Patent ID: 8586710

Claim:
A process for gram scale production of PEG-r-metHuG-CSF comprising conjugating r-metHuG-CSF in storage buffer solution having molarity in the range of 10 mM to 50 mM comprising a polyol having the formula C n H 2n+2 O n where n is from 3 to 6, or a carbohydrate, or a derivative selected from the group consisting of methyl glycosides, glucoronic acids, amino sugars and N-acetyl glucosamines thereof at pH 5.0 to a PEG aldehyde selectively at a free amine moiety at the N terminal end on the r-metHuG-CSF in presence of a reducing agent characterized in that the PEG aldehyde is added in stoichiometric molar ratio of 2.5 relative to r-metHuG-CSF, wherein the monopegylated product is having a purity of at least 80% and the other molecular size impurities are less than 10%.