Compositions and Methods for Assaying hERG Channel Binding

Abstract

The present invention provides compositions and methods useful for assaying binding of compounds to the hERG K + channel. According to a method of the present invention, a compound of interest is added to the hERG K + channel in the presence of a selenium analog of a competitive inhibitor of the hERG K + channel. Next, the amount of the selenium analog of the competitive inhibitor that bound to the hERG K + channel is quantified using mass spectrometry. The quantified amount can then be used to determine the amount of the compound of interest that bound to the hERG K + channel. A selenium analog of any competitive inhibitor of the hERG K + channel may be used according to the present invention, including but not limited to selenium analogs of the small molecule dofetilide; the peptide BeKm-1; or a combination of both.

1 . A composition having the formula: 
       
         
           
           
               
               
           
         
         or a pharmaceutically acceptable salt thereof. 
       
     
     
         2 . The composition as set forth in  claim 1 , wherein said pharmaceutically acceptable salt is an acetate, TFA, maleate or hydrochloride salt. 
     
     
         3 . The composition as set forth in  claim 1 , wherein said composition binds hERG K +  channel with a K i  in the range of about 4 nM to about 25 nM. 
     
     
         4 . A method of detecting binding of a compound to a hERG K +  channel, comprising:
 a) adding said compound to said hERG K +  channel in the presence of a selenium analog of a competitive inhibitor of said hERG K +  channel;   b) quantifying the amount of said selenium analog of said competitive inhibitor that bound to said hERG K +  channel using mass spectrometry; and   c) determining the amount of said compound that bound to said hERG K +  channel based on said quantifying.   
     
     
         5 . The method as set forth in  claim 4 , wherein said selenium analog of said competitive inhibitor is selected from the group consisting of di-seleno-dofelitide, (SeC) 7 -BeKm-1 and (MeSeC) 0 -BeKm-1. 
     
     
         6 . The method as set forth in  claim 4 , wherein said selenium analog of said competitive inhibitor is a combination of di-seleno-dofetilide and (SeC) 7 -BeKm-1 or di-seleno-dofelitide and (MeSeC) 0 -BeKm-1 
     
     
         7 . The method as set forth in  claim 4 , wherein said mass spectrometry is MALDI-TOF mass spectrometry, electrospray mass spectrometry, or ICP mass spectrometry. 
     
     
         8 . The method as set forth in  claim 4 , wherein said quantifying comprises quantifying the amount of selenium bound to said hERG K +  channel. 
     
     
         9 . The method as set forth in  claim 4 , wherein said selenium analog of said competitive inhibitor has a K i  that is within an order of magnitude of the K i  of an unmodified version of said competitive inhibitor. 
     
     
         10 . The method as set forth in  claim 4 , wherein said selenium analog of said competitive inhibitor has a K i  that is within about 3 times the K i  of an unmodified version of said competitive inhibitor.