No need to apologize. Amgen has several unexpired G-CSF PEGylation patents in the US 5,824,778, US 5,824,784 (the one you've found), US 6,166,183. From a quick look i suspect they only cover PEGylation when PEG molecule is attached to any amino acid via a carboxyl group at the N-terminus of the protein. Ratiopharm uses a different PEGylation method. See also #msg-65405618