J Pharm Pharmaceut Sci (www.ualberta.ca/~csps) 1 (2):48-59, 1998
Biotech Pharmaceuticals and Biotherapy: An Overview
Broadly, the history of pharmaceutical biotechnology includes Alexander Flemings discovery of penicillin in a common mold, in 1928, and the subsequent developmentprompted by World War II injuriesof large-scale manufacturing methods to grow the organism in tanks of broth. Pharmaceutical biotechnology has since changed enormously.
Two breakthroughs of the late 1970s became the basis of the modern biotech industry: the interspecies transplantation of genetic material, and the fusion of tumor cells and certain leukocytes. The cells resulting from such fusionhybridomasreplicate endlessly and can be geared to produce specific antibodies in bulk.
Modern pharmaceutical biotechnology encompasses gene cloning and recombinant DNA technology. Gene cloning comprises isolating a DNA-molecule segment that corresponds to a single gene and synthesizing ("copying") the segment. Recombinant DNA technology, or gene splicing, comprises altering genetic material outside an organismfor example, by inserting into a DNA molecule a segment from a very different DNA moleculeand making the altered material (recombinant DNA) function in living things.
Recombinant DNA technology enables modifying microorganisms, animals, and plants so that they yield medically useful substances, particularly scarce human proteins (by giving animals human genes, for example). This review, however, focuses not on pharmaceutical biotechnologys methods but on its products, notably recombinant pharmaceuticals. It describes various types of biotech pharmaceuticals, their safety and effectiveness relative to the safety and effectiveness of conventionally produced pharmaceuticals, and the regulation of biotech pharmaceuticals.
In the context of this review, "biotechnology" refers to the use of living things or parts of living things to create or modify drugs and other substances; to modify food crops and other macroscopic organisms; or to adapt microorganisms to agricultural, medical, or other purposes.
Biotechnology encompasses such disparate processes as industrial fermentation, gene therapy, and cloning. The medical repercussions of advances in biotech have been impressive, but the implications of those advances for human health are no less than staggering.
Biotechnology produces biotherapeutic agents on industrial scales. These agents include both novel agents and agents formerly available only in small quantities. Crude vaccines were used in antiquity in China, India, and Persia. For example, vaccination with scabs that contained the smallpox virus was a practice in the East for centuries. In 1798 English country doctor Edward Jenner demonstrated that inoculation with pus from sores due to infection by a related virus could prevent smallpox far less dangerously. Humankind has benefited incalculably from the implementation of vaccination programs.
Insulin replacement therapy has been in use for decades. Before Canadian physiologists Frederick Banting and Charles Best discovered and isolated insulin in 1921, nearly all persons diagnosed with diabetes died within a few years after the diagnosis. In the mid-1960s several groups reported synthesizing the hormone.
Virtually all biotherapeutic agents in clinical use are biotech pharmaceuticals. A biotech pharmaceutical is simply any medically useful drug whose manufacture involves microorganisms or substances that living organisms produce (e.g., enzymes). Most biotech pharmaceuticals are recombinantthat is, produced by genetic engineering. Insulin was among the earliest recombinant drugs.
Genetic engineeringalso known as bioengineering, gene splicing, and recombinant DNA technologycomprises altering DNA molecules outside an organism and making the resultant molecules function in living things. Multicellular organisms that have been genetically engineered to produce substances medically useful to humans include cows, goats, sheep, and rats, and corn, potato, and tobacco plants. Genetic engineering is revolutionizing medicine: enabling mass production of safe, pure, more effective versions of biochemicals the human body produces naturally.
Genetic engineering is central to modern biotherapys backbone: pharmaceutical biotechnology. Pharmaceutical biotechnology involves using microorganisms, macroscopic organisms, or hybrids of tumor cells and leukocytes:
For example, before the development of recombinant human insulinwhich became the first manufactured, or commercial, recombinant pharmaceutical in 1982animals (notably pigs and cattle) were the only nonhuman sources of insulin. Animal insulin, however, differs slightly but significantly from human insulin and can elicit troublesome immune responses. Recombinant human insulin is at least as effective as insulin of animal origin, is safer than animal-source insulin, and can satisfy medical needs more readily and more affordably.
Pharmaceutical biotechnologys greatest potential lies in gene therapy. Gene therapy is the insertion of genetic material into cells to prevent, control, or cure disease. It encompasses repairing or replacing defective genes and making tumors more susceptible to other kinds of treatment.
