Potent conjugates and hydrophilic linkers

Abstract

Linkers for binding drugs to cell binding agents are modified to hydrophilic linkers by incorporating a polyethylene glycol spacer. The potency or the efficacy of the cell-binding agent-drug conjugates is surprisingly enhanced several folds in a variety of cancer cell types, including those expressing a low number of antigens on the cell surface or cancer cells that are resistant to treatment. A method for preparing maytansinoids bearing a thioether moiety and a reactive group which allows the maytansinoid to be linked to a cell-binding agent in essentially a single step is also provided.

1 - 17 . (canceled) 
     
     
         18 . A maytansinoid having a thioether moiety that bears a reactive group represented by the formula (5):
   D′-Y′—V-Q-W—Z′  (5)
   wherein:   D′ represents a sulfhydryl-bearing maytansinoid;   V is an optional linear, branched or cyclic alkyl, alkenyl or alkynyl group having from 1 to 10 carbon atoms;   W is an optional linear, branched or cyclic alkyl, alkenyl or alkynyl group having from 1 to 10 carbon atoms;   Y′ represents a thioether bond;   Q represents an optional aromatic or a heterocyclic moiety; and   Z′ represents an amine or sulfhydryl reactive group.   
     
     
         19 . The maytansinoid of  claim 18 , wherein the sulfhydryl-bearing maytansinoid is N 2′ -deacetyl-N 2′ -(3-mercapto-1-oxopropyl)-maytansine (DM1) or N 2′ -deacetyl-N 2′ -(4-mercapto-4-methyl-1-oxopentyl)maytansine (DM4). 
     
     
         20 . The maytansinoid of  claim 18 , represented by the following structural formula: 
       
         
           
           
               
               
           
         
       
     
     
         21 . The maytansinoid of  claim 18 , represented by the following structural formula: 
       
         
           
           
               
               
           
         
       
     
     
         22 . The maytansinoid of  claim 18 , represented by the following structural formulae, 7a or 7b: 
       
         
           
           
               
               
           
         
       
     
     
         23 . A process for the preparation of the maytansinoid of  claim 18  comprising reacting the thiol-containing maytansinoid with a heterobifunctional crosslinker represented by the following chemical equation:
   D′+Y″—V-Q-W—Z′→D′-Y′—V-Q-W—Z′  (6)
 
 wherein: 
 D′ represents a sulfhydryl-bearing maytansinoid; 
 V is an optional linear, branched or cyclic alkyl, alkenyl or alkynyl group having from 1 to 10 carbon atoms; 
 Q represents an optional aromatic or a heterocyclic moiety; 
 W is an optional linear, branched or cyclic alkyl, alkenyl or alkynyl group having from 1 to 10 carbon atoms;
 Z′ is an amine or sulfhydryl reactive group; 
 Y″ represents a sulfhydryl-reactive moiety; and 
 
 Y′ represents a thioether bond between the sulfhydryl-bearing maytansinoid and the crosslinker. 
 
     
     
         24 . The process of  claim 23 , wherein the sulfhydryl-bearing maytansinoid is N 2′ -deacetyl-N 2′ -(3-mercapto-1-oxopropyl)-maytansine (DM1) or N 2′ -deacetyl-N 2′ -(4-mercapto-4-methyl-1-oxopentyl)maytansine (DM4). 
     
     
         25 . The process of  claim 23 , wherein Y″ is a maleimido or haloacetamide. 
     
     
         26 . A process for the preparation of cytotoxic conjugates of maytansinoids and cell binding agents linked via a non-cleavable bond said process comprising reacting a cell binding agent with a compound of formula Z′—W-Q-V—Y′-D′ to provide a cell binding agent conjugate of formula CB—(Z″—W-Q-V—Y′-D′) m  
 wherein, 
 Z′ represents an amine or sulfhydryl reactive group; 
 W is an optional linear, branched or cyclic alkyl, alkenyl or alkynyl group having from 1 to 10 carbon atoms; 
 Q represents an optional aromatic or a heterocyclic moiety; 
 V is an optional linear, branched or cyclic alkyl, alkenyl or alkynyl group having from 1 to 10 carbon atoms; 
 Y′ represents a thioether bond; 
 D′ represents a sulfhydryl bearing maytansinoid; 
 CB represents a cell-binding agent; 
 Z″ represents a thioether bond or an amide bond; and 
 m is an integer from 2 to 8. 
 
     
     
         27 . The process of  claim 26 , wherein the sulfhydryl-bearing maytansinoid is N 2′ -deacetyl-N 2′ -(3-mercapto-1-oxopropyl)-maytansine (DM1) or N 2′ -deacetyl-N 2′ -(4-mercapto-4-methyl-1-oxopentyl)maytansine (DM4). 
     
     
         28 . The process of  claim 26 , wherein CB is an antibody, a single chain antibody or an antigen-binding fragment of an antibody. 
     
     
         29 . The process of any one of  claims 26  to  28 , wherein the cell binding agent conjugate of formula CB—(Z″—W-Q-V—Y′-D′) m  is purified. 
     
     
         30 . The process of  claim 26 , wherein the cell-binding agent and the compound of formula Z′—W-Q-V—Y′-D′ are reacted by mixing a solution of the cell-binding agent in aqueous buffer, optionally containing up to 20% organic solvent, with a solution of the compound of formula Z′—W-Q-V—Y′-D′ in organic solvent or a mixture of organic solvent and aqueous buffer or water, and allowing the reaction to proceed for between 5 minutes to 72 hours 
     
     
         31 . The process of  claim 26 , wherein the conjugate is purified by chromatography, dialysis, tangential flow filtration or a combination of said methods. 
     
     
         32 . A compound represented by the following structural formula: 
       
         
           
           
               
               
           
         
       
     
     
         33 . A compound represented by the following structural formula: