What Is Keytruda® (pembrolizumab)?

Reviewed by: HU Medical Review Board | Last reviewed: June 2023

Keytruda® (pembrolizumab) may be used for the treatment of locally recurrent unresectable (has returned following prior treatment and cannot be removed by surgery) or metastatic (has spread to other parts of the body) triple-negative breast cancer (TNBC). In this circumstance, Keytruda must be combined with chemotherapy, and the tumor must express the PD-L1 protein.1

Keytruda is also used to treat early-stage TNBC that is high risk and is given with chemotherapy prior to surgery, then continued following surgery as a single drug to help reduce the risk of the cancer coming back.1

Triple-negative breast cancer is a difficult-to-treat and aggressive cancer. Up to 1 in 5 people with breast cancer have triple-negative cancer.2

What are the ingredients in Keytruda?

The active ingredient in Keytruda is pembrolizumab.3

How does Keytruda work?

Keytruda is a monoclonal antibody and a type of immunotherapy. Monoclonal antibodies are created in the lab to mimic the antibodies that are naturally produced by the body to kill germs. Antibodies can also target specific areas of cancer cells to block cancer growth or kill cancer cells.2

Keytruda targets the PD-1 receptor found on certain immune system cells. It blocks the proteins that bind to the receptor. When this pathway is affected by cancer cells, the cancer can grow and spread without being kept in check by the immune system. By blocking the PD-1 pathway, Keytruda can help the body’s immune system fight the cancer.2

What are the possible side effects of Keytruda?

The most common side effects of Keytruda when given with chemotherapy include1,3

  • Fatigue
  • Nausea, diarrhea, constipation, and vomiting
  • Hair loss (alopecia)
  • Rash
  • Cough
  • Decreased appetite
  • Headache
  • Shortness of breath
  • Fever
  • Numbness or tingling in extremities
  • Mouth sores
  • Swelling of mucous membranes
  • Weight loss
  • Stomach pain
  • Muscle pain
  • Joint pain
  • Trouble sleeping

Keytruda may also cause serious side effects, including:3

  • Lung problems (pneumonitis)
  • Intestinal problems (colitis)
  • Liver problems
  • Endocrine gland problems
  • Kidney problems
  • Severe skin reactions
  • Organ transplant rejection

These are not all the possible side effects of Keytruda. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with Keytruda.

Things to know about Keytruda

Keytruda also has been approved to treat several other types of cancer, including certain types of lung, skin, bladder, cervical, colon, kidney, and blood cancers.3

Keytruda can harm an unborn baby. If you can become pregnant, you should use birth control during treatment and for some time after the last dose of Keytruda. You should also not breastfeed during treatment with Keytruda and for some time after the last dose. Talk to your doctor about your options for birth control and breastfeeding while taking Keytruda.3

Before beginning treatment for breast cancer, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

For more information, read the full prescribing information of Keytruda.

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