The short answer
Immune checkpoint inhibitors are a type of immunotherapy that blocks the off signals that keep your immune system from attacking cancer. By blocking checkpoint proteins, they free T cells to kill cancer cells. They treat many cancers but can also cause inflammation as a side effect.
Immune checkpoints are a normal part of the immune system that keeps immune responses from harming healthy cells.
Some cancers use checkpoints to send an off signal that stops T cells from attacking them.
Checkpoint inhibitors block these off signals, letting T cells kill cancer cells.
They are approved to treat many cancer types, including melanoma, lung, and bladder cancer.
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The full explanation.
The simple version
Your immune system has built-in brakes. These brakes, called immune checkpoints, are a normal part of the immune system. Their job is to keep an immune response from getting so strong that it destroys healthy cells in your body.
The problem is that some cancers learn to use these brakes to protect themselves. Immune checkpoint inhibitors are a type of immunotherapy that releases the brakes so your immune system can fight the cancer.
Checkpoint inhibitors take the brakes off your immune system so it can attack cancer.
How checkpoints normally work
Immune checkpoints engage when proteins on the surface of immune cells called T cells recognize and bind to partner proteins on other cells, such as some tumor cells. These are called immune checkpoint proteins.
When the checkpoint protein and its partner protein bind together, they send an off signal to the T cells. In healthy tissue, this off signal is protective — it stops the immune system from attacking your own cells. But when a tumor sends this off signal, it can prevent the immune system from destroying the cancer.
How the drugs help
Immune checkpoint inhibitors work by blocking checkpoint proteins from binding with their partner proteins. This prevents the off signal from being sent, which allows the T cells to kill cancer cells.
Different drugs target different checkpoints:
- One type acts against a checkpoint protein called CTLA-4.
- Others act against a checkpoint protein called PD-1 or its partner protein PD-L1.
Some tumors turn down the T cell response by producing a lot of PD-L1, so blocking PD-1 or PD-L1 can free the T cells to attack.
Which cancers they treat
Immune checkpoint inhibitors are approved to treat some people with a variety of cancer types, including:
- breast cancer
- bladder cancer
- cervical cancer
- colon cancer
- head and neck cancer
- Hodgkin lymphoma
- liver cancer
- lung cancer
- renal cell cancer (a type of kidney cancer)
- skin cancer, including melanoma
- stomach cancer
- rectal cancer
- any solid tumor that is not able to repair certain errors in its DNA
Side effects to know about
Immune checkpoint inhibitors can cause side effects that affect people in different ways. What you may have depends on how healthy you are before treatment, your type of cancer, how advanced it is, the drug you receive, and the dose. Doctors and nurses cannot know for sure when or if side effects will occur or how serious they will be, so it is important to know which signs to look for.
Common side effects include:
- rash
- diarrhea
- fatigue
Rarer side effects can include widespread inflammation. Depending on which organ is affected, inflammation can lead to skin changes and itching, cough and chest pain from the lungs, belly pain and diarrhea from the colon, diabetes from the pancreas, hepatitis (liver), and problems with the pituitary gland, heart muscle, kidneys, thyroid, or nervous system.
Because side effects can involve inflammation in different organs, report new symptoms to your team quickly.
Words to know
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Common questions
▸What are immune checkpoints?
Immune checkpoints are a normal part of the immune system. Their role is to prevent an immune response from being so strong that it destroys healthy cells. They work when proteins on immune cells called T cells bind to partner proteins on other cells, sending an off signal.
▸How do checkpoint inhibitors work?
Some tumors use checkpoints to send an off signal that stops T cells from attacking them. Checkpoint inhibitors block checkpoint proteins from binding with their partner proteins. This prevents the off signal from being sent, which allows the T cells to kill cancer cells.
▸Which checkpoint proteins do these drugs target?
One type of drug acts against a checkpoint protein called CTLA-4. Others act against a checkpoint protein called PD-1 or its partner protein PD-L1. Some tumors turn down the T cell response by making a lot of PD-L1.
▸Which cancers are treated with checkpoint inhibitors?
They are approved to treat many cancers, including breast, bladder, cervical, colon, head and neck, liver, lung, kidney (renal cell), stomach, and rectal cancers, Hodgkin lymphoma, and skin cancers such as melanoma. They can also treat any solid tumor that cannot repair certain DNA errors.
▸What side effects can checkpoint inhibitors cause?
Common side effects include rash, diarrhea, and fatigue. Rarer side effects involve widespread inflammation. Depending on the organ affected, inflammation can cause problems in the skin, lungs, colon, liver, kidneys, heart, thyroid, pancreas, or nervous system.
▸Can doctors predict my side effects?
No. Doctors and nurses cannot know for sure when or if side effects will occur or how serious they will be. That is why it is important to know which signs to look for and what to do if they happen.
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