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Keytruda (pembrolizumab)

Keytruda® (pembrolizumab) is a type of immunotherapy. It is used to treat melanoma that:1

  • Cannot be removed with surgery (unresectable) or
  • Has spread to distant parts of the body (metastasized)

Keytruda does not come in generic form. Keytruda is similar to Opdivo® (nivolumab), another drug approved to treat unresectable or metastatic melanoma.

Keytruda is approved to treat other cancers as well, including: non-small cell lung cancer, head and neck cancer, and classical Hodgkin lymphoma, along with others.1

How does Keytruda work?

Keytruda prevents melanoma cells from hiding from your immune system’s T-cells. Keytruda is described in many ways, including:

  • immune checkpoint inhibitor
  • anti-PD-1 therapy
  • PD-1 inhibitor

T-cells (T-lymphocytes) are a type of white blood cell.2 T-cells fight cancer and infection. They travel through the body, checking whether the cells they find are normal (healthy) or foreign (unhealthy). A receptor on the outside surface, called PD-1, does the checking. PD-1 stands for “programmed death receptor-1.”

Cancer cells try to hide from T-cells. They have proteins called PD-L1 or PD-L2 (programmed death ligand-1 or 2) on their outside surface. When PD-L1 or PD-L2 binds (connects) to PD-1, it basically acts like an “off switch” for the T-cell. This makes the T-cell ignore the cancer cell.

Keytruda binds to the PD-1 receptor.1 This blocks the receptor from interacting with PD-L1 or PD-L2. The T-cell is able to identify and attack the cancer cell.

How effective is Keytruda?

Keytruda was studied in people who had been treated previously with Yervoy® (ipilimumab) and people who had not. Yervoy was first approved in 2011. It is the standard of care. This means that new medications are compared with Yervoy to see if they work as well or better.

No previous treatment with Yervoy. In a high quality study, two frequencies of treatment with Keytruda were compared with Yervoy in 834 patients.3 At 6 months, approximately 47% of patients treated with Keytruda had progression-free survival. In comparison, approximately 27% of the patients treated with Yervoy progression-free survival. Progression-free survival is how long a person survives after treatment without the cancer getting worse. The median progression-free survival with Keytruda was 4.1 months for patients treated every 3 weeks and 5.5 months for patients treated every 2 weeks.1

The 12-month survival rates were approximately 68% for Keytruda taken every 3 weeks, approximately 74% for Keytruda taken every 2 weeks, and 58% with Yervoy.3

Previous treatment with Yervoy and targeted therapy. In another study, two doses of Keytruda were compared with chemotherapy in 540 patients.4 The patients in this study had already been treated with Yervoy. Some also had tried a BRAF or MEK inhibitor.

At 6 months, the progression-free survival rate in patients treated with Keytruda was 34% to 38%.4 In comparison, the progression-free survival rate was 16% for the people treated with chemotherapy. The median progression-free survival with Keytruda was 2.9 months.1

How is Keytruda given?

Before receiving Keytruda, read the Medication Guide that comes in the package. Talk to your doctor about how often and how many treatments you will need.

Keytruda is taken through an intravenous (IV) line. Your doctor will administer Keytruda. Keytruda is usually given every 3 weeks. It takes about 30 minutes to administer the medication.

What are the side effects of Keytruda?

The most common side effects of Keytruda are:1

  • Feeling tired
  • Itching
  • Diarrhea or constipation
  • Decreased appetite
  • Rash
  • Fever
  • Cough or shortness of breath
  • Muscle, bone, or joint pain
  • Nausea

Keytruda can cause your immune system to attack normal (healthy) organs and tissue. Rare but serious possible side effects are:

  • Lung inflammation (pneumonitis)
  • Intestinal inflammation (colitis)
  • Liver inflammation (hepatitis)
  • Problems with hormone glands (thyroid, pituitary, adrenal, pancreas)
  • Kidney inflammation and kidney failure
  • Other problems (rash, changes in eye sight, muscle pain or weakness, joint pain, low red blood cell count, hearing problems)

Keytruda is infused (put) into your vein through an IV line. Severe, life-threatening infusion reactions can occur. Symptoms include chills, shaking, shortness of breath, wheezing, itching, rash, flushing, dizziness, fever, and feeling like you may pass out.1

Who should not take Keytruda?

Keytruda can harm an unborn baby.1 Women who could become pregnant should use birth control during treatment and for at least 4 months after the last dose of Keytruda. Do not breastfeed while taking Keytruda or for 4 months the last dose.

Tell your doctor about any medical conditions you have, especially:

  • Immune system problems (Crohn’s disease, ulcerative colitis, lupus).
  • Previous organ transplant.
  • Lung or breathing problems.
  • Liver problems.

What precautions are needed when taking Keytruda?

You will need regular blood tests to check for side effects of Keytruda. Your doctor may prescribe corticosteroids or hormone replacement medicines to treat certain side effects.1

During treatment and for at least 4 months after the last dose of Keytruda:1

  • Women who can become pregnant should use birth control.
  • Women should not breastfeed.
Written by: Sarah O'Brien | Last reviewed: October 2018.
  1. Keytruda® [prescribing information]. Whitehouse Station, NJ: Merck & Co, Inc; March 2017.
  2. PubMed Health. T-Lymphocytes (T-Cells). Accessed April 7, 2017 at:
  3. Robert C, Schachter J, Long GV, et al; KEYNOTE-006 investigators. Pembrolizumab versus ipilimumab in advanced melanoma. N Engl J Med. 2015;372:2521-2532.
  4. Ribas A, Puzanov I, Dummer R, et al. Pembrolizumab versus investigator-choice chemotherapy for ipilimumab-refractory melanoma (KEYNOTE-002): a randomised, controlled, phase 2 trial. Lancet Oncol. 2015;16:908-918.