Methods for treating pain

Abstract

The present invention features methods and compositions for preventing, reducing, or treating a traumatic, metabolic, or toxic peripheral nerve lesion or pain including neuropathic pain, inflammatory, and nociceptive pain by administering to a mammal a compound that reduces expression or activity of BH4. This reduction may be achieved by reducing activity of a BH4 synthetic enzyme, including GTP cyclohydrolase, sepiapterin reductase, or dihydropteridine reductase; antagonizing the cofactor function of BH4 or BH4-dependent enzymes; or blocking BH4 binding to membrane bound receptors. The invention provides methods for diagnosing pain or a peripheral nerve lesion in a mammal by measuring levels of BH4 or its metabolites in biological sample or the levels or activity of any one of the BH4 synthetic enzyme in tissue samples of a mammal. Disclosed are screening methods that use BH4 or BH4 synthetic enzymes, BH4-dependent enzymes, and BH4-binding receptors to identify therapeutics for the treatment, prevention, or reduction of pain.

What is claimed is: 
     
         1 . A method of treating, reducing, or preventing pain or the consequences or development of a peripheral nerve lesion in a mammal, said method comprising administering to said mammal a composition that reduces the tetrahydrobiopterin (BH4) biological activity in an amount sufficient to treat, reduce, or prevent pain or the exacerbation of a peripheral nerve lesion due to overproduction of BH4. 
     
     
         2 . The method of  claim 1 , wherein said mammal is a human. 
     
     
         3 . The method of  claim 1 , wherein the pain is reduced by reducing the BH4 levels in primary sensory neurons or dorsal horn neurons. 
     
     
         4 . The method of  claim 3 , wherein said primary sensory neurons are in a dorsal root ganglion or a trigeminal ganglion. 
     
     
         5 . The method of  claim 4 , wherein said dorsal horn neurons are in the spinal cord or spinal nucleus of the trigeminal in the brainstem. 
     
     
         6 . The method of  claim 1 , wherein the reduction in BH4 biological activity is the result of a reduction in BH4 synthesis or recycling. 
     
     
         7 . The method of  claim 1 , wherein said BH4 biological activity is reduced by increasing the expression, GTPCH-binding, or activity of GTP cyclohydrolase feedback regulatory protein (GFRP). 
     
     
         8 . The method of  claim 6 , wherein said reduction in BH4 synthesis is the result of a reduction in the level or biological activity of at least one enzyme selected from the group consisting of sepiapterin reductase (SPR), Pyruvoyltetrahydropterin Synthase (PTPS), GTP cyclohydrolase (GTPCH), Pterin-4α-carbinolamine dehydratase, and dihydropteridine reductase (DHPR). 
     
     
         9 . The method of  claim 8 , wherein said reduction in BH4 synthesis is the result of a reduction in the biological activity of at least one enzyme selected from the group consisting of sepiapterin reductase (SPR), GTP cyclohydrolase (GTPCH), and dihydropteridine reductase (DHPR). 
     
     
         10 . The method of  claim 8 , wherein the biological activity of at least two of said enzymes is reduced. 
     
     
         11 . The method of  claim 10 , wherein the biological activity of at least three of said enzymes is reduced. 
     
     
         12 . The method of  claim 8 , wherein said biological activity is reduced by at least 10%. 
     
     
         13 . The method of  claim 12 , wherein said biological activity is reduced by at least 40%. 
     
     
         14 . The method of  claim 1 , wherein said composition comprises methotrexate. 
     
     
         15 . The method of  claim 1 , wherein said composition comprises at least one compound selected from the group consisting of 2,4 diamino 6-hydroxypyrimidine (DAHP), Tetrahydro-L-biopterin, L-Sepiapterin, 7,8-dihydro-L-Biopterin, 6,7-dimethyltetrahydropterin hydrochloride, and 8-bromo-cGMP. 
     
     
         16 . The method of  claim 1 , wherein said composition comprises at least one compound selected from the group consisting of N-acetyl-serotonin (NAS), N-Chloroacetylserotonin, N-Methoxyacetylserotonin, and N-Chloroacetyldopamine. 
     
