The following section is on a treatment of cancer, it is not a guide on how to perform it, nor is it a guide as to the side effects or how to prepare for treatment. The following section is designed to give readers an in-depth understanding of the treatment, how it functions, and why it functions. Please note that researchers are constantly working to find new treatments or improve current ones, this means the subject(s) discussed below are likely to change as medicine improves.
Targeted therapies are drugs that treat cancer meaning it falls into the category of chemotherapy, it is explored separately in this section as it functions differently to traditional chemotherapy. The difference between chemotherapy and targeted therapy is that targeted therapy is calibrated to specific proteins in cancer cells not on other cells. Immunotherapy can also be considered a type of targeted therapy as it targets specific proteins as well, however this section only explores targeted therapies that do not utilise the immune system.
The main type of targeted therapy left over under these specifications are small molecule inhibitors. These small molecule inhibitors are small enough to passively pass through cell membranes and are made to target specific functions within the cell. Cells that have mutated to use different proteins than regular cells could be targeted, or processes that are only currently necessary for cancer growth such as angiogenesis.
Small molecule inhibitors usually function by binding with kinases where they would usually bind to other molecules, this blocks their ability to bind with other molecules thus inhibiting their function. Kinases are used in a most processes that go on within a cell, many cancers arise from mutations that synthesise abnormal kinases. Thus many different types of small molecule kinase inhibitors have been developed to target specific abnormal kinases. These molecules can be further split into multikinase small molecule inhibitors or selective small molecule kinase inhibitors depending on whether the drug targets a variety of kinases or a specific one. Selective small molecule kinase inhibitors often require testing to see if the specific kinase is present.
There is also another class of less common small molecule inhibitors known as selective small molecule nonkinase inhibitors. Selective small molecule nonkinase inhibitors do not target kinases, they can target any function within the cell however usually the process is to do with DNA. Some of these drugs inhibit proteins related to DNA repair such as PARP inhibitors, this allows for other treatments that damage DNA such as chemotherapy or radiation therapy to be more effective. Another class if nonkinase inhibitors are epigenetic inhibitors. Epigenetics refers to how the environment and behavior of proteins can effect DNA expression without changing the DNA code itself. Epigenetic inhibitors therefore target specific proteins that can cause epigenetic dysregulation.
Due to the specific nature of targeted therapy many drugs within these categories can function very differently, if interested a more in depth guide on specific examples of these drugs can be found here: https://pmc.ncbi.nlm.nih.gov/articles/PMC9560750/#mco2181-sec-0220
Note: Because targeted therapies rely on specific abnormal proteins or processes not all cases of cancer will have available targeted medications. Because mutation is by nature unpredictable even cancers of the same type may not have the same abnormalities, meaning some may be able to receive targeted therapy while others aren’t.
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