What are targeted cancer drugs?

Targeted cancer drugs work by ‘targeting’ those differences that help a cancer cell to survive and grow. They are one of the main treatments for some cancers. For example, advanced melanoma and some types of leukaemia. 

Researchers are also looking at targeted drugs in clinical trials for many types of cancer.

There are many different types of targeted drugs. These are grouped together depending on how they work. These groups include:

• monoclonal antibodies
• cancer growth blockers
• drugs that block cancer blood vessel growth
• PARP inhibitors

How do targeted cancer drugs work?

Cancer cells have changes in their genes (DNA ) that make them different from normal cells. These changes mean that they behave differently. Cancer cells can grow faster than normal cells and they die less easily too. Cancer cells also sometimes spread.

The changes in genes that cause one cancer type are often different to the genetic changes causing another. For example, the changes that make a lung cancer grow can be different to ones that make a breast cancer grow. And the changes in the genes of one person who has lung cancer might be different to the changes in someone else with lung cancer.

Targeted drugs target those differences that help a cancer to grow and spread. There are many different targets on cancer cells and different drugs that target them.

Different ways of working

Targeted drugs might:

• stop cancer cells from dividing and growing
• seek out cancer cells and kill them
• encourage the immune system to attack cancer cells
• stop cancers from growing blood vessels
• help carry other treatments such as chemotherapy, directly to the cancer cells

You might hear some targeted drugs called biological therapies. 

Can you have targeted cancer drugs?

Whether you have targeted therapy depends on:

• the type of cancer you have

• how far your cancer has spread (the stage)

• other cancer treatments you’ve had

Ask your specialist about targeted cancer drugs and they can explain:

• whether this treatment is suitable for you

• what the aim of treatment would be

• what it would involve and the side effects

Testing

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

Your cancer specialist can tell you if this applies to your treatment. This is not the case for all targeted drugs 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 use some tissue from a biopsy or operation you have already had. Or they might be able to test using a blood sample.

Types of targeted drugs

There are many different types of targeted drugs. These are grouped together depending on how they work. So for example, cancer growth blockers stop the proteins that trigger the cancer cell to divide and grow. 

Some targeted drugs stop cancers from growing blood vessels. A cancer needs a good blood supply to provide itself with food and oxygen and to remove waste products. The process of growing new blood vessels is called angiogenesis. Drugs that stop cancers from growing blood vessels are called anti angiogenic drugs. Anti angiogenic drugs can slow the growth of the cancer and sometimes shrink it. 

Other groups include a particular type of drug, such as a monoclonal antibody. These target specific proteins on cancer cells.

There isn't a simple way of grouping targeted drugs that is easy to follow. This can sometimes be confusing. Some drugs belong to more than one group because they work in more than one way. For example, a drug that works by blocking cancer cell growth may also be a monoclonal antibody.

Some monoclonal antibodies trigger the immune system to attack and kill cancer cells. So these monoclonal antibodies are also a type of immunotherapy. 

For ease, we have grouped targeted drug therapy into:

• monoclonal antibodies

• cancer growth blockers

• drugs that block cancer blood vessel growth

• PARP inhibitors

Histology independent therapy (HITs)

HITs are a new type of targeted cancer drug. You might also here them called tumour agnostic therapy.

HITs are different to other targeted therapies because they treat any type of cancer that has a certain gene change. Most targeted cancer drugs are for a specific cancer type.

For example, larotrectinib and entrectinib are the names of 2 HIT drugs. Both of these drugs are a treatment for solid cancers that have a neurotrophic tyrosine receptor kinase (NTRK) gene change.

Researchers are looking at existing targeted drugs that are already approved treatments for some cancer types. They want to see if they can pick out drugs that might work for other cancer types with a specific gene change.