Tykerb Immune Targeted Therapy for Breast Cancer
Q. I've been taking Herceptin for quite some time for my advanced HER2-positive breast cancer. The Herceptin worked for awhile, but now it's stopped. My oncologist says he has another "targeted therapy," Tykerb, which I'll take with a chemo drug, Xeloda. What's a targeted therapy?
A. A targeted therapy (or immune targeted therapy) is a manufactured antibody that "targets" specific properties of cancer cells: their production of protein, their use of enzymes, or their ability to form new blood vessels to support growth. It leaves healthy cells alone, which is a plus.
Q. Can we backtrack a minute? What's HER2-positive mean, anyway?
A. Cells do three things: they grow, they rest, and they repair themselves. Genes inside the chromosomes in your cells regulate their activity, telling them when to grow, and when to stop growing and rest. If the genes malfunction, the patterns of growth/rest/repair are disrupted.
In HER2-positive breast cancer, there's an excess of HER2 genes in the chromosomes of some of your cells. These genes tell the cells to grow extra protein receptors on their surface. With these extra receptors, the cells keep getting signals to grow, rather than to rest or repair. They grow much faster than the cells around them; this wild, uncontrolled growth turns them into cancer cells. Twenty-five percent of all breast cancers are HER2-positive.
Q. So, what does Tykerb do, specifically?
A. Tykerb (lapatinib) is an antibody that blocks the HER2 protein. Unlike Herceptin, which attaches itself to protein receptors on the outside of cancer cells (effectively blocking the "grow" message), Tykerb stops HER2 protein from working from within the cell. In addition, it blocks another abnormal protein within the cell. Since the mechanism by which it works is significantly different than that of Herceptin, it's been found to be effective in women with metastatic breast cancer for whom Herceptin had quit working.
Tykerb, which received FDA approval in April 2007, actually appears to be more effective than Herceptin and easier to administer (it's taken in pill form, not by injection), right from the get-go. In clinical trials, women taking Tykerb were surviving significantly longer than women on Herceptin, so much so that researchers put a quick end to the trials, advising women to switch to Tykerb immediately. So Tykerb may actually be in the process of supplanting Herceptin for women with HER2-positive metastatic breast cancer.
Q. How will I take Tykerb? Is it a pill?
A. Yes, Tykerb is a pill. You'll probably take five pills (1250mg) a day, either an hour before or after eating-in other words, on an empty stomach. However, researchers discovered that just two pills (500mg), when taken with food (specifically, high-fat food), are every bit as effective as five pills. And, when taken with food and grapefruit juice both, a single pill may deliver as much medication to the bloodstream as those original five pills. In addition, fewer pills seems to result in fewer side effects, most notably diarrhea. So keep in touch with your doctor for the latest updates about how to take Tykerb. As mentioned at the beginning of this FAQ, Tykerb was approved in combination with Xeloda, so patients should be taking both together.
Q. Might as well ask - what about side effects of Tykerb?
A. Thankfully, Tykerb doesn't carry the serious potential side effects that Herceptin does: it hasn't been shown to do any heart damage. Main side effects are diarrhea, rash, and redness/tingling in the hands and feet. Rarer side effects include nausea/vomiting, and fatigue. Thankfully, all of these side effects can (usually) be successfully treated.
One troubling "side effect" is the cost of Tykerb: you'll find the price of Tykerb is up around $2900 a month. Which is another reason to keep in touch with your doctor about how many pills a day you need to take; cutting down on the number of doses will save you (or your insurance company).