Quality by Design (QbD) implementation requires more-extensive experimentation to be able to establish the design space for
the process and the product. With the biotechnology companies under pressure to contain cost of manufacturing, the use of
high-throughput tools has emerged as a necessary enabler of QbD.
The biotechnology industry is gradually adopting the elevated regulatory expectations that have been laid out via initiatives
such as the Quality by Design (QbD) and Process Analytical Technology (PAT) in the past decade (1–4). This requires enhanced
process and product understanding that comes from a more extensive experimentation than that which traditionally has been
performed. Parallel to these rising expectations, the biopharmaceutical industry has been under increasing scrutiny and pressure
to contain the cost of healthcare, especially in developed economies. This has renewed the focus of process development efforts
toward cost reduction and efficiency improvement. There is a growing need for technologies that can provide us with the required
data (information) within the constraints on resources, time, and cost that exist at biopharmaceutical companies today. High-throughput
process development tools and approaches fit the bill and appear to offer a solution to this challenge.
Advances in upstream process development leading to increases in fermentation and cell culture titers have shifted the bottleneck
of process development to downstream processing of biologicals. Chromatography is perhaps the most significant unit operation
in downstream processing of biomolecules, often the primary step for purification. Simplicity of the operation, easy scaleup,
cost effectiveness, and robust performance are some of the advantages associated with chromatographic purification. However,
optimization of chromatography steps is often a resource- and time-intensive task, and it involves identification of the main
effects of the various process parameters. Furthermore, interactions of the process parameters have significant impact on
product quality and process consistency. A high-throughput process development (HTPD) platform involving use of miniaturized
instrumentation coupled with automated liquid handling devices provides a parallel and efficient way for process development
(5).
This column installment aims to provide an overview of the various HTPD tools and approaches that are commercially available
today. We hope that this will be of interest to the practitioners in academia and industry that are engaged in process development
of biotechnology products. We also present a case study to illustrate practical applications of these approaches.
The Role of Chromatography in Bioprocessing
Purification methods for therapeutic biotechnology products are focused primarily on separation of the various entities that
are present at the microbial fermentation or mammalian cell culture stage of process development. These include product modifications
such as PEGylation, glycosylation, and acylation; undesirable host cell–related modifications such as truncation, acylation,
and methylation; and undesirable process modifications such as aggregation, oxidation, and deamidation. Furthermore, there
are numerous host cell–related (host-cell proteins, DNA, viruses, and so forth) and process-related (antifoaming agents, extractables,
leachables, and so forth) impurities that may be present in the final product. Each of these species can impact the safety
or efficacy of the biotech product, and hence it is critical for the product to have sufficiently high purity and for the
process to consistently meet the quality expectations (6).
Table I: Modes of action and significant process parameters that affect different types of chromatography
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Process chromatography has remained the mainstay for purifying and separating the product from the above-mentioned variants
and impurities. The mechanistic basis of separation can be differential ionic or hydrophobic interactions or a combination
of both. Size-based separations can also be performed. Table I lists the different types of chromatographic separations based
on the mode of action, along with some of the key process parameters that impact their performances. A large variety of modes
of action is available in the commercial market, and for each mode of action, there are many resins available from each of
the major vendors of chromatography media. This variety provides practitioners with enormous flexibility in choosing the optimal
media for a given application, and it is a key reason why chromatographic steps have established themselves as the workhorses
of downstream processing of biological molecules.
Chromatography is performed most commonly in a column format, where the column is packed with spherical beads (resins). More
recently, membrane chromatography has emerged as an alternative that has been shown to work for a subset of the applications.
The latter involves use of synthetic microporous or macroporous membranes as chromatography media and offers low pressure
drop along with reduced radial and axial dispersion, in comparison to traditional chromatography (7).
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