Telling Friend
from Foe New targeted drugs disrupt processes that are unique to cancer cells.
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What’s the ideal cancer drug? It’s one that is lethal to malignant cells, but leaves normal cells unscathed. Unfortunately, while chemotherapy attacks tumors, it can have a big impact on healthy tissues, as well.
Now, researchers are using discoveries in tumor biology and genetics to create drugs that do a better job of recognizing cancer cells. According to physicians at Froedtert & The Medical College of Wisconsin, many of these new “targeted drugs” are able to zero in on difficult cancers, while causing fewer side effects for patients.
A Larger Window for Therapy
How are targeted drugs different from traditional chemotherapy drugs? “It can be an artificial distinction,” said James Thomas, MD, PhD, Medical College of Wisconsin medical oncologist. “Even older chemotherapy drugs still had ‘targets’ within cancer cells.”
The main difference is how unique the target is to cancer. Most traditional chemotherapy drugs affect all rapidly dividing cells: that means they kill cancer, but are also toxic to healthy tissues. As a result, Dr. Thomas said, they offer a very small “therapeutic window” — a thin margin between too little drug to kill the cancer and too much drug for the patient.
“The term ‘targeted drug’ refers to the next generation of compounds designed to target processes that are more unique to cancer cells than normal cells,” Dr. Thomas said. Side effects are still an issue, but toxicity is generally lower. “With many of these drugs, patients feel quite a bit better — and the drug works better against the cancer.”
Taking Aim at the Oddities of Cancer
While the idea of cancer is frightening, cancer cells actually have many vulnerabilities. “The genetic differences of cancer cells can sometimes make them uniquely susceptible to targeted drugs,” Dr. Thomas said.
For example, many cancer cells lack normal mechanisms for repairing damage to their DNA. “They don’t stop to repair themselves, but just keep going, which is why they end up being cancerous,” Dr. Thomas said. Cancer cells depend on an alternative repair mechanism involving PARP, a key protein. “A
new class of targeted drugs specifically inhibits PARP,” he said. “Certain breast cancers are vulnerable to these drugs.”
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froedtert.com/cancer James Thomas, MD, PhD Clinical Cancer Center
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