Targeted cancer therapies are drugs that target specific parts of cancer cells, such as proteins or genes, that help cancers grow and spread. They also may go after other types of cells that help cancers grow and spread. For some types of cancer, targeted therapies may work better than other treatments.
The FDA has approved targeted therapies for more than 15 types of cancer, including those of the breast, prostate, colon, and lung. But they only work if your tumor has the right target. And targeted therapies can often stop working if the target changes or your cancer finds a way around the treatment.
Researchers are learning more about the changes that drive cancer. This could lead to better targeted therapies in the future.
Types of Targeted Therapies
There are two main types of targeted therapies: small molecule medicines and monoclonal antibodies.
Small molecule medicines are small enough to slip inside cancer cells and destroy them.
You can often spot small molecule meds because their generic name ends in “-ib.” For example, imatinib (Gleevec) treats chronic myelogenous leukaemia (CML) and other cancers by blocking signals that tell tumour cells to grow.
Monoclonal antibodies are too big to get into cells. Instead, they attack targets on the outside of cells or right around them. Sometimes they’re used to launch chemo and radiation straight into tumours. You usually get them through an IV in a vein in your arm at a hospital or clinic. Sometimes they’re given as a shot.
The generic names of monoclonal antibodies end in “-mab.” Bevacizumab (Avastin) is a monoclonal antibody that works by blocking blood vessels that feed tumours.
Scientists have come up with many small molecule meds and monoclonal antibodies that make use of different targets to treat cancer in different ways.
Hormone therapies stop your body from making the hormones some breast and prostate cancers need to grow, or they keep the hormones from working.
Breast cancer medicines like tamoxifen block the female hormone oestrogen. Aromatase inhibitors lower the amount of oestrogen in your body. For prostate cancer, doctors may prescribe meds that block male sex hormones or stop your body from making them.
Signal transduction inhibitors are the most common targeted therapies. They block signals that tell cells to divide too much and too fast.
One example is the breast cancer medication trastuzumab (Herceptin). A protein on the outside of cells called HER2 receptor picks up signals telling the cell to grow and divide. HER2-positive breast cancers make too much of this protein, so the cancer keeps getting told “Grow! Grow! Grow!” Trastuzumab can slow or stop this type of breast cancer by latching onto HER2 receptor proteins, like putting tinfoil over the windows.
Gene expression modulators. This type of targeted therapy works to change the proteins that control the way the instructions of genes in cancer cells get carried out, or are expressed, because it’s abnormal.
Apoptosis inducers. Cancer cells often find a way around the natural process of apoptosis, where healthy cells die when they’re old or damaged. Apoptosis inducers cause cancer cells to go through normal cell death.
Bortezomib (Velcade) is a drug that does this to lymphoma and multiple myeloma, a blood cancer. Scientists are also studying plant compounds like resveratrol (found in red wine) to see if they might trigger cancer cell death.
Angiogenesis inhibitors block the growth of blood vessels that cancer cells form to get their nutrients and oxygen. Some target a substance called vascular endothelial growth factor (VEGF). Others go after different substances that trigger blood vessel growth. If a tumor already has a blood supply, targeted therapies can get rid of it.
Immunotherapies use your immune system to destroy cancer cells. Some boost your immune system so it does a better job of hunting down cancer. Others mark tumor cells so it’s easier for your immune system to find them.