(SARTORIUS STEDIM BIOTECH)
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Biomanufacturing of a biopharmaceutical blockbuster product such as a monoclonal antibody or a plasma-derived product is characterized
by high production costs. These costs are mainly attributed to the high capital investments into a current good manufacturing
practices (CGMP) biotechnology facility, which can exceed $1 billion (1). There is, however, ongoing downward pressure on
treatment costs as governments and managed-care groups focus on ways to reduce spending on healthcare. In addition, there
is downward pressure on the cost of goods (COGs) from companies marketing such products to enhance revenue streams (2).
New manufacturing concepts and platforms are therefore required to meet commercial expectations for existing and upcoming
new drugs. Product yields must be improved and the process must use manufacturing space and resources more efficiently. Reevaluating
existing purification schemes and redefining the process may reduce the COGs by as much as 50% (2).
The concept of a generic technology platform for the purification of multiple drug candidates enables faster drug development
and earlier definition of the commercial process and facilitates the effective utilization of manufacturing space. A key element
to consider for any new biopharmaceutical manufacturing platform is the use of disposable equipment (disposables). This practice,
together with the requirement for a viral clearance strategy, has led to the development of disposable nanofiltration technology.
Using disposable nanofilters within the downstream process has been proven to reduce capital expenditure for housings and
reduce labor, cleaning, and validation costs. Disposable nanofilters are capable of turning fixed costs into variable costs
with single-use membrane technology. These costs become relevant as cash-out only when the plant is in operation and the nanofiltration
step is up and running.
Purification process
Figure 1: Purification process overview. (Figure 1 courtesy of the authors.)
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The data presented in this article outline the challenges of integrating a large-scale SP Sepharose column ("Resolute" 1000
mm DAP/M column, Pall UK, Portsmouth, UK) with a disposable nanofiltration setup, to meet flow expectations of 1000 L/h and
batch volumes of 10,000 L. This chromatography and nanofiltration process is used to purify an ovine-derived polyclonal antibody
product at Protherics UK (3). The technology platform for purification of this polyclonal antibody fragment is outlined in
Figure 1.
Figure 2: The authors with a Pall "Resolute" 1600 mm DAP/M column. (Figure 2 courtesy of Protherics UK.)
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The IgG is captured by an MEP "Hypercel" chromatography gel (Pall UK) in a Resolute 1600 mm DAP/M column (Pall UK) (see Figure
2). The captured IgG is then digested with papain and diafiltered. The resulting Fab is further purified and polished by Q-Sepharose
FF (GE Healthcare, Chalfont St. Giles, UK) and SP Sepharose chromatography steps. The purified Fab fragment is then subject
to nanofiltration, followed by concentration and drug formulation.
For this ovine-based product, the nanofiltration step is the cornerstone of the virus clearance strategy, targeting small
nonenveloped viruses. Regulatory expectations are that the nanofiltration step provides robust and efficient removal of small
nonenveloped viruses (porcine parvo virus [PPV] is the model virus being used) and achieves a 4-log10 (or greater) reduction.
When developing a manufacturing platform for this product, disposability was a prime consideration to ensure simplification
of the process, reduction of labor, increased flexibility, and elimination of cross-contamination. The 20-nm nanofiltration
was introduced at the end of the purification process where the purity of the product is the highest and filter blockage due
to contaminants is the lowest. Protein concentration at this stage is 2–6 mg/mL, and pH is 7.0–7.8.
