Process-related impurities host-cell proteins

Bulk and Intermediate Purification primarily for removal of process-related impurities, e.g. reagents, host cell proteins, DNA, endotoxins some product-related impurities common methods ... 

Immunoassays are the most specific and sensitive techniques available for detecting protein impurities. There are two classes of protein impurities that are most often analyzed with these techniques host-cell proteins and protein additives, both of which are process-related impurities. Although protein additives are known entities and therefore amenable to other quantitative... 

Process-related impurities encompass those that are derived from the manufacturing process, that is, cell substrates (e.g., host cell proteins, host cell DNA), cell culture (e.g., inducers, antibiotics, or media components), or downstream processing. Product-related impurities (e.g., precursors and certain degradation products) are molecular variants arising during manufacture and/or storage that do not have properties comparable with those of the desired product with respect to activity, efficacy, and safety. 

Process-related impurities encompass aU possible material that is used during manufacture and which might still be present in the final product These include cell components (e.g., host cell protein, DNA and RNA) and components of the cell culture medium (e.g., antibiotics, inducers, media). In addition, possible downstream-derived components (e.g., enzymes, (bio)-chemical reagents, inorganic salts and solvents) must be considered. Any adventitiously introduced material which is not part of the manufacturing process of either DS or DP is considered as a contaminant. For viral products and processes, special attention is paid to endogenous or adventitious viruses, which should ideally not be present or at least be removed/inac-tivated by the manufacturing process. 

Of these molecular variants, one is the desired product with the desired properties with respect to biological activity and efficacy. Some structurally related variants (referred to as product related ) exhibit similar properties to the desired product and are therefore not considered as impurities. However, there may also be structurally related variants with altered properties with respect to biological activity, efficacy and/ or safety, which must be considered as impurities. In addition to the molecular variants of the protein (or protein-like) product, additional process-related substances may be part of a biotechnological drug substance, e.g., cell culture media, host cell proteins, DNA residuals, solvents, bacteria and/or viruses. This suggests that the determination of purity of these products (which is referred to as purity estimation rather than purity determination ) is a complex analytical issue. A purity estimation consists of both the definition of the heterogeneity of the protein (or proteinlike) product, and the identification and quantitation of product- and process-re-... 

The separation tasks for ion-exchange chromatography differ mainly by the type of expression system used. The most abundant systems are mammalian cells, microbial cells (yeast), and the bacterial organism E. coli. All expression systems have a common feature that they not only generate the target protein but also process related impurities, such as host cell proteins, DNA, viruses, endotoxins. In addition the downstream process has to isolate the active form of the target molecule from all its derivatives, for example, oxidated, deamidated, acetylated forms, dimers, aggregates, and unfolded proteins. 

The ability of the purification process to eliminate product related or host cell derived proteins, nucleic acid, carbohydrates, viruses, or other undesirable impurities, including undesirable media derived and chemical components, must be thoroughly investigated, as well as the reproducibility of the process. 

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