Checkpoint inhibitors for immunotherapy

How checkpoint inhibitors work

The white blood cells known as lymphocytes are an important part of the immune system. There are 2 main types of lymphocytes – T-cells and B-cells. They travel through the body looking for germs and abnormal cells and work together to destroy them.

Checkpoint inhibitors help T-cells to recognise and attack cancer. Below is a simplified explanation of this process.

T-cells and checkpoint inhibitors

What T-cells usually do

Your immune system’s T-cells circulate throughout the body looking for abnormal cells to destroy. The T-cells carry “checkpoints”, special proteins with names such as PD-1, PD-L1 and CTLA-4.

What checkpoints usually do

Checkpoints act as natural brakes to stop T-cells destroying healthy cells.

How some cancer cells use checkpoints

In some people, cancer cells use checkpoints to stop T-cells from seeing the cancer cells as abnormal.

What checkpoint inhibitors do

Checkpoint inhibitors are special drugs that block these checkpoints so that the T-cells can once again find and attack the cancer. 

How checkpoint inhibitors are given

Checkpoint inhibitors are prescribed by a medical oncologist (a doctor who treats cancer with drug therapies) or haematologist (a doctor who treats blood cancers). They are given as a liquid through a drip inserted into a vein (intravenous infusion). Sometimes 2 or more drugs may be given together, such as 2 checkpoint inhibitors, or a checkpoint inhibitor with 1–2 chemotherapy drugs or a targeted therapy drug.

You will usually have treatment as an outpatient, which means you visit the hospital or treatment centre for the infusion and then go home again. Checkpoint inhibitors are usually given in repeating cycles, with rest periods of 2–6 weeks between cycles.

How often and how long you have the treatment depends on the type of cancer, the type of checkpoint inhibitor, how the cancer responds to the treatment, and what side effects you may experience. Many people stay on checkpoint inhibitors for up to 2 years. Clinical trials are underway to test whether ongoing treatment is needed or if checkpoint inhibitor therapy can be given for a shorter period of time once it has started working.

Most cancers have treatment protocols that set out which drugs to have, how much and how often. You can find information about protocols for checkpoint inhibitors and other cancer drugs at eviQ, which provides cancer treatment information. Your specialist may need to tailor the protocols to your individual situation.

Like many other cancer treatments, checkpoint inhibitor drugs are often not safe to use if you are pregnant or breastfeeding. Ask your doctor for advice about contraception. If you become pregnant, let your medical team know immediately.