Structure-Based Site-Specific PEGylation of Fibroblast Growth Factor 2 Facilitates Rational Selection of Conjugate Sites

Abstract

Polyethylene glycol modification (PEGylation) can enhance the pharmacokinetic properties of therapeutic proteins by the attachment of polyethylene glycol (PEG) to the surface of a protein to shield the protein surface from proteolytic degradation and limit aggregation. However, current PEGylation strategies often reduce biological activity, potentially as a result of steric hindrance of PEG. Overall, there are no structure-based guidelines for selection of conjugate sites that retain optimal biological activity with improved pharmacokinetic properties. In this study, site-specific PEGylation based on the FGF2-FGFR1-heparin complex structure is performed. The effects of the conjugate sites on protein function are investigated by measuring the receptor/heparin binding affinities of the modified proteins and performing assays to measure cell-based bio-activity and in vivo stability. Comprehensive analysis of these data demonstrates that PEGylation of FGF2 that avoids the binding sites for fibroblast growth factor receptor 1 (FGFR1) and heparin provides optimal pharmacokinetic enhancement with minimal losses to biological activity. Animal experiments demonstrate that PEGylated FGF2 exhibits greater efficacy in protecting against traumatic brain injury-induced brain damage and neurological functions than the non-modified FGF2. This rational structure-based PEGylation strategy for protein modification is expected to have a major impact in the area of protein-based therapeutics.

Keywords: FGF2; FGF2-FGFR-heparin; site-specific PEGylation; structure-based PEGylation.