ABSTRACT
Most antibody manufacturers currently use a three-column platform comprising Protein A affinity chromatography for product
capture, followed by anion exchange (AEX) chromatography in flow-through mode to extract negatively charged contaminants,
and then cation exchange (CEX) chromatography or hydrophobic interaction chromatography (HIC) in retention mode to remove
positively charged contaminant species. This article presents a new process that uses membrane adsorbers for both flow-through
and retention steps in antibody polishing. The process shows that a membrane adsorber in retention mode can be used efficiently
in a commercial antibody manufacturing process.
SARTORIUS STEDIM BIOTECH GMBH
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Antibodies have been at the forefront of the biopharmaceuticals market for most of the last decade, and judging by the hundreds
of antibody-based products at all stages of the clinical pipeline, these will continue to dominate the market for the foreseeable
future.1 About half of all biopharmaceutical process trains have been designed for the production of monoclonal antibodies, and the
industry has focused on a small number of platform technologies optimized to squeeze every last milligram of product from
the feedstream.2 The vast majority of companies currently producing monoclonal antibodies (MAbs) use a three-column platform approach comprising
Protein A affinity chromatography for product capture, followed by anion exchange (AEX) chromatography in flow-through mode
to extract negatively charged contaminants such as host cell protein (HCP), endotoxins, host DNA, and leached Protein A, and
then cation exchange (CEX) chromatography or hydrophobic interaction chromatography (HIC) in retention mode to remove positively
charged contaminant species including residual HCP and product aggregates.
One disadvantage of this approach is that as cell culture titers increase, the downstream process becomes a bottleneck and
costs increase in line with production scale, i.e., there is no economy of scale. The industry has been evaluating strategies
to address such capacity and cost issues and has investigated different approaches, some at the low-technology end of the
spectrum and others at the high-technology end. Among the latter, membrane adsorbers offer a flexible and cost-effective solution
to some of the bottlenecks in antibody manufacture and are gaining acceptance as an alternative to traditional resin-based
chromatography, particularly because they eliminate cleaning and validation costs, provide flexibility in production train
design and scale-up, and can be used in viral clearance steps.3–5 Membrane adsorbers are thin, synthetic, microporous or macroporous membranes that are derivatized with functional groups
akin to those on the equivalent resins. The membranes are stacked 10–15 layers deep in a comparatively small cartridge, generating
a much smaller footprint than columns with a similar output. This reduces buffer consumption but increases the flow rate even
though the bed height is much lower and there is a reduced pressure drop. Despite the increased flow rate, adsorption is efficient
because the transport of solutes to their binding sites in a membrane adsorber occurs mainly by convection, while pore diffusion
(the predominant mechanism in resins) is minimal. These benefits reduce process times to less than 10% of those associated
with traditional stainless-steel columns.6 Another important advantage is the linear scale-up for parameters such as frontal surface area, bed volume, flow rate, and
static binding capacity, while normalized dynamic binding capacity remains fairly constant at 10% or complete breakthrough.7 Scaling up process-scale operations therefore is a lot less troublesome than would be the case for standard resins, making
the processing of up to 100-kg batches of antibodies a realistic proposal.8
