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Weapons of ‘mass’ destruction

It’s a problem cancer researchers are trying to surmount: Powerful chemotherapy treatments not only kill tumors but damage healthy cells as well, causing side effects that diminish the quality of a patient’s life. To address this problem, doctors are testing “smart drugs” that work their way into tumors and deliver a lethal dose of anticancer toxins. Called targeted therapy, this type of cancer treatment promises to leave healthy cells unharmed by targeting only the proteins and other molecules that allow cancer to grow and divide.

Types of smart drugs

No two cancers are exactly the same, varying in type, stage and location as well as in the defects within cells that promote malignancy. Smart drugs also vary—both in how and when they fight cancer. While many smart drugs are currently being studied, some have Food and Drug Administration (FDA) approval for specific use:

  • Small molecule drugs block certain proteins that promote uncontrolled growth in cancer cells. Gleevec, for example, can be used to treat several types of leukemia and other blood cell cancers as well as two kinds of solid tumors.
  • Cell-death-inducing drugs interfere with proteins needed by cancer cells to grow and divide without dying. These drugs promote apoptosis, or cancer cell death. One drug, Velcade, has been approved to treat multiple myeloma that’s unresponsive to other treatments.
  • Angiogenesis inhibitors stop new blood vessels needed to feed tumors from forming. Interestingly, the drug Avastin was shown to temporarily improve the ability of a tumor’s blood vessels to deliver chemotherapy and radiation. This drug is now approved for treatment of both colorectal and lung cancer. Some doctors also consider the following to be targeted therapies:
  • Gene therapy, still being studied, involves removing or replacing genes with the aim of limiting cancer-cell growth.
  • Monoclonal antibodies are made in the lab and used to interfere with cancer cell growth or deliver other anticancer drugs to tumors. Nine monoclonal antibodies have been approved to treat cancer, including Herceptin for women with advanced breast cancer.

Not for every cancer patient

Since smart drugs target specific factors that vary from person to person, these drugs don’t work for everyone. Clinical trials on humans tell doctors which patients may benefit from these drugs. Doctors also consider a person’s health status before recommending smart drugs. Although targeted therapy is generally less toxic to patients than conventional chemotherapy, some smart drugs have caused problems ranging from rashes and diarrhea (which may diminish in time or with a dosage adjustment) to more serious conditions like heart damage and internal bleeding.

Smart drugs by themselves aren’t a miracle cure—sometimes they prolong life by only a few months—yet scientists hope they may provide a window of time in which therapies like radiation and chemotherapy can be used more effectively to stop cancer.