Largescale Production Of Recombinant Proteins

Protein and polypeptide-based new molecular entities that exhibit desirable phar-macologic activities are further evaluated in preclinical tests in appropriate animal models to characterize pharmacokinetics and toxicology. To do so, the drug candidate must be produced in larger scale, typically in quantities of milligrams to grams, than the amounts required for early studies in cells and in vitro. At this stage the yield of product per host organisms that carry recombinant genes, and the efficiency of product purification, take center stage. Both of these parameters are key determinants of the profit margins of the therapeutic protein product if marketed.

One of the key requirements in producing a given recombinant protein on a large scale is the need to identify host cells with maximum efficiency in producing proteins that are safe and effective at a reasonable cost. Theoretically, if the yield of recombinant protein recovered from each type of cell is equivalent and purification costs are similar, prokaryotic cells with the highest growth rates will be less expensive than eukaryotic cells to produce the protein of interest. In reality, choosing host cells for recombinant protein production is not always a simple or logical process (Box 4.6).

In the hope of being the first to reach the market, pharmaceutical companies often will develop plasmid vectors that can be expressed in multiple hosts. During the early phase of the scale-up process, the efficiency of recombinant protein expression in each host will be optimized, and the purification process for each host system, along with the yield and quality of the product, will be evaluated. A list of host cells and their advantages and disadvantages are presented in Table 4.8. Information regarding the pharmaceutical properties of the recombinant proteins (e.g., glycosylation, which requires post-translational modification) that may influence residence time or distribution to target tissue must also be considered in the selection of host cells.

Only eukaryotic cells are capable of

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