Current broad groups of targeted therapies include:1
- Hormone therapies slow or stop the growth of hormone-sensitive tumours, which require certain hormones to grow. For example, Anastrazole targets amomatase and is indicated for hormone dependent postmenopausal breast cancer.5
- Signal transduction inhibitors block the activities of molecules that participate in signal transduction, the process by which a cell responds to signals from its environment. For example, Gleevec / imatinib / STI571 is used in early chronic myeloid leukaemia which is driven by one oncoprotein, Brc-Abl. 6
- Apoptosis inducers cause cancer cells to undergo a process of controlled cell death called apoptosis. For example, Temsirolimus is an mTOR inhibitor used in advanced renal cell carcinoma.5
- Angiogenesis inhibitors block the growth of new blood vessels to tumours (a process called tumour angiogenesis). For example, bevacizumab is a monoclonal antibody that recognizes and binds to vascular endothelial growth factor. 5
- Immunotherapies trigger the immune system to destroy cancer cells. Some immunotherapies are monoclonal antibodies that recognize specific molecules on the surface of cancer cells. These antibodies are produced by recombinant DNA technology and may consist of human and non-human protein, or be partially or fully humanised. Chimeric antibodies are more likely to elicit hypersensitivity reactions due to pre-existing immunity to foreign animal protein.7 Monoclonal antibodies that deliver toxic molecules can cause the death of cancer cells specifically. For example, trastuzumab targets HER2 and is indicated for HER2-positive for breast cancer. 5
- Cancer treatment vaccines are designed to treat cancers that have already developed by strengthening the body’s natural defences against the cancer. For example, sipuleucel-T (Provenge®) is designed to stimulate an immune response to prostatic acid phosphatase (PAP), an antigen that is found on most prostate cancer cells.8
Certain agents may fall under more than one category. For example:9
- trastuzumab is a monoclonal antibody and also falls under the EGFR targeted therapy category
- gefitinib is an EGFR tyrosine kinase inhibitor and also has action as an angiogenesis inhibitor.
The SCN needs to keep abreast of current and investigational biological and molecular targeted agents and their application in clinical practice. As knowledge of molecular processes improves, the categories and application of biotherapeutic agents will evolve. The large number of agents currently under investigation may be approved for clinical practice. Existing agents may also have application in the treatment of new diagnostic groups and in combination with antineoplastic agents.
A list of approved targeted therapies in Australia was published in Cancer Forum in 2013.
Brown, M.P. & Burdett, N. (2013) Targeted therapies, aspects of pharmaceutical and oncological management. Cancer Forum, 37 (1)
Identify an example where a targeted therapy is being used in combination with antineoplastic agents.
Explain the rationale for combining this biological agent with antineoplastic agents.
Describe one targeted therapy that has application in more than one cancer.
Explain the mechanism of action of the targeted therapy identified in response to learning activity 3.