Biologically Cleavable Tetrapeptide Linking Agents

Abstract

Tetrapeptide linkers for reversibly linking a first compound to a amine-containing second compound are described. Compounds containing the tetrapeptide linkers and methods of using the tetrapeptide linkers are also described.

1 . A composition comprising:
   R 5 -A 4 -A 3 -A 2 -A 1 -R 6   (formula IV)
   wherein
 R 5  is a first compound, 
 R 6  is an amine-containing second compound, 
 A 4  is a natural, non-natural isomeric, or synthetic hydrophobic L amino acid 
 A 3  is an uncharged hydrophilic or basic hydrophilic L amino acid, 
 A 2  is a natural, non-natural isomeric, or synthetic hydrophobic L amino acid, 
 A 1  is L-proline, L-leucine, or L-N-methyl alanine, and 
 A 1  is linked to R 6  via an amide bond. 
   
     
     
         2 . The composition of  claim 1 , wherein A 4  and A 2  are independently L-valine, L-leucine, L-isoleucine, or L-phenylalanine. 
     
     
         3 . The composition of  claim 1 , wherein A 3  is L-citrulline, L-asparagine, or L-lysine. 
     
     
         4 . The composition of  claim 1 , wherein A 4  and A 2  are independently L-valine, L-leucine, L-isoleucine, or L-phenylalanine, and A 3  is L-citrulline, L-asparagine, or L-lysine. 
     
     
         5 . The composition of  claim 1 , wherein A 4  and A 2  are both L-phenylalanine, A 3  is L-citrulline, and A 1  is proline. 
     
     
         6 . The composition of  claim 1 , wherein R 6  is a polyamine. 
     
     
         7 . The composition of  claim 1 , wherein R 6  is a membrane active polyamine. 
     
     
         8 . A composition comprising:
   (R 5 -A 4 -A 3 -A 2 -A 1 ) n -P   wherein
 R 5  comprises a targeting group or a steric stabilizer, 
 A 4  is a natural, non-natural isomeric, or synthetic hydrophobic L amino acid 
 A 3  is an uncharged or basic hydrophilic L amino acid, 
 A 2  is a natural, non-natural isomeric, or synthetic hydrophobic L amino acid, 
 A 1  is L-proline, L-leucine, or L-N-methyl alanine, 
 P comprises a polyamine, 
 n is an integer greater than or equal to 1, and 
 each A 1  is linked to an amine on the polyamine via an amide bond. 
   
     
     
         9 . The composition of  claim 8 , wherein A 4  and A 2  are independently L-valine, L-leucine, L-isoleucine, or L-phenylalanine. 
     
     
         10 . The composition of  claim 8 , wherein A 3  is L-citrulline, L-asparagine, or L-lysine. 
     
     
         11 . The composition of  claim 8 , wherein A 4  and R 2  are independently L-valine, L-leucine, L-isoleucine, or L-phenylalanine, and A 3  is L-citrulline, L-asparagine, or L-lysine. 
     
     
         12 . The composition of  claim 8 , wherein A 4  and A 2  are both L-phenylalanine, A 3  is L-citrulline, and A 1  is proline. 
     
     
         13 . The composition of  claim 8 , wherein P is a membrane active polyamine. 
     
     
         14 . A tetrapeptide modifying agent for reversibly attaching a first compound to an amine-containing compound via a biologically labile tetrapeptide linker comprising:
   R 5 -A 4 -A 3 -A 2 -A 1 -R 7      wherein
 R 5  represents the first compound, 
 A 4  is a natural, non-natural isomeric, or synthetic hydrophobic L amino acid, 
 A 3  is an uncharged or basic hydrophilic L amino acid, 
 A 2  is a natural, non-natural isomeric, or synthetic hydrophobic L amino acid, 
 A 1  is L-proline, L-leucine, or L-N-methyl alanine, and 
 R 7  comprises an amine-reactive group. 
   
     
     
         15 . The tetrapeptide modifying agent of  claim 14 , wherein A 4  and A 2  are independently L-valine, L-leucine, L-isoleucine, or L-phenylalanine. 
     
     
         16 . The tetrapeptide modifying agent of  claim 14 , wherein A 3  is L-citrulline, L-asparagine, or L-lysine. 
     
     
         17 . The tetrapeptide modifying agent of  claim 14 , wherein A 4  and A 2  are independently L-valine, L-leucine, L-isoleucine, or L-phenylalanine, and A 3  is L-citrulline, L-asparagine, or L-lysine. 
     
     
         18 . The tetrapeptide modifying agent of  claim 14 , wherein A 4  and A 2  are both L-phenylalanine, A 3  is L-citrulline, and A 1  is proline. 
     
     
         19 . The tetrapeptide modifying agent of  claim 14 , wherein R 7  is tetrafluoro phenyl or N-hydroxysuccinimide. 
     
     
         20 . The tetrapeptide modifying agent of  claim 14 , wherein the agent has the structure represented by: