O Biotechnologyderived Pharmaceutical Products

More than 2 dozen FDA-approved biotechnology-derived pharmaceutical products are listed in Table 27.9. There are more than 200 other products in various stages of develop-ment.74 The FDA-approved products fall loosely into five major categories: enzymes, hormones, lymphokines, hematopoietic factors, and biologicals. A detailed discussion of all of these products is beyond the scope of this chapter. Because most of these products are proteins or peptides, a cursory evaluation of them and their uses80 follows.

Figure 27.7 • Summary of a typical rDNA process used in the commercial-scale production of human proteins.

rDNA-DERIVED ENZYMES

Alteplase, Recombinant.

discussed previously.

Alteplase (Activase) was

Dornase Alpha. Dornase alpha, rhDNAse (Pulmozyme), is a mucolytic enzyme identical with the natural human DNAse and is used in the treatment of cystic fibrosis. Patients with cystic fibrosis suffer from decreased pulmonary function and infections caused by the secretion of thick mucus. Proteins contained in the mucus are bound to extracellular DNA, produced as a result of disintegration of bacteria in the lungs. This enzyme is involved in cleaving extracellular DNA and separates DNA from proteins, allowing proteolytic enzymes to break down proteins and thus decrease the viscosity of mucus in the lungs.81 Proteins bound to extracellular DNA are not susceptible to proteolytic enzymes.82 Dornase alpha is a glycoprotein containing 260 amino acids that is commercially produced in genetically engineered Chinese hamster ovary cells.

Dornase alpha is indicated for the treatment of cystic fibrosis in conjunction with other available therapies, such as antibiotics, bronchodilators, and corticosteroids. Adult dosage is 2.5 mg inhaled once daily, administered via a recommended nebulizer. Dornase alpha should not be mixed or diluted with other agents in the nebulizer because of the possibility of adverse physicochemical changes that may affect activity. Common adverse effects include sore throat, hoarseness, and facial edema.

Imiglucerase. Imiglucerase (Cerezyme)80 is a glycoprotein containing 497 amino acid residues and is N-glycosyl-ated at four different positions. It is an analog of the natural human enzyme jS-glucocerebrosidase and contains arginine at position 495 instead of the histidine in the natural enzyme. It is commercially produced in genetically engineered Chinese hamster ovary cells.

Like the natural enzyme, imiglucerase catalyzes the hydrolysis of glucocerebroside, a glycolipid, to glucose and ceramide within the lysosomes of phagocytic cells. Gaucher disease is caused by a deficiency of this enzyme, which results in the accumulation of glucocerebroside within tissue macrophages. The glycolipid-engorged macrophages are known as Gaucher cells and are responsible for the numerous clinical manifestations of Gaucher disease. The common clinical manifestations of Gaucher disease are severe anemia, thrombocytopenia, and skeletal complications that include osteonecrosis and osteopenia.

Imiglucerase is indicated for the long-term replacement therapy of Gaucher disease. It is administered intravenously at an initial dose of 2.5 to 60 U/kg, infused over 1 to 2 hours. This dose is usually repeated every 2 weeks. Both the dose and the frequency of administration may be varied, however, depending on the response.83 Common adverse effects include dizziness, headache, abdominal discomfort, nausea, and rash.

rDNA-DERIVED HORMONES

The rDNA-derived hormones include insulin human injection USP (Humulin R, Novolin R, Velosulin Human), growth hormone (somatotropin; Humatrope), and somatrem (Protropin). All of these products, as well as other products containing human insulin, have been discussed in this chapter.

rDNA-DERIVED CYTOKINES

Interferons.80 Interferons are natural glycoproteins produced by virtually all eukaryotic cells; they possess im-munomodulating, antiviral, and cytotoxic activities. This family of glycoproteins is produced by cells in response to a wide range of stimuli.84 In humans, interferons bind to cellular receptors, which leads to the synthesis of more than a dozen proteins that contribute to viral resistance. The antiviral effects of interferons may be caused by inhibition of the synthesis of viral mRNA or proteins or prevention of viral penetration or uncoating.85,86 Based on their antigenic subtypes, the interferons are classified into three major groups: a, S, and y. ^-Interferon and jS-interferon are produced by virtually all cells in response to a viral infection and various other stimuli. y-Interferon is produced specifically by the T lymphocytes and the natural killer (NK) cells. y-Interferons have greater immunoregulatory, but lower antiviral, effects than a- or S-interferons.86 More than 12 subspecies of a-interferons, 1 jS-interferon, and 2 y-interferons are known to exist. In general, the interferons are glycoproteins consisting of 165 to 166 amino acid residues. There are four rDNA-derived a-interferons available for clinical use around the world and three available in the United States (described next). All a-interferons exhibit antiviral and antiproliferative activity, enhance phagocytic activity, and augment specific cytotoxicity of lymphocytes for certain target cells.87 The most common adverse effects of a- and ¡-interferons include flulike symptoms, bone marrow suppression, neurotoxic effects, hypocalcemia, anorexia and other gastrointestinal symptoms, and weight loss.

Interferon Alfa-2a, Recombinant. Interferon alfa-2a, recombinant (Roferon), is produced from genetically engineered E. coli and contains 165 amino acid residues. At position 23, interferon alfa-2a has a lysine residue. The pharmaceutical product contains a single a-interferon subtype. A murine monoclonal antibody is used during purification by affinity chromatography. Interferon alfa-2a is used in the treatment of hairy cell leukemia and acquired immunodeficiency syndrome (AIDS)-related Kaposi sarcoma. It is absorbed well after intramuscular or intravenous administration and has a half-life of 5 to 7 hours when administered by the intramuscular route. The solution should be stored in the refrigerator at 36°F to 46°F and should not be frozen or shaken.

Peginterferon Alfa-2a, Recombinant. Interferon alfa-2a, recombinant (Roferon), is produced from genetically engineered E. coli. It is interferon, alfa-2a utilizing a 40 kd polyethylene glycol (PEG) strand to allow for stable therapeutic serum levels of alpa-2a for up to 168 hours on a single dose. This process is known as PEGylation and involves the process of attaching strands of the polymer PEG to molecules in an attempt to make them safer and more effective as therapeutic agents. The physiochemical changes in the drug increase systemic retention as well as influence the binding affinity to the cell receptors. The therapeutic usefulness of peginterferon alpfa-2a is in the treatment of hepatitis C.

Interferon Alfa-2b, Recombinant. Interferon alfa-2b, recombinant (Intron A), also contains a single subtype of a-interferon. It is a glycoprotein containing 165 amino acid residues and is commercially produced from genetically engineered E. coli. It differs from interferon alfa-2b in possessing an arginine residue at position 23. It is used in the treatment of hairy cell leukemia, condyloma acuminata (genital warts), AIDS-related Kaposi sarcoma, hepatitis C, and hepatitis B. It is administered intramuscularly or subcutaneously with a half-life of 2 to 3 hours and via intravenous infusion with a half-life of 8 hours. The reconstituted solution is stable for 1 month when stored at a temperature of 36°F to 46°F.

Interferon Alfa-n3 (Injection). Interferon alfa-n3 (Alferon N) is a polyclonal mixture of up to 14 natural a-in-terferon subtypes and contains 166 amino acid residues. Its commercial production involves induction of pooled units of human leukocytes with an avian virus (Sendai virus). The purification process involves immunoaffinity and filtration chromatography. It is indicated primarily by intralesional injection for the treatment of genital warts. The solution should be stored at a temperature of 36°F to 46°F and should not be shaken.

Interferon Beta-1a. Interferon beta-1a (Rebif, Avonex), has biological effects similar to those of natural ¡-interferon and a-interferons. Unlike beta-1b, which is produced in modified E. coli, beta-1a is produced in mammalian cells. It has been shown to slow the progression of multiple sclerosis as well as reduce the rate of relapse of this disease.

Interferon Beta-1b, Recombinant. Interferon beta-1b, recombinant (Betaseron), has biological effects similar to those of natural ¡-interferon and a-interferons. The natural 3-interferon is a glycoprotein containing 166 amino acid residues. The rDNA product differs from the natural form, in that it is not glycosylated, it lacks the amino-terminal methio-nine, and it has serine in the place of methionine at position 17.88 It is used for a wide variety of indications via intravenous, intramuscular, subcutaneous, intrathecal, and intrale-sional routes. Its primary indication is for the prevention of exacerbations in patients suffering from relapsing/remitting multiple sclerosis. Recommended dosage is 8 million units, administered subcutaneously, every other day. It also is indicated in the treatment of malignant glioma and malignant melanoma. Recommended temperature for storage is 36°F to 46 °F, and unused reconstituted solution should be discarded.

Aldesleukin. Aldesleukin, interleukin-2 (Proleukin),80 is an rDNA-derived lymphokine that differs structurally from native interleukin-2 (IL-2) but has biological activity similar to that of the natural lymphokine.89 Natural IL-2 is produced primarily by the peripheral blood lymphocytes and contains 133 amino acid residues. The immunoregula-tory effects of aldesleukin include enhancing mitogenesis of lymphocytes, stimulating the growth of IL-2-dependent cell lines, enhancing cytotoxicity of lymphocytes, inducing lymphokine-activated killer (LAK) cells and NK cells, and inducing interferon-y production. The exact mechanism of the antitumor activity of aldesleukin in humans is unknown.

The rDNA process involves genetically engineered E. coli (pBR 322 plasmids). The gene for IL-2 was synthesized after first isolating and identifying the mRNA from the human Jurkat cell line and then preparing the complementary DNA (cDNA). The IL-2 gene was genetically engineered before it was hybridized into pBR 322 plasmid. Further manipulation of the hybridized plasmid resulted in the production of a modified IL-2, aldesleukin.90 Aldesleukin differs structurally from the native IL-2 in that the former is not glycosylated, it lacks the N-terminal alanine residue, and it has serine in the place of cysteine at position 125. Noncovalent, molecular aggregation of aldesleukin is different from IL-2, and the former exists as a microaggregate of 27 molecules.

The primary indication for aldesleukin is in the treatment of adult metastatic renal carcinoma. It is administered via intravenous infusion in doses of 10,000 to 50,000 U/kg every 8 hours for 12 days. It is primarily metabolized by the kidneys, with no active form found in the urine. Aldesleukin causes serious adverse effects in patients, including fever, hypotension, pulmonary congestion and dyspnea, coma, gastrointestinal bleeding, respiratory failure, renal failure, arrhythmias, seizures, and death.

rDNA-DERIVED HEMATOPOIETIC FACTORS

Hematopoietic growth factors are glycoproteins produced by a number of peripheral and marrow cells. More than 200 billion blood cells are produced each day; and the hematopoietic factors, along with other lymphopoietic factors such as the stem cell factor and the interleukins, are involved in the proliferation, differentiation, and maturation of various types of blood cells derived from the pluripotent stem cells.

Erythropoietin.80 Erythropoietin is a heavily glycosyl-ated protein containing 166 amino acid residues. It is pro duced primarily by the peritubular cells in the cortex of the kidney, and up to 15% is produced in the liver. It is the principal hormone responsible for stimulating the production of red blood cells from erythroid progenitor cells, erythrocyte burst-forming units, and erythrocyte colony-forming units.91 Small amounts of erythropoietin are detectable in the plasma; however, most of the hormone is secreted by the kidneys in response to hypoxia or anemia, when levels of the hormone can rise more than 100-fold.