The FDA approved more biotech drugs in 1997 than in the previous several years combined. The laundry list of human health conditions for which the FDA has approved recombinant drugs includes AIDS, anemia, certain cancers (Kaposis sarcoma, leukemia, and colorectal, kidney, and ovarian cancers), certain circulatory problems, certain hereditary disorders (cystic fibrosis, familial hypercholesterolemia, Gauchers disease, hemophilia A, severe combined immunodeficiency disease, and Turners syndrome), diabetic foot ulcers, diphtheria, genital warts, hepatitis B, hepatitis C, human growth hormone deficiency, and multiple sclerosis.
Table 1 lists biotech pharmaceuticals that the U.S. Food and Drug Administration (FDA) has approved.
I. Types of Biotech Pharmaceuticals
Many biotech pharmaceuticals are similar or identical to proteins that healthy human bodies produce routinely for normal functions. In addition to gene-therapy drugs, there are seven major types:
Cytokines are hormonelike molecules that can control reactions between cells. They activate immune-system cells such as lymphocytes and macrophages.Table 1: Some Approved Biotech Drugs.
Cytokines that have recombinant variants or versions include those described below.
Below are descriptions of recombinant enzymes and diseases against which they are effective.
Recombinant human insulin became the first manufactured, or commercial, recombinant pharmaceutical in 1982, when the FDA approved human insulin for the treatment of cases of diabetes that require the hormone. Before the development of recombinant human insulin, animals (notably pigs and cattle) were the only nonhuman sources of insulin. Animal insulin, however, differs slightly but significantly from human insulin and can elicit troublesome immune responses. The therapeutic effects of recombinant human insulin in humans are identical to those of porcine insulin, and it acts as quickly as porcine insulin, but its immune-system side effects are relatively infrequent. Further, it can satisfy medical needs more readily and more affordably.
Other recombinant hormones include those described below.
Inadequate bodily synthesis of any of the many clotting factors can prevent effective clotting. The FDA has approved two clotting-related recombinant drugs: abciximab for the prevention of blood clotting as an adjunct to angioplasty, and recombinant antihemophiliac factor (rAHF) for the treatment of hemophilia A. Hemophilia A is a lifelong hereditary disorder characterized by slow clotting and consequent difficulty in controlling blood loss, even from minor injuries. About 20,000 persons in the United States alone have this condition, which is due to a deficiency of antihemophiliac factor (AHF, or factor VIII). Before the introduction of rAHF, treatment of hemophilia A required protein concentrates from human plasma. Such concentrates could contain contaminants (e.g., HIV), and the lifetime treatment of a single patient required thousands of blood contributions.
Persons with hemophilia B lack factor IX. They require either factor IX concentrates from pooled human blood or factor IX from cell cultures (some of which are genetically engineered). In July 1997 Scotlands Roslin Institute announced the birth of the first genetically engineered sheep clone. The clone carries a human gene for factor IX, and it gives milk that contains the factor. (Other multicellular organisms that have been genetically engineered to produce substances that are or may be medically useful to humans include cows, goats, and rats, and corn, potato, and tobacco plants.) (6) (7)
In every modern vaccine the main or sole active ingredient consists of killed microorganisms, nonvirulent microorganisms, microbial products (e.g., toxins), or microbial components that have been purified. All these active ingredients are antigens: substances that can stimulate the immune system to produce specific antibodies. Such stimulation leaves the immune system prepared to destroy bacteria and viruses whose antigens correspond to the antibodies it has learned to produce. Although conventionally produced vaccines are generally harmless, some of them may, rarely, contain infectious contaminants. Vaccines whose active ingredients are recombinant antigens do not carry this slight risk.
More than 350 million persons worldwide are infected with the virus that causes hepatitis B, a major cause of chronic inflammation of the liver, cirrhosis of the liver, and liver cancer. (8) Hepatitis B kills a million people each year worldwide. About 1.25 million Americans harbor the hepatitis B virus (HBV); 30 percent of them will eventually develop a serious liver disease. About 300,000 children and adults in the U.S. become infected with HBV each year, and 5,000 Americans die annually from liver disease caused by the virus. The first hepatitis B vaccine available in the U.S. was made with derivatives of plasma from persons with chronic HBV infections. A recombinant vaccinewhose sole active ingredient is a recombinant (and thus uncontaminated) antigenhas replaced it. Use of this vaccine is very cost-effectiveespecially in North America, since interferon treatment of hepatitis B is very expensive.
