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JAMA Oncology Patient Page
April 2015

Immune Checkpoint Inhibitors

JAMA Oncol. 2015;1(1):115. doi:10.1001/jamaoncol.2015.0137

The immune system helps protect the body from infection and other diseases, including cancer.

Immune checkpoint inhibitors are cancer treatment drugs that prevent immune cells from being turned off by cancer cells.

How Does the Immune System Work?

During an immune response, the immune system turns on to attack potentially harmful agents. The immune system also has ways to turn off. This limits the immune response and prevents damage to healthy tissues.

T lymphocytes,or T cells, are immune system cells that can kill cancer cells. A T cell has special locations on its surface called receptors. Other cells or molecules attach to these receptors and turn the T cell on (activation) or off.

How Do Immune Checkpoint Inhibitors Work?

Some cancer cells bind to receptors on activated T cells and turn them off. Immune checkpoint inhibitors are drugs that prevent cancer cells from turning off T cells. This allows T cells to infiltrate a tumor and stop it from growing.

Conventional chemotherapy drugs often shrink a tumor within weeks, but immune checkpoint inhibitors can take several months to work. These drugs can initially cause the tumor to swell, making it appear that the tumor is growing. This is called pseudoprogression. It occurs because of the large number of activated T cells and other immune system cells and substances that enter the tumor. The brief increase in tumor size may be followed by shrinking or eradication of the tumor.

The US Food and Drug Administration has approved several immune checkpoint inhibitors for the treatment of metastatic melanoma. These approved drugs include ipilimumab (Yervoy; Bristol-Myers Squibb), nivolumab (Opdivo; Bristol-Myers Squibb), and pembrolizumab (Keytruda; Merck Sharp & Dohme Corp). These drugs are also being tested for treatment of many other cancers.

Possible Immune-Related Side Effects

Because immune checkpoint inhibitors prevent T cells from being turned off, these drugs affect the balance of the immune system. In addition to infiltrating tumors, activated T cells can attack the body’s own cells. This is called an autoimmune reaction and occurs in about 10% of patients taking these drugs.

Immune-related side effects usually occur 6 to 12 weeks after starting treatment and may include

  • Diarrhea

  • Rash

  • Difficulty breathing

  • Eye irritation

  • Yellowing of the skin (jaundice)

  • Change in energy level

Be sure to let your doctor know if you develop any new symptoms while taking an immune checkpoint inhibitor. Your doctor might temporarily stop the drug or prescribe a steroid to decrease the immune response.

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Section Editor: Howard (Jack) West, MD.
The JAMA Oncology Patient Page is a public service of JAMA Oncology. The information and recommendations appearing on this page are appropriate in most instances, but they are not a substitute for medical diagnosis. For specific information concerning your personal medical condition, JAMA Oncology suggests that you consult your physician. This page may be photocopied noncommercially by physicians and other health care professionals to share with patients. To purchase bulk reprints, call (312) 464-0776.
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Article Information

Published Online: March 5, 2015. doi:10.1001/jamaoncol.2015.0137.

Conflict of Interest Disclosures: None reported.