therapeutic products
1.
In protein therapy, the concentration of those proteins is increased whose absence or low level leads to diseases.
In the course of gene therapy, the insertion of the appropriate gene into the host genome can be problematic; the vector can induce toxic, immunogenic, inflammatory or even tumorigenic processes or can trigger immune responses. Some diseases affecting large populations (cardiovascular diseases, tumors) have complex pathomechanisms and cannot be associated with only one defective gene, thus gene therapy cannot be applied in these cases.
Contrary to gene therapy in the course of protein therapy a well-designed protein in a proper amount is administered into the body and the effect is more well-defined. Targeting can be more problematic as the protein may be broken down or cleared from the body before its effect can be developed and side-effects can also appear as it is possible that the therapeutic protein exerts its activity not only where it is supposed to, thereby causing undesired side-effects (Figure 15.1.).
Figure 15.1. Figure 15.1. Gene therapy versus protein therapy.
15. The application of therapeutic
• Enzymes: digestion enzymes or other enzymes (like urokinase)
• Clotting factors
• Therapeutic antibodies
• Antibody mimetics
• Vaccines
• Small peptide-based drugs – peptide hormons like insulin, glucagon Application of enzymes for therapeutic purposes
Enzymes are used for treating enzyme-deficiencies in the body. In many cases the different digestion enzymes (such as trypsin, lipase, and amylase) need to be supplemented but supplementation of other enzymes, like urokinase after optical surgeries, may also be necessary.
In the course of enzyme replacement therapy the appropriate enzyme is administered intravenously into the patient’s body in high doses. The model of the therapy was developed in rats by Mark J. Poznansky and Damyanti Bhardwaj. Currently the therapy is available for some diseases, where the deficient or defective enzyme is supplemented by the appropriate recombinant enzyme.
• Gaucher disease – supplementation of recombinant glucocerebrosidase
• Fabry disease – supplementation of recombinant alpha galactosidase
• MPS I – Hurller syndrome (mucopolysaccharidosis) supplementation of the specific recombinant enzyme
• MPS II - Hunter syndrome (mucopolysaccharidosis) supplementation of the specific recombinant enzyme
• MPS VI - Maroteaux-Lamy syndrome (mucopolysaccharidosis) supplementation of the specific recombinant enzyme
• Pompe disease – supplementation of human recombinant acidic alpha glucosidase Supplementation of blood coagulation factors
The supplementation of the proper factors is administrated in the therapy of different types of hemophilia.
Isolation from concentrated human blood and placenta is one method for the production of blood coagulation factors, however, large amount cannot be gained, the product can be immunogenic and there is a risk for Creuzfeld-Jacobs disease. Therefore, blood coagulation factors applied nowadays are recombinant proteins produced in bacteria or in cell cultures. These methods make the large-scale production possible, but post-translational modifications can vary depending on the applied cell type.
Therapeutic antibodies
Therapeutic antibodies are a clinically promising group of therapeutic proteins. They are successfully used for treating various diseases like different tumors, cardiovascular diseases, inflammatory diseases, macular degeneration, sclerosis multiplex, viral infections or for preventing rejection following transplantations.
Radioactive tags, cytokines, immunotoxins, drug proforms, liposomes etc. can be bound to therapeutic antibodies. An antibody attached to the tumor cell can attract killer cells that destroy tumor cells or if a biotinylated radioactive tag is attached to the antibody and it is concentrated on the tumor cell surface, it can cause the death of the tumor cell.
In antibody-dependent cell mediated cytotoxicity (ADCC) therapeutic proteins are targeted against the tumor cells. The constant region of the antibody attracts the killer cells of the immune system, and they bind to the therapeutic proteins via their Fc receptors and kill the cells (Figure 15.2.).
15. The application of therapeutic proteins. Possible administration, perspectives and future possibilities.
The national and international requirements for protein therapeutic
products
Figure 15.2. Figure 15.2. The mechanism of ADCC. (ADCC – antibody dependent cell mediated cytotoxicity).
Her2 – human epidermal growth factor receptor 2 - is a tyrosine kinase receptor in the plasma membrane, and plays an important role in cell growth. It is proto-oncogene, 15-20 % of breast cancers overexpress Her-2 on their surface. Her-2 also appears in ovarian, womb and gastric cancers. By the injection of trastuzumab or herceptin - antibody against Her-2 – the antibody binds to the surface of Her-2 positive cells and destroys the tumor cells by ADCC (Figure 15.3.).
Figure 15.3. Figure 15.3. Administration of antibodies against Her2 in breast cancer.
15. The application of therapeutic proteins. Possible administration, perspectives and future possibilities.
The national and international requirements for protein therapeutic
products
Antibodies are applied not only in tumor therapies. Antibodies against TNF alpha can be used in the treatment of psoriasis, rheumatoid arthritis, Crohn disease, spondilitis etc. (Figure 15.4.).
Rho(D) immunoglobulin is an IgG anti-D antibody which was applied for the first time in 1968. Rh negative mothers who give birth to Rh positive babies or had somehow got in contact with Rh positive blood are immunized with this antibody.
Figure 15.4. Figure 15.4. Administration of protein therapeutics with TNF alfa inhibitor
effect in order to suppress the immune system.
15. The application of therapeutic
Antibody mimetics are a group of organic compounds that are not structurally related to antibodies but are able to bind antigens and have similar functions to antibodies. Ecallantide is a 60-amino acid polypeptide that specifically binds to kallikrein and inhibits its function. It is applied in the treatment of hereditary angioedema (HAE) and decreases blood-loss in the course of cardiothoracic surgeries.
Application of virus-like particles for immunization purposes
Virus-like particles usually contain a protein-like part of a virus and are able to generate immune responses.
They are produced in a recombinant form by cell cultures and applied as vaccines following the proper purification steps. Vaccines against human papilloma virus (HPV) and hepatitis B are like this.
Small peptide-based drugs - peptide hormone production
The production of peptide hormones (insulin, glucagon) is carried out by protein biotechnological methods.
In the body, insulin is produced by the beta cells of the pancreas and its main function is the regulation of blood-sugar level and the initiation of growth signals. In its absence diabetes develops. This can be type 1 diabetes (congenital or juvenile diabetes) or type 2 diabetes (adult-onset diabetes). According to WHO data in 2000, 2.8% of the whole population suffered from diabetes but according to the prognosis by 2030 as much as 5.5% of the whole population will have been affected. So far, the insulin supplementation has had a great importance and is available for everybody in the form of human recombinant products.
In the body, glucagon is produced by the alpha cells of the pancreas. It is the most important hormone, which elevates blood-sugar level and is used in medical practice for the treatment of hyperglycemia. In pharmaceutical industry it is produced in recombinant form by E.coli strains.
Requirements for protein therapeutic products
Regarding protein therapeutic products, the licensing process is the same as in the case of drugs the FDA (Food and Drug Administration and EMEA (European Medicine Agency) license the marketing. In Hungary, ÁNTSZ and OGYI are the institutes in charge. An organization of FDA, the Center for Biologics Evaluation and
15. The application of therapeutic proteins. Possible administration, perspectives and future possibilities.
The national and international requirements for protein therapeutic
products
antigeneicity. Since the vast majority of the products were produced by cell cultures, the purity of the protein is not 100 %, the products may contain materials originated from bacteria or other species, etc.
Currently, more than 700 licensed therapeutic protein products are registered but only a part of them are in regular application, since in many countries users are distrustful of certain products and, instead, use traditional drugs in therapy.