The Ebola virus, first identified in 1976, causes Ebola hemorrhagic fever, one of the deadliest viral diseases known. About 5090 percent of patients infected with the Ebola virus consequently die. In 1997 American researchers announced that an experimental recombinant vaccine against the virus had proved effective in mice and guinea pigs.
Because of immune-system inadequacy, some groupsinfants and young children, for exampletend to respond poorly to vaccination against certain bacterial infections (e.g., streptococcal pneumonia). Preliminary research suggests that antibacterial vaccines that contain specific antibodies are more effective against such diseases than are comparable conventional vaccines, which do not contain antibodies. (9)
Although vaccines traditionally have been designed to prevent only infectious diseases, the development of individualized vaccinesvaccines made from the cancer cells of each patientto restrain, prevent the recurrence of, or cure some forms of cancer is promising. Researchers at the U.S. National Cancer Institute have demonstrated that a special vaccine plus interleukin-2 can shrink tumors in patients with metastatic melanoma. (10) The vaccine used in this study contained a melanoma-antigen variant more effective than the original antigen at attracting to cancer sites T lymphocytes that are destructive to tumors.
Another prospect is effective inoculation by ingestion. In February 1998 U.S. researchers announced that they had genetically engineered potatoes to produce a "vaccine" against cholera. (11) Every year five million people contract cholera, and 200,000 die from it. The "vaccine" is a nontoxic, relatively heat-stable protein that can elicit an immune response even when it is ingested as a potato constituent.
All the antibodies the immune system normally produces in response to a specific antigen are capable of marking (binding to) that antigen, but these antibodiestermed "polyclonal"are varied, not identical. Monoclonal antibodies (MoAbs) that share a specific antigenic target are identical and are more sensitive to that target than are polyclonal antibodies for the same antigen. MoAbs are the products of hybridomascells that result from the biotech fusion of bone-marrow tumor cells and B lymphocytes. Hybridomas can be geared to produce specific MoAbs continuously.
Theoretically, a MoAb designed for a particular antigen on cancer cells can initiate an immune response that would destroy cancer cells without harming normal cells. At least 26 MoAbs are undergoing clinical testing as anticancer agents (12), but the medical potential of MoAbs extends to many other diseases.
For example, the FDA has approved the MoAb drug muromonab-CD3 for the treatment of immune-system rejection of transplanted hearts, kidneys, and livers. Muromonab-CD3 restrains immune response and thus increases the likelihood that the transplant will function. More recently, the FDA approved the immunosuppressant daclizumab (Zenapax) for the prevention of kidney-transplant rejection. Daclizumabs active ingredient is a "humanized" MoAb; 90 percent of the MoAbs amino-acid structure is human. Thus, the likelihood of an allergic reaction to it is low.
Another MoAb, infliximab (cA2), appears effective against Crohns disease, an immune-system disorder marked by intestinal inflammation. (13) Infliximab is specific for a factor in the development of the disease.
The medical utility of MoAbs is not limited to therapeutics. Because of their ability to bind to specific antigens, MoAbs have been used for many years to identify antigen-carrying disease agents and to locate them in the human body. Recently, British researchers designed MoAbs that may be useful in determining whether cancer has spread from breast tissue to axillary lymph nodes. The spread of cancer to other parts of the body is likelier if the cancer has spread to lymph nodes than if it has not. Traditionally, determining whether the lymph nodes have been affected involves surgery. But using radiolabeled MoAbs specific to antigens on malignant cells enables locating such cells with an instrument comparable to a Geiger counter and may decrease the need for surgery.
The ability of MoAbs to bind to, and thus tag, specific proteins also makes them potentially useful in the diagnostic imaging of internal organs and tumors.
Other Biotech Drugs
Listed below are a few of the hundreds of other biotech drugs that are either in clinical use or undergoing scientific investigation.
Table 2 describes several other biotech pharmaceuticals undergoing clinical investigation.Table 2: Miscellaneous Biotech Pharmaceuticals Undergoing Clinical Investigation.
