Method for treating cystic fibrosis

Abstract

The present invention provides a method of identifying CFTR-binding compounds for treating cells having a reduced apical Cl − conductance, such as cystic fibrosis cells. This identification method involves the use of polypeptide Iα, which constitutes a portion of the CFTR protein. The present invention also provides a method of treating CF cells by contacting cells having a reduced apical Cl − conductance with a therapeutically effective quantity of a compound selected by the present inventive identification method. Preferred compounds for such treatment have little or no affinity for adenosine cell receptors. The present invention provides novel compounds useful in practicing the present inventive method, as well as pharmaceutical compositions containing such compounds.

What is claimed is:  
     
         1 . A polypeptide selected from the group comprising polypeptide Iα [SEQ ID NO:1], polypeptide Iβ [SEQ ID NO:3], and polypeptide Io [SEQ ID NO:4].  
     
     
         2 . The polypeptide of  claim 1 , wherein said polypeptide is linked covalently to an affinity chromatography matrix.  
     
     
         3 . The polypeptide of  claim 2 , wherein said affinity chromatography matrix is sepharose, agarose, polyacrylamide, or cellulose.  
     
     
         4 . A method for identifying a CFTR-binding compound comprising contacting a putative CFTR-binding compound with polypeptide Iα [SEQ ID NO:1] under conditions sufficient to allow for binding of said putative CFTR-binding compound to said polypeptide Iα, and determining whether such binding occurred, an indication that said putative CFTR-binding compound is a CFTR-binding compound.  
     
     
         5 . The method of  claim 4 , wherein said CFTR-binding compound has a neutral or negative-affinity for polypeptide Iβ [SEQ ID NO:3] or polypeptide Io [SEQ ID NO:4].  
     
     
         6 . The method of  claim 4 , wherein said CFTR-binding compound causes the aggregation of liposomes when added to a composition comprising said liposomes.  
     
     
         7 . The method of  claim 4 , wherein said CFTR-binding compound causes the aggregation of chromaffin granules when added to a composition comprising said chromaffin granules.  
     
     
         8 . The method of  claim 7 , wherein said composition consists essentially of said chromaffin granules in 1 mM CaCl 2 .  
     
     
         9 . A method of treating cystic fibrosis in a mammal in need of such treatment, comprising administering a therapeutically effective amount of a compound having the formula  
       
         
           
           
               
               
           
         
       
       wherein R 1  and R 3  are the same and are C 1 -C 6  alkyl or C 1 -C 6  alkenyl, R 7  is C 1 -C 6  alkyl or hydrogen, and R 8  is C 4 -C 8  cycloalkyl, and wherein the K i  with respect to said compound and an adenosine receptor is at least 0.01.  
     
     
         10 . The method of  claim 9 , wherein R 1  and R 3  are methyl, propyl, or allyl, R 7  is methyl or hydrogen, and R 8  is cyclopentyl or cyclohexyl.  
     
     
         11 . The method of  claim 9 , wherein said mammal is a human.  
     
     
         12 . The method of  claim 11 , wherein said compound is selected from the group consisting of 1,3-dipropyl-7-methyl-8-cyclopentylxanthine, 1,3-dipropyl-7-methyl-8-cyclohexylxanthine, 1,3-diallyl-8-cyclohexylxanthine, and 8-cyclohexyl caffeine.  
     
     
         13 . The method of  claim 12 , wherein said compound is 1,3-diallyl-8-cyclohexylxanthine.  
     
     
         14 . The method of  claim 9 , wherein said compound is administered to the lung of said human.  
     
     
         15 . The method of  claim 14 , wherein said compound is administered as an aqueous pharmaceutical composition containing from about 0.001 to about 0.01% w/w of said compound.  
     
     
         16 . The method of  claim 9 , wherein said K i  is at least 0.05.  
     
     
         17 . A compound having the formula  
       
         
           
           
               
               
           
         
       
       wherein (a) R 1  and R 3  are the same and are methyl or allyl, R 7  is ethyl, cyclopropylmethyl or hydrogen, and R 8  is cyclohexyl, provided that R 1  is allyl when R 7  is hydrogen and R 1  is methyl when R 7  is ethyl or cyclopropylmethyl, or (b) R 1  and R 3  are both methyl, and R 7  is hydrogen or methyl, and R 8  is cyclohexyl-methyl or cycloheptyl.  
     
     
         18 . The compound of  claim 17 , wherein said compound is 1,3-diallyl-8-cyclohexylxanthine.  
     
     
         19 . A pharmaceutical composition comprising a pharmaceutically acceptable carrier and a compound having the formula  
       
         
           
           
               
               
           
         
       
       wherein (a) R 1  and R 3  are the same and are methyl or allyl, R 7  is ethyl, cyclopropylmethyl or hydrogen, and R 8  is cyclohexyl, provided that R 1  is allyl when R 7  is hydrogen and R 1  is methyl when R 7  is ethyl or cyclopropylmethyl, or (b) R 1  and R 3  are both methyl, and R 7  is hydrogen or methyl, and R 8  is cyclohexylmethyl or cycloheptyl.  
     
     
         20 . The pharmaceutical composition of  claim 19 , wherein said compound is 1,3-diallyl-8-cyclohexylxanthine.  
     
     
         21 . A polynucleotide selected from the group consisting of polynucleotide Iα [SEQ ID NO:2], polynucleotide Iβ [SEQ ID NO:5], and polynucleotide Io [SEQ ID NO:6].