A solid-phase PEGylation strategy for protein therapeutics using a potent FGF21 analog

Fibroblast growth factor 21 (FGF21) is an endocrine-acting hormone that has the potential to treat metabolic diseases, such as type 2 diabetes and obesity. Development of FGF21 into a therapeutic has been hindered due to its low intrinsic bio-stability, propensity towards aggregation and its susceptibility to in vivo proteolytic degradation. In order to address these shortcomings, we've developed recombinant human FGF21 variants by strategically introducing cysteine residues via site-directed mutagenesis, and have also developed a solid-phase nickel affinity PEGylation strategy, whereby engineered, surface-exposed cysteine residues of immobilized proteins were used as a platform to efficiently and site-selectively conjugate with PEG-maleimide. The engineered PEGylated FGF21 conjugates retained its biological functions, as well as demonstrated an increase in half-life by over 211.3 min. By demonstrating the biological activity of the FGF21 analog as a prototype, we have also provided a “generalized” solid-phase approach to effectively increase serum half-life of protein therapeutics.