Radioconjugation method

Abstract

The present invention relates to the field of radiopharmaceuticals for in vivo imaging, in particular to a method of labelling a biological targeting molecule with a radioisotope. The method of the invention is particularly suitable for use with an automated synthesizer apparatus. Also provided are precursors in sterile form, as well as cassettes comprising such precursors useful in the method.

What is claimed: 
     
         1 . A method for radiolabelling a biological targeting molecule which comprises:
 (i) providing a compound of Formula (IB)
   Q-[linker]-X 1    (IB)
 
   (ii) deprotection of the protected compound of Formula (IB) of step (i) to give an aminooxy compound of Formula (IIB) respectively
   Q-[linker]-O—NH 2    (IIB)
 
   (iii) condensation of the aminooxy compound of Formula (IIB) with a carbonyl compound of Formula (IIIB),
   [BTM]-(C═O)Y 1    (IIIB)
 
   to give a radiolabelled conjugate of Formula (IVB):
   [BTM]-(CY 1 )═N—O-[linker]Q   (IVB)
 
   
       wherein:
 [BTM] is a biological targeting molecule; 
 X 1  is a protected aminooxy group of formula: 
 
       
         
           
           
               
               
           
         
         wherein R 1  and R 2  are independently chosen from C 1-3  alkyl, C 1-3  fluoroalkyl or C 4-6  aryl; 
         Q is a group which comprises a radioisotope suitable for PET or SPECT imaging in vivo; 
         Y 1  is H, C 1-6  alkyl or C 4-10  aryl, [linker] is a linker group. 
       
     
     
         2 . The method of  claim 1 , where R 1  and R 2  are independently C 1-3  alkyl. 
     
     
         3 . The method of  claim 1 , where Y 1  is H. 
     
     
         4 . The method of  claim 1 , where Q is chosen from  18 F,  123 I,  99m TC,  68 Ga or  64 Cu. 
     
     
         5 . The method of  claim 4 , where Q is  18 F. 
     
     
         6 . The method of  claim 1 , where the BTM comprises a single amino acid, a 3-100 mer peptide, an enzyme substrate, an enzyme antagonist an enzyme agonist, an enzyme inhibitor or a receptor-binding compound. 
     
     
         7 . The method of  claim 6 , where the BTM comprises an Affibody™. 
     
     
         8 . The method of  claim 6 , where the BTM comprises a 3-100 mer peptide which is chosen from Peptide A, Peptide B, Peptide C and Peptide D. 
     
     
         9 . The method of  claim 8 , wherein Peptide A is an Arg-Gly-Asp peptide. 
     
     
         10 . The method of  claim 8 , wherein Peptide B is an Arg-Gly-Asp peptide which comprises the fragment 
       
         
           
           
               
               
           
         
       
     
     
         11 . The method of  claim 8 , wherein Peptide B is of formula (A): 
       
         
           
           
               
               
           
         
         wherein X 1  is either —NH2 or 
       
       
         
           
           
               
               
           
         
         wherein a is an integer of from 1 to 10. 
       
     
     
         12 . The method of  claim 8 , wherein Peptide B is a Fluciclatide molecule: 
       
         
           
           
               
               
           
         
       
     
     
         13 . The method of  claim 8 , wherein Peptide C is a c-Met binding cyclic peptide which comprises the amino acid sequence: 
       
         
           
                 
               
                   -Cys a -X 1 -Cys c -X 2 -Gly-Pro-Pro-X 3 -Phe-Glu-Cys d -Trp- 
                 
                   Cys b -Tyr-X 4 -X 5 -X 6 - 
                 
             
                
                
               
            
           
         
         Wherein X 1  is Asn, His or Tyr;
 X 2  is Gly, Ser, Thr or Asn; 
 X 3  is Thr or Arg; 
 X 4  is Ala, Asp, Glu, Gly or Ser; 
 X 5  is Ser or Thr; 
 X 6  is Asp or Glu; 
 and Cys a-d  are each cysteine residues such that residues a and b as well as c and d are cyclised to form two separate disulfide bonds. 
 
       
     
     
         14 . The method of  claim 8 , wherein Peptide D is a lantibiotic peptide of formula: 
       
         
           
                 
               
                   Cys a -Xaa-Gln-Ser b -Cys c -Ser d -Phe-Gly-Pro-Phe-Thr c - 
                 
                   Phe-Val-Cys b -(HO-Asp)-Gly-Asn-Thr a -Lys d   
                 
             
                
                
               
            
           
         
         wherein Xaa is Arg or Lys;
 Cys a -Thr, Ser b -Cys b  and Cys c -Thr c  are covalently linked via thioether bonds; 
 Ser d -Lys d  are covalently linked via a lysinoalanine bond; 
 HO-Asp is β-hydroxyaspartic acid. 
 
       
     
     
         15 . The method of  claim 1 , where steps (ii) and (iii) are carried out simultaneously. 
     
     
         16 . The method of  claim 1 , where the condensation step (iii) is carried out in the presence of aniline. 
     
     
         17 . The method of  claim 1 , which is carried out using an automated synthesizer apparatus. 
     
     
         18 . The method of  claim 17 , wherein said automated synthesizer comprises a single-use, disposable cassette. 
     
     
         19 . A method of preparation of a radiopharmaceutical composition, wherein said radiopharmaceutical composition comprises the radiolabelled conjugate of Formula (IVB) as defined in  claim 1 , together with a biocompatible carrier in a form suitable for mammalian administration, and said method of preparation comprises the radiolabelling method of  claim 1 . 
     
     
         20 . A protected compound of Formula (IB)
   Q-[linker]-X 1    (IB)
   wherein Xis a protected aminooxy group of formula:   
       
         
           
           
               
               
           
         
         wherein R 1  and R 2  are independently chosen from C 1-3  alkyl, C 1-3  fluoroalkyl or C 4-6  aryl; 
         and Q is a group which comprises a radioisotope suitable for PET or SPECT imaging in vivo.