Tykerb (chemical name: lapatinib) is approved by the U.S. Food and Drug Administration (FDA):
- to be given in combination with Xeloda (chemical name: capecitabine), a type of chemotherapy, to treat advanced-stage, HER2-positive breast cancer that has stopped responding to anthracycline and taxane chemotherapy and Herceptin (chemical name: trastuzumab)
- to be given in combination with Femara (chemical name: letrozole), a type of hormonal therapy, to treat postmenopausal women diagnosed with hormone-receptor-positive, HER2-positive metastatic breast cancer
Doctors can choose to use Tykerb to treat other stages of breast cancer whether or not that particular use is officially approved by the FDA.
Tykerb is a pill taken by mouth.
Learn more about:
- How Tykerb works
- Is Tykerb right for you?
- What to expect when taking Tykerb
- Paying for Tykerb
- Tykerb side effects
How Tykerb works
Cancer cells grow in an uncontrolled fashion. Tykerb works inside the cancer cell by interfering with certain proteins, called kinases, that can stimulate this uncontrolled growth.
Genes are like instruction manuals that tell each cell in the body how to grow, what kind of cell become, and how to behave. They do this by ordering the cell to make special proteins that cause a certain activity — such cell growth, rest, or repair.
Some cancer cells have abnormalities in genes that tell the cell how much and how fast to grow. Sometimes the cancer cells have too many copies of these genes with abnormalities. When there are too many copies of these genes, doctors refer to it as “overexpression.” With some forms of gene overexpression, cancer cells will make too many of the proteins that control cell growth and division, causing the cancer to grow and spread.
Some breast cancer cells make (overexpress) too many copies of a particular gene known as HER2 (human epidermal receptor 2). The HER2 gene makes a protein called known as a HER2 receptor. HER2 receptors are like ears, or antennae, on the surface of all cells. Breast cancer cells that overexpress the HER2 gene make too many HER2 receptor proteins and are said to be HER2-positive.
HER2 receptors use protein signals, called kinases, to control how much energy the cells have to grow and multiply. Breast cancer cells that overexpress HER2 can have too much kinase activity, so the cancer cells grow too much, too fast.
Tykerb is a HER2 inhibitor that works by interfering with HER2-related kinases inside the cell, limiting the amount of energy breast cancer cells have to grow and multiply. By limiting the amount of energy, Tykerb can slow or stop the growth of breast cancer.
Tykerb is a targeted therapy, but unlike Herceptin and Avastin (chemical name: bevacizumab) it is not an immune targeted therapy. Immune targeted therapies are versions of naturally occurring antibodies that work like the antibodies made by our immune systems. Tykerb is a chemical compound, not an antibody.
Tykerb works differently than Herceptin and Perjeta (chemical name: pertuzumab), which are also HER2 inhibitors. Herceptin and Perjeta block the HER2 protein on the surface of breast cancer cells. Perjeta targets a different area on the HER2 receptor than Herceptin does, so it's believed to work in a way that is complementary to Herceptin. Tykerb blocks the HER2 protein inside the cell. It's because of this different mechanism that Tykerb may be effective against HER2-positive cancers that have stopped responding to Herceptin.
Is Tykerb right for you?
Four different tests can be used to figure out if the cancer is HER2-positive and if it will likely respond to Tykerb:
IHC is the most commonly used test to see if a tumor has too much of the HER2 receptor protein on the surface of the cancer cells.
The IHC test gives a score of 0 to 3+ that measures the amount of HER2 receptor protein on the surface of cells in a breast cancer tissue sample. If the score is 0 to 1+, it’s called “HER2 negative.” If the score is 2+, it's called "borderline." A score of 3+ is called “HER2 positive.”
If the IHC test results are borderline, it’s likely that a FISH test will be done on a sample of the cancer tissue to determine if the cancer is HER2-positive.
FISH (Fluorescence In Situ Hybridization)
The FISH test also looks to see if the cancer is HER2-positive. This test is the most accurate, but it is more expensive and takes longer to return results. This is why an IHC test is usually the first test done to see if a cancer is HER2-positive. The FISH test shows how many copies of the HER2 gene are in tumor cells. The more copies of the gene, the more HER2 receptors the cells have.
With the FISH test, you get a score of either "positive" or "negative" (some hospitals call a negative test "zero"). If the cancer is FISH positive, it will probably respond well to Tykerb.
SPoT-Light HER2 CISH (Subtraction Probe Technology Chromogenic In Situ Hybridization)
The SpoT-Light HER2 CISH test looks for how many copies of the HER2 gene are in the tumor cells of a breast cancer tissue sample. The SPoT-Light test is less complicated than the FISH or IHC tests.
With the SPoT-Light test, you get a score of either "positive" or "negative." If the cancer is SPoT-Light HER2-positive, it will probably respond well to Tykerb.
Inform HER2 Dual ISH (In Situ Hybridization)
The Inform HER2 Dual ISH test uses a special stain that makes HER2 proteins change color. The test can be used on tissue samples that have been stored in wax or other chemicals. The Inform HER2 Dual ISH test offers more precise results than the IHC HER2 test. It is also less expensive and doesn’t need the special microscope of the FISH HER2 test.
With the Inform HER2 Dual ISH test, you get a score of either “HER2 positive” or “HER2 negative.”
Learn more in Breast Cancer Tests.
What to expect when taking Tykerb
Tykerb is prescribed with the chemotherapy medication Xeloda or with the hormonal therapy medicine Femara. All three medicines are pills that are taken orally.
You can take Tykerb indefinitely in order to keep the cancer under control. Your doctor would only stop you from taking Tykerb if the cancer stopped responding to it or if you experience any severe side effects.
Paying for Tykerb
If your doctor decides to prescribe Tykerb, you may be eligible to enroll in the Patient Assistance Foundation, sponsored by Novartis (the maker of Tykerb). For more information, you can also call 1-800-277-2254.
Tykerb side effects
Tykerb can cause some side effects that are usually not severe and can be treated successfully. The most common side effects are:
Dosages can be adjusted to help ease these side effects. In severe cases of diarrhea, it may be necessary to stop taking the medication.
Very rarely, Tykerb has been found to cause mild heart damage. If heart damage occurs, Tykerb is discontinued and heart-strengthening medication can bring heart function back to normal. Anyone who is considering taking Tykerb and has a preexisting heart condition should be monitored carefully before and during treatment.
Tykerb does not seem to cause the more severe heart and lung problems associated with Herceptin.
- Tykerb (lapatinib) prescribing information. Novartis. East Hanover, NJ. 2018. Available at https://www.pharma.us.novartis.com/sites/www.pharma.us.novartis.com/files/tykerb.pdf.