Marketed recombinant proteins

When sufficiently high levels of expression and protein accumulation are achieved, efficient downstream processing protocols must be developed to insure product quality and the economic feasibility of production. As the demand for safe, recombinant pharmaceutical proteins continues to expand, the market potential of plant-produced recombinant proteins is considerable. Molecular farming can produce recombinant proteins at a lower cost than traditional expression systems based on microbial or animal cell culture, and without the risk of contamination with human pathogens. 

Recombinant proteins with unique properties can potentially generate new markets and penetrate into existing markets if they can be supplied on a large scale. An ideal system would produce the safest biologically active material at the lowest cost, and would be used in combination with an inexpensive and simple purification process. So far, there have been several examples of the high-yield production of recombinant proteins in transgenic crop plants, mainly in the area of molecular medicines such as antibodies, enzymes and vaccines [45, 48-50]. Modern agricultural practices offer... 

Mammalian cell suspension cultures are the preferred choice for large-scale recombinant protein production in stirred-tank bioreactors. The most widely used systems are Chinese hamster ovary (CHO) cells and the murine myeloma fines NSO and SP2/0. In half of the biological license approvals from 1996-2000, CHO cells were used for the production of monoclonal antibodies and other recombinant glycosylated proteins, including tPA (tissue plasminogen activator) and an IgGl fusion with the tumor necrosis factor (TNF) receptor, the latter marketed as Enbrel [7]. 

After the approval of the first product, recombinant insulin, in 1982, progress in the development of new recombinant protein pharmaceuticals was slow ([10], Fig. 17.1). The number of biotechnology-derived drugs and vaccines approved by the US Food and Dmg Administration (FDA) has increased significantly only since 1995. More recently, sales of biologies have skyrocketed, e.g. from 900 million in 1999 to an estimated 3.5 billion in 2001 for monoclonal antibodies [11]. The annual global market for biopharmaceuticals is estimated to have increased from 12 billion US to 30 billion US in 2003 [12]. 500 candidate biopharmaceuticals are undergoing clinical evaluation and over one hundred protein-based therapeutics are in the... 

The pharmaceutical industry anticipates that molecular farming will save time and money compared to traditional production systems. Because of bottlenecks and production costs, many biologies will never reach the market and the intended patients, or will do so only with great delays, if molecular farming fails. However, a number of points in the production of plant-derived proteins have yet to be addressed appropriately. In order to fulfill all requirements and obtain regulatory approval, the questions outlined above have to be answered for each recombinant protein. Last but not least, economical factors will decide whether molecular farming in plants will increase the number of available products. 

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. 

All pharmaceuticals marketed in the United States, including biotechnology products, must be proven safe and effective for their intended use. The FDA requires that all recombinant proteins and other biotechnology products be produced by a manufacturer holding a certified Biologic License Establishment (BLE). The pharmaceutical company is required to collect safety and efficacy data, first in animal studies and subsequently in clinical trials. This information is submitted in a new drug... 

Many recombinant proteins that are not antibodies are also on the market for distinct applications (see Chapter 16). Examples are factor VIII for hemophilia A treatment (Bayer, 1993, produced from BHK cells), erythropoietin as an anti-anemic agent (Amgen, 1989, produced from CHO cells) and /1-interferon for the treatment of multiple sclerosis (Biogen and Serono, 1996, produced from CHO cells). 

The biotechnology industry has evolved significantly since the introduction in 1982 of human insulin synthesized in Escherichia coli—the first Food and Drug Administration (FDA)-approved recombinant therapeutic agent in the United States. Since then, over 75 other recombinant proteins have been introduced. The list is comprised of cytokines, hormones, monoclonal antibodies, and vaccines. There are more than 1100 companies competing for this market, and the current sale of these products comprises approximately 10% of the sales of all therapeutic products sold in the United States. One such product, erythropoietin, an erythropoiesis-stimulating factor also known... 

Currently, 60 to 70 percent of all biotherapeutics based on recombinant proteins are produced in cultivated mammalian cells.8 Mammalian systems are often preferred over other hosts, such as bacteria, plants, and yeast, because of their capability for proper protein folding, assembly, and posttranslational modification. The quality and efficacy of a protein can thus be enhanced when expressed in mammalian cells. With the recent expansion in the biotherapeutics market, the demand for proteins derived from mammalian cells... 

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