Pharmaceutical biotechnologys greatest potential lies in gene therapy. Gene therapy is the insertion of genetic material into cells to prevent, control, or cure disease, especially genetic disorders. It encompasses repairing or replacing defective genes and making tumors more susceptible to other kinds of treatment. Thus, gene therapys potential for preventing and curing disease is vast. It has proved somewhat useful in the treatment of certain rare genetic diseases, such as cystic fibrosis and familial hypercholesterolemia. (15)
Carriers of therapeutic genes include:
Existing modes of gene therapy can restrain the replication of pathogenic microorganisms, can eliminate defective cells, and can increase the resistance of normal cells to drugs harmful to them (e.g., certain anticancer agents). (17) For example, the Multiple Drug Resistance (MDR) gene enables production of a protein that removes various foreign chemicals from cells. Introduction of the MDR gene into the bone-marrow cells of patients with advanced cancer seems safe and may protect their bone marrow from the toxic side effects of chemotherapy. It may thus make high-dose chemotherapy safer and improve recovery.
Another anticancer strategy undergoing investigation, antiangiogenesis gene therapy, involves introducing genetic material to a limited area to decrease the formation of blood vessels there. (18) Decreasing angiogenesis at the site of a tumor decreases the tumors ability to grow and spread.
A form of gene therapy with the opposite effect on blood-vessel formation has also been developed. Preliminary research suggests that "therapeutic angiogenesis," or VEGF gene therapy, may be effective against sensory neuropathy (19) (specifically, a loss of feeling in the feet) and critical limb ischemia (an arterial disease marked by a decrease in the supply of oxygen-rich blood to the legs). Such a decrease can result in gangrene and the need for amputation. "VEGF" stands for vascular endothelial growth factor, a protein that can induce angiogenesis. Scientists have modified a relatively harmless respiratory virus so that it bears the gene for VEGF. Injection of the material that carries the VEGF gene directly into defective parts of the heart might eventually supersede surgical procedures used to treat coronary artery disease. (20) As many as 600,000 cardiac patients a year might benefit from VEGF gene therapy.
(Viruses can elicit an immune response, and in any case using viruses to convey genes is not a very accurate means of sending genetic material to target cells. In chimeraplasty, an experimental mode of gene therapy, chimeraplasts"repairman" molecules that are hybrids of RNA and recombinant DNAconvey the gene.  Chimeraplasty may enable gene transmission that is more accurate than viral or microbial gene transmission.)
In January 1998 researchers reported that introduction of the active gene for human telomerase reverse transcriptase (hTRT)a vital component of the enzyme telomeraseinto normal human cells had resulted in a marked increase in the cells life span without making the cells otherwise abnormal (e.g., cancerous) (22) Most human cells do not produce hTRT but contain all the other components of telomerase. (23) Normal cells that lack telomerase can replicate only about 50 times. Each time one divides, it loses DNA from its telomeres (the natural, protective ends of its chromosomes). Without telomerase, which is key to the synthesis of telomeres, shortening of the telomeres ultimately brings cell division to a halt, whereupon the cell dies. Because the hTRT gene of sperm cells, egg cells, and cancer cells is active, they can divide perpetually. It is theoretically possible to destroy cancer cells safely by neutralizing telomerase or by modifying the hTRT gene. Controlling various age-related disorders, such as heart disease, with the hTRT gene may also be feasible. (24) Specific cells from a patient could be rejuvenated and then cultured to replace, for example, the patients hardened arterial tissue or burned or wrinkled skin.
II. Safety and Effectiveness
Many biotech agents are identical to, or differ only slightly from, proteins the human body produces naturally; thus, biotech pharmaceuticals tend to have a lower potential for adverse reactions than do conventionally produced pharmaceuticals.
Many biopharmaceutical substances lack stability and/or are not absorbable in a medically useful form through the gastrointestinal tract, the lungs, or the skin. In the gastrointestinal tract, for example, digestive chemicals normally break down protein products. Even injection may not ensure effective delivery to the target cells. To be effective, many injected drugs need to survive transport through the liver and encounters with enzymes. Therefore, how biopharmaceuticals are delivered is very critical.
Drug-delivery innovations relevant to biopharmaceuticals include those described below.
PEG likewise slows the breakdown of another enzyme, L-asparaginase, which the body produces naturally. Pegaspargase, a combination of PEG and recombinant L-asparaginase, can improve the condition of children with lymphoblastic leukemia.
