Ansamitocins

Abstract

Improved purification methods for ansamitocins are disclosed.

1 . A method for preparing purified ansamitocins comprising the steps of: 
 a. culturing an ansamitocin-producing microorganism in a liquid culture medium;    b. treating the culture medium to facilitate solvent extraction of ansamitocins;    c. extracting ansamitocins from the culture medium with an aromatic hydrocarbon solvent;    d. concentrating the extracted ansamitocins; and    e. purifying the ansamitocins by crystallization.    
     
     
         2 . A method for preparing purified ansamitocins comprising the steps of: 
 a. culturing an ansamitocin-producing microorganism in a liquid culture medium;    b. extracting ansamitocins from the culture medium with an aromatic hydrocarbon solvent;    c. concentrating the extracted ansamitocins; and    d. purifying the ansamitocins by crystallization.    
     
     
         3 . The method of  claim 1  or  2  wherein the ansamitocin producing microorganism is Actinosynnema spp.  
     
     
         4 . The method of  claim 3  wherein the Actinosynnema spp. is  Actinosynnema pretiosum  ATCC 31565.  
     
     
         5 . The method of  claim 3  wherein the Actinosynnema spp. is  Actinosynnema pretiosum  ATCC 31281.  
     
     
         6 . The method of  claim 1  wherein the treatment is heating at about 75° C.  
     
     
         7 . The method of  claim 1  or  2  wherein the solvent is toluene.  
     
     
         8 . The method of  claim 7  wherein the ratio of toluene to heat-treated culture medium is about 1:1.  
     
     
         9 . The method of  claim 8  wherein the extraction is at about 45° C.  
     
     
         10 . The method of  claim 1  or  2  wherein the solvent is xylene.  
     
     
         11 . The method of  claim 10  wherein the ratio of xylene to heat-treated culture medium is about 1:1.  
     
     
         12 . The method of  claim 11  wherein the extraction is at about 45° C.  
     
     
         13 . The method of  claim 1  or  2  wherein the ansamitocins comprise acylated ansamitocins that can undergo reductive cleavage to form maytansinol.  
     
     
         14 . Ansamitocins prepared by the process of  claim 1  or  2 .  
     
     
         15 . A cell-binding agent maytansinoid complex prepared by converting ansamitocins prepared by the process of  claim 1  or  2  into the cell-binding agent maytansinoid complex.  
     
     
         16 . The cell-binding agent maytansinoid complex of  claim 15  wherein the cell-binding agent is an antibody.