Almost all existing cancer treatments and drugs are poisons that are created to attack and kill cancer cells, or at least slow their growth. However, most of these treatments attack not just cancer cells, they also kill healthy cells. People taking the medications often suffer awful side effects on top of whatever the cancer is already damaging. Patients become weak and thin. They lose their color and their hair.
Thankfully, the next revolution in cancer treatment has possibly arrived. The treatment is called “molecularly targeted therapy.” The therapy consists of drugs designed at the molecular level of the cell to specifically attack and kill only the cancer cells of a specific type of cancer. They are customized to recognize specific molecules unique to specific cancers. The model medication leading the way is Glivec, which is also known as STI571. It is active against a rare form of leukemia called chronic myeloid leukemia, or CML. It is characterized by excessive overproduction of white blood cells. About 7,000 Americans are diagnosed with CML each year.
Physicians are hopeful that the drug could provide a model for similar drugs to treat cancers affecting thousands more people. This year alone, over 1 million Americans will be diagnosed with cancer. Paul A. Bunn Jr., president-elect of the American Society of Clinical Oncology stated, “This is as important as it gets. A cancer-specific target, a drug specifically designed for the target, the most effective agent ever. Read my lips, this is real, not mice.”
Director of the Leukemia Program at the Oregon Health Sciences University in Portland, Doctor Brian Druker, is the main researcher on the medicine, which is being developed by Novartis Pharmaceuticals. Druker says, “If we understand the critical abnormalities that drive a cancer, we can target the cancer with an effective and non-toxic therapy. We need to identify the critical abnormalities in each and every cancer so drugs like STI571 can be developed for each cancer.”
The current issue of the New England Journal of Medicine has two studies led by Druker on the clinical benefits of STI571 in treating leukemia. The conclusions were recently released. Doctor Lou Fehrenbacher, a hematology/oncology specialist at Kaiser Permanente Medical Center in Vallejo, California, said in an email to ABCNEWS: “The major importance of this drug is the nature of its discovery. The enzyme was isolated, reproduced, and then a drug to inhibit it was engineered.” These molecular “designer” drugs are created working backward from a known abnormal molecule specific to a definitive type of cancer. After the molecule is identified, a drug can be created that interferes with that molecule. So these drugs, by design, have a very limited spectrum of use. Dr. Grover Bagby Jr., director of the Oregon Cancer Institute at OHSU said, “This drug will not have broad applicability in a wide variety of tumors, precisely because it is targeted to a specific small set of molecules.”
FDA Planning Fast Track Treatment In addition to CML, Druker discovered in 1993 that STI571 also worked against a rare gastrointestinal cancer, gastrointestinal stromal tumor, or GIST. It is effective due to an enzyme unique to GIST that is related to the original target enzyme in CML. A study that appears in the current issue of the New England Journal of Medicine on the clinical outcome of one GIST patient in Finland treated with STI571 showed a considerable reduction in the size of the individual’s tumor. Additional findings from larger clinical trials of STI571 for GIST will be presented at the American Society of Clinical Oncology meeting in May. Glivec is getting a priority review by the Food and Drug Administration for treatment of CML as a result of its positive clinical findings which will be available to patients within the next few months.