Producing Recombinant Protein Biopharmaceuticals

Immediate release tablets are formulated to release the (API) as soon as possible to hasten absorption. Modified release formulations release the API at a controlled rate. Modified release formulations can be classified into controlled release and extended release formulations. The intention of these formulations is to allow a reduction in dosing frequency or diminish the fluctuation of drug levels on repeated administration compared with that observed with the immediate release form of the drug. 

As Walsh (2003) noted, yeast cells (particularly Saccharomyces cerevisiae) have several characteristics that make them useful production systems for recombinant biopharmaceuticals  

Approved therapeutic proteins are used in various conditions, including diabetes, bone marrow transplantation, and vaccination. 

The genetic manipulation of animal cells allows the production of therapeutic proteins in animal cell culture systems. Mammalian cells such as Chinese hamster ovarian cells and baby hamster kidney cells are commonly used. These mammalian hosts produce recombinant proteins that have almost identical properties to those made by human cells. However, the use of mammalian cells does have disadvantages. As noted earlier, they are expensive to use. This is influenced by their more complex nutritional requirements, their slower growth, and their increased susceptibility to physical damage (Walsh, 2003). 

The process of fermentation is used in various industrial settings, including the production of protein biopharmaceuticals. This process involves growing cells and microbes for the production of the desired product in large quantities under well-specified conditions. Fermentation procedures are typically optimized in a systematic manner in a pilot plant with a fermentor with a capacity on the order of 30 liters, and engineers determine the best strategies to develop fermenters with a capacity on the order of 100,000 liters (Ho and Gibaldi, 2003). 

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Many of the initial biopharmaceuticals approved were simple replacement proteins (e.g. blood factors and human insulin). The ability to alter the amino acid sequence of a protein logically coupled to an increased understanding of the relationship between protein structure and function (Chapters 2 and 3) has facilitated the more recent introduction of several engineered therapeutic proteins (Table 1.3). Thus far, the vast majority of approved recombinant proteins have been produced in the bacterium E. coli, the yeast S. cerevisiae or in animal cell lines (most notably Chinese hamster ovary (CHO) cells or baby hamster kidney (BHK) cells. These production systems are discussed in Chapter 5. 

The expression of recombinant proteins in cells in which they do not naturally occur is termed heterologous protein production (Chapter 3). The first biopharmaceutical produced by genetic engineering to gain marketing approval (in 1982) was recombinant human insulin (tradename Humulin ), produced in E. coli. An example of a more recently approved biopharmaceutical that is produced in E. coli is that of Kepivance, a recombinant keratinocyte growth factor used to treat oral mucositis (Chapter 10). Many additional examples are provided in subsequent chapters. 

This section briefly overviews how biopharmaceutical substances are produced in a biopharmaceutical/biotech manufacturing facility. As the vast bulk of biopharmaceuticals are proteins synthesized in recombinant prokaryotic (e.g. E. coli) or eukaryotic (e.g. mammalian cells) production systems, attention will focus specifically upon these. 

Although numerous cell lines have been screened for their efficiency as a host system for recombinant protein production, only a few have shown favorable properties for the expression of biopharmaceuticals (Hauser, 1997). Regulatory and economic issues for large-scale production and the intended application of the recombinant protein (diagnosis, therapy, etc.) have to be carefully considered (Makrides and Prentice, 2003). Three mammalian cell lines are now commonly used by the pharmaceutical industry Chinese hamster ovary (CHO) cells, the murine myeloma SP2/0 and the NS0 cell line (see Table 3.1). These cell lines have been used to produce 11 of 21 therapeutic products approved from 1996 to 2000 (Chu and Robinson, 2001). 

Any mammahan ceU line has the basic machinery to express and secrete recombinant protein, and huge numbers of ceU fines with suitable growth properties are available from various tissues and species. The smaU number of cell fines industrially used for manufacturing is, therefore, surprising. Two hamster cell fines, the Chinese hamster ovary cell fine (CHO) and the baby hamster kidney cell fine (BHK), and two geneticaUy related mouse cell fines, the myeloma NSO derived from BALB/c mice, and the hybridoma SP2-0, a fusion of the myeloma with B cells from the same mouse strain, supply most of the mammalian ceU-based biopharmaceuticals, whether marketed or still under development Once commonly accepted as producers, a large body of information about... 

This chapter reviews progress and challenges in the area of production of recombinant proteins, in particular biopharmaceuticals, in plants. Different expression platforms are summarized, including those based on the use of transgenic, transplastomic or transfected plants as production hosts. The quality and yield of recombinant proteins produced in and purified from plants, as well as progress in clinical trials with plant-made pharmaceutical proteins are described. The advantages, limitations and biological safety aspects of plant-based production of biopharmaceuticals are discussed. 

The 1990s and the beginning of the twenty-first century mark a new era of transgenic biopharmaceutical production in plant and animal cells. Researchers all over the world explore various ways to produce biopharmaceuticals in large volumes at a low cost. Scientists at Ventria Bioscience have developed a protein expression system, ExpressTec, which expresses recombinant proteins, enzymes and sec-... 

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