Preparation of romidepsin

Abstract

The invention provides an improved process for preparing romidepsin. The process involves producing, purifying, or storing romidepsin under conditions that prevent the formation of undesired adducts. Purifying romidepsin at an apparent pH lower than approximately 6.0 (e.g., between an apparent pH of 4.0 and 6.0) has been discovered to prevent the reduction of the disulfide bond of romidepsin and the subsequent formation of dimerized, oligomerized, or polymerized adducts. The invention also provides compositions of monomeric romidepsin free of dimerized, oligomerized, or polymerized adducts.

1 .- 26 . (canceled) 
     
     
         27 . A composition of romidepsin,
 wherein the romidepsin is substantially free of dimerized, oligomerized, or polymerized romidepsin, and   wherein the romidepsin is prepared by purifying the romidepsin in at least one step at an apparent pH below 6.0.   
     
     
         28 . The composition of  claim 27 , wherein the apparent pH is between 4.0 and 6.0. 
     
     
         29 . The composition of  claim 27 , wherein the apparent pH is kept below 6.0 using an organic acid. 
     
     
         30 . The composition of  claim 29 , wherein the organic acid is acetic acid. 
     
     
         31 . A composition of romidepsin, wherein the romidepsin is prepared by the method of purifying romidepsin from a fermentation broth, wherein at least a portion of the step of purifying is performed at an apparent pH below 6.0. 
     
     
         32 . A composition comprising romidepsin, wherein substantially all the romidepsin is monomeric. 
     
     
         33 . A composition comprising romidepsin, wherein at least 98% of the romidepsin is monomeric. 
     
     
         34 . The composition of  claim 33 , wherein at least 99% of the romidepsin is monomeric. 
     
     
         35 . The composition of  claim 33 , wherein at least 99.5% of the romidepsin is monomeric. 
     
     
         36 . The composition of  claim 33 , wherein at least 99.9% of the romidepsin is monomeric. 
     
     
         37 . The composition of  claim 33 , wherein at least 99.95% of the romidepsin is monomeric. 
     
     
         38 . A composition comprising romidepsin, wherein the composition is substantially free of dimerized, oligomerized, or polymerized romidepsin. 
     
     
         39 . A composition comprising romidepsin, wherein the composition is at least 98% pure romidepsin. 
     
     
         40 . The composition of  claim 39 , wherein the composition is at least 99% pure romidepsin. 
     
     
         41 . The composition of  claims 39 , wherein the composition is at least 99.5% pure romidepsin. 
     
     
         42 . The composition of  claim 39 , wherein the composition is at least 99.8% pure romidepsin. 
     
     
         43 . The composition of  claim 39 , wherein the composition is at least 99.9% pure romidepsin. 
     
     
         44 . The composition of  claim 39 , wherein the composition is at least 99.95% pure romidepsin. 
     
     
         45 . The composition of  claim 39 , wherein the composition contains less than or equal to 1.0% total impurities and less than or equal to 0.2% individual impurities. 
     
     
         46 . The composition of  claim 39 , wherein the composition contains less than or equal to 0.5% total impurities and less than or equal to 0.1% individual impurities. 
     
     
         47 . The composition of  claim 39 , wherein a solution of the composition in chloroform yields no precipitate at a concentration of approximately 20 mg/mL. 
     
     
         48 . The composition of  claim 31 ,  32 ,  33 ,  38 , or  39 , wherein a solution of the composition in chloroform at a concentration of approximately 20 mg/mL has an optical rotation ranging from +38° to +47°. 
     
     
         49 . The composition of  claim 48 , wherein the optical rotation ranges from +39° to +41°. 50. The composition of  claim 48 , wherein the optical rotation is approximately +40°.