Biological therapy is a generic term that does not mean any specific therapeutic procedure, but rather a new and modern approach to treatment of many diseases, particularly the therapy of malignant diseases and autoimmune disorders.
The biological treatment is related to increasing knowledge about the inner metabolism of our organism, reactions occurring at the molecular level, detection of certain cell receptors (specific structures on the surface of cell membranes and inside the cells that define the cells and trigger various reactions).
The philosophy of the biological treatment aims to create a substance, which specifically influences the metabolism and immune system to gain advantage against certain diseases. In many cases, the biological therapy focuses on specific inhibition or strengthening of the immune system. Of course, even the biological treatment is not a miracle; it has its limitations and many side effects.
Nowadays, biological therapy is used regularly in many specialized medical departments. Due to the higher cost, the biological therapy is not indicated to anyone, but rather to more severe forms of certain diseases that do not respond to classical therapy.
For better understanding, I would like to present several substances used in biological therapy:
Imatinib is used in therapy of chronic myeloid leukemia (CML). CML is caused by a chromosomal disorder in a certain cell that causes excessive expression of tyrosine kinase, which is important in cell signaling and affects cell cycle in terms of increased propagation. This leads to excessive multiplication and cancer formation. Imatinib acts as a specific blocker of tyrosine kinase and thus successfully suppresses proliferation of tumor cells in CML.
This is an artificially produced antibody targeting the so-called endothelial growth factor VEGF-A. More simply said, it is an antibody against vascular growth factor. The idea is clever. Tumor tissue needs nourishment and thanks to the factor VEFG-A, it forms its own blood vessels that supply the tumor with oxygen and nutrients. Blocking the VEGF-A disrupt the blood vessel production and the transport of nutrients to the tumor. Bevacizumab has achieved a great success in therapy of the colon cancer.
Adalimumab is used to treat Crohn's disease and psoriasis. The active drug substance is an artificial antibody that binds to TNF-alpha and inactivates it. TNF-alpha is a compound, which is of great importance in the immune system. Normally, the TNF-alpha helps in immune reactions against infectious diseases and cancers. In Crohn's disease, however, the TNF-alpha is associated with aggressive autoimmune reaction against intestinal mucosa and suppression of TNF-alpha significantly reduces the clinical symptoms.
This interesting drug is also an artificial antibody which is, this time directed against surface receptor CD20 located on the surface of immature B-lymphocytes. And why would we want to target B-lymphocytes? Well, it is important, for example against tumor-altered B-lymphocytes in chronic lymphotic leukemia. The big advantage is the fact that healthy mature B-lymphocytes producing antibodies lose the CD20 receptor and therefore, they are not destroyed by rituximab. In addition, rituximab is also used in a number of autoimmune diseases (for example in SLE).
Trastuzumab is an artificial antibody that targets the so-called HER2 receptor. The receptor exists on cell membranes in certain forms of breast cancer. The presence of the HER2 receptor used to be originally associated with a worse prognosis, since this receptor promotes more rapid multiplication of tumor cells. However, the invention of trastuzumab has completely changed the situation, because suppression of the HER2 receptor sharply reduces the proliferation of tumor cells. In breast cancers whose cells lack the HER2 receptor, trastuzumab has no effect.
This artificial compound is able to bind to TNF-alpha and inhibit its function. This helps to suppress abnormal immune response in a number of autoimmune diseases.
There are many possible side effects that depend on the type and use of biological treatment. They may appear nonspecific flu-like symptoms (fever, joint pain and fatigue), rash, swelling, nausea and vomiting. Biological therapy, which suppresses the immune system, may be associated with more common infections and possible reactivation of some dormant infections already present in the body. This includes for example tuberculosis.
Biological therapy is an advanced form of treatment. Its importance is going to grow with increasing knowledge of physiological mechanisms in our body and their pathological changes.