methods for cancer prevention or treatment or the regulation of the formation of carcmogens by administering a CYP2A6 inhibitor to an mdividual Compositions containing a CYP2A6 inhibitor are also provided for use in these methods
• This mvention provides methods for enhancing oral nicotme therapy, such as oral administration of nicotme bitartrate, by inhibiting nicotme metabolism through selective inhibition of CYP2A6, optionally with further selective inhibition of CYP2B6
• Preferred inhibitors of CYP2A6 include coumarin, methoxsalen and tranylcypromine This method may be used to treat a condition requiring nicotine administration, preferably by administering a CYP2A6 inhibitor taken together with an oral formulation of nicotine, optionally also administering a CYP2B6 inhibitor.
• Preferred inhibitors of CYP2A6 include coumarin, methoxsalen and tranylcypromine.
• the present inventors have surprisingly found that several natural products, are inhibitors of the enzyme CYP2A. Accordingly, the present invention provides a method of inhibiting CYP2A comprising administering an effective amount of a natural product or an extract of a natural product to an individual in need thereof, this method being useful in treating conditions requiring regulation of CYP2A activity.
• the natural product is Hypericum or a Hypericum extract.
• the natural product is Cichorium intybus or Bougainvllra spectabillis or an extract thereof.
• This invention also provides a composition
• a composition comprising an oral formulation of nicotine and a CYP2A6 inhibitor, optionally also containing a CYP2B6 inhibitor.
• Preferred inhibitors of CYP2A6 include coumarin, methoxsalen and tranylcypromine.
• Figure 1 illustrates the results of a study showing CYP2A6 activity in heterozygous CYP2A6 individuals and wild-type CYP2A6 individuals as a function of time after administration of a CYP2A6 substrate;
• Figure 2A-2D show chemical structures of some representative CYP2A6 inhibitors
• Figure 3 is a graph illustrating a correlation between fasted morning and non-fasted afternoon coumarin (C) testing sessions;
• Figure 4 is a graph showing a time course of total 7-hydroxycoumarin concentration detected in the plasma of subjects given 100 mg of coumarin;
• Figures 5 and 6 illustrate results of a study described in Example 1; Figure 7 illustrates mean plasma nicotine concentrations in the study reported in Example 8,
• Figure 8 illustrates current desire to smoke m the study reported in Example 8
• Figure 9 illustrates mean breath carbon monoxide in the study reported m
• Figure 10 illustrates the ratio of increased plasma nicotine to increased breath carbon monoxide m Example 9,
• Figure 11 illustrates mean number of cigarettes consumed during the smokmg period m
• Figure 12 illustrates the mean number of cigarette puffs taken m each 10- mm period during the smokmg period m
• Figure 12 illustrates the mean number of cigarette puffs taken m each 10- mm period during the smokmg period m
• Figure 13 illustrates the mean latency period between the first two cigarettes in Example 9
• Figure 14 illustrates the mean grams of tobacco burned m
• Figure 15 illustrates the effect of CYP2A6 inhibitors methoxsalen and tranylcypromine on increasing the bioavailability of nicotine supplied orally, with concommitant reduction m the desire to smoke
• Figure 16 is a graph illustrating the effect of Hypericum extracts on nicotme metabolism by expressed human cDNA CYP2A6
• Figure 17 is a graph showing the mean plasma concentration of nicotme versus time, m the presence of St John's Wort or a placebo
• Figure 18 is a bar graph showing the mean plasma concentration of nicotme m the presence of St John's Wort or a placebo
• Figure 19 are graphs illustrating effect of esculehn on nicotme metabolism by human liver micorsomes
• Figure 20 shows the chemical structure of various compounds found m natural products
• the present invention relates to the diagnosis, prophylaxis and treatment of conditions requirmg a reduction m the activity of a CYP2A enzyme
• CYP2A as used herein means all isoforms of CYP2A including but not limited to CYP2A(CYP1), CYP2A6, CYP2A7, CYP2A12, CYP2A13 and CYP2A16
• the enzyme is CYP2A6 As described in copending International patent application S N
• CYP2A6 is a major nicotine metabolizing enzyme in human livers and that by inhibiting CYP2A6 the metabolism of nicotine to continine in the liver is inhibited.
• DIAGNOSTIC METHODS are a major nicotine metabolizing enzyme in human livers and that by inhibiting CYP2A6 the metabolism of nicotine to continine in the liver is inhibited.
• the present inventors have shown that individuals who carry CYP2A6 mutant alleles (i) have a decreased risk of becoming a smoker, (ii) will smoke less if he/she becomes dependent and /or (iii) may be at relatively lower risk for cancer due to both decreased smoke exposure and decreased CYP2A6-mediated activation of tobacco smoke and other procarcinogenic substrates.
• the present invention provides a method for determining the risk of an individual becoming a smoker comprising determining the genotype or phenotype of a CYP2A allele in the individual wherein the presence of a mutant allele is predictive of a decreased risk of smoking.
• the CYP2A enzyme is CYP2A6.
• Tobacco smoke contains a number of tobacco-specific procarcinogen nitrosamines, for example the N-nitrosodiethylamine and 4-(methylnitrosamino)-l-(3- pyridyl)-l-butanone (NNK). These compounds are termed pro- or pre-carcinogens, as they are activated by the body.
• NNK 4-(methylnitrosamino)-l-(3- pyridyl)-l-butanone
• these tobacco smoke procarcinogens can be activated by CYP2A6 (Crespi, et al., "Human cytochrome P450IIA3: cDNA sequence, role of the enzyme in the metabolic activation of promutagens, comparison to nitrosamine activation by human cytochrome P450IIE1,” Car cino genesis 11(8):1293-1300 (1990); Yamazaki, et al., "Cytochrome P450 2E1 and 2A6 enzymes as major catalysts for metabolic activation of N-nitrosodialkylamines and tobacco-related nitrosamines in human liver microsomes," Car cino genesis 13(10):1789-94 (1992)).
• individuals who have CYP2A6 null alleles may also be less efficient at bioactivating tobacco smoke procarcinogens to carcinogens.
• This is of particular interest as ethnic variation in frequencies for CYP2A6 variant alleles exist (Nowak et al., 1998; Fernandez-Salguero P, et al., "A genetic polymorphism in coumarin 7-hydroxylation: sequence of the human CYP2A genes and identification of variant CYP2A6 alleles," Am. ].
• individuals carrying CYP2A6 defective alleles may have a decreased risk of developing tobacco-related cancers and other medical complications for three reasons. 1) They have a decreased risk of becoming a smoker. 2) If they do become tobacco-dependent, they smoke less than those without impaired nicotine metabolism resulting in lower exposures to tobacco-related procarcinogens (Law, et al., "The dose-response relationship between cigarette consumption, biochemical markers and risk of lung cancer," Br. ]. Cancer 75(11):1690-1693 (1997)). 3) They may activate fewer tobacco-related procarcincogens. These three factors suggest a significant reduction in tobacco-related cancers for carriers of a CYP2A6 defective allele(s).
• the present invention provides a method for determining the risk of an individual for developing cancer comprising determining the genotype or phenotype of a CYP2A allele in the individual wherein the presence of a mutant allele is predictive of a decreased risk of developing cancer.
• the CYP2A enzyme is CYP2A6.
• the diagnostic aspect of this invention includes both phenotypic and genotypic methods for determining whether an individual has wild-type or mutant alleles for CYP2A6.
• the phenotypic assay may be performed by a metabolic study which is in effect an in vivo enzyme assay for CYP2A6 activity. This assay may be performed by administering a dose of a CYP2A6 substrate, for example nicotine or coumarin, and monitoring the physiological levels of the substrate and /or the product of enzymatic metabolism of the substrate in the individual at one or more time points during and subsequent to administration of the test dose.
• the levels will be measured in a biological fluid, such as blood, plasma, or urine, using well known assays for the particular components, examples of which are disclosed herein.
• Example 3 An example of an in vivo phenotype and enzyme activity assay is provided in Example 3 below. This phenotypic assay can be used to classify individuals based on their normally expressed level of CYP2A6, which will correspond generally with the genotype of the individual as homozygous for fully active CYP2A6, heterozygous or homozygous for a lower activity allele, in decreasing order of nicotine metabolic rate.
• the diagnostic aspect is also based on analysing a DNA-containing bodily sample from the individual for the presence of a mutant allele of human cytochrome P450 enzyme CYP2A6.
• mutant allele is meant to encompass any allele having decreased or absent CYP2A6 activity, i.e., including null alleles.
• the presence of the mutant allele of CYP2A6 can be determined by conventional genotyping or phenotyping assays.
• CYP2A6 alleles have been identified including, but not limited to, the wild-type allele (referred to throughout this specification as “CYP2A6*1”), and two defective or null mutant alleles ("CYP2A6*2" and "CYP2A6*3", respectively (see, Fernandez-Salguero, et al. 1995), the contents of which are hereby incorporated by reference).
