Patent ID: 8507245

Claim:
A pharmaceutical composition for treating an arginine-dependent disease comprising a polyethylene glycol-arginase conjugate having a polyethylene glycol moiety covalently attached to a genetically-modified human arginase, wherein said genetically-modified human arginase has a single amino acid position for covalently attaching to the polyethylene glycol moiety, wherein said polyethylene glycol-arginase conjugate has a serum circulation half-life higher than the serum circulation half-life of pure, unmodified human arginase, wherein said polyethylene glycol-arginase conjugate has decreased immunogenicity compared to the immunogenicity of pure, unmodified human arginase, wherein said single amino acid position is sufficiently far from the active site of the genetically-modified human arginase such that the polyethylene glycol attachment does not interfere with the active site, wherein the genetically-modified human arginase comprises SEQ ID NO: 6 and the single amino acid position for the attachment of polyethylene glycol is position 45 of SEQ ID NO: 6 (Cys 45 ).