Monoclonal antibodies (MABs)

Some monoclonal antibodies (MABs) are a type of immunotherapy. They work by triggering the immune system and helping it to attack cancer. This page is about MABs that affect the immune system.

Some MABs work in a more targeted way. For example, they can block signals that tell cancer cells to divide. You can read more about this in our information about targeted cancer drugs.

What are monoclonal antibodies?

Antibodies are found naturally in our blood and help us to fight infection. MAB therapies mimic natural antibodies but are made in a laboratory. Monoclonal just means all one type. So each MAB is a lot of copies of one type of antibody. 

Many different MABs are available to treat cancer. They work in different ways and some work in more than one way. 

How do monoclonal antibodies (MABs) work?

A MAB works by recognising and finding specific proteins on cells. Some work on cancer cells, others target proteins on cells of the immune system.

Each MAB recognises one particular protein. They work in different ways depending on the protein they are targeting. 

Diagram showing a monoclonal antibody attached to a cancer cell

MABs work as an immunotherapy in different ways. Some MABs work in more than one way. 

They can:

  • trigger the immune system to attack and kill cancer cells
  • act on cells to help the immune system attack cancer cells

Trigger the immune system

Some MABs trigger the immune system to attack and kill cancer cells.

Although cancer cells are abnormal, they develop from normal cells so they can be difficult for the immune system to spot.

Some MABs attach themselves to cancer cells, making it easier for the cells of the immune system to find them. This process is called antibody-dependent cell-mediated cytotoxicity or ADCC.

Below is a short video showing how MABs work when they trigger the immune system.

Examples of MABS that work in this way include:

  • rituximab (Mabthera) – a treatment for chronic lymphocytic leukaemia (CLL) and some types of non Hodgkin lymphoma
  • cetuximab (Erbitux) – a treatment for advanced bowel cancer and head and neck cancer
  • trastuzumab (Herceptin) – used to treat breast cancer and stomach cancer

You can find more information about these in our list of cancer drugs. 

Help the immune system to attack cancer

Other MABs work by acting on cells of the immune system. For example, a type of immunotherapy called checkpoint inhibitors. Checkpoint inhibitors block proteins that stop the immune system attacking cancer cells.

Checkpoint inhibitors block different proteins, including:

  • CTLA-4 (cytotoxic T lymphocyte associated protein 4)
  • PD-1 (programmed cell death protein 1)
  • PD-L1 (programmed death ligand 1)

So you might hear these drugs named after these checkpoint proteins – for example, CTLA-4 inhibitors, PD-1 inhibitors and PD-L1 inhibitors. 

Examples of checkpoint inhibitors include:

  • ipilimumab (Yervoy) - a treatment for advanced melanoma
  • nivolumab (Opdivo) 
  • pembrolizumab (Keytruda)

Nivolumab and pembrolizumab are used to treat several different types of cancer.

Other monoclonal antibodies

Other MABs work in a more targeted way. For example, they can block signals that tell cancer cells to divide. You can read more about this in our information about targeted cancer drugs.

How you have them

You usually have MAB treatment through a drip (infusion) into a vein. There are a few MABs you have as an injection under the skin (subcutaneous injection).

How often you have treatment and how many treatments you need will depend on:

  • which MAB you have
  • the type of cancer you have


Before you have some types of MAB you might need to have tests using some of your cancer cells or a blood sample to find out whether the treatment is likely to work. These tests look for changes in certain proteins or genes. 

You cancer specialist can tell you if this applies to your treatment. This is not the case for all MABs and you don’t always need this test.

To test your cancer cells, your specialist needs a sample (biopsy) of your cancer. They might be able to test some tissue from a biopsy or operation you have already had. 

Side effects

All treatments have possible side effects. These can vary depending on the type of MAB you have. 

Allergic reaction during treatment

A common side effect of some MABs is an allergic reaction to the drug. This reaction is most likely to happen during treatment and when you first have the treatment. 

If this is possible with your drug, you might have paracetamol, a steroid and an antihistamine drug before treatment to prevent a reaction.

An allergic reaction can include these symptoms, though you may not have all of them:

  • breathlessness
  • fever and chills
  • an itchy rash
  • flushes and faintness

Your nurse will monitor you and treat any symptoms if they happen.

General side effects

Side effects might include:

  • skin changes such as red and sore skin or an itchy rash
  • diarrhoea
  • tiredness
  • flu-like symptoms such as chills, fever, dizziness
  • feeling or being sick
Contact your doctor or nurse if you have these symptoms, particularly if you have diarrhoea, a rash or flu-like symptoms. They can decide whether you need treatment.

Specific side effects

Some MABS have specific side effects which can sometimes be serious. For example, some MABs can cause heart problems or increase your risk of bleeding. Your team will tell you about this before your start treatment.

For more information about the side effects of your treatment, go to the individual drug pages.

This page is due for review. We will update this as soon as possible.

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    VT De Vita, TS Lawrence and SA Rosenberg
    Lippincott, Williams and Wilkins, 2015

  • Electronic Medicines Compendium
    Accessed January 2021

  • Recognizing and managing on toxicities in cancer immunotherapy
    L Yang and others
    Tumour Biology, 2017. Volume 39, Issue 3:1010428317694542

  • State of the art in anti-cancer mAbs
    SM Chiavenna and others
    Journal of Biomed Science, 2017. Volume 24, Issue 15

  • Clinical development of targeted and immune based anti-cancer therapies
    N A Seebacher and others
    Journal of Experimental Clinical Cancer Research 2019 Apr 11: 38 (1): 156

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. If you need additional references for this information please contact with details of the particular issue you are interested in.

Last reviewed: 
21 Jan 2021
Next review due: 
18 Jan 2024

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