• the CYP2A6*2 allele differs from the wild-type allele by a single point mutation which leads to a leucine to histidine amino acid change at codon 1609. In vitro and in vivo studies have demonstrated that this allele is a null allele.
• CYP2A6*3 allele Mutations in the CYP2A6*3 allele occur in exons 3, 6, and 8. Very recently an additional CYP2A6 allele was identified which consists of an entire CYP2A6 gene deletion (Nunoya K et al., 1998 "A new deleted allele in the human cytochrome P450 2A6 (CYP2A6) gene found in individuals showing poor metabolic capacity to coumarin and (+)-cis-3,5-dimethyl-2-(3- pyridyl)thiazolidin-4-one hydrocholoride (SM-12502). Pharmacogenetics 1998, 8: 239-249.
• mutant alleles which encode CYP2A6 enzymes with reduced activity may be found in individuals identified by the phenotypic and /or genotypic methods of this invention, and these individuals will also be expected to have lower risk of developing cancer and decreased risk of smoking.
• the individual contemplated for the diagnostic methods of this invention may be found in individuals identified by the phenotypic and /or genotypic methods of this invention, and these individuals will also be expected to have lower risk of developing cancer and decreased risk of smoking.
• the prophylactic and therapeutic methods described below may be any type of mammal, but is preferably a primate, and more preferably a human.
• the bodily sample is a fluid such as blood or blood plasma.
• the bodily sample can be tissue. See, for example, Sambrook et al., Molecular Cloning: A Laboratory Manual, 2nd Edition, Cold Spring Harbor Laboratory Press (1989), the contents of which are hereby incorporated by reference, for discussion of general assay techniques useful with the diagnostic methods described herein.
• CYP2A6 activity in a group (Group I) of individuals having heterozygous CYP2A6 activity (i.e., each individual in this group had a single mutant allele of CYP2A6 and a single active allele of CYP2A6) and a group of individuals (Group II) having wild type CYP2A6 activity (i.e. each individual in this group had two active alleles of CYP2A6).
• Blood plasma samples from each of the individuals in both groups were take post-administration of coumarin (100 mg) at 35 minutes, 45 minutes and 75 minutes.
• Coumarin 7-hydroxylation was used to assess the compliment activity of CYP2A6.
• the results of the phenotyping assay clearly show that the Group I individuals have a significantly lower CYP2A6 activity (less than half at 35 and 45 minutes) than the Group II individuals.
• 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 using techniques described herein. For example, coumarin 7-hydroxylation has been used to measure CYP2A6 activity (see, Cholerton, et al. (1992) and Rautio, et al. (1992)).
• CYP2A6 is the major nicotine metabolizing enzyme in human livers suggests that the enzyme can be assayed in an individual to determine the individual's risk of developing tobacco dependence. Determination of CYP2A6 levels may also be used to select and monitor in an individual appropriate conventional nicotine replacement therapies such as the nicotine patch and nicotine gum. It is unlikely that conventional nicotine replacement therapies (e.g. nicotine gum, nicotine patch, spray, pulmonary inhalation or other forms) will have a high success outcome if an individual has high levels of CYP2A6, although such individuals may be good candidates for enhanced NRT according to the methods described herein.
• conventional nicotine replacement therapies e.g. nicotine gum, nicotine patch, spray, pulmonary inhalation or other forms
• the present invention relates to methods for the prophylaxis and treatment of conditions requiring a reduction in the activity of a CYP2A enzyme.
• the prophylactic /therapeutic aspect of the present invention relates to treatment and prevention of smoking, in vivo carcinogen formation and cancer in an individual. Each of this involves administration to an individual of a CYP2A inhibitor, preferably a CYP2A6 inhibitor.
• the present invention provides a method of preventing, treating or regulating smoking in an individual comprising administering an effective amount of one or more substances selected from the group consisting of (i) substances which inhibit CYP2A activity; (ii) substances which inhibit transcription, translation of the gene encoding CYP2A, or both; (iii) substances which delete all or a portion of the gene encoding CYP2A.
• the CYP2A is CYP2A6.
• smoking prevention and “preventing smoking”, as used throughout this specification, 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.
• 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.
• 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.
• the measure of tobacco smoke exposure can be measured by analyzing breath carbon monoxide.
• the present invention provides a method of regulating the formulation of a carcinogen in an individual comprising administering an effective amount of one or more substances selected from the group consisting of (i) substances which inhibit CYP2A activity; (ii) substances which inhibit transcription, translation of the gene encoding CYP2A, or both; (iii) substances which delete all or a portion of the gene encoding CYP2A.
• the CYP2A is CYP2A6.
• 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.
• 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).
• the present invention provides a method of preventing cancer in an individual comprising administering an effective amount of one or more substances selected from the group consisting of (i) substances which inhibit CYP2A activity; (ii) substances which inhibit transcription, translation of the gene encoding CYP2A, or both; (iii) substances which delete all or a portion of the gene encoding CYP2A.
• the CYP2A is CYP2A6.
• cancer prevention and “preventing 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.
• inhibitor and “inhibition”, in the context of the present invention, are intended to have a broad meaning and encompass substances which directly or indirectly (e.g., via reactive intermediates, metabolites and the like) act on CYP2A to inhibit or otherwise regulate the ability of CYP2A to catalyze metabolism of a substrate.
• Other substances which act indirectly on CYP2A include those substances which inhibit transcription and/or translation of the gene encoding CYP2A.
• CYP2A6 inhibition and "CYP2A6 inhibitor” are intended to have a broad meaning and encompass any substance which: (i) inhibits CYP2A6 activity; (ii) inhibits transcription and /or translation of the gene encoding CYP2A6; or (iii) deletes or removes the gene encoding CYP2A6.
• Particularly preferred substances are those which alter the kinetics for metabolism of nicotine to cotinine, alter smoking behavior, alter the likelihood of addiction to smoking in a population of non-smokers, or alter the kinetics of formation for carcinogens whose formation from procarcinogens is catalyzed by CYP2A, and more preferably exhibit the biological altering effect without producing other biological effects at significant levels.
• a substance will "selectively" inhibit CYP2A activity when the substance can alter the kinetics for metabolism of nicotine to cotinine, alter smoking behavior, alter the likelihood of addiction to smoking in a population of non-smokers, or alter the kinetics of formation for carcinogens whose formation from procarcinogens is catalyzed by CYP2A generally at a dosage level which is lower than the dosage of the substance which is effective for production of another biological effect.
• methoxsalen acted to increase plasma levels of nicotine and to reduce desire to smoke m dependent smokers at levels that were one-fourth the therapeutic dose for treatment of psoriasis by methoxsalen
• CYP2A6 CYP2A6 Inhibitors means an amount effective and at doses and for periods of time necessary to achieve the desired results, this may mean limiting doses where the desired result is selective inhibition and selectivity is achieved through differential inhibition of CYP2A
• the substances inhibit CYP2A6 CYP2A6 Inhibitors
• the present invention relates to a method of regulating nicotine metabolism to cotinine in an individual compnsmg selectively inhibiting CYP2A6 Inhibition of CYP2A6 may be achieved using one or more of the following (l) substances which inhibit CYP2A6 activity, or (n) substances which inhibit transcription and /or translation of the gene encodmg CYP2A6
• Substances which inhibit CYP2A6 activity include substances which specifically bmd to CYP2A6 and thereby inhibit its activity Examples of such substances mclude antibodies which are specific for CYP2A6 mcludmg for example, the monoclonal antibody described by Pearce R, et al ("Species differences and interindividual variation in liver microsomal cytochrome P450 2A enzymes effects on coumarin, dicumarol, and testosterene oxidation," Arch Bwchem Biophys , 298(1) 211-225 (1992)), and commercially available antibodies such as MAB2A6 and monoclonal CYP2A6, sold by Gentest Corporation, Woburn, Mass , U S A , XenoTech 2A6 sold by XenoTech LLC, Kansas City, KS, U S A and polyclonal CYP2A6 sold by Research Diagnostics, Inc, Flanders, N J , U S A
• Preferred inhibitors of CYP2A6 include methoxsalen, psoralen, tranylcypromine, pilocarpine, couma ⁇ n, chromone, esculetin, phenelzme, paroxetme, selegiline and pargylme
• Substances which inhibit CYP2A6 activity also mclude substances havmg a lactone stiructure with a carbonyl oxygen
• Non-limiting examples of such substances mclude coumarm (The Merck Index, Eleventh Edition Budava ⁇ , S , ed Merck & Co Inc , 1989, No 2563), furanocouma ⁇ n, methoxsalen (The Merck Index, No 5911), lmperato ⁇ n (The Merck Index, No 4839), psoralen (The Merck Index, No 7944), ⁇ -naphthoflavone, isopimpmellm, ⁇ -naphthoflavone, bergapten (The Merck Index, No 1173), sphondin, coumatetralyl (racumin), and (+)-c ⁇ s-3,5-d ⁇ methyl-2-(3-pyr ⁇ dyl)-th ⁇ azohd ⁇ m-4-one (SM-12502) (Nuno
• 9491 including cis, trans, (+) and (-) isomers, trioxsalen, alaproclate, phenelzine, pargyline, paroxitine, selegiline, amphetamine, bupropion, buspirone, citalopram, desmethylcitalopram, doxeprine, fluoxetin, naltrexone, norfluoxetine, nortriptyline, sertraline, trazodone, viaqualine, zimelidine, chromone, bergapten and narigenin. All of the substances thati nhibit CYP2A6 activity include racemic mixtures of the compounds as well as the cis, trans, (+) and (-) isomers.
