An anti-EGFR antibody
Panitumumab
A targeted antibody for RAS wild-type bowel cancer, given by drip by oncology teams.
What is Panitumumab?
Panitumumab is a targeted cancer medicine (a monoclonal antibody) used for bowel cancer that has normal (RAS wild-type) genes. It is given by a specialist oncology team as a drip into a vein, often with chemotherapy. It works in a similar way to cetuximab, blocking the EGFR growth protein, so the cancer is tested for RAS genes first. Its typical side effects are an acne-like skin rash, low magnesium and diarrhoea. Infusion reactions can happen, so you are watched closely during treatment.
Education and reference only. This is a plain-language guide to Panitumumab — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Panitumumab is a monoclonal antibody, a laboratory-made protein that targets EGFR, a growth protein on some cancer cells. It is used for bowel cancer that has normal (RAS wild-type) genes, often alongside chemotherapy. It works in a similar way to cetuximab. It is not a tablet; it is given by oncology specialists as a drip into a vein. The brand name is Vectibix.
How it works
EGFR is a protein on the cell surface that signals cells to grow and divide, and some bowel cancers depend on it. Panitumumab attaches to EGFR and blocks this growth signal, which can slow or shrink the cancer, especially when combined with chemotherapy. As with cetuximab, it only works if the cancer's RAS genes are normal (wild-type), because a faulty RAS gene keeps the growth signal switched on inside the cell regardless of EGFR. Blocking EGFR in the skin and gut explains the acne-like rash, the drop in magnesium and the tendency to diarrhoea.
Company & origin
Originated / developed by: Amgen.
A targeted cancer antibody used in the UK by oncology teams for bowel cancers with normal (RAS wild-type) genes.
Practical use
How to take Panitumumab
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- It is given by your oncology team as a drip into a vein, often alongside chemotherapy; it is never taken as a tablet.
- Look after your skin with the moisturisers and advice your team gives, and protect your skin from the sun, as a rash is common.
- Tell your team promptly about diarrhoea, as it is common and can be treated to keep you well and hydrated.
- Attend blood tests to check your magnesium and other levels, which may need topping up.
- Report a severe or infected rash, or muscle cramps or twitching that can signal low magnesium.
Weighing it up
Advantages & disadvantages of Panitumumab
Advantages
- Specifically targets EGFR and can slow or shrink suitable RAS wild-type bowel cancers.
- Works well alongside chemotherapy as part of a planned course.
- Infusion reactions are generally less common than with some similar antibodies.
Disadvantages
- Commonly causes an acne-like skin rash that can be uncomfortable and need skin care.
- Lowers magnesium levels and can cause diarrhoea, needing monitoring and management.
- Only helps bowel cancers with normal (RAS wild-type) genes, so testing is needed first.
Practical use
Good to know
Panitumumab is only used when bowel cancer testing shows normal (RAS wild-type) genes, as it will not help cancers with a faulty RAS gene. Like cetuximab, the most noticeable effect is an acne-like rash on the face and upper body, which can be uncomfortable but is often a sign the medicine is working; your team can advise on skin care and sun protection. It commonly lowers magnesium, which is checked and replaced if needed, and it can cause diarrhoea, which should be reported early so it can be managed. Infusion reactions are generally less common than with cetuximab but can still happen, so you are watched closely. Tell your team about a severe or infected rash, or symptoms of low magnesium such as cramps or twitching.
Who should not take it / use with caution
- It is not used for bowel cancers that have a faulty (mutated) RAS gene, as it will not work.
- Anyone who has had a serious allergic reaction to panitumumab should not receive it again.
- It is avoided in pregnancy because it can harm the developing baby, so effective contraception is advised.
Monitoring
- Regular blood tests to check magnesium and other salts, with replacement if they fall.
- Watching the skin for rash and signs of infection, with skin-care advice, and managing diarrhoea.
- Infusion-reaction checks and review of how the cancer is responding.
Side effects
- An acne-like skin rash, often on the face and upper body, which can be a sign it is working.
- Low magnesium in the blood and diarrhoea, which are monitored and managed.
- Tiredness, dry or cracked skin, sore mouth and, less often, infusion reactions.
Key interactions
- Given as a planned combination with chemotherapy rather than an accidental interaction.
- Other medicines or conditions that lower magnesium may add to the effect, so levels are watched.
- Tell your team about all your medicines so monitoring and skin care can be tailored.
Available as: Given by oncology teams as a drip into a vein.
Answers
Panitumumab: frequently asked questions
How is panitumumab different from cetuximab?
Both are antibodies that block the EGFR growth protein in RAS wild-type bowel cancer; they are very similar, and infusion reactions are generally a little less common with panitumumab.
Why was my cancer tested for RAS genes?
Panitumumab only helps bowel cancers with normal (RAS wild-type) genes; if the RAS gene is faulty, the growth signal stays switched on and the medicine will not work.
Why do I have a skin rash?
Panitumumab blocks EGFR, which is also active in the skin, so an acne-like rash is common and is often a sign it is working; your team can advise on skin care.
Will it upset my stomach?
Diarrhoea is common, so tell your team early; it can usually be managed with simple treatments and good hydration. Low magnesium is also checked with blood tests.
Is panitumumab a tablet?
No. It is given by your oncology team as a drip into a vein, usually alongside chemotherapy, and is not available as a tablet.
Authoritative sources
- BNF
- NICE CKS
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