Compositions Of Engineered Human Arginases And Methods For Treating Cancer

Abstract

Compositions and methods for the treatment of cancer are described, and, more preferably, to the treatment of cancers that do not express, or are otherwise deficient in, argininosuccinate synthetase, with enzymes that deplete L-Arginine in serum. In one embodiment, the present invention contemplates an arginase protein, such as a human Arginase I protein, comprising at least one amino acid substitution and a metal cofactor, said protein comprising an increased catalytic activity when compared with a native human Arginase I.

1 - 45 . (canceled) 
     
     
         46 . A composition comprising a variant human Arginase I protein, wherein the protein comprises the wild-type Arginase I amino acid sequence except that it has:
 at least one amino acid substitution at a position selected from His101, Asp124, His126, Asp128, Asp232, Asp234, Asp181, Ser230 and Cys303; and optionally lacks N-terminal methionine; and   wherein the protein is in a complex with a non-native metal cofactor, wherein the non-native metal cofactor is cobalt.   
     
     
         47 . The composition of  claim 46 , wherein the protein exhibits a k cat /K m  greater than 400 mM −1  s −1  at 37° C. and pH 7.4. 
     
     
         48 . The composition of  claim 46 , wherein the protein lacks an N-terminal methionine. 
     
     
         49 . The composition of  claim 46 , wherein the protein is covalently linked to polyethylene glycol. 
     
     
         50 . The composition of  claim 49 , wherein the polyethylene glycol comprises PEG-5000. 
     
     
         51 . The composition of  claim 46 , wherein the protein comprises an amino acid substitution at position Cys303. 
     
     
         52 . The composition of  claim 46 , wherein the protein comprises at least two amino acid substitutions. 
     
     
         53 . The composition of  claim 46 , wherein the protein comprises at least one amino acid substitution selected from the group consisting of: Asp181Ser, Ser230Cys, Ser230Gly, Cys303Phe, Cys303Ile, Glu256Gln, Asp181Glu, and Ser230Ala. 
     
     
         54 . The composition of  claim 46 , wherein the composition is buffered to pH 7.4. 
     
     
         55 . A method of treating cancer, the method comprising administering to a subject in need thereof a composition comprising a variant human Arginase I protein, wherein the protein comprises the wild-type Arginase I amino acid sequence except that it has:
 at least one amino acid substitution at a position selected from His101, Asp124, His126, Asp128, Asp232, Asp234, Asp181, Ser230 and Cys303; and optionally lacks N-terminal methionine; and   wherein the protein is in a complex with a non-native metal cofactor, wherein the non-native metal cofactor is cobalt.   
     
     
         56 . The method of  claim 55 , wherein the protein exhibits a k cat /K m  greater than 400 mM −1  s −1  at 37° C. and pH 7.4. 
     
     
         57 . The method of  claim 55 , wherein the protein lacks an N-terminal methionine. 
     
     
         58 . The method of  claim 55 , wherein the protein is covalently linked to polyethylene glycol. 
     
     
         59 . The method of  claim 58 , wherein the polyethylene glycol comprises PEG-5000. 
     
     
         60 . The method of  claim 55 , wherein the protein comprises an amino acid substitution at position Cys303. 
     
     
         61 . The method of  claim 55 , wherein the protein comprises at least two amino acid substitutions. 
     
     
         62 . The method of  claim 55 , wherein the protein comprises at least one amino acid substitution selected from the group consisting of: Asp181Ser, Ser230Cys, Ser230Gly, Cys303Phe, Cys303Ile, Glu256Gln, Asp181Glu, and Ser230Ala. 
     
     
         63 . The method of  claim 55 , wherein the composition is buffered to pH 7.4. 
     
     
         64 . The method of  claim 55 , wherein the cancer is an arginine auxotrophic cancer.