• derivatives of tranylcypromine, coumarin and methoxsalen include pharmaceutically acceptable salts, esters and complexes of tranylcypromine, coumarin and methoxsalen including potassium and sodium salts, and amino acid, carbohydrate and fatty acid complexes.
• suitable analogs of coumarin may be selected based upon their functional similarity to coumarin, including the ability to inhibit the metabolism of nicotine to cotinine by CYP2A6.
• Examples of functional analogs of coumarin include 7-methoxycoumarin, 7-methylcoumarin, and 7-ethoxycoumarin and all structures shown in Figures 2A, 2B, 2C.
• Analogs of coumarin may also be selected based upon their three dimensional structural similarity to coumarin - i.e., the lactone/carbonyl structure.
• CYP2A6 inhibitors of the present invention include natural products or extracts of a natural product capable of inhibiting CYP2A6, such as Hypericum or a Hypericum extract or Cichorium intybus or Bougainvllra spetabillis or an extract thereof.
• Hypericum as used herein as synonymous with Hypericum perforatum, St. John's Wort, Goatweed and Klamath Wee.
• the phrase "Hypericum or an extract of Hypericum” as used herein includes the whole plant Hypericum perforatum or a derivative, extract, isolate or purified component thereof that can inhibit CYP2A activity. This includes natural components of the plant and synthetic analogues.
• a preferred extract of Hypericum is a methanol extract.
• Derivatives of Hypericum which may be used in the methods and compositions of the invention include hypericin, pseudohypericin, quercetin, hyperoside, quercitrin, isoquercitrin, rutin, campherol, luteolin, 13-II8-biopigenin, 1,3,6,7- tetrahydroxyxanthone, procyanidines, hyperforin, ethereal oil, phenol carbonic acids (e.g. chlorogenic acid), xanthone, phenylpropanes, flavonol derivatives, biflavones, proanthocyanidins, xanthones, phloroglucinols, naphthodianthrones and essential oil constitutes.
• phenol carbonic acids e.g. chlorogenic acid
• xanthone phenylpropanes
• flavonol derivatives flavonol derivatives
• biflavones proanthocyanidins
• Suitable derivatives of Hypericum may be selected based upon their ability to inhibit CYP2A with greater than 50% inhibition, and /or a Ki less than 300 ⁇ M.
• Cichorium intybus or Bougainvllra spectabillis or an extract thereof includes the whole plants Cichorium intybus or Bougainvllra specabillis or a derivative, extract, isolate or a purified component thereof that can inhibit CYP2A activity. This includes natural components of the plants as well as synthetic analogues.
• a preferred extract from Cichorium intybus or Bougainvllra spectabillis is esculetin, esculin or esculin monohydrate.
• Substances which inhibit transcription and /or translation of the gene encoding CYP2A6 include a nucleic acid sequence encoding the CYP2A6 gene (GenBank Accession No. HSU22027) or parts thereof (e.g., the region which is about 20 nucleotides on either side of nucleotide 790 (ATG), and the splice sites 1237, 2115, 2499, 3207, 4257, 4873, 5577 and 6308), inverted relative to their normal orientation for transcription - i.e., antisense CYP2A6 nucleic acid molecules.
• antisense nucleic acid molecules may be chemically synthesized using naturally occurring nucleotides or variously modified nucleotides designed to increase the biological stability of the molecules or to increase the physical stability of the duplex formed with CYP2A6 mRNA or the CYP2A6 gene.
• the antisense sequences may be produced biologically using an expression vector introduced into cells in the form of a recombinant plasmid, phagemid or attenuated virus in which antisense sequences are produced under the control of a high efficiency regulatory region, the activity of which may be determined by the cell type into which the vector is introduced.
• a nucleic acid molecule containing the antisense sequences may be introduced into cells in a subject using conventional techniques, such as transformation, transfection, infection, and physical techniques such as electroporation or microinjection. Chemical methods such as coprecipitation and incorporation of DNA into liposomes may also be used to deliver antisense sequences.
• the molecules may also be delivered in the form of an aerosol or by lavage.
• Suitable vectors or cloning vehicles for transferring the nucleic acid molecules are known in the art. Examples of suitable vectors include retroviral vectors, adenoviral vectors, and DNA virus vectors.
• the CYP2A6 inhibitor is at least one member selected from the group comprising coumarin, methoxsalen, tranylcypromine, derivatives thereof and analogs thereof (see Figure 2A).
• CYP2A6 may also be selectively inhibited in the method of the invention by interfering with the transcription of the gene encoding CYP2A6 using gene transfer methods such as targeted gene mutagenesis using allelic replacement, insertional inactivation, or deletion formation.
• gene transfer methods such as targeted gene mutagenesis using allelic replacement, insertional inactivation, or deletion formation.
• allelic gene exchange using non- replicating or conditionally-replicating plasmids has been used widely for the mutagenesis of eukaryotes. Allelic exchange can be used to create a deletion of the CYP2A6 gene. Exemplary methods of making the alterations set forth above are disclosed by Sambrook, et al. (1989).
• CYP2B6 inhibitors may also be used in combination with inhibitors of
• Inhibitors of CYP2B6 include one or more of the following (i) substances which inhibit CYP2B6 activity; or (ii) substances which inhibit transcription and /or translation of the gene encoding CYP2B6. CYP2B6 inhibitors may also be used alone to inhibit nicotine metabolism in an individual.
• Substances which inhibit CYP2B6 activity include substances which specifically bind to CYP2B6 and thereby inhibit its activity.
• examples of such substances include antibodies which are specific for CYP2B6 including for example, commercially available antibodies such as anti-CYP2B6 sold by Gentest Corporation, Woburn, Mass.,
• Substances which inhibit CYP2B6 activity also include substances selected from phenylethyl amines, diphenylbarbiturates, diethyl substituted barbiturates and hydantoins.
• diphenhydramine and its derivatives including orphenadrine (The Merck Index, No. 6831), and derivatives or analogs of orphenadrine, and other antihistamines, anticholinergic substances such as cholines and analogs and derivatives thereof may be used as CYP2B6 inhibitors in various embodiments of the methods and compositions of the invention.
• Antibodies such as polyclonal CYP2B1/2, polyclonal CYP2B1 and polyclonal CYP2B6 sold by Gentest Corporation, Woburn, Mass., U.S.A., also bind specifically to CYP2B6 such that they also inhibit the activity of CYP2B6.
• Derivatives of orphenadrine which may be used in the methods and compositions of the invention include pharmaceutically acceptable salts, esters and complexes of orphenadrine including potassium and sodium salts, and amino acid, carbohydrate and fatty acid complexes.
• suitable analogs of orphenadrine may be selected based upon their functional similarity to orphenadrine, including the ability to inhibit CYP2B6.
• Analogs of orphenadrine may also be selected based upon their three dimensional structural similarity to orphenadrine.
• Substances which inhibit transcription and /or translation of the gene encoding CYP2B6 include a nucleic acid sequence encoding the CYP2B6 gene (see Figure 2B, GenBank Accession No.
• HSP452B6 for the mRNA sequence of CYP2B6) or parts thereof (e.g., the region which is on either side of nucleotide 9 (ATG), and the sites 111, 274, 424, 585, 762, 904, 1092, and 1234 nt), inverted relative to their normal orientation for transcription - i.e., antisense CYP2B6 nucleic acid molecules.
• antisense nucleic acid molecules may be produced and introduced into cells using conventional procedures as described herein.
• CYP2B6 may also be selectively inhibited in a method of the invention by interfering with the transcription of the gene encoding CYP2B6 using conventional gene transfer methods as discussed herein.
• the CYP2B6 inhibitor employed is orphenadrine and derivatives or analogs of orphenadrine.
• An inhibitor of CYP2A6 or CYP2B6 may be targeted to the enzyme using antibodies specific to an epitope of the enzyme.
• bispecific antibodies may be used to target an inhibitor.
• the bispecific antibodies contain a variable region of an antibody specific for at least one epitope of CYP2A6 or CYP2B6, and a variable region of a second antibody which is capable of binding to an inhibitor.
• the bispecific antibodies may be prepared by forming hybrid hybridomas, using procedures known in the art such as those disclosed in Staerz, et al. ("Hybrid hybridoma producing a bispecific monoclonal antibody that can focus effector T-cell activity," Proc. Natl. Acad. Sci.
• Bispecific antibodies may also be constructed by chemical means using conventional procedures such as those described by Staerz, et al. ("Hybrid antibodies can target sites for a attack by T cells," Nature, 314(6012):628-31 (1985)) and Perez, et al. ("Specific targeting of cytotoxic T cells by anti-T3 linked to anti-target cell antibody,” Nature, 316(6026):354-6 (1985)), or by expression of recombinant immunoglobulin gene constructs.
• the present invention also includes a nicotine replacement therapy comprising contemporaneously administering to an individual in need thereof (a) oral nicotine and (b) one or more substances selected from the group consisting of (i) substances which inhibit CYP2A activity; (ii) substances which inhibit transcription, translation of the gene encoding CYP2A, or both; (iii) substances which delete all or a portion of the gene encoding CYP2A.
• the inhibitor is an inhibitor of CYP2A6 such as methoxsalen or tranylcypromine .
• compositions comprising two substances so that they are both biologically active in the individual 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 the two substances within a few hours of each other, or even 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 view of the details provided herein on the biological activities of CYP2A6 substrates and inhibitors.
• two substances will be administered substantially simultaneously, i.e., within minutes of each other, or in a single composition that contains both substances.
• a CYP2A6 inhibitor which acts by deleting or removing the gene encoding CYP2A6 could be administered months or even years before administration of nicotine or a procarcinogen that would otherwise be converted to a carcinogen by CYP2A6, and the effects due to the two administrations may still be contemporaneous.
• substances which may be used in the methods of this invention include other substances that alter the kinetics for metabolism of nicotine to cotinine, alter smoking behavior, alter the likelihood of addiction to smoking in a population of non-smokers, alter the kinetics of formation for carcinogens whose formation from procarcinogens is catalyzed by CYP2A. All of these substances have in common an ability to reduce the activity of CYP2A enzymes in an individual.
• the present disclosure therefore provides a method of screening for a substance that inhibits a CYP2A enzyme in an individual comprising assaying for a substance which selectively (i) inhibits CYP2A6 activity, (ii) inhibits transcription and /or translation of the gene encoding CYP2A6, or (iii) deletes or removes the gene encoding CYP2A6.
• inhibitory activity of a particular substance identified herein or an analog or derivative thereof may be confirmed by testing in experimental model systems and in clinical studies, for example as outlined below and exemplified in the Examples herein. Furthermore, specificity or selectivity of a substance listed above or a substance newly identified by screening as described herein may be determined or confirmed as described hereinbelow. While no particular test is mandated by this invention, the usefulness of a particular substance (e.g., a substance not specifically listed hereinabove or referred to in Figure 2A-2D) as a CYP2A6 inhibitor may be readily determining by testing the substance as follows. In vitro Inhibition
• An initial screen to select candidate inhibitors for use in the methods according to this invention comprises:
• CYP2A6 comparing the results of such assay to controls in the absence of the substance to determine if the test substance inhibits CYP2A6 and thereby is capable of inhibiting CYP2A enzymes.
• Substrates of CYP2A6 which may be used in the in vitro test for identification of substances for use in methods of the invention, as well as in the in vivo tests below, include nicotine, coumarin, analogs thereof and derivatives thereof. The corresponding reaction products for nicotine and coumarin are cotinine and 7- hydroxycoumarin, respectively.
• CYP2A6 used in the method of the invention may be obtained from natural, recombinant, or commercial sources.
• CYP2A6 may be obtained by recombinant methods such as those described by Nesnow S, et al. ("N-nitrosodiethylamine and 4- (methylnitrosamino)-l-(3-pyridyl)-l-butanone induced morphological transformation of C3H/10T1/2CL8 cells expressing human cytochrome P450 2A6," Mutation Research, 324:93- 102 (1994)). Cells or liver microsomes expressing CYP2A6 may also be used in the method.
• Conditions which permit the formation of a reaction product may be selected having regard to factors such as the nature and amounts of the test substance and the substrate.
• the results using the substrates in the presence and absence of the test substance may be compared to results using methoxsalen or tranylcypromine as controls which show positive inhibition tests.
• the reaction product, unreacted substrate, or unreacted CYP2A6 may be isolated by conventional isolation techniques, for example, salting out, chromatography, electrophoresis, gel filtration, fractionation, absorption, polyacrylamide gel electrophoresis, agglutination, or combinations thereof.
• CYP2A6 or substrate, or a labeled substance may be utilized.
• Antibodies, CYP2A6, substrate, or the substance may be labeled with a detectable marker such as a radioactive label, antigens that are recognized by a specific labeled antibody, fluorescent compounds, enzymes, antibodies specific for a labeled antigen, and chemiluminescent compounds.
• the substrate used in the method of the invention may be insolubilized.
• it may be bound to a suitable carrier.
• suitable carriers are agarose, cellulose, dextran, Sephadex, Sepharose, carboxymethyl cellulose polystyrene, filter paper, ion-exchange resin, plastic film, plastic tube, glass beads, polyamine-methyl vinyl- ether-maleic acid copolymer, amino acid copolymer, ethylene-maleic acid copolymer, nylon, silk, etc.
• the carrier may be in the shape of, for example, a tube, test plate, beads, disc, sphere etc.
• the insolubilized CYP2A6, substrate, or substance may be prepared by reacting the material with a suitable insoluble carrier using known chemical or physical methods, for example, cyanogen bromide coupling.
• a suitable in vivo test method comprises the steps of:
• a subtherapeutic dose of nicotine e.g., 1.0, 2.0 or 4.0 mg expressed as the base
• Analogous methods may be used for screening for a substance that regulates nicotine metabolism to cotinine in an individual by inhibiting transcription and /or translation of the gene encoding CYP2A6.
• a screening method for such substances comprises the steps of:
• a host cell for use in the method of the invention may be prepared by transfecting a suitable host with a nucleic acid molecule comprising a nucleic acid sequence encoding CYP2A6.
• a nucleic acid sequence encoding CYP2A6 may be constructed having regard to the sequence of the CYP2A6 gene (see the sequence under Genbank Accession number HUS22027, incorporated herein by reference) following procedures known in the art.
• Suitable transcription and translation elements may be derived from a variety of sources, including bacterial, fungal, viral, mammalian, or insect genes. Selection of appropriate transcription and translation elements is dependent on the host cell chosen, and may be readily accomplished by one of ordinary skill in the art.
• Such elements include: a transcriptional promoter and enhancer or RNA polymerase binding sequence, a ribosomal binding sequence, including a translation initiation signal. Additionally, depending on the host cell chosen and the vector employed, other genetic elements, such as an origin of replication, additional DNA restriction sites, enhancers, and sequences conferring inducibility of transcription may be incorporated into the expression vector. It will also be appreciated that the necessary transcription and translation elements may be supplied by the native CYP2A6 gene and /or its flanking sequences.
• reporter genes are genes encoding a protein such as ⁇ -galactosidase, chloramphenicol acetyltransferase, firefly luciferase, or an immunoglobulin or portion thereof such as the Fc portion of an immunoglobulin, preferably IgG. Transcription of the reporter gene is monitored by changes in the concentration of the reporter protein such as ⁇ -galactosidase, chloramphenicol acetyltransferase, or firefly luciferase. This makes it possible to visualize and assay for expression of CYP2A6 and in particular to determine the effect of a substance on expression of CYP2A6.
• Suitable host cells include a wide variety of prokaryotic and eukaryotic host cells, including bacterial, mammalian, yeast or other fungi, viral, plant, or insect cells. Protocols for the transfection of host cells are well known in the art (see, Sambrook, et al. (1989)).
• Nanji M, et al. (“Expression in a baculovirus system of a cDNA encoding human CYP2A6," Biochem. Soc. Trans. , 22 (1994)) describe the expression of a cDNA encoding human CYP2A6 in a baculovirus system; Nesnow, S., et al. (1994) and Tiano HF, et al.
• Host cells which are commercially available may also be used in the method of the invention.
• the h2A3 now known as h2A6
• h2B6 cell lines available from Gentest Corporation are suitable for the screening methods of the invention.
• Substances which pass the in vitro screening test for alteration of expression of CYP2A6 preferably are then subjected to an in vivo test to confirm their suitability for use in the methods of this invention, by .analogy to the in vivo test for inhibitors of CYP2A enzyme activity.
• the above mentioned methods may be used to identify negative regulators of nicotine metabolism to cotinine in brain and liver thereby affecting conditions requiring regulation of nicotine metabolism.
• compositions may be achieved by population studies of the effects of the substances on the kinetics for metabolism of nicotine to cotinine, on smoking behavior, on the likelihood of addiction to smoking in a population of non- smokers, and /or on the kinetics of formation for carcinogens whose formation from procarcinogens is catalyzed by CYP2A. Such studies are a routine matter for the skilled clinician in view of the guidance provided herein and the exemplary studies described in the Examples below.
• the invention provides a pharmaceutical composition for use in treating a condition requiring a reduction in the activity of a CYP2A enzyme comprising an effective amount of one or more substances which selectively inhibit CYP2A6, and a pharmaceutically acceptable carrier, diluent, or excipient.
