Patent ID: 7470779

Claim:
A process for decreasing a level of aggregate of pegylated protein isoforms, wherein the pegylated protein is a growth hormone antagonist, said process comprising the steps of: (a) providing said pegylated protein isoforms; and (b) separating said pegylated protein isoforms by anion exchange chromatography using an anion exchange resin under sufficient conditions to decrease said level of said aggregate, wherein said level of said aggregate is less than 6% by weight based on the total weight of said isoforms and said aggregate, and wherein said pegylated protein isoforms comprises one or more of the isoforms PEG-1, PEG-2, PEG-3, PEG-4, PEG-5, PEG-6, PEG-7, PEG-8, and PEG-9 and any aggregate, trisulfide impurity and des-phe impurity thereof, and wherein said human growth hormone antagonist is B-2036.