This information is about panitumumab which is one of a group of cancer drugs, known as monoclonal antibodies. This drug is being tested as a treatment for people with advanced cancer (cancer that has spread to other parts of the body), particularly advanced cancer of the large bowel (colon and rectum). Panitumumab is currently only being used as part of research trials.

When a drug is being developed it has to go through various stages of research, called clinical trials or studies. These are intended to establish a safe dosage, to discover what side effects the drug may have and to find out which cancers it may be used to treat. The trials also find out how effective the drug is, whether it is better than the existing treatments, or has extra benefit when given with these treatments.

At this stage, Panitumumab is only available to a small number of people in the UK, usually in clinical trials. In certain circumstances it may also be given to
individual patients who have been selected by their doctor as suitable (this is called a named-patient basis).

Many drugs that are thought to be promising may be found not to be as good as existing treatments, or to have side effects that outweigh any benefits. For this reason, doctors and other medical staff carry out frequent and careful checks on the progress of each patient who is having one of these developmental drugs. If you are taking a developmental drug your doctor will explain all about the drug, the procedures being used and how you will be looked after while you are taking it. If at any time you have concerns, you should ask your doctor or nurse for information and advice.

Monoclonal antibodies can destroy some types of cancer cells, while causing little harm to normal cells. They recognise certain proteins or receptors that are found on the surface of some types of cancer cells. The monoclonal antibody recognises the protein or receptor and 'locks' on to it (like a key in a lock).

There are different types of antibodies that work in different ways. Once the monoclonal antibody has attached to the protein or receptor it can:

• Trigger the body’s immune system to attack the cancer cell and cause the cell to be destroyed.
• Block a receptor from connecting with a different protein that helps the cell to grow. This may stop the cells from growing and dividing, or prevent cancer cells from developing a new blood supply.

Panitumumab belongs to a subgroup of monoclonal antibodies, known as epidermal growth factor receptor (EGFR) inhibitors.

Epidermal growth factor (EGF) is a protein that is present in the body. There are receptors for EGF on the surface of many types of cancer cell. When EGF binds to these receptors, chemical signals are triggered which cause the cells to grow and reproduce.

Panitumumab attaches itself to the EGF receptor, and prevents it from being activated. This stops the internal chemical signals, and inhibits the growth of cancer cells that have the EGFR on their surface. It works in a different way from both chemotherapy and hormonal therapy.

Tests may be done to check the level of EGFR present in the tumour; these ill tell if you are likely to benefit from panitumumab. Testing can be done on samples of the cancer cells at the same time as diagnosis of the cancer, or using cells from previous biopsies or surgery.

Panitumumab is a liquid. The nurse or pharmacist will prepare the drug.

Panitumumab is given through a small tube (cannula) inserted into a vein. It may be given in combination with chemotherapy drugs, or alone.

Panitumumab is given as a drip (infusion) over one hour, either once a week or once every two weeks.

In clinical trials, people have their panitumumab and chemotherapy given through a fine plastic tube which is inserted under the skin and into a vein near the collarbone (a central line), or passed through a vein in their arm (a PICC line). Your doctor or nurse will explain more about this to you.

Each person's reaction to cancer treatment is unique. Some people have very few side effects, while others may experience more. The side effects described in this information will not affect everyone who is given panitumumab. The drug may be used in combination with chemotherapy, so people will also have side effects from the chemotherapy. The side effects mentioned below are those caused by panitumumab.

We have outlined the most common side effects, but have not included those that are very rare and therefore extremely unlikely to affect you. As panitumumab is a new treatment, we do not know all the possible side effects it may cause. If you notice any effects that you think might be due to the drug, but that are not listed in this information, please discuss them with your doctor or nurse.

Skin rash This is the most common side effect of the drug and it affects most people. It occurs after 2–3 weeks of treatment, usually in the form of a rash, rather like acne, which appears on the face and the upper part of the body. It often gradually fades over the following weeks, even if your treatment with panitumumab continues.

Diarrhoea This can usually be easily controlled with medicine, but let your doctor know if it is severe or continues. It is important to drink plenty of fluids if you have diarrhoea.

Tiredness and a general feeling of weakness This is also known as fatigue. It is important to allow yourself plenty of time to rest.

Feeling sick (nausea) and being sick (vomiting) There are very effective anti-sickness drugs to prevent, or greatly reduce, sickness (nausea) and vomiting. If you experience this, it may begin a few hours after the treatment is given, and can last for up to a few days. If the sickness is not controlled, or continues, tell your doctor, who can prescribe other anti-sickness drugs which may be more effective.

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

• Rowinsky EK et al. Safety, pharmacokinetics, and activity of ABX-EGF, a fully human anti-epidermal growth factor receptor monoclonal antibody in patients with metastatic renal cell cancer. J Clin Oncol, 2004; 22: 3003-3015
• Malik I et al. Safety and efficacy of panitumumab monotherapy in patients with metastatic colorectal cancer (mCRC). Proc Amer Soc Clin Oncol, 2005, abstract 3520.
• Hecht J et al. Panitumumab therapy with irinotecan, 5-fluorouracil, and leucovorin (IFL) in metastatic colorectal cancer (mCRC) patients: a pharmacokinetic (PK) analysis. Proc Amer Soc Clin Oncol, 2005, abstract 259
• www.amgen.com Website of Amgen (Nov 2005).

For further references, please see the general bibliography.