Targeted therapy drugs are a lot like Navy Seals behind enemy lines: stealth and clandestine operatives with different specialties. They create very strategic problems for their target: cancer. And they’re so good at it that they may be the next beachhead in the war on cancer.
First, cancer cell profiles are analyzed at the molecular level and, once a specific target can be identified, a drug is designed to make it malfunction. Some rewire the intricate network of signals that govern how the tumor communicates growth instructions. Blocking these signals can stop the disease progression and, in some cases, actually cause the cancer to self destruct.
I participated in a clinical trial of a monoclonal antibody drug that did exactly this. Its code name was APOMAB, which stood for Apoptosis (or cell suicide) and MAB for monoclonal antibodies (cloned antibodies of a single type). And, because it was engineered to affect cancer cells, it ignored healthy ones. It was nothing like chemo at all.
Many targeted therapies are available to cancer patients now, such as those targeting the cellular receptor for estrogen. Most Estrogen Receptor-positive (ER-positive) breast cancer tumors and some forms of ovarian cancer feed on estrogen. By binding a drug to the estrogen receptor, it blocks estrogen from binding to it. Tamoxifen is an example of this drug.
Aromastase inhibitors are another class of drugs targeted at estrogen - in this case, an enzyme that produces estrogen. Once blocked, the lower estrogen levels keep the cancer in check and retard the body’s ability to produce more tumors. This treatment is only useful for post-menopausal women because active ovaries can produce enough of the enzyme to override the treatment. Arimidex and Femara are two commonly used drugs of this type.
Another form of breast cancer, called HER-2 (Human Epidermal Growth Receptor 2) Positive, is treated with a monoclonal antibody drug that binds to the HER-2 receptor. This drug, named Herceptin, not only keeps the cancer from growing; it may cause the patient’s immune system to attack the cancer.