This information is about lapatinib, also known as Tyverb®, which belongs to a group of cancer drugs known as tyrosine kinase inhibitors. It is mainly being used to treat women with advanced breast cancer, but it is also being researched as a treatment for people with other cancers.

Some cancer cells have particular proteins called growth factor receptors on their surface. Stimulation of these receptors on the outside of the cell activates something called a tyrosine kinase enzyme inside the cell, which can prompt the cancer cell to grow.

Specific drugs have been developed to stop (or inhibit) the enzyme, and therefore stop the growth factor receptor from activating the cancer cell. These drugs are known as tyrosine kinase inhibitors (TKIs).

A group of growth factor receptors known as the erbB (or HER) receptors have been found on several different types of cancer cells. Lapatinib targets two of these receptors:

• erbB1 (also known as epidermal growth factor receptor, EGFR)
• erbB2 (also known as HER2).

Lapatinib stops the action of EGFR and HER2. It targets the inside part of the receptors, preventing the tyrosine kinase enzyme from being activated - which may then stop the cell dividing. Lapatinib may therefore stop the cancer cells from growing.

Lapatinib works in a different way from both chemotherapy and hormonal therapy. It also works very differently to trastuzumab (Herceptin®), another treatment against HER2 that targets and blocks the outside part of the growth factor receptor.

Tests may be done to check the level of EGFR or HER2; these will tell if you are likely to benefit from lapatinib. Testing can be done at the same time as diagnosis, or samples of cancer cells from previous biopsies or surgery may be used.

Lapatinib is a tablet.

Lapatinib should be taken every morning, either an hour before or an hour after food. It should not be taken with grapefruit juice.

Your doctor or specialist nurse may invite you to take part in a research trial using lapatinib. Lapatinib is being researched as a treatment for different types of cancer. At first, it will be used for people with breast cancer that has spread to other parts of the body or come back after initial treatment (advanced breast cancer), or for people who have tried other treatments including trastuzumab (Herceptin®). Lapatinib should be taken with a chemotherapy tablet called capecitabine (Xeloda®).

Lapatinib is also being studied for use in earlier stages of breast cancer, and in other types of cancer such as kidney cancer and head and neck cancer.

Each person’s reaction to cancer treatment is different. Some people have very few side effects, while others may experience more. The side effects described here will not affect everyone who has lapatinib.

We have outlined the most common side effects that can occur with lapatinib, although side effects are generally mild. As it is a new treatment not all the possible side effects are known. Because lapatinib is given with other cancer treatments, you may also get side effects associated with these other treatments. If you notice any effects that you think may be due to the drug, but that are not listed here, please discuss them with your doctor or nurse.

Diarrhoea is the most common side effect with lapatinib and develops around one week after treatment. Mostly it is not serious and gets better after about a week. Diarrhoea usually doesn’t need any treatment, but if necessary, it can be easily controlled with medicine. Let your doctor know if you have severe diarrhoea or if it continues. It is important to drink plenty of fluids if you develop this problem.

Skin rash An acne-like rash can develop after 2–3 weeks of treatment. It usually appears on the face and the upper part of the body. The rash should gradually fade over the following weeks, even if you continue to have treatment. Lapatinib also causes hand-foot syndrome which causes reddening, soreness and cracking of the skin on the palms of the hands and the soles of the feet. This should start to improve once treatment finishes.

Tiredness and feeling weak You may feel very tired during your treatment. It is important to allow yourself plenty of time to rest.

Feeling sick (nausea) or being sick (vomiting) Your doctor can prescribe very effective anti-sickness (anti-emetic) drugs to prevent or greatly reduce nausea and vomiting. If the sickness is not controlled, or continues, tell your doctor, who can prescribe other anti-sickness drugs which may be more effective.

Indigestion and heartburn This is a common side effect. If you have any indigestion or heartburn it can usually be relieved by taking an antacid. You should leave a gap of at least an hour before or after taking your lapatinib, before taking the antacid. Let your doctor or nurse know if you have any indigestion that isn’t relieved.

Stomach cramps and bloating Let your doctor know if you get any stomach cramps or bloating. If necessary they can prescribe medicines to help relieve this.

Loss of appetite A dietitian or specialist nurse at your hospital can give advice about how to boost your appetite, cope with eating difficulties and maintain your weight.

Mouth sores and ulcers Your mouth may become sore and you may notice small ulcers during your treatment. Drink plenty of fluids and clean your teeth regularly and gently with a soft toothbrush, as this can help to reduce the risk mouth problems. Tell your nurse or doctor if you have these problems, as special mouthwashes and medicines to prevent or clear mouth infection, can be prescribed. 

Constipation This can usually be relieved by drinking plenty of fluids; eating a high-fibre diet and taking gentle exercise. Sometimes you may need to take medicines to stimulate your bowel (laxatives). These can be prescribed by your doctor.

Muscle and joint pains You may notice that you have muscle or joint pains, especially in your back. Let your doctor know if you develop these as they can prescribe painkillers.

Headaches These can usually be controlled with simple painkillers. Let your doctor know if the headaches are severe or are not relieved with painkillers.

Difficulty sleeping Some people find that they have trouble sleeping while taking lapatinib. Having a warm bath or a hot milky drink before bed can be helpful. Using relaxation techniques or CDs may also help. If you still have trouble sleeping, talk with your doctor about night sedation.

Your liver may be temporarily affected Rarely lapatinib may cause changes in the way that your liver works, although it will return to normal when the treatment is finished. The changes are unlikely to cause you any harm, but your doctor will monitor this carefully. Samples of your blood will be taken from time to time to check that your liver is working properly.

Changes in the way your heart works Lapatinib may cause changes in the muscle of the heart. This can affect how the heart works. Tests to see how well your heart is working may sometimes be carried out before the drug is given and during treatment.

Other medicines Some medicines can be harmful to take when you are being treated with lapatinib. Let your doctor know about any medications you are taking, including non-prescribed drugs such as complementary therapies and herbal drugs, or medicines you have bought over the counter.

Fertility Your ability to become pregnant or father a child may be affected by taking this drug. It is important to discuss fertility with your doctor before starting treatment.

Contraception It is not advisable to become pregnant or father a child while you are taking lapatinib, as there may be a risk that the developing foetus will be harmed. It is important to use effective contraception during treatment and for at least a few months afterwards. Again, discuss this with your doctor.

• It is important to take your tablets at the right times. You must take them as directed by your doctor, nurse or pharmacist.
• Keep the tablets in a safe place out of the reach of children - as lapatinib could harm them
• If your doctor decides to stop the treatment, return any remaining tablets to the hospital pharmacist. Do not flush them down the toilet or throw them away.
• If you are sick just after taking the tablets let your doctor know as you may need to take another dose. Do not take another tablet without first asking your doctor, nurse or pharmacist.
• If you forget to take a tablet do not take a double dose. Inform your doctor and keep to your regular dose schedule.

This section has been compiled using information from a number of reliable sources including:

• Multitargeted, Oral Therapy for Solid Tumors: An Expert Interview With Dr. Howard Burris III. Medscape Hematology-Oncology, April 2006.
• Geyer C et al. Lapatinib plus capecitabine compared with capecitabine alone for HER 2-positive advanced breast cancer. NEJM, 2006 Dec 28;355(26):2733-43.

For further references, please see the general bibliography.