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FDA Approves Keytruda for Advanced or Metastatic Merkel Cell Carcinoma

The U.S. Food and Drug Administration (FDA) has granted approval for Keytruda® (pembrolizumab) as a treatment for advanced or metastatic Merkel cell carcinoma in both adults and children.1 Merkel cell carcinoma (MCC) is a rare and difficult-to-treat skin cancer that is more likely to recur and is fatal in one-third of cases.2

Demonstrated effectiveness in clinical trials

Keytruda was evaluated by the FDA under priority review as a breakthrough therapy. This designation provides a faster review process and is given to treatments that meet an unmet need in serious conditions. The approval was based on data from a clinical trial which involved 50 patients with recurrent locally advanced or metastatic MCC who had not received prior systemic therapy for their advanced disease. (Most of the patients had previously had surgery or radiation therapy.)

Keytruda was administered as an intravenous (IV) infusion every three weeks. The overall response rate was 56%, meaning 56% of patients receiving Keytruda had significant shrinkage in their tumors. In addition, 24% of the patients had a complete response rate. The duration of the response was also significant: in 54%, Keytruda kept the MCC from worsening or spreading for 12 months or more, and in 96%, Keytruda kept the MCC from worsening for 6 months or more.1,3

How Keytruda works

Keytruda is a type of immunotherapy, medicines that stimulate the body’s immune system to recognize and fight cancer cells. Keytruda is a type of immune checkpoint inhibitor. T-cells (a type of white blood cell that is important in fighting cancer and foreign invaders in the body) have receptors on the surface of their cells that act like brakes. One of these brakes is called PD-1 (programmed death receptor-1). Some cancer cells evolve to engage these brakes, escaping the immune system’s defenses and causing the T-cells to ignore the cancer cells. Keytruda blocks the PD-1 receptor on T-cells, preventing the cancer cell from engaging that brake and allowing the T-cells to recognize the cancer cells.3

Common side effects of Keytruda

The most common side effects (experienced by at least 20% of patients receiving Keytruda in clinical trials) included fatigue, muscle or bone pain, decreased appetite, itchy skin (pruritus), diarrhea, nausea, rash, fever, cough, difficulty breathing, constipation, pain, and abdominal pain.1 These are not all the possible side effects of Keytruda. Patients should talk to their doctor about what to expect and report any side effects that are concerning or that don’t go away.

Who should not take Keytruda?

Keytruda should not be used in women who are pregnant or planning to become pregnant, as it can harm an unborn baby. Women who are able to become pregnant should use birth control during treatment and for at least 4 months following the last dose of Keytruda.3

It is not known if Keytruda passes into breastmilk, and women who are breastfeeding or plan to breastfeed should not use Keytruda.3

Keytruda should not be used in people with immune system problems, those who have previously had organ transplants, or those with kidney, endocrine, or liver problems. Patients should discuss all their medical conditions with their doctor prior to starting treatment with Keytruda.3

This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

  1. FDA approves pembrolizumab for Merkel cell carcinoma. U.S. Food and Drug Administration. Available at Accessed 12/20/18.
  2. What is Merkel cell carcinoma? Available at Accessed 12/20/18.
  3. Keytruda prescribing information. Available at Accessed 12/20/18.


    11 months ago

    What is on the horizon for immune system compromised Merkel Cell survivors?

    Many of us with Merkel Cell have autoimmune disorders. This as well as Northern European descent, light hair, light eyes add up to a genetic predisposition. I feel that there is a chance Blue Light treatment was a cause of this cell mutation.
    I caught my tumor at less than 2cm… After 16 months, a wide excision, (3 total surgeries) 30 radiation treatments, 40 hyperbaric treatments I am clear and wound healed.
    Immunotherapy is not approved for us with autoimmune conditions. We are precluded from test groups.
    I am stage 1A, and could not hope for better at present.
    Autoimmune conditions at 1A have a 65% survival rate at 5 years, without autoimmune it goes up to over 90% for10 years.
    Currently, I am healed, clear and hopeful. Now dealing again only with Polymyalgia Rhuematica.
    I have also had 7 MOHS surgeries for basal and squamous over the last 9 years.
    I have worked 10 to 12 hour days all the way through.
    Best of health and luck to all!

  • Nina M moderator
    11 months ago

    Thank you for commenting here, @mattelliott. I am hoping we’ll continue to learn more about Merkel treatments and especially those that are available to those with autoimmune conditions. I do hope that you are able to stay at this stage and see clear results. I wanted to tag @Amy here, because she had mentioned wanting to connect with others dealing with Merkel Cell. Best to you! – Nina, Team

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