BIOPHARMACEUTICAL MANUFACTURING - Risk Management Applications in Pharmaceutical and Biopharmaceutical Manufacturing - page 337

temperatures, long hold times, inappropriate processing times, and degradation
due to shear. Given the fragility and the high value of the cell-derived products,
cell separation must be accomplished with minimum cell damage, degradation,
and loss of product activity during the recovery process. Therefore, thorough
process/equipment risk assessments need to be performed for quick and efficient
recovery and to mitigate product loss.
Inefficient Purification Conditions Downstream processing is used for the
removal of a variety of process- and product-related impurities, typically
via efficient, orthogonal, and robust purification processes. However, many
downstream processes often consist of only two or three separation steps, and
usually avoid conditioning steps such as ultrafiltration/diafiltration (UF/DF) for
buffer exchange to reduce the total number of processing steps. This strategy
can significantly increase the risk that contaminants are not completely removed
during the purification process, especially if complex microbial feedstocks or E.
coli lysates are used as starting materials. In addition, a typical chromatographic
purification step has numerous operating parameters that can impact its
performance. Therefore, it is important to apply risk analysis at the process
characterization stage to identify key process parameters that may impact the
purification process and product quality.
Viral Contamination The major concern when using mammalian cell lines for
production of a biotechnology product is the risk of viral contamination. Such
contamination could have serious clinical consequences and can arise from source
cell lines from infected animals, virus endogenous to the cell line, use of con-
taminated reagents or equipment, and improper handling of the cell line.
There are three complementary approaches that are generally employed to
reduce the risk of viral contamination. Specifically, these approaches are as fol-
lows:
• Selecting and testing cell lines and raw materials (including cell culture
media and animal-derived raw materials) for the absence of undesirable
viruses that may be infectious and/or pathogenic for humans
• Assessing the capacity of the manufacturing process to inactivate or remove
infectious viruses.
• Testing the product at appropriate stages during production for the absence
of contaminating infectious viruses.
The selection of a cell line with undetectable virus levels and the use of con-
taminant free raw materials are essential for the production of therapeutic proteins
by cell culture. However, even with such a cell line, the absence of viral con-
tamination is not guaranteed, so the downstream processing must demonstrate
sufficient viral clearance. Viral inactivation (by acidic pH conditions and/or by
addition of detergent) along with virus removal (by centrifugation or filtration)
are methods generally used to minimize the risk of viral contamination. In addi-
tion, viral clearance can be demonstrated through viral spiking and challenge