Therapeutic and diagnostic methods dependent on CYP2A enzymes

Abstract

A method of regulating the activity of human cytochrome P450 isozyme CYP2A6 to control nicotine metabolism or decrease the production of carcinogens from procarcinogens, such as those present in tobacco smoke, in an individual by selectively inhibiting CYP2A6. Various prophylactic (i.e., prevention and treatment) compositions and methods are also described, including an improved oral nicotine composition and method comprising the use of nicotine together with an inhibitor of the CYP2A6 enzyme. Furthermore, it has been discovered that the presence in an individual of a mutant allele of human cytochrome P450 enzyme CYP2A6 (referred to throughout this specification as “CYP2A6” for brevity) is predictive of an individual who: (1) has 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. This invention provides diagnostic methods for predicting tobacco dependence risk and risk for cancers related to CYP2A6 substrates in an individual by analyzing for the presence of a mutant genotype for human cytochrome P450 enzyme CYP2A6 in an individual, ranging from gene duplication (multiple copies of CYP2A6) to single or even no copies due to null alleles or gene deletion.

1 . A method for the treatment of a condition requiring a reduction in the activity of a CYP2A enzyme comprising administering to an individual in need thereof an effective amount of one or more substances selected from the group consisting of (i) a substances which inhibits CYP2A activity; (ii) a substances which inhibit transcription of a gene encoding CYP2A, (iii) a substance which inhibits translation of a gene encoding CYP2A, and (iv) a substances which deletes all or a portion of the gene encoding CYP2A.  
     
     
         2 . The method according to  claim 1  wherein said CYP2A enzyme is CYP2A6.  
     
     
         3 . The method according to  claim 33  wherein said condition is smoking and inhibition of the CYP2A enzyme inhibits the conversion of nicotine to cotinine.  
     
     
         4 . (Cancelled)  
     
     
         5 . The method according to  claim 3 , wherein said nicotine is formulated for oral administration.  
     
     
         6 . The method according to  claim 5 , wherein said one or more substances and said nicotine are formulated in a single composition.  
     
     
         7 . The method according to  claim 1 , wherein said substance is psoralen, tranylcypromine, pilocarpine, coumarin, chromone, esculetin, phenelzine, paroxetine, selegiline, pargyline, or combinations thereof.  
     
     
         8 . The method according to  claim 1 , wherein said substance is-tranylcypromine.  
     
     
         9 . The method according to  claim 8 , wherein tranylcypromine is administered in an amount from 0.1 mg to 80 mg.  
     
     
         10 - 11 . (Cancelled)  
     
     
         12 . The method according to  claim 1 , further comprising contemporaneously administering an inhibitor of CYP2B6.  
     
     
         13 . The method according to  claim 1 , wherein said condition is cancer and inhibition of the CYP2A enzyme inhibits the metabolism of a procarcinogen to a carcinogen.  
     
     
         14 . The method according to  claim 13 , wherein said procarcinogen is a N-nitrosodialkylamine selected from the group consisting of N-nitrosodiethylamine, N- nitrosodimethylamine, and 4-(methylnitrosamino)-1-) (3-pyridyl)-1-butanone.  
     
     
         15 . The method according to  claim 1 , wherein said individual is suffering from a condition selected from (i) addiction to tobacco, (ii) risk of developing an addiction to tobacco, (iii) risk of developing a smoking associated cancer, and (iv) exposure to one or more compounds which are converted to carcinogens by CYP2A6.  
     
     
         16 . A composition comprising an effective amount of one or more substances in admixture with a suitable diluent or carrier wherein said substance is selected from the group consisting of (i) a substance which inhibits CYP2A activity; (ii) a substance which inhibits transcription of a gene encoding CYP2A, (iii) a substance which inhibits translation of a gene encoding CYP2A, and (iv) a substance which deletes all or a portion of the gene encoding CYP2A.  
     
