Browsing through the program for BPI Boston 2015 I was really excited to see Abhinav Shukla is chairing a session in the Recovery & Purification track on novel approaches to non-chromatographic purification. The session will be on Tuesday afternoon starting at 1.25pm.
Like I explained in last week’s blog the subject it’s a subject that is particularly to my heart as it’s the field I worked in as a fresh engineer in my first role upon completing my doctorate.
Bottlenecks in downstream processing
Packed-bed chromatography is, of course, the workhorse of large-scale therapeutic protein purification. The selectivity of chromatography steps especially when operated together as part of an integrated downstream purification train allows very high levels of drug purity to be achieved ensuring patient safety.
The trade-off from a method like this which has such a great ability to resolve different molecular species to give a pure product is that capacity and throughput can be compromised. This was not such an issue during the early days of the industry but as it has developed and bioreactor productivity has increased at a near exponential rate the reliance on chromatography has arguably lead to bottlenecks in purification processes.
The cost of Protein A chromatography
For some within the industry the greatest concern is around Protein A affinity chromagraphy which is an extremely common capture step for monoclonal antibodies once harvested from bioreactors. The extremely high selectivity of Protein A resin means it has a somewhat lower capacity than some alternatives and its high cost of manufacture is reflected in its cost. Though significant advances have been made in Protein A resin technology over the past 20 years there is still significant interest in finding a suitable alternative. The cost of such a consumable means it is imperative biomanufacturers must take care when using and storing the resin to maximize its lifetime.
Novel methods for therapeutic protein purification
Elastin-like polypeptides (ELP) are fascinating biopolymers that will reversibly transition from soluble molecules to insoluble form at relatively low temperatures. A modest temperature increase will allow an ELP-tagged protein to precipitate out of solution where it can be purified from contaminants using a traditional solid-liquid separation technique such as centrifugation or hollow fibre microfiltration. Resolubilization into a desired solvent or buffer will occur when the temperature of the suspended purified protein is reduced. A great description of the method for purifying ELP-tagged proteins without recourse to chromatography is described in a publication from Ashutosh Chilkoti and others of Duke University.
Author of the 2013 article ‘Emerging Challenges to Protein A’ (BioProcess International. Oct 1, 2013) Pete Gangnon is scheduled to present at the session and hopefully will be sharing more insights into highly innovative antibody purification process he describes in the article. Gangnon highlights two techniques used in combination with one another, firstly chromatin-directed clarification followed by an approach called steric exclusion chromatography which uses polyethylene glycol and hydrophilic particle surfaces. These techniques used with a Capto Adhere chromatography step to complete the purification process gave yields of over 80% while reducing host cell protein levels to <1ppm and aggregate to <0.1%.
What is your experience?
Have you tried non-chromatographic purification methods? How successful was it? Do you think that packed-bed chromatography may have had its day?
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