     
         17 . The method of  claim 1 , wherein said composition comprises a compound having the formula: 
       
         
           
           
               
               
           
         
       
       wherein
 R 1  is H, C 1-6  alkyl, halo, NO 2 , CN, CO 2 R 4 , CONR 4 R 5 , SO 2 R 4 , SO 2 NR 4 R 5 , OR 4 , or NR 4 R 5 , wherein each of R 4  and R 5  is, independently, H, C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl, 
 R 2  is H, C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl, and 
 R 3  is H, C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, C 1-4  alkheteroaryl, CO 2 R 6 , CONR 7 R 8 , SO 2 R 6 , or SO 2 NR 7 R 8 , wherein R 6  is C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl and each of R 7  and R 8  is, independently, H, C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl; 
 R 3  is as above and R 1  and R 2  together are represented by 
 
       
         
           
           
               
               
           
         
       
       wherein 
       the N, O, or S of the R 1 /R 2  linkage forms a bond to the pyrimidinone ring and each of R 9 , R 10 , R 11 , R 12 , and R 13  is, independently H, C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl;
 R 3  is as above and R 1  and R 2  together are represented by 
 
       
         
           
           
               
               
           
         
       
       wherein the N of the R 1 /R 2  linkage forms a bond to the pyrimidinone ring, each of R 12  and R 13  is as above, and R 14  is OR 4 , halo, NO 2 , CN, CO 2 R 7 , CONR 7 R 8 , SO 2 R 7 , SO 2 NR 7 R 8 , C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl, wherein each of R 4 , R 7  and R 8  is, independently, H, C 1 -C 6  alkyl, C 6 -C 12  aryl, C 1 -C 4  alkaryl, heteroaryl, or C 1 -C 4  alkheteroaryl; or
 R 1  and R 2  together are represented by 
 
       
         
           
           
               
               
           
         
       
       wherein the N of the R 1 /R 2  linkage forms a bond to the pyrimidinone ring, each of R 9 , R 10 , R 11 , and R 14  are as above, R 3  does not exist, and a double bond is formed between the carbon bearing R 14  and the nitrogen bearing R 2 . 
     
     
         18 . The method of  claim 17 , wherein said composition comprises a compound of formula (I), wherein
 R 1  is H, C 1-6  alkyl, halo, NO 2 , CN, CO 2 R 4 , CONR 4 R 5 , SO 2 R 4 , SO 2 NR 4 R 5 , OR 4 , or NR 4 R 5 , wherein each of R 4  and R 5  is, independently, H, C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl,   R 2  is H, C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl, and   R 3  is H, C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, C 1-4  alkheteroaryl, CO 2 R 6 , CONR 7 R 8 , SO 2 R 6 , or SO 2 NR 7 R 8 , wherein R 6  is C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl and each of R 7  and R 8  is, independently, H, C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl.   
     
     
         19 . The method of  claim 1 , wherein said composition comprises a compound of formula: 
       
         
           
           
               
               
           
         
       
       wherein
 R 1  and R 2  together are represented by 
 
       
         
           
           
               
               
           
         
       
       wherein 
       the N, O, or S of the R 1 /R 2  linkage forms a bond to the pyrimidinone ring and each of R 9 , R 10 , R 11 , R 12 , and R 13  is, independently H, C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl. 
     
     
         20 . The method of  claim 1 , wherein said composition comprises a compound of formula: 
       
         
           
           
               
               
           
         
       
       wherein
 R 3  is as above and R 1  and R 2  together are represented by 
 
       
         
           
           
               
               
           
         
       
       wherein the N of the R 1 /R 2  linkage forms a bond to the pyrimidinone ring, each of R 12  and R 13  is as above, and R 14  is OR 4 , halo, NO 2 , CN, CO 2 R 7 , CONR 7 R 8 , SO 2 R 7 , SO 2 NR 7 R 8 , C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl, wherein each of R 4 , R 7  and R 8  is, independently, H, C 1 -C 6  alkyl, C 6 -C 12  aryl, C 1 -C 4  alkaryl, heteroaryl, or C 1 -C 4  alkheteroaryl. 
     
