FDA approves treatment for patients with MSI-H or d-MMR biomarkers

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Resources and Research Blog
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July 2020 Update

In July 2020, the Federal Drug Administration (FDA) approved pembrolizumab (Keytruda) as a first-line treatment for colorectal cancer patients with microsatellite instability-High (MSI-H) tumors. 

Previously, in 2017, the FDA had approved pembrolizumab for solid tumors that progressed following prior treatment and who had no satisfactory alternative treatment options and patients with colorectal cancer that had progressed following treatment with certain chemotherapy drugs.

This updated approval is based off of clinical trial data from the phase 3 KEYNOTE-177 study. Researchers found that pembrolizumab lowered the risk of cancer progression or death by 40% and doubled progression free survival when compared to the standard-of-care chemotherapy.


On May 23, 2017, the FDA approved a new treatment option for patients who have the microsatellite instable-high (MSI-H) or deficient mismatch repair (d-MMR) biomarkers. This is the first time the FDA has approved a treatment based on a biomarker. Previous treatment options for colorectal cancer have been approved based on cancer location in the body (for example, the colon or lung).

The FDA press release states,

“Keytruda (pembrolizumab) is indicated for the treatment of adult and pediatric patients with unresectable or metastatic solid tumors that have been identified as having a biomarker referred to as microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR). This indication covers patients with solid tumors that have progressed following prior treatment and who have no satisfactory alternative treatment options and patients with colorectal cancer that has progressed following treatment with certain chemotherapy drugs.”

Read more from the FDA’s press release

Read more about pembrolizumab (Keytruda) from our Nov. 2015 blog post

What does this mean for patients?

  1. All colorectal cancer patients should know their MSI/MMR status*, especially patients with metastatic CRC because they now have a new treatment option.  If you don’t know your MSI/MMR status, talk with your doctor. Go here for more info on MSI/MMR.
  2. If you are MSI-H or dMMR and have metastatic CRC, talk to your doctor about this new treatment option.

  3. Research is quickly evolving! Learn more about clinical trials. If you’re an MSS-CRC patient, use our new Clinical Trial finder.
  4. Advocacy impacts patients! This drug was granted a “breakthrough therapy designation” thanks to the “Advancing Breakthrough Therapies for Patients Act of 2012” – a bill Fight CRC supported in a campaign led by Friends of Cancer Research. Stay informed. Register to be an advocate now!

*Reference: Molecular Biomarkers for the Evaluation of Colorectal Cancer; Guideline From the American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology http://www.archivesofpathology.org/doi/pdf/10.5858/arpa.2016-0554-CP

Disclosure: Fight Colorectal Cancer has received funding from Merck Oncology, the producers of Keytruda® (pembrolizumab), in the form of unrestricted educational grants. We maintain ultimate authority over website content and the content written in this article.