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CHAPTER OBJECTIVES

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  • Compare and contrast biologic and small-molecule drugs in terms of their mechanism of action, design, and development hurdles.

  • Discuss why biologic drugs may require delivery and/or targeting systems.

  • Describe the main methods used to deliver and target biologic drugs and give examples.

  • Explain the difference between active and passive targeting.

  • State whether generic biologics exist, and if not, describe why.

  • Explain in general terms the pharmacokinetic differences between small-molecule and biologic drugs and why these differences exist.

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Many diseases occur as a result of variability in the genes involved in producing essential enzymes or proteins in the body. The genes are coded in deoxyribonucleic acid (DNA), helical double-stranded molecules folded into chromosomes in the nucleus of cells. The Human Genome Project was created more than a decade ago to sequence the human genome. This national effort is continuing to yield information on the role of genetics in congenital defects, cancer, disorders involving the immune system, and other diseases that have a genetic link.

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The ever-evolving genetic basis of disease will continue to provide novel opportunities for the development of new drugs to treat these disorders, particularly in the field of biotechnology. The discovery of recombinant DNA (rDNA) technology and its application to new drug development has revolutionized the biopharmaceutical industry. Previously, the pharmaceutical industry relied on the use of relatively simple small drug molecules to treat disease. Modern molecular techniques have changed the face of new drug development to include larger, more sophisticated and complex drug molecules. These large biopharmaceuticals have enormous potential to treat disease in ways previously unavailable to small drug molecules. As a result, biotechnology, or the use of biological materials to create a specific product, in this case pharmaceuticals, has become an important sector of the pharmaceutical industry and accounts for the fastest growing class of new drugs in the market. Nucleic acid, protein and peptide drugs, and diagnostics are the main drug products emerging from the biopharmaceutical industry.

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BIOTECHNOLOGY

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Protein Drugs

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The human genome produces thousands of gene products that prevent disease and maintain health. Many may have therapeutic applications if supplemented to normal or supraphysiologic levels in the body. Most of the biologic molecules listed in Table 20-1 are normally present in the body in small concentrations but are used for certain therapeutic indications. For example, some diseases such as insulin-dependent diabetes result from insufficient production of a natural product, in this case insulin. For these patients, the treatment is to supplement the patient’s own insulin production with recombinant human insulin (eg, Humulin). Similarly, human recombinant growth hormone (Protropin, Nutropin) and gluco­cerebrocidase (Ceredase, Cerezyme) are used to treat growth hormone deficiency and Gaucher’s disease, respectively.

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Table Graphic Jump Location
TABLE 20-1A Sample of Approved Recombinant Drugs

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