Decreased erythropoietin production is one of several potential causes of anemia of chronic renal disease. Other causes of anemia of chronic renal disease include infection or inflammatory condition in the kidneys, iron deficiency, marrow damage, and vitamin or mineral deficiency. Regardless of the underlying disease causing renal failure, erythropoi-etin levels decrease in patients with renal failure. Until rDNA technology was used to produce commercial quantities of erythropoietin, it was obtained from the urine of patients suffering from severe aplastic anemia. This process of obtaining natural hormone was costly and time-consuming and produced only small quantities of the hormone.

Epoetin Alfa. Epoetin alfa, rEPO (Epogen, Procrit), is the recombinant human erythropoietin produced in Chinese hamster ovary cells into which the human erythropoietin gene has been inserted. These mammalian cells glycosylate the protein in a manner similar to that observed in human cells.92

Epoetin alfa is indicated in anemic patients with chronic renal failure, including both those who require regular dialysis and those who do not. Epoetin alfa is also indicated in anemia associated with AIDS, treatment of AIDS with zi-dovudine, frequent blood donations, and neoplastic diseases. It is indicated to prevent anemia in patients who donate blood prior to surgery for future autologous transfusions and to reduce the need for repeated maintenance transfusions.93 The hormone is available as an isotonic buffered solution, which is administered by the intravenous route. The solution should not be frozen or shaken and is stored at 36°F to 46°F.

Colony-Stimulating Factors.80 Colony-stimulating factors are natural glycoproteins produced in lymphocytes and monocytes. These factors bind to cell-surface receptors of hematopoietic progenitor cells and stimulate proliferation, differentiation, and maturation of these cells into recognizable mature blood cells.93 Colony-stimulating factors produced by rDNA technology have the same biological activity as the natural hormones. Currently, there are two colony-stimulating factors commercially produced by rDNA technology. These products are discussed next.

Filgrastim. Filgrastim, rG-CSF (Neupogen), is a 175-amino acid polypeptide produced in genetically engineered E. coli cells containing the human granulocyte colony-stimulating factor (G-CSF) gene. Filgrastim differs from the natural hormone in that the former is not glycosylated and contains an additional methionine group at the N-terminus, which is deemed necessary for expression of the gene in E. coli.

Filgrastim specifically stimulates the proliferation and maturation of neutrophil granulocytes and, hence, is considered lineage specific. Accepted indications for filgrastim include the following: (a) to decrease the incidence of febrile neutropenia in patients with nonmyeloid malignancies who receive myelosuppressive chemotherapeutic agents, thus lowering the incidence of infections in these patients; (b) to accelerate myeloid recovery in patients undergoing autolo-gous bone marrow transplantation; and (c) in AIDS patients, to decrease the incidence of neutropenia caused by the disease itself, or by drugs used to treat the disease. The usual starting dose for filgrastim is 5 /ug/kg per day in patients with nonmyeloid cancer who receive myelosuppressive chemotherapy.

Filgrastim solution should be stored at 36°F to 46°F and used within 24 hours of preparation. The solution should not be shaken or allowed to freeze. Any solution left at room temperature for more than 6 hours should be discarded. The most frequent adverse effects of filgrastim are medullary bone pain, arthralgia, and myalgia.

Sargramostim. Sargramostim, rGM-CSF (Leukine), is a glycoprotein commercially produced in genetically engineered yeast cells. Its polypeptide chain contains 127 amino acids. It differs from the natural hormone by substitution of leucine at position 23 and variations in the glycosylation.94 Sargramostim is a lineage-nonspecific hematopoietic factor, because it promotes the proliferation and maturation of granulocytes (neutrophils and eosinophils) and monocytes (macrophages and megakaryocytes).

The primary indication for sargramostim is in myeloid engraftment following autologous bone marrow transplantation and hematopoietic stem cell transplantation. Handling, storage precautions, and adverse effects are similar to those for filgrastim.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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