For many decades, scientists have been wondering how to tackle specific cancer cells without harming the normal cells in the human body. Chemotherapy, radiotherapy, surgery and other modalities of treatment employed for battling the cancers did have its successes although many gave rise to side effects with little prognostic value. Targeted cancer therapies, on the other hand, are designed to interfere with specific molecules involved in the process of cancer cell growth and spread and thereby to be more specific, prognostically effective while having much lesser side effects.
The U.S. Food and Drug Administration (FDA) have approved many targeted cancer therapies and due to their action at the molecular level, these therapies are also called “molecularly targeted drugs,” “molecularly targeted therapies,” or other similar names. These drugs are usually approved to be used with specific types of cancers and there are many more targeted cancer treatments at the stage of clinical trials, which are waiting to obtain approval before being issued to the medical community.
In general, targeted cancer therapies can be classified as drugs that interfere with the signaling mechanisms of the cell growth or the process of blood vessel development, therapies which can induce cell death, drugs that stimulate the immune system to act against the cancer cells, and drugs which can deliver specific toxins into the cancer cells to derail its functioning.
When looking into more detail, the National Cancer Institute (NCI) describe some of the targeted therapies as aimed at specific enzymes and growth factor receptors involved in the cancer cell proliferation. These drugs belong to the signal inhibitors mentioned earlier. This category of therapies include drugs such as Imatinib mesylate used for gastrointestinal stromal tumors and Dasatinib used for Chronic Myeloid Leukemia (CML) or Acute Lymphoblastic Leukemia (ALL). A second type of drugs which has the ability to interfere with the proteins that regulate gene expression and other cellular function have also been described by the NCI. Vorinostat and Romidepsin, which are used for treating cutaneous T-cell lymphomas, belong to this category of targeted cancer therapy.
When talking about drugs initiating cancer cell death or apoptosis, Bortezomib, which is a drug, used to treat people with multiple myeloma and Pralatrexate, which is used for treating some patients with peripheral T-cell lymphoma, are two examples. Another category of drugs belonging to targeted cancer therapies has the ability to block the growth of blood vessels (angiogenesis), which is essential for large tumors to proliferate. Bevacizumab and Sorafenib are two examples for this type of drugs and are used for treating glioblastoma and hepatocellular carcinoma respectively.
Apart from the above types of drugs, therapies such as Rituximab and Alemtuzumab act on stimulating the body’s own immune system through a mechanism of binding into a cancer cell and allowing the immune system to recognize it as a ‘foreign entity’. Monoclonal antibodies, which are used as targeted cancer therapies, will deliver toxic molecules into the cancer cells and thereby destroy the cells from within. Tositumomab and ibritumomab tiusetan are two examples of this type of drugs.
Lastly, the NCI also consider cancer vaccine and gene therapy as part of targeted cancer therapies, because they also act by inhibiting the growth and the proliferation of specific cancer cells rather than acting on all types of cells in the human body.