Peptide ligands for prostate specific antigen

Abstract

The present invention relates to novel peptide ligands for prostate specific antigen (PSA) binding specifically with it and enhancing its enzyme activity, to a process for preparation of these peptides, to diagnostic and pharmaceutical compositions comprising these peptides, to the use of these peptides for pharmaceutical and research preparations, to methods using these peptides in diagnostic assays for determination of the concentrations of various molecular forms of PSA, to methods for modulating the PSA enzyme activity and PSA activity dependent conditions by using these peptides either in vivo or in vitro and to the use of these peptides in procedures for biochemical isolation and purification of PSA.

1 . A peptide comprising:
 at least 6 amino acids bonded together to form a peptide backbone comprising at least one pair of cysteines which are spaced apart by at least two amino acids and interconnected by a disulfide bond to form a cyclic structure defined by the cysteines, intermediary amino acids and the disulfide bond,   wherein said peptide selectively binds to free prostate specific antigen.   
     
     
         2 . The peptide according to  claim 1 , wherein the peptide backbone comprises at least two pairs of cysteines interconnected by disulfide bonds. 
     
     
         3 . The peptide according to  claim 2 , wherein the peptide enhances the enzymatic activity of prostate specific antigen. 
     
     
         4 . The peptide according to  claim 1 , wherein said peptide is represented by formula (I)
   CX 1 X 2 X 3 X 4 X 5 X 6 X 7 X 8 C  (I)   
       wherein
 X 1  is V or I, 
 X 2  is F, I, W or P, 
 X 6  is Y, N or L, 
 C is cysteine, and 
 each of X 3 , X 4 , X 5 , X 7  and X 8  is independently selected from an amino acid residue. 
 
     
     
         5 . The peptide according to  claim 4 , wherein X 1  is V or I, X 2  is F or I and X 6  is Y or N. 
     
     
         6 . The peptide according to  claim 4 , wherein X 1  is V, X 2  is F, X 6  is Y and each of X 3 , X 4 , X 5 , X 7  and X 8  is an amino acid residue independently selected from the group consisting of T, S, D, Y A, F, E, P and L. 
     
     
         7 . The peptide according to  claim 4 , wherein X 1  is V, X 2  is I, X 6  is N and each of X 3 , X 4 , X 5 , X 7  and X 8  is an amino acid residue independently selected from the group consisting of Y, D, G, H, W, P and V. 
     
     
         8 . The peptide according to  claim 4 , wherein X 1  is I, X 2  is F, X 6  is Y or N, and each of X 3 , X 4 , X 5 , X 7  and X 8  is an amino acid residue independently selected from the group consisting of E, P, D, S, Y, G, F, I and L. 
     
     
         9 . The peptide according to  claim 4 , wherein X 1  is V or I, X 2  is F, I, W or P, X 5  is D or N, X 6  is Y, N or L, X 7  is A or N, X 8  is F or Y, each of X 3  and X 4  is independently selected from an amino acid residue. 
     
     
         10 . The peptide according to  claim 1 , wherein said peptide is represented by formula (II)
   CX 1 X 2 X 3 X 4 X 5 X 6 X 7 X 8 X 9 X 10 C  (II)   
       wherein
 X 1  is V, T or R, 
 X 2  is F, 
 X 6  is Y, 
 X 8  is Y or T 
 X 9  is L 
 X 10  is V or M, 
 C is cysteine, and 
 each of X 3 , X 4 , X 5  and X 7  is independently selected from an amino acid residue. 
 
     
     
         11 . The peptide according to  claim 10 , wherein X 1  is V, X 2  is F, X 6  is Y, X 8  is Y, X 9  is L, X 10  is V and each of X 3 , X 4 , X 1  and X 7  is independently selected from the group consisting of A, H, N and D. 
     
     
         12 . The peptide according to  claim 11 , wherein X 1  is V, T, or R, X 2  is F, X 6  is Y, X 7  is D or N, X 8  is Y or T, X 9  is L, X 10  is V or M, and each of X 3 , X 4  and X 5  is independently selected from the group consisting of A, H, N and D. 
     
     
         13 . The peptide according to  claim 1 , wherein said peptide is represented by formula (IV)
   CX 1 X 2 X 3 CX 4 X 5 X 6 CX 7 X 8 X 9 X 10 C  (IV)   
       wherein
 X 1  is L, 
 X 3  is T or Y, 
 X 7  is R or W, 
 C is cysteine, and 
 each of X 2 , X 4 , X 5 , X 6 , X 8 , X 9  and X 10  is independently selected from an amino acid residue. 
 
     
     
         14 . The peptide according to  claim 13 , wherein X 1  is L and X 3  is T. 
     
     
         15 . A peptide according to  claim 1 , wherein said peptide is selected from the group consisting of 
       
         
           
                 
                 
                 
                 
               
                     
                     
                 
                     
                   CVFTSDYAFC, 
                   (SEQ ID NO 1) 
                     
                 
                     
                     
                 
                     
                   CVIYDGNHWC, 
                   (SEQ ID NO 2) 
                 
                     
                     
                 
                     
                   CIFEPDYSYC, 
                   (SEQ ID NO 3) 
                 
                     
                     
                 
                     
                   CVFDDLYSFC, 
                   (SEQ ID NO 4) 
                 
                     
                     
                 
                     
                   CTFSVDYKYLMC, 
                   (SEQ ID NO 5) 
                 
                     
                     
                 
                     
                   CVFAHNYDYLVC, 
                   (SEQ ID NO 6) 
                 
                     
                     
                 
                     
                   CRFDKEYRTLVC, 
                   (SEQ ID NO 7) 
                 
                     
                     
                 
                     
                   CVAYCISSLCYYC, 
                   (SEQ ID NO 19) 
                 
                     
                     
                 
                     
                   CVWYTGNTWC, 
                   (SEQ ID NO 20) 
                 
                     
                     
                 
                     
                   CVFDALYTFC, 
                   (SEQ ID NO 21) 
                 
                     
                     
                 
                     
                   CVIYPGNVWC, 
                   (SEQ ID NO 22) 
                 
                     
                     
                 
                     
                   CIFDGFYILC, 
                   (SEQ ID NO 23) 
                 
                     
                     
                 
                     
                   CVPYLGLWLC, 
                   (SEQ ID NO 24) 
                 
                     
                   and 
                 
                     
                     
                 
                     
                   CMFDPMYMWMTC. 
                   (SEQ ID NO 25) 
                 
                     
                     
                 
             
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
       
     
     
         16 . A protein comprising the peptide according to any of  claims 1  to  15 , wherein said protein selectively binds to free prostate specific antigen, and enhances its enzymatic activity. 
     
     
         17 . A diagnostic composition comprising at least one peptide according to any one of  claims 1  to  15 , and a diagnostically acceptable carrier and/or labelling substance. 
     
     
         18 . A pharmaceutical composition comprising at least one peptide according to any one of  claims 1  to  15 , and a pharmaceutically acceptable carrier and/or labelling substance. 
     
     
         19 . A method for therapeutically treating conditions dependent on prostate specific antigen (PSA)-producing cells in mammals, comprising administering to a mammal in need thereof a peptide according to any one of  claims 1  to  15  in an effective amount to bind to free PSA in said mammal, and enhances its enzymatic activity in said mammal.