• the invention provides a pharmaceutical composition for use in smoking prevention, smoking treatment, smoking regulation, regulating carcinogen formation, cancer prevention .and/or cancer treatment. A method of treatment using such a composition is also provided.
• the treatment methods and compositions of the invention may also be used together with other active compounds, including such other active compounds which are susceptible to CYP2A6-mediated metabolism leading to an inhibition or reduction in effectiveness of the other active compound.
• Conditions requiring regulation 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).
• the pharmaceutical compositions and treatment methods of the invention may be used to diminish a subjects desire to smoke and thereby alter smoking behaviour.
• the pharmaceutical compositions and treatment methods of the invention 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.
• 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 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 and compositions of the invention in modifying and maintaining behavioural components may be particularly useful in reducing smol ing 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.
• compositions and treatment methods of the invention are also particularly suited to regulate nicotine metabolism in individuals or populations having high levels of CYP2A6.
• 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 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.
• 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 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; and other drug dependencies in the individuals.
• nicotine-related disorders such as opioid related disorders
• proliferative diseases such as opioid related disorders
• cognitive, neurological or mental disorders include 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.
• CYP2A6 is known to metabolize several procarcinogens such as NNK (Crespi CL, et al., "A tobacco smoke-derived nitrosamine, 4- (methylnitrosamino)-l-(3-pyridyl)-l-butanone, is activated by multiple human cytochrome P450s including the polymorphic human cytochrome P4502D6," Carcinogenesis, 12(7):1197-201 (1991)), aflaxtoxin BI (Yun CH, et al., "Purification and characterization of human liver microsomal cytochrome P-450 2A6," Molec.
• NNK Non-spi CL, et al., "A tobacco smoke-derived nitrosamine, 4- (methylnitrosamino)-l-(3-pyridyl)-l-butanone, is activated by multiple human cytochrome P450s including the polymorphic human cytochrome P4502D6," Carcinogenesis, 12(7):11
• inhibitors of CYP2A6 may be useful in the prophylaxis (e.g., inhibition of CYP2A6 substrates thereby decreasing genotoxicity, cytotoxicity and /or mutagenicity) and treatment of malignant diseases, and, without limitation, the above-mentioned conditions and diseases.
• Formulation .and Dosing The pharmaceutical compositions of the invention contain substances which inhibit CYP2A described in detail herein or substances identified using the methods of the invention.
• the active substances can be administered alone, but are generally administered with a pharmaceutical carrier etc. (see below), selected on the basis of the chosen route of administration and standard pharmaceutical practice.
• 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.
• 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.
• a second inhibitor to a substance (e.g., enzyme) that is capable of inhibiting the metabolism of the CYP2A6 inhibitor.
• a second 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.
• 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.
• 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 selectively 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 mutant alleles, one mutant allele or no mutant alleles at the CYP2A6 gene locus.
• Example 1 we confirmed that such variations can exist in the genetic material of a population. It is, therefore, an aspect of this invention to provide a method for determining the CYP2A6 activity in an individual containing two mutant alleles, one mutant allele or no mutant alleles at a gene locus for the CYP2A6 gene, the method comprising the steps of:
• step (b) determining the amount of CYP2A6 present in the individual; and (c) correlating the results of assaying in step (a) and the amount of CYP2A6 in step (b) to determine an appropriate dosage for that individual of a substance which (i) selectively inhibits CYP2A6 activity, or (ii) selectively inhibits transcription and/ or translation of the gene encoding CYP2A6.
• the individual recipient may be any type of mammal, but is preferably a human. Generally, the recipient 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 herein.
• coumarin 7-hydroxylation has been used to measure CYP2A6 activity (Cholerton, et al. (1992); and Rautio, et al., (1992)).
• the methods and compositions of the invention may be preferably used in individuals or populations having high levels of CYP2A6, or in individuals where the behavioural components of smoking are significant.
• a daily oral dosage of an active ingredient such as coumarin or methoxsalen can be about 0.01 to 80 mg/kg of body weight, preferably 0.01 to 20, more preferably 0.05 to 3 mg/kg of body weight.
• a dose of 0.03 to 50 mg/kg of coumarin, methoxsalen or tranylcypromine per day in divided doses one to multiple times a day, preferably up to four times per day, or in sustained release form is effective to obtain the desired results.
• coumarin or methoxsalen or tranylcypromine 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 substance described in detail herein or identified using the methods 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 substances for the present invention can be administered for oral, topical, rectal, parenteral, local, inhalant or intracerebral use.
• the substances are administered in intranasal form via topical use of suitable intranasal vehicles, or via transdermal routes, using forms of transdermal skin patches known to those of ordinary skill in that art.
• the dosage administration will be continuous rather than intermittent throughout the dosage regimen.
• the substances can also be administered by way of controlled or slow release capsule system and other drug delivery technologies.
• the active substances can be combined with an oral, non-toxic, pharmaceutically acceptable, inert carrier such as lactose, starch, sucrose, glucose, methyl cellulose, magnesium stearate, dicalcium phosphate, calcium sulfate, mannitol, sorbitol and the like; for oral administration in liquid form, the oral active substances can be combined with any oral, non-toxic, pharmaceutically acceptable inert carrier such as ethanol, glycerol, water, and the like. Suitable binders, lubricants, disintegrating agents, and colouring agents can also be incorporated into the dosage form if desired or necessary.
• an oral, non-toxic, pharmaceutically acceptable, inert carrier such as lactose, starch, sucrose, glucose, methyl cellulose, magnesium stearate, dicalcium phosphate, calcium sulfate, mannitol, sorbitol and the like
• any oral, non-toxic, pharmaceutically acceptable inert carrier such as ethanol, glycerol
• Suitable binders include starch, gelatin, natural sugars such as glucose or beta-lactose, corn sweeteners, natural and synthetic gums such as acacia, tragacanth, or sodium alginate, carboxymethylcellulose, polyethylene glycol, waxes, and the like.
• Suitable lubricants used in these dosage forms include sodium oleate, sodium stearate, magnesium stearate, sodium benzoate, sodium acetate, sodium chloride, and the like.
• disintegrators include starch, methyl cellulose, agar, bentonite, xanthan gum, and the like.
• Gelatin capsules may contain the active substance and powdered carriers, such as lactose, starch, cellulose derivatives, magnesium stearate, stearic acid, and the like. Similar carriers and diluents may be used to make compressed tablets. Tablets and capsules can be manufactured as sustained release products to provide for continuous release of active ingredients over a period of time. Compressed tablets can be sugar coated or film coated to mask any unpleasant taste and protect the tablet from the atmosphere, or enteric coated for selective disintegration in the gastrointestinal tract. Liquid dosage forms for oral administration may contain colouring and flavouring agents to increase patient acceptance.
• Water a suitable oil, saline, aqueous dextrose, and related sugar solutions and glycols such as propylene glycol or polyethylene glycols, may be used as carriers for parenteral solutions.
• Such solutions also preferably contain a water soluble salt of the active ingredient, suitable stabilizing agents, and if necessary, buffer substances.
• suitable stabilizing agents include antioxidizing agents such as sodium bisuifate, sodium sulfite, or ascorbic acid, either alone or combined, citric acid and its salts and sodium EDTA.
• Parenteral solutions may also contain preservatives, such as benzalkonium chloride, methyl- or propyl-paraben, and chlorobutanol.
• Liposome delivery systems such as small unilamellar vesicles, large unilamellar vesicles, and multilamellar vesicles.
• Liposomes can be formed from a variety of phospholipids, such as cholesterol, stearylamine, or phosphatidylcholines.
• Substances described in detail herein and identified using the methods of the invention may also be coupled with soluble polymers which are targetable drug carriers.
• polymers examples include polyvinylpyrrolidone, pyran copolymer, polyhydroxypropylmeth-acrylamidephenol, polyhydroxyethylaspartamidephenol, or polyethyl-eneoxide-polylysine substituted with palmitoyl residues.
• the substances may also be coupled to biodegradable polymers useful in achieving controlled release of a drug.
• Suitable polymers include polylactic acid, polyglycolic acid, copolymers of polylactic and polyglycolic acid, polyepsilon caprolactone, polyhydroxy butyric acid, polyorthoesters, polyacetals, polydihydropyrans, polycyanoacylates, and crosslinked or amphipathic block copolymers of hydrogels.
• the substances can also be affixed to rigid polymers and other structures such as fullerenes or Buckeyballs.
• compositions suitable for administration contain about 1 milligram to 1500 milligrams of active substance per unit.
• the active ingredient will ordinarily be present in an amount of about 0.5-95% by weight based on the total weight of the composition.
• CYP2A6 preferably methoxsalen and /or tranylcypromine
• CYP2A6 are particularly effective inhibitors of CYP2A6 and of the metabolism of an oral formulation of nicotine and as such, enhance the effect of oral nicotine replacement therapies.
• these inhibitors are effective in inhibiting nicotine metabolism and thereby increasing plasma concentrations of nicotine, particularly when the nicotine is orally ingested thereby enhancing oral nicotine replacement therapies.