Biotech Pharmaceutical Purity
Nearly all biotech agents are proteins and have to be isolated from proteinaceous substances. Thus, the most common impurities in recombinant drugs are proteinaceous. Protein impurities can cause allergic reactions or make the therapeutic effects of the drug different from the intended therapeutic effects.
A slight difference between a recombinant protein and its endogenous counterpart can elicit an adverse immune response. Recombinant protein preparations derived from bacterial cultures may also contain small amounts of nitrogen-containing bacterial contaminants that can elicit an adverse response. (26)
Contamination occurs about as often in the manufacture of products from traditional cell cultures as in the manufacture of products from recombinant cultures. Adherence to modern standards of manufacture can keep such contamination infrequent. (27) In any case, even low-level microbial contamination of recombinant cultures is easily detectable. (28)
Biotech Pharmaceutical Stability
Protein molecules are larger and less stable than the molecules of conventionally produced pharmaceutical agents.
Stability is particularly important with larger protein molecules, because their in vivo effects often depend on their three-dimensional structure. (29) Even without a change in the order and kind of the amino acid components, a change in the three-dimensional structure of a biotech product can render it medically useless. For example, at low concentrations, interferons, interleukins, and certain other biotech molecules have a tendency to adhere to glass and plastic. Such adsorption may denature the molecule, and a loss of potency can result. This is often preventable by coating the insides of containers used in drug administration with human serum albumin before placing the drug in the containers. (30)
The shell of water around a protein molecule critically affects its structure. (31) Removal of all water from a protein usually changes its structure irreversibly. Thus, freeze-drying of biotech proteins is complicated and care must be given to prevent denaturation. A common practice is the use of humectants to increase the stability of biotech protein powders.
Expiration-dating of pharmaceuticals is based on tests of the drugs pre-administration stability. Generally, estimates of a pharmaceuticals shelf life are based on "accelerated" testing, in which the temperature and humidity are considerably higher than the temperature and humidity recommended for commercial storage. But because heat can affect protein structure, the utility of accelerated testing for expiration-dating biotech pharmaceuticals is very limited. To establish expiration dates for protein-based pharmaceuticals, manufacturers necessarily conduct real-time stability studies on such preparations under recommended storage conditions.
III. Regulation of Biotech Pharmaceuticals
Regulatory agencies such as the U.S. Food and Drug Administration (FDA) oversee sales of "human therapeutics" and other lawful products categorized as drugs and presented for application to humans. Regulatory approval of any such product must precede its sale. To obtain FDA approval, manufacturers must submit to the agency voluminous information about the product, including reports of scientific findings concerning medical effectiveness, purity, stability, and side effects (e.g., due to impurities or high dosing). By the time approval has been obtained, a company may have spent five to ten years and more than $200 million seeking it.
The consensus of many national and international groups is that biotech risk is primarily a function of product characteristics, and that it is not a function of rDNA technology. (32) In other words, these organizations have decided that biotech pharmaceuticals should be judged according to the components (e.g., active ingredients and contaminants) and the effects (e.g., side effects) of each pharmaceutical, and not according to how they were made. Consistent with this consensus, the FDAs approach to recombinant drugs and other biotech pharmaceuticals is the same as its approach to conventional biologicals.
In the United States, the Environmental Protection Agency (EPA) and the National Institutes of Health (NIH) also influence pharmaceutical biotech research. The EPA regulates releases of recombinant microorganisms into the environment, and the NIH repeatedly updates biotech research guidelines that recipients of federal funds must follow. (33) Many biotech researchers who do not receive such funds also follow these guidelines.
Recombinant DNA technology is revolutionizing medicine, i.e., enabling mass production of safe, pure, more effective versions of biochemicals the human body produces naturally. Through gene therapy, the potential of biotech pharmaceuticals for curing chronic and "incurable" diseases and improving the human condition is limitless. With sensible regulatory requirements and expeditious product review by regulatory agencies, biotech pharmaceuticals can within decades become unprecedented preventers and relievers of human suffering.
1Corresponding author: Jack Raso,The American Council on Science and Health, 1995 Broadway, 2nd Floor, New York, New York, USA 10023-5860
Published by the Canadian Society for Pharmaceutical Sciences.
Copyright © 1998 by the Canadian Society for Pharmaceutical Sciences.