Tykerb: 7 things you should know

Medically reviewed by Carmen Pope, BPharm. Last updated on Sep 21, 2023.

1. How it works

• Tykerb (lapatinib) is a dual kinase inhibitor that is used in combination with other medicines to treat certain types of hormone receptor-positive (HER-2) positive breast cancer in postmenopausal women or HER-2 positive breast cancer that has progressed or spread after treatment with other cancer medicines.
• Tykerb is a dual tyrosine kinase inhibitor and works by blocking two kinases that can stimulate cell division - Epidermal Growth Factor Receptor (EGFR) and human epidermal growth factor receptor 2 (HER-2). Some cells have too many of these proteins which can lead to uncontrolled cell growth and cancer. Blocking these proteins helps stop or slow the spread of breast cancer cells. Tykerb is a targeted drug therapy used in the treatment of HER-2-positive metastatic breast cancers.
• Tykerb belongs to the class of medicines known as tyrosine kinase inhibitors. Specifically, it is a dual EGFR/HER2 inhibitor. It may also be called a targeted treatment.

2. Upsides

• May be used in addition to Xeloda (capecitabine) to treat HER-2 positive breast cancer that has advanced or spread (metastasized) in patients who have already received treatment that includes an anthracycline, a taxane, and trastuzumab.
• May also be used in combination with Femara (letrozole) to treat HER-2 positive breast cancer in post-menopausal women when hormonal treatment is indicated.
• Tykerb is not a traditional chemotherapy drug, it is an oral targeted treatment because it works on specific proteins in breast cancer to help slow or stop the spread of cancer cells.
• Taken orally (by mouth).

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

• Common side effects affecting more than 20% of people include indigestion, loss of appetite, nausea, vomiting, diarrhea, rash, itching, dry skin, pain or redness on the palms of your hands or the soles of your feet (palmar-plantar erythrodysesthesia), problems with your fingernails or toenails, feeling weak or tired, nosebleeds, mouth sores, or headache. Discontinue if severe skin reactions occur.
• Hair-thinning or hair loss (alopecia) was reported in about 10% to 13% of patients receiving Tykerb plus other medicines. In most patients, hair loss is a reversible side effect if treatment is stopped.
• Tykerb has also been associated with decreases in left ventricular ejection fraction (LVEF). Confirm normal LVEF before starting treatment with Tykerb and monitor throughout.
• Liver toxicity has occurred. Perform baseline liver function tests every 4 to 6 weeks during treatment. Discontinue Tykerb and do not restart if severe liver toxicity occurs.
• Severe diarrhea has also been reported. Manage with antidiarrheal agents and replace fluids and electrolytes.
• Has also been associated with interstitial lung disease and pneumonitis. Discontinue if patients experience severe respiratory symptoms.
• May prolong the QT interval. Consider an ECG before initiation and monitor throughout treatment.
• The dosage of Tykerb may need modification for people with cardiovascular disease, severe liver disease, diarrhea, and with concomitant CYP3A4 drug interactions.
• Do not use Tykerb if you are pregnant. It could harm the unborn baby. If you are of childbearing potential, use effective contraception during treatment with Tykerb. Do not breastfeed.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

Tykerb (lapatinib) is an oral dual kinase inhibitor that is usually used in combination with other medicines to treat HER-2 positive breast cancer in postmenopausal women or HER-2 positive breast cancer that has progressed or spread after treatment with other cancer medicines. Common side effects include diarrhea, palmar-plantar erythrodysesthesia, nausea, rash, vomiting, and fatigue.

