Derivatives 1 and 2 are acylating reagents, whereas derivatives 3–11 contain reactive acyl groups referenced as acylating agents. Protein modification with all of these agents results in acylated amine-containing linkages: amides derived from active esters 3–6 and 11 or carbamates derived from 7–10. Alkylating reagents 12 and 13 react with proteins forming secondary amine conjugation with amino-containing residues. As represented in Figure 7(a), tresylate

12 alkylates directly, while acetaldehyde Inhibitors,research,lifescience,medical 13 is used in reductive alkylation reactions. Numbers 1–13 represent the order in which these activated polymers were introduced [6, 36]. Figure 7 (a) mPEG-based protein-modifying methods. Protein modification with all of these agents results in acylated amine-containing linkages: amides, derived Inhibitors,research,lifescience,medical from active esters 3–6 and 11, or carbamates, derived from 7 to 10. Alkylating reagents 12 and … Adagen (pegademase bovine), used for the treatment of severe combined immunodeficiency disease (SCID), is developed using PEG polymer. PEG chemistry may results in side reaction or weak linkages upon conjugation with polypeptides and low-molecular-weight linear PEGs (≤12kDa). It is prepared by first reacting mPEG (Mw 5000Da) with selleck inhibitor succinic anhydride spacer. The resulting carboxylic group of Inhibitors,research,lifescience,medical PEG succinic acid is activated with N-hydroxysuccinimide (NHS) by

using carbodiimide coupling agents. The NHS group is displaced by nonspecific reaction with nucleophilic amino acid Inhibitors,research,lifescience,medical side chains [37]. Another PEG prodrug of Enzon (Oncaspar®) is also synthesized by the use of PEG succinimidyl succinate [37]. The PEG ester and thioesters are highly susceptible to hydrolysis and thus modification occurs primarily at the amines forming amides. The PEGylated CERA protein conjugate, a product of Hoffmann-LaRoche (Mircera) is synthesized by attachment of an NHS-activated monomethoxy PEG butanoic acid to lysine 46 and 52 on erythropoietin (EPO) [38, 39]. Also, Hoffman-La Inhibitors,research,lifescience,medical Roche, Inc.’s peginterferon α2a (Pegasys) is prepared by conjugating PEG with the

side chain and N-terminal amine groups of lysine spacer, forming a biscarbamate. Then on activation of the carboxylic acid with NHS, it helps the of branched PEG chain linker form stable amide bonds with 11 possible lysine residues. Monosubstituted conjugate can also be synthesized by the same reaction process by limiting the amount of PEG chain linker used in the conjugation step. While, PEG-Intron by Schering-Plough (peginterferon α2b) is a covalent conjugate of interferon alfa-2b linked to a single unit of Mw 12000 PEG [40] is a covalent conjugate of interferon alfa-2b linked to a single unit of Mw 12000 PEG. The interferon conjugates are synthesized by condensing activated PEG, wherein a terminal hydroxy or amino group can be replaced by an activated linker, and reacting with one or more of the free amino groups in the interferon (Figure 8).