With the rapid advances in the field of biotechnology during the last decade, many peptides and proteins have been produced and evaluated for therapy of various diseases, including cancer. However, rapid clearance and the possibility of immunogenicity after the in vivo administration of these biotechnology-driven products have impeded their marketing. To circumvent these problems, synthetic and natural polymers such as polyethylene glycol (PEG) and dextrans, respectively, have been covalently attached to proteins, and some of these protein-polymer conjugates have shown promising therapeutic results. The conjugation of proteins with polymers usually causes a reduction in the recognition of the protein by the immune system, resulting in a decrease in protein clearance and immunogenicity. Most of the protein-polymer conjugates retain the pharmacologic activity of the protein, although to a lesser extent than the native protein. Additionally, in most of the examples in the literature, a significant increase in the plasma half life of the protein more than compensates for any reduction in the pharmacologic effects of the polymer-protein conjugates. Therefore, polymer conjugation in most cases would result in a net increase in the pharmacologic activity of the protein.
The intent of this article is to review the pharmacokinetics and pharmacodynamics of proteins conjugated to PEG which is one of the most widely used synthetic polymers for protein conjugation