5. Tips

• Before you take Tykerb, tell your doctor if you have heart disease, liver disease, an electrolyte imbalance (low potassium or magnesium), or a personal or family history of long QT syndrome. You should not use Tykerb if you are allergic to lapatinib.
• Take Tykerb on an empty stomach, at least 1 hour before or 1 hour after a meal. You may swallow each tablet one at a time, but take the entire dose (all tablets) at the same time each day. Take Tykerb exactly as prescribed by your doctor. Do not take more or less than recommended.
• If you miss a dose, take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up for the missed dose.
• When used with Femara, the usual dose of Tykerb is 6 tablets taken once daily every day. Femara is also taken every day. When used with Xeloda, Tykerb is usually taken in a 21-day cycle. You will take Tykerb in a dose of 5 tablets once daily for all 21 days in a row. You will take Xeloda twice daily for only the first 14 days of the cycle. This 21-day cycle is then repeated. Xeloda must be taken with food or within 30 minutes of eating.
• Tykerb can cause severe or fatal liver problems. Call your doctor at once if you have signs of liver problems: upper stomach pain, itching, dark urine, clay-colored stools, or jaundice (yellowing of the skin or eyes).
• Also call your doctor at once if you have a headache with chest pain and severe dizziness, fainting, fast or pounding heartbeats, severe or ongoing diarrhea, new or worsening cough, wheezing, chest pain, shortness of breath, or a severe skin reaction.
• Get emergency medical help if you have signs of an allergic reaction to Tykerb, such as hives; difficulty breathing; or swelling of your face, lips, tongue, or throat.
• You will need blood tests every 4 to 6 weeks to check your liver function. Your heart function may also need to be checked using an electrocardiograph or ECG (sometimes called an EKG).
• Do not use Tykerb if you are pregnant. It could harm the unborn baby or cause birth defects. Use effective birth control to prevent pregnancy while you are using this medicine. Tell your doctor right away if you become pregnant. It is not known whether lapatinib passes into breast milk or if it could harm a nursing baby. You should not breastfeed while you are taking this medicine.

6. Response and effectiveness

• The combination of Tykerb plus capecitabine (T+C) has a better response than capecitabine alone. Trials that investigated the endpoint “Time to Progression” (TTP) – defined as the time to tumor progression or death from breast cancer from enrollment in the trial, reported a significant difference for those women assigned T+C compared with those assigned capecitabine alone. The number of TTP events was 82 to 121 for women assigned T+C compared to 102 to 126 for those assigned capecitabine alone. Response rates ranged from 23.7% to 31.8% in those given T + C compared to 13.9 to 17.4% given capecitabine alone.
• This result was significant enough to stop further enrolment in the trial after 4 months, unblind the trial, and transfer those women receiving capecitabine alone to treatment with Tykerb plus capecitabine. These women were followed for another 2 years with the median overall survival reported as 75 weeks in the Tykerb plus capecitabine group compared with 65.9 weeks in those women who originally only received capecitabine. After 2 years, 76% had died in the Tykerb plus capecitabine group compared with 82% in the capecitabine group alone.

7. Interactions

Medicines that interact with Tykerb may either decrease its effect, affect how long it works, increase side effects, or have less of an effect when taken with Tykerb. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with Tykerb include:

• antacids or stomach acid reducers such as Prilosec or Nexium
• antibiotics or antifungal medicines
• antidepressants
• heart or blood pressure medications
• medicines used to treat HIV or AIDS
• seizure medications
• St. John's wort.

Grapefruit and grapefruit juice may interact with lapatinib and lead to unwanted side effects. Avoid the use of grapefruit products while taking Tykerb.

Tykerb inhibits CYP3A4, CYP2C8, and P-glycoprotein (P-gp, ABCB1)and is a weak inhibitor of CYP3A4 in vivo. Caution when using substrates of these enzymes that have a narrow therapeutic window. Avoid strong CYP3A4 inhibitors, such as clarithromycin, erythromycin, diltiazem, itraconazole, ketoconazole, ritonavir, verapamil, goldenseal and grapefruit.

Avoid strong CYP3A4 inducers, such as phenobarbital, phenytoin, rifampicin, St. John's Wort, and glucocorticoids. If unavoidable, consider a gradual dose increase of Tykerb.

Note that this list is not all-inclusive and includes only common medications that may interact with Tykerb. You should refer to the prescribing information for Tykerb for a complete list of interactions.

References

• Tykerb Prescribing Information. Updated Aug 3, 2023. https://www.drugs.com/pro/tykerb.html#s-34073-7

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Tykerb only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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