     
         21 . The method of  claim 1 , wherein said composition comprises a compound of formula: 
       
         
           
           
               
               
           
         
       
       wherein
 R 1  and R 2  together are represented by 
 
       
         
           
           
               
               
           
         
       
       wherein the N of the R 1 /R 2  linkage forms a bond to the pyrimidinone ring, each of R 9 , R 10 , R 11 , and R 14  are as above, R 3  does not exist, and a double bond is formed between the carbon bearing R 14  and the nitrogen bearing R 2 . 
     
     
         22 . The method of  claim 1 , wherein said composition comprises a compound of formula: 
       
         
           
           
               
               
           
         
       
       wherein
 R 1  and R 2  together are represented by 
 
       
         
           
           
               
               
           
         
       
       wherein 
       the N, O, or S of the R 1 /R 2  linkage forms a bond to the pyrimidinone ring and each of R 9 , R 10 , R 11 , R 12 , and R 13  is, independently H, C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl. 
     
     
         23 . The method of  claim 1 , wherein said composition comprises a compound of formula: 
       
         
           
           
               
               
           
         
       
       wherein
 R 3  is as above and R 1  and R 2  together are represented by 
 
       
         
           
           
               
               
           
         
       
       wherein the N of the R 1 /R 2  linkage forms a bond to the pyrimidinone ring, each of R 12  and R 13  is as above, and R 14  is OR 4 , halo, NO 2 , CN, CO 2 R 7 , CONR 7 R 8 , SO 2 R 7 , SO 2 NR 7 R 8 , C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl, wherein each of R 4 , R 7  and R 8  is, independently, H, C 1 -C 6  alkyl, C 6 -C 12  aryl, C 1 -C 4  alkaryl, heteroaryl, or C 1 -C 4  alkheteroaryl. 
     
     
         24 . The method of  claim 1 , wherein said composition comprises a compound of formula: 
       
         
           
           
               
               
           
         
       
       wherein
 R 1  and R 2  together are represented by 
 
       
         
           
           
               
               
           
         
       
       wherein the N of the R 1 /R 2  linkage forms a bond to the pyrimidinone ring, each of R 9 , R 10 , R 11 , and R 14  are as above, R 3  does not exist, and a double bond is formed between the carbon bearing R 14  and the nitrogen bearing R 2 . 
     
     
         25 . The method of  claim 18 , wherein said composition comprises a compound selected from the group consisting of 
       
         
           
           
               
               
           
         
       
     
     
         26 . The method of  claim 1 , wherein said composition comprises a compound having the formula: 
       
         
           
           
               
               
           
         
       
       wherein
 R 15  is H, C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl; and 
 R 16  is H, C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, C 1-4  alkheteroaryl, CO 2 R 17 , CONR 18 R 19 , SO 2 R 17 , or SO 2 NR 18 R 19 , wherein R 17  is C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl and each of R 18  and R 19  is, independently, H, C 1-6  alkyl, C 6-12  aryl, heteroaryl, C 1-4  alkaryl, or C 1-4  alkheteroaryl. 
 
     
     
         27 . The method of  claim 1 , wherein said pain is acute pain. 
     
     
         28 . The method of  claim 1 , wherein said pain is chronic pain. 
     
     
         29 . The method of  claim 1 , wherein said pain is selected from the group consisting of peripheral and central neuropathic pain, inflammatory pain, functional pain nociceptive pain, and headache. 
     
     
         30 . A method of diagnosing pain or a peripheral nerve lesion in a mammal, said method comprising detecting an increase in BH4, BH4 metabolite, BH4 precursor, or BH4 intermediate in a biological sample from said mammal. 
     
     
         31 . A method of diagnosing pain or a peripheral nerve lesion in a mammal, said method comprising detecting an increase in the activity or level of a BH4 synthetic enzyme in primary sensory neurons or dorsal horn neurons of said mammal.