Tykerb (lapatinib) may be effective at shrinking breast cancer tumors in the brain, researchers say. This drug is called a targeted therapy because it can kill cancer cells and leave normal cells alone. Tykerb targets HER2 and EGFR, two proteins that function abnormally in breast cancer cells.
A study was conducted that included 241 breast cancer patients with brain metastasis that continued to progress after radiation treatment and Herceptin therapy.
The study concluded that nearly half of the patients, 46 percent, experienced at least a twenty percent reduction in the size the the brain tumors.
The researchers concluded "Tykerb has promise in the treatment of brain metastasis".
1. The "targets" that the new "smart drugs" go after can be located on the "inside" or "outside" of a cancer cell. The most common targets on the outside are receptors, proteins that help relay chemical messages. And many targets on the inside are enzymes, proteins that help speed up chemical reactions in the body.
Very large molecule drugs (Taxol and Herceptin) don't have a convenient way of getting access to the large majority of cells. Plus, there is multicellular resistance, the drug affecting only the cells on the outside may not kill cells if they are in contact with cells on the inside, which are protected from the drug. The cells may pass small molecules back and forth. And large molecule drugs cannot permeate the blood-brain barrier (BBB), to give added effects to the central nervous system (CNS).
Small molecule drugs can seek out cancer cells and attack them from within. Exciting results have come from studies of multitargeted tyrosine kinase inhibitors, small molecules that act on multiple receptors in the cancerous cell, like Tykerb. It can act on killing two rogue proteins as opposed to Herceptin targeting only one of the proteins. Tykerb could offer hope in treating the spread of cancer to the brain, for those patients that it would work.
Posted at 7:38PM on Jul 24th 2007 by Gregory D. Pawelski