Most cancer drugs have a reputation for attacking both cancer cells and healthy cells. So not only do cancer patients have to deal with the cancer wreaking havoc on their body, but the side effects of the drugs as well.
But there may be a new solution on the market, and it’s called “molecularly targeted therapy.” The drugs are designed to specifically attack and kill only the cancer cells of a specific type of cancer. And they are tailor made to recognize specific molecules unique to specific cancers.
The drug that is leading the way is Glivec, which is also known as STI571. It is active against a rare form of leukemia known as chronic myeloid leukemia, or CML, which is characterized by excessive overproduction of white blood cells.
1.3 million Americans will be diagnosed with cancer this year, and doctors are hopeful that Glivec could provide a model for similar drugs to treat other cancers.”This is as important as it gets. A cancer-specific target, a drug specifically designed for the target, the most effective agent ever,” says Paul A. Bunn Jr., president-elect of the American Society of Clinical Oncology. “Read my lips, this is real, not mice.”
The main researcher on the drug is Dr. Brian Druker, director of the Leukemia Program at the Oregon Health Sciences University in Portland, and it’s being developed by Novartis Pharmaceuticals.
“If we understand the critical abnormalities that drive a cancer, we can target the cancer with an effective and non-toxic therapy,” Druker says. “We need to identify the critical abnormalities in each and every cancer so drugs like STI571 can be developed for each cancer.”
The study results of Drukers, in which they show the clinical benefits of STI571 in treating leukemia, were released today in the New England Journal of Medicine. In an email to ABCNEWS, Dr. Lou Fehrenbacher, a hematologist/oncology specialize at Kaiser Permanente Medical Center in Vallejo, California, said “The major importance of this drug is the nature of its discovery [it is a logically engineered creation]…. The enzyme was isolated, reproduced, and then a drug to inhibit it was engineered.”
These “designer” drugs are created working backward from a known abnormal molecule specific to a certain type of cancer. Once the molecule is identified, a drug can be designed that interferes with that molecule. Because of this, these drugs have a very limited spectrum of use.
According to Dr. Grover Bagby Jr., director of the Oregon Cancer Institute at OHSU, “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. “
In 1993, Druker discovered that STI571 also worked against a rare gastrointestinal cancer – gastrointestinal stromal tumor, or GIST. The reason it is effective is because of an enzyme unique to GIST that is related to the original target enzyme in CML. In one of the case studies in the current issue of the New England Journal of Medicine, it show the clinical outcome of a GOST patient in Finland who as treated with STI571, and it shows a significant reduction in the size of the patient’s tumor.
The 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. A result of its positive clinical findings will be available to patients within the next few months.