Development of an integrated continuous PEGylation and purification Process for granulocyte colony stimulating factor

PEGylation of therapeutic proteins has long been recognized as a safe and effective approach to enhance pharmacokinetic properties of proteins by increasing the in-vivo half-life and thereby the bioavailability. Despite all the benefits linked to PEGylation, high cost of PEGylated products has hindered accessibility of these products to patients. Continuous processing offers a solution to this predicament with its proven capability to improve economics without sacrificing product quality. In this study, we report the development of an integrated continuous PEGylation and purification process for a therapeutic protein, PEG-GCSF. The methodology to achieve this consisted of developing the batch PEGylation and purification protocols followed by their conversion into an integrated continuous process. A batch process involving rapid and highly productive PEGylation (reaction completion within one hour of reaction time) followed by cation exchange chromatography was developed. Enabling technologies like coiled flow inversion reactor, inline concentrator and counter-current chromatography, were utilized for the successful conversion of the batch process to continuous mode. The final integrated continuous process consisted of continuous PEGylation in a coiled flow inverter reactor followed by four column continuous counter-current cation exchange chromatography. Continuous chromatography was performed in a novel displacement mode, wherein all the multi-PEGylated impurities were removed in the loading flow-through and the pure mono-PEGylated protein was obtained in a single step salt elution. In combination with our previously established GCSF manufacturing train, the end-to-end continuous manufacturing process starting from inclusion bodies to unformulated PEG-GCSF drug substance was successfully run for 12 h. All attributes were found to be consistent over the period of operation with product purity > 99 % and high molecular weight impurities < 0.5 %. We hope that the current study will lay the foundation for implementation of continuous processing as a method to improve manufacturability of PEGylated therapeutic proteins.