Just last week, the U.S. Food and Drug Administration approved the cancer medicine— Keytruda® (generic name pembrolizumab)— to treat cancers that have a specific genetic mutation or biomarker. This is the first time a cancer treatment has been approved based on a biomarker rather than the body location where the cancer originates.
What is Keytruda?
Keytruda was first introduced in 2014 and is part of a new class of drugs called PD-1 or PD-L1 inhibitors that help the immune system fight cancer by blocking a mechanism tumors use to evade detection. By blocking this pathway, Keytruda enables the body’s immune system to attack cancer cells.
Already approved to treat a variety of cancers including melanoma, lung cancer, head and neck cancer, Hodgkin lymphoma, and urothelial carcinoma,[i] Keytruda can now also be used to treat adult and pediatric patients whose cancer has the biomarker MSI-H (microsatellite instability) or dMMR (mismatch repair).
For decades, cancer