     
         17 . The composition of  claim 16  wherein said CYP2A enzyme is CYP2A6.  
     
     
         18 . The composition of  claim 16 , wherein said condition is smoking and inhibition of the CYP2A enzyme inhibits the conversion of nicotine to cotinine.  
     
     
         19 . The composition of  claim 18 , wherein said composition further comprises nicotine.  
     
     
         20 . (Cancelled)  
     
     
         21 . The composition of  claim 16 , wherein said substance which inhibits CYP2A is selected from psoralen, tranylcyprornine, pilocarpine, coumarin, chromone, esculetin, phenelzine, paroxetine, selegiline and pargyline.  
     
     
         22 . A method for enhancing the effectiveness of a nicotine replacement therapy comprising contemporaneously administering to an individual in need thereof (a) nicotine and (b) one or more substances selected from the group consisting of (i) a substance which inhibits CYP2A activity; (ii) a substance which inhibits transcription of a gene encoding CYP2A, (iii) a substance which inhibits translation of a gene encoding CYP2A, and (iv) a substance which deletes all or a portion of the gene encoding CYP2A.  
     
     
         23 . The method according to  claim 22 , wherein said substance which inhibits CYP2A6 and is selected from psoralen, tranylcypromine, pilocarpine, coumarin, chromone, esculetin, phenelzine, paroxetine, selegiline and pargyline.  
     
     
         24 . A kit for use in the method of  claim 22  comprising (a) nicotine and (b) one or more substances selected from the group consisting of (i) a substance which inhibits CYP2A activity, (ii) a substance which inhibits transcription of a gene encoding CYP2A, (iii) a substance which inhibits translation of a gene encoding CYP2A, and (iv) a substance which deletes all or a portion of the gene encoding CYP2A.  
     
     
         25 . A method for determining the risk of an individual becoming a smoker or 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 smoking.  
     
     
         26 . (Cancelled)  
     
     
         27 . A method according to  claim 25 , wherein said CYP2A enzyme is CYP2A6.  
     
     
         28 . A method according to  claim 25 , comprising analyzing a DNA-containing bodily sample from the individual for the presence of a mutant allele of human cytochrome P450 isozyme CYP2A6.  
     
     
         29 . A method according to  claim 28 , wherein said DNA-containing bodily sample is selected from a bodily fluid, a blood sample, blood plasma, and peripheral leukocytes.  
     
     
         30 . A kit for use in the method of  claim 25 , comprising means to identify a mutant allele of CYP2A6.  
     
     
         31 . The method of  claim 25 , the method comprising the steps of: administering a dose of a CYP2A6 substrate to the individual and determining in a bodily sample from the individual the level of said CYP2A6 substrate or a metabolite of said CYP2A6 substrate.  
     
     
         32 . A kit for use in the method of  claim 31 , comprising a CYP2A6 substrate and means for quantifying said CYP2A6 substrate or a metabolite of said CYP2A6 substrate.  
     
     
         33 . A method according to  claim 2 , further comprising contemporaneously administering nicotine.  
     
     
         34 . The method according to  claim 1 , wherein said substance is coumarin.  
     
     
         35 . The method according to  claim 34 , wherein coumarin is administered in an amount from 1 mg to 1000 mg.  
     
     
         36 . A composition comprising nicotine and an effective amount of one or more substances in admixture with a suitable diluent or carrier wherein said one or more substances are selected from the group consisting of (i) a substance which inhibits CYP2A activity; (ii) a substance which inhibits transcription of a gene encoding CYP2A, (iii) a substance which inhibits translation of a gene encoding CYP2A, and (iv) a substance which deletes all or a portion of the gene encoding CYP2A.  
     
     
         37 . The method according to  claim 1 , wherein said individual is suffering from a condition selected from malignant disease, psychosis, schizophrenia, Parkison's disease, anxiety, depression, alcoholism, opiate dependence, memory deficits, ulcerative colitis, and cholinergic deficits.