Analytical characterization of in vitro refolding in the quality by design paradigm: Refolding of recombinant human...

Protein based therapeutics dominate most pharmaceutical pipelines today. For a therapeutic product to be effective, it is important that it is in its native form as slight modifications have been known to result in significantly different performance in the clinic. When expressed in hosts such as Escherichia coli, formation of inactive insoluble aggregates of proteins popularly known as inclusion bodies occurs in most cases. This necessitates the need for in vitro refolding to generate the native (and active) form of the therapeutic protein. This paper aims to provide an approach to generate a deeper understanding of refolding of a therapeutic protein and then to use it for its optimal production commercially. Recombinant human granulocyte colony stimulating factor has been chosen as the model protein. Seven orthogonal analytical tools have been used to elucidate the refolding process. By strategically using these tools protein refolding has been segregated into a series of well-defined sequence of events, starting from the unfolded random coil and ending with the uniquely folded metastable state. The study also suggests the choice of tools that can be used to monitor each event. We believe that this paper successfully demonstrates an approach to generate deeper understanding of the protein refolding process as per the expectations laid out in the Quality by Design paradigm.