Glycine rich sequences with pharmacokinetic enhancing properties of PEG polymers

DESCRIPTION (provided by applicant): Protein drugs have been approved for many therapeutic indications and represent a rapidly growing segment of the pharmaceutical industry. However, many approved protein drugs and candidates in development fail to reach their potential efficacy due to suboptimal pharmacokinetic properties and immunogenicity concerns. These properties include short circulating half-lives, short shelf lives, low solubility, rapid kidney clearance and susceptibility to proteolytic degradation. The modification of proteins with hydrophilic chemical polymers like polyethylene glycol (PEG) is a clinically validated approach to addressing these limitations. However, the challenges associated with chemical modification procedures required for the attachment of these polymers present significant challenges. Our ultimate goal is to generate amino acid sequences that mimic the physiochemical properties of hydrophilic chemical polymers like PEG. Our proposal is based on the observation that glycine rich sequences (GRS) which contain few hydrophobic amino acids will not fold into compact 3-dimensional structures but will adopt random conformations with large hydrodynamic radii similar to PEG. We hypothesize that they will confer similar pharmacokinetic improvements when attached to therapeutic proteins. These sequences can be attached to proteins using conventional recombinant technology and thus completely obviates the need for chemical modifications steps. We have synthesized a 198 amino acid glycine rich sequence based on sequences that occur in human proteins. We aim to express this protein and systematically test its physiochemical and biological properties relevant to pharmacokinetic enhancement. Our specific aims are: 1) Produce 5 mg of a purified GRS protein in E. coli expression system for downstream characterization and studies. 2) Characterize serum stability, protease resistance and biophysical properties of the GRS protein. 3) Characterize plasma pharmacokinetics and immunogenic potential of the GRS protein in animal models. In Phase II, we will perform detailed optimization of GRS for high-level expression, plasma half-life extension and reduced immunogenicity. We aim to advance optimized GRS which are fused to pharmaceutically active proteins like interferon-alpha or G-CSF into animal and clinical studies. Our ultimate goal is to validate and make this method readily applicable to therapeutic proteins. Our project aims to generate glycine rich sequences that can be attached recombinantly to therapeutic proteins to improve their pharmacokinetic properties. This approach would circumvent the difficulties associated with the modifying proteins with hydrophilic polymers like PEG.