• this invention provides a composition for enhancing the effect of oral nicotine replacement therapy, comprising an inhibitor of CYP2A6 and nicotine formulated for oral ingestion.
• the substances described in detail herein and/or identified using the screening method described above together with nicotine, form the active ingredient, and are typically administered in admixture with suitable pharmaceutical diluents, excipients, or carriers suitably selected with respect to the intended form of administration, that is, oral tablets, capsules, elixirs, syrups and the like, consistent with conventional pharmaceutical practices.
• oral formulation within the invention can be in the form of: (i) a single composition comprising both the CYP2A6 inhibitor and nicotine, or (ii) a kit comprising independently administered compositions comprising the CYP2A6 inhibitor and nicotine, respectively.
• the administration is preferably substantially contemporaneous
• the preferred CYP2A6 inhibitors methoxsalen and/or tranylcypromine are administered with oral formulations of nicotine the plasma concentrations of nicotine have mcreased over the plasma concentrations when nicotine is orally digested without administering the CYP2A6 ⁇ nh ⁇ b ⁇ tor(s) Combination of Inhibitors
• a preferred embodiment of the mvention provides a method for treatmg conditions requirmg regulatmg nicotme metabolism to cotmme comprising admmistermg an effective amount of a CYP2A6 inhibitor and an effective amount of a CYP2B6 inhibitor to selectively inhibit nicotine metabolism to cotinine
• the CYP2A6 inhibitor is methoxsalen or an analog or derivative thereof
• the CYP2B6 inhibitor is orphenadrme, or an analog or derivative thereof
• the inhibitors may be admmistered concurrently, separately or sequentially
• the admmistration of the inhibitors is substantially contempraneous
• the doses of the CYP2A6 inhibitor e coumarin, methoxsalen
• a CYP2B6 inhibitor e , orphenadrine
• Subjects were unrelated healthy individuals each with 4 Caucasian grandparents and were divided into three groups.
• TD tobacco Dependent only
• DSM-IV Diagnostic Statistician Manual of the American Psychiatric Association
• the second group comprised Alcohol and Tobacco Dependent (AT, DSM-F/) subjects including 60 males aged 17 to 61 years old (mean (SD): 37.2 years old (9.94 years)), and 10 females aged 19 to 66 years old (mean (SD): 41.4 years old (11.89 years)).
• the third group was an exposure control group consisting of None-Tobacco Dependent (NTD( subjects, who had previously tried smoking, but had never become dependent. This group included 86 males 19 to 59 years old (mean (SD): 29.2 years old (8.6 years)), and 77 females 19 to 58 years old (mean (SD): 27.4 years old (8.4 years)).
• CYP2A6 genotyping of each subject was performed on genomic DNA isolated from peripheral leukocytes as described by Fernandez-Salguero, et al. (1995). Briefly, the assay consisted of a CYP2A6 gene-specific nested PCR amplification followed by a RFLP analysis.
• CYP2A6 genotype was determined using nested PCR and RFLP as described by Fernandez-Salguero, et al. (1995). The first amplification, which is CYP2A6 gene-specific, was used to increase the specificity for the CYP2A6 gene (versus other CYP2A genes). Exon 3 was utilized in the second amplification because both the CYP2A6*2 -and CYP2A6*3 mutant alleles contain nucleotide changes leading to amino acid changes in this region of the CYP2A6 gene.
• the first amplification was performed using the XL-PCR kit (Parkin-Elmer Co., Norwalk, Connecticut). A 100 ⁇ l reaction mixture of 0.2 ⁇ M of primer F4 and R4, 200 ⁇ M dNTPs, 0.8 mM magnesium acetate, and 2 U of rTthl DNA polymerase and 400 to 600 ng of genomic DNA used. The amplification was performed in a MJ DNA Engine (MJ Research, Inc., Watertown, Massachusetts) at 93°C for 1 minute, 66°C for 6 minutes and 30 seconds for 31 cycles. The second amplification was performed in a reaction mixture containing 0.5 ⁇ M of primers E3F and E3R, 200 ⁇ M dNTPs, 1.5 mM MgCl 2 , 2.5 U of Taq DNA polymerase
• reaction conditions were as follows: 94°C for 3 minutes, followed by 31 cycles of 94°C for 1 minute, 60°C for 1 minute and 72°C for 1 minute.
• the second amplification yielded a PCR product 201 bp in length which was digested with Xcm I (New England Biolabs) and Dde I (New England Biolabs and Pharmacia Biotech) to detect the CYP2A6*2 and CYP2A6*3 mutations, respectively (cutting indicates the presence of the mutation).
• Concentrations of enzymes and PCR product, total volume and digestion time were determined empirically to optimize cutting efficiency with a minimal amount of time and enzyme.
• Xcm I digestion reactions were carried out at 37°C for 2 hours in a 30 ⁇ l reaction mixture containing IX NEBuffer 3 (100 mM NaCl, 50 mM Tris-HCl, 10 mM MgCl 2 , 1 mM DTT pH 7.9 @ 25°C), dH 2 0, and 2 U of Xcm I.
• IX NEBuffer 3 100 mM NaCl, 50 mM Tris-HCl, 10 mM MgCl 2 , 1 mM DTT pH 7.9 @ 25°C
• Dde I digestions were carried out at 37°C for 2 hours in a 30 ⁇ l reaction mixture containing One-Phor-AU (OPA) buffer (Pharmacia Biotech) and 2 U of Dde I. Digestion products were analysed on ethidium-stained 3% agarose gels.
• OPA One-Phor-AU
• CYP2A6*3 allele frequencies were lower m the dependent smokers (TD and AT) than m the exposure control group (NTD) CYP2A6*2 3 0% versus 3 1% and CYP2A6*3 44% versus
• nicotme is important in establishing and maintaining tobacco dependence, variability in nicotine pharmacokmetics could have a profound influence on whether individuals become smokers
• the data produced in this study demonstrates an under-representation of individuals carrying 1 or 2 of the CYP2A6 defective alleles m a tobacco dependent population (TD + AT) when compared to a never tobacco dependent (NTD) control population While not wishmg to be bound by any particular theory or mode of action, this may be caused when individuals who carry CYP2A6 defective alleles, upon smoking, experience higher nicotine levels and greater aversive effects to the nicotme As a result, the mdividual may discontmue smokmg and be less likely to become tobacco dependent Therefore, the data produced m this study mdicates that individuals who carry 1 or 2 of the CYP2A6 defective or mutant alleles, and who try smokmg, are at lesser risk for becoming tobacco dependent than individuals who have two active CYP2A6 allele
• tobacco smoke contains a number of tobacco specific procarcinogen nitrosamines, such as N-nitrosodialkylamines - e.g., N-nitrosodiethylamine (the Merck Index, No. 6557), N-nitrosodimethylamine (The Merck Index, No. 6558) and 4- methylnitrosamino)-l-)3-pyridyl)-l-butanone (Crespi, et al. 1990; Yamazaki, et al. 1992).
• procarcinogens can be activated by CYP2A6, individuals who carry CYP2A6 defective alleles will be advantageously inefficient at bioactivating tobacco smoke procarcinogens to carcinogens.
• the data produced in the study of this Example demonstrates that a single genetically polymorphic gene, the CYP2A6 gene, is related, and in some cases predictive, of whether an individual becomes a smoker.
• the CYP2A6 gene variants alter the number of cigarettes that he/she smokes.
• the CYP2A6 genotype directly influences the risk for tobacco dependence, alters the amount of tobacco consumed, and plays a role in tobacco-related cancer susceptibility.
• One envisaged application of the present invention is the genetic identification of an individual's risk for smoking and related cancers. Identification of high and low risk individuals will allow targeted prevention, treatment and education.
• Coumarin is a selective and specific substrate for human CYP2A6 and can be used to: (1) identify individuals who are potential therapeutic exclusions for use of CYP2A6 inhibitors; (2) for dosage refinement based on the initial level of activity of CYP2A6; and (3) for risk factor assessment in identifying individuals who will not benefit from the treatment or who may be at risk to toxicity from agents which are inhibitors and substrates themselves of CYP2A6.
• the Coumarin Test exists in two forms: (1) Coumarin Test When Only Urine is Available
• Coumarin 5 mg formulated in a capsule or other dose form is administered orally to fasted individuals after voiding of residual bladder urine.
• Urine is collected for the first 2 hours and for the subsequent 6 hours.
• the amount of urinary excretion of the coumarin metabolite 7 hydroxy-coumarin (free and conjugated) is determined by determining the concentration of these metabolites on the urine using an HPLC assay as described in an earlier example.
• the relative activity of CYP2A6 is reflected in the total amounts of 7 hydroxy-coumarin excreted in the sampling periods separately and combined and the activity can be expressed as the ratio of the percent coumarin excretion (amount excreted in the first 2 hours/-amount excreted in 8 hours) x 100.
• This percent excretion ranges from values less then 20% in individuals without CYP2A6 activity to > 80% in individuals with high activity.
• This test can be equally effectively and reliably be applied to smokers and non-smokers and may be used at any time of day with out apparent effect of the smoking condition or time of day on the results.
• the test demonstrates high within subject reproducibility with a linear r of > 0.9. See Figure 3 for results of a study in which smokers and nonsmokers were given coumarin in the morning and afternoon on each of 2 separate days. High within subject reproducibility and reliability is demonstrated.
• a plasma-based test of CYP2A6 activity has been developed and applied to individuals of known genotype. Individuals ingest coumarin 5.0 mg orally and 45 minutes later a blood sample is drawn in a heparinized (or other anticoagulant containing tube). The sample is spun and the plasma separated. The plasma is analysed by HPLC to quantitate 7 hydroxycoumarin (total after deconjugation with beta glucuronidase incubation). High analytical sensitivity is required in order to use 5.0 mg of coumarin. When such sensitivity is not available, the dose of coumarin may be increased up to 50 mg. HPLC analysis of 7-hydroxycoumarin in urine and plasma:
• Urine or plasma samples (0 5 ml) are hydrolyzed with 0 2 ml of ⁇ - glucuronidase acetate buffer solution (15 mg/ml acetate buffer, 0 2 M, pH 5 0) at 37°C for 30 mm Extraction is followed with 2 ml ether by vortex for 5 mm and centrifuged at 3000 rpm for 10 mm Ether extract (1 2 ml) is transferred to another clean tube and dried down under nitrogen gas The residue is reconstituted m the HPLC mobile phase (see below), and injected onto HPLC
• HPLC analysis The HPLC system consists of Hewlett Packard 1050 HPLC system (pump, autosampler and UV detector) and HP3396II mtegrator The chromatographic separation was performed with an HP Sphe ⁇ sorb-ODS2 column (125 x 4 mm I D , 5 ⁇ m) Samples were eluted with a mobile phase of acetonit ⁇ le water acetic acid of 150 850 2 (v/v/v) at a flow rate of 1 0 ml/mm, and monitored by a UV detector at a wavelength of 324 nm for 7- hydroxycoumarm and 280 nm for coumarm Samples are quantitatively determmed by an external standard method
• the CYP2A6 activity is expressed as the concentration of 7 hydroxycoumarm m the plasma at various points in time (e g 20, 30, 45 and 75 minutes) or as the ratio of coumarm / 7 hydroxy-coumarm in the plasma at that time
• the preferred mode of use is a simple plasma sample at 20 or 30 mmutes after the oral admmistration of coumarm m which both coumarm and 7-hydroxycouma ⁇ n are quantified and m which the coumarin to 7-hydroxycouma ⁇ n ration is used as the dex of CYP2A6 activity
• Blank urine or plasma samples showed no interfering peak for 7- hydroxycoumarm or coumarm Sensitivity of this method is 1 ng/ml urine or plasma Intraday and mter-day variations are less than 10% This analysis is lmear from 1 ng to 4000 ng/ml
• Figure 4 is a graph showing a time course of total 7-hydroxycoumarm concentration detected in the plasma of subjects given coumarm Figure 4 illustrates various time courses based on correspondmg genotypes for CYP2A6 B.
• mutant alleles which decrease CYP2A6 activity in an individual can be screened in a DNA sample usmg the materials and screening method described m
• the plasma kinetics of nicotine and coumarin were compared after oral administration in 10 smokers and 9 non-smokers (12 males, 7 females) of known CYP2A6 genotype.
• the dose of nicotine was 4.0 mg (expressed as base) and the dose of coumarin was
• the plasma concentration of nicotine, cotinine, coumarin and 7-OH-coumarin were measured as described above.
• CYP2A6 enzyme was expressed in tissues in which tobacco-related cancers occur (e.g., lung and bladder).
• tissue distribution of the CYP2A6 mRNA was examined in various human tissues using Northern blot analysis. Briefly mRNA from numerous tissues was loaded onto gels and separated by electrophoresis. The mRNA was then transferred to membranes and probed with radioactive CYP2A6 cDNA probe. Evidence was found for the expression of CYP2A6 in uterus, ovaries, colon, small intestine, testis, bladder, heart, stomach, prostate, skeletal muscle, pancreas and lung.
• procarcinogens found in tobacco-smoke can be activated by CYP2A6.
• CYP2A6 In order to determine whether there was a significant contribution to cancer rates due to activation of procarcinogens by CYP2A6, independent of its role in smoking, a study was made of individuals with a tobacco-related cancer who were non-smokers. These individuals were passively exposed to tobacco smoke procarcinogens, therefore providing a group in which the role of the CYP2A6 null alleles in the activation of procarcinogens could be tested independently of the role of this enzyme on smoking behaviour.
• methoxsalen CYP2A6 inhibitor
• the four test days were broken down into one placebo day (no drug given) (day 1) and three methoxsalen (10 mg t.i.d. p.o.) treatment days 2, 3, 4), such that medication was taken at 8:00 a.m., 3:00 p.m. and 10:00 p.m. each day.
• a smoking log was completed. This log asked subjects to document the number of cigarette smoked from 8:00 a.m. to 3:00 p.m. to 10:00 p.m., and 10:00 p.m. to 8:00 a.m. Study days 1 and 2 could be separated, but days 2, 3 and 4 were required to be consecutive.
• Urine samples can be analyzed for 24 h NNAL, NNAL glucuronide, creatinine and cotinine.
• the larger decrease in the index of smoke exposure indicates: 1) the smokers decreased the intensity of their smoking due to inhibition of CYP2A6 and slowed nicotine elimination despite being told to not change their smoking; 2) methoxsalen in these doses is an effective inhibitor of CYP2A6; and 3) methoxsalen and other CYP2A6 inhibitors will decrease production of NNAL or related substances and the activation of other carcinogens in vivo.
• EXAMPLE 7 Influence of the CYP2A6 null alleles on tobacco-smoke exposure leading to lung cancer.
• the effect of the CYP2A6 null alleles on activation of procarcinogens was examined in an epidemiological study of lung cancer.
• the allele frequencies in DNA samples from 227 individuals with lung cancer was determined. Following diagnosis of lung cancer and resection of the tumor and surrounding lung tissue, the DNA was extracted and genotyped for CYP2A6.
• those individuals who had wt/wt CYP2A6 activity required an average of only 45 pack-years prior to lung cancer detection.
• those individuals with a CYP2A6 null allele, who activate less of the procarcinogens required considerably more procarcinogen exposure prior to detection of lung cancer (e.g., 54 pack-years).
• those individuals with decreased CYP2A6 activity activate less of the tobacco-smoke procarcinogens and require greater exposure before lung cancer is detected.
• the subjects for the study were smokers following a specified abstinence regimen as set out below. There were 12 subjects. The smokers underwent placebo p.o. and two separate cotreatments 30
• liver damage liver damage, blood dyscrisias (counterindications for tranylcypromine);
• symptoms suggestive of cardiac disease or hypertension
• Subjects were medically assessed for discharge no earlier than +2:00 h and were discharged after all measures were complete at +3:00 h. Subjects were not allowed to smoke until after their discharge. The schedule was in certain circumstances delayed by up to 20 minutes, consistent across the four days, in order to allow three subjects to be tested on the same day.
• Methoxsalen is marketed in Canada in two forms, one of relatively low bioavailability (trade name Oxsoralen®) and two of approximately twice as high a bioavailability (Oxsoralen-Ultra® and Ultra MOP®).
• the package insert for Ultra MOP® (Canderm Pharmacal Ltd.) recommends a daily dose of 30 mg to 50 mg for any patient weighing 51 kg or more. Subjects were restricted to a minimum body weight of 51 kg, in order to allow the use of a fixed 30 mg dose for all subjects; the dose was not adjusted for larger subjects.
• Capsules of methoxsalen 10 mg and tablets of tranylcypromine 10 mg (Parnate®) were used in their marketed forms. Because it was a randomized but single- blind study, subjects were able to recognize that the capsule forms and number varied from day to day, but they did not know which form represented which drug. Lactose tablets were used for the placebo.
• each day's drug supply consisted of one or three capsules, as set out in Table 4, in addition to nicotine 4 mg.
• the investigators were unaware of the distribution to preserve random allocation.
• Plasma and urinary nicotine and cotinine were determined using an HPLC method with a UV detector. Specifically, 1 mL of sample, 50 ⁇ L (2 ⁇ g/mL) of the internal standard (N-ethylnornicotine) and 1 mL of trichloroacetic acid (10%) were pipetted into each tube (12 mL). The tube was capped, vortex-mixed for a few seconds, and then centrifuged at 30,000g for 5 minutes. The clear supernatant was decanted in a second tube. To this protein-free plasma extract was added 0.5 mL of a 5 M potassium hydroxide solution and 6 mL of methylene chloride.
• the second tube was then capped, agitated for 30 minutes in a horizontal shaker and then centrifuged to separate the phases.
• the aqueous phase (the top layer) was aspirated, and 3.0 mL of 0.5 N hydrochloric acid solution was added to the organic phase and vortex-mixed for 30 seconds.
• the phases were separated by centrifugation, and the aqueous phase was transferred to a clean tube with 0.5 mL of 5 M potassium hydroxide solution, followed by addition of 5 m L of methylene chloride and vortex mixing for 30 seconds.
• the phases were separated by centrifugation, the aqueous (top) layer was aspirated, and 200 ⁇ l methanolic hydrochloric acid (10 mmol HCl in methanol) was added to the remaining solution and mixed gently. The organic solvent was then evaporated under nitrogen in a water bath at 40°C The sides of the tube were washed with 200 ⁇ L of meth,anolic hydrochloric acid and the solution was evaporated. The residue was reconstituted in 100 ⁇ L of 30% methanol and 90 ⁇ L thereof was injected in the HPLC column.
• the chromatographic separation was performed with a SupelcoTM 5-8347 LC-8-DB (150 x 4.6 mm, 5 ⁇ m).
• the sensitivity of the nicotine assay is ⁇ 1 ng/mL and that of the cotinine is ⁇ 5 ng/mL.
• Conjugates in urine were determined after hydrolysis with ⁇ -glucuronidase, when appropriate.
• Plasma nicotine concentration was determined using the above-mentioned assay, and the results are illustrated in Figure 7 as the mean for all subjects.
• Cardiovascular measures transduced by a Hewlett/ Packard 78352C Adult Patient Monitor and recorded directly into a computer included heart rate and blood pressure (while seated).
• Figure 7 illustrates the mean plasma nicotine concentrations measured just prior to oral drug administration and for three hours thereafter (during which no smoking was allowed). As illustrated, the combined methoxsalen/nicotine and tranylcypromine/nicotine treatments both induce an increase in mean plasma nicotine concentration that is at least four times as large as that induced by the placebo/nicotine combination.
• Figure 8 illustrates the self-rated "Current desire to smoke" evaluation, using a visual analog scale scored from 0 to 100. As illustrated, both the methoxsalen/nicotine and tranylcypromine/nicotine combination reduced the desire to smoke significantly more than does the placebo/nicotine combination.
• This Example demonstrates: the kinetic effectiveness of methoxsalen- enhanced oral nicotine replacement therapy in briefly abstinent smokers; and the behavioural effectiveness of methoxsalen-enhanced oral nicotine replacement therapy in briefly abstinent smokers.
• Example 8 There were 11 subjects. The subject inclusion and exclusion criteria used in Example 8 were used in this Example.
• Methoxsalen 10 mg capsules were used, as in Example 1, and capsules of royal jelly were used as the placebo. Capsules were dispensed in an opaque vial, and neither subjects nor investigators viewed the capsules prior to the subjects placing them directly into their mouths.
• Nicotine 4 mg capsules were prepared as in Example 8, and corresponding royal jelly capsule placebos containing only lactose were also prepared. Subjects took the three methoxsalen/placebo capsules and one nicotine/placebo capsule either all at once or consecutively.
• the treatment order was counterbalanced across the two sexes and the two times of day to the extent possible.
• the order of the treatments was determined by a computerized randomization program.
• the treatment was double-blind. As in Example 8, there was a morning and afternoon schedule.
• Study sessions were scheduled twice each day, with three subjects running simultaneously, beginning at 8:30/8:40/8:50 am and at 1:00/1:10/1:20 pm. Sessions lasted for about 4 hours. Prior to each session, subjects were allowed to smoke, eat, and drink caffeine as they desired up to 90 minutes before each session, at which time they stopped eating and drinking (other than water). Each session began 60 minutes before a drug/placebo/nicotine were taken. The precise schedule is set out in Table 5. Table 5
• the first post-cigarette abstinence period lasted 90 minutes, of which the last 60 minutes were post administration of placebo/drug/nicotine.
• the second abstinence period was included to facilitate repeated measures of the post-smoking breath carbon monoxide (CO).
• CO breath carbon monoxide
• the subject On the three occasions when blood samples were collected, the subject also answered a brief questionnaire about possible study drug symptoms and effects and about desire to smoke. Additionally, on the third occasion, there were also questions about perception of the cigarettes smoked during the free smoking period. This questionnaire (see Appendix A) is based on the one used in the nicotine gum study (Nemeth-Coslett, et al. (1987)).
• the primary dependent variable measured was the change in breath CO during the free-smoking period, measured as the mean of the three samples 10, 20, and 30 minutes post-smoking minus the mean of the two samples 10 and 0 minutes pre-smoking.
• Other dependent variables measured were the change in plasma nicotine between 0 and 150 minutes post-drug, the responses to the symptom and rating scales, the consumption of tobacco in the free smoking period (measured as the weight of butts remaining subtracted from the weight of the same number of unsmoked cigarettes), and the puff timing and count from analysis of the videotapes.
• Dependent variables were evaluated in an analysis of variance, with the treatment drug combinations as the primary independent variable of interest, with sex, morning /afternoon schedule, and treatment order as additional explanatory variables removed from the error term.
• Figure 9 illustrates the mean breath carbon monoxide concentration measured just prior to oral drug administration, 60 minutes later (no smoking allowed) and after the 90 minute free smoking period.
• the combined methoxsalen/nicotine treatment results in a significant and large reduction in the increased in breath carbon monoxide during the smoking phase.
• the carbon monoxide levels increased in the combined methoxsalen/nicotine treatment group only 30% of that seen in the other conditions, reflecting a large reduction in smoking and smoke exposure. This reduction may be attributable due to any combination of fewer puffs, shallower puffs and /or puffs held for a shorter duration before exhalation.
• Figure 10 illustrates the ratio of the increased plasma nicotine concentration to increased breath carbon monoxide concentration over the 90 minute free smoking period.
• this Figure illustrates the measure of potential reduction in smoke exposure that might occur while dependent smokers replenish their systemic plasma nicotine content.
• the methoxsalen/nicotine treatment stands apart from all three of the other treatments and from their mean, more than doubling the gain in nicotine per unit of increase in breath carbon monoxide concentration.
• Figure 11 illustrates the commonly used measure of smoking: the mean number of cigarettes smoked during the 90 minute period. As illustrated, the combined methoxsalen/nicotine treatment is associated with the least smoking, however number of cigarettes consumed is an insensitive measure of smoke exposure and smoking behaviour compared to breath carbon monoxide concentration.
• Figure 12 illustrates the mean cumulative number of puffs taken by the end of each 10 minute period during the 90 minute free smoking period, and the data is summarized by the area under this curve. This area would increase if either the total number of puffs increased, or if the same number were consumed earlier thereby shifting the curve to the left.
• the methoxsalen/nicotine treatment is associated with the fewest cumulative number of cigarette puffs.
• Figure 13 illustrates that the number of grams of tobacco burned is significantly less in the methoxsalen/nicotine treatment group. Again, this measure is less sensitive than direct measures of smoking behaviour and smoke exposure (e.g., breath carbon monoxide concentration and nicotine /breath carbon monoxide concentration).
• Figure 14 illustrates that the inhibition of CYP2A6 metabolism of nicotine achieves the reduction in breath carbon monoxide by changing nicotine-regulated smoking behaviour.
• the latency between cigarettes is significantly prolonged by the combined methoxsalen/nicotine treatment.
• methoxsalen 3 mg, 10 mg or 30 mg
• tranylcypromine 2.5 mg or 10 mg
• methoxsalen 10 and 30 mg M10 and M30, Figure 15
• tranylcypromine 2.5 and 10 mg T2.5 and T10, Figure 15
• Nicotine metabolism was monitored in vitro. Inhibitor assessment was carried out by comparing the assay including 50 ⁇ l tris buffer with the extracts prepared in Example 11 (50 ⁇ l, diluted in tris buffer). Human liver microsomes or CYP2A6 microsomes were used The concentration of inhibitor in Hypericum was calculated on the basis of an apparent molecular weight of the inhibitor of 504 and a concentration of 0 3% active material m the plant material when diluting to yield concentrations of 20, 10, 5, 1, 0 1 and
• the mcubation was carried out at 37°C for 30 mm An internal standard (50 ⁇ l, caffeme, 0 05 mg/ml) was added to the mcubation mixture, followed by DCM (1ml) The mixture was shaken for 10 min and centrifuged for 5 mm at 3,000 g The top layer was aspirated HCl (0 01 N, 100 ⁇ l) was added, followed by shaking for 1 mm, then centrifuge for 5 mm at 3,000 g 30 ⁇ l of the HCl layer was j ected for HPLC
• Figure 16 demonstrates the inhibition of nicotme metabolism with (1) cold methanol extract of Hypericum, (2) a hot methanol extract of Hpericum, (3) purified
• Hypericum can inhibit CYP2A6 activity
• Esculetin a compound found in Cichorium intybus and Bougainvllra spectabillis, was tested for its ability to inhibit nicotine metabolism by CYP2A6 using the methods set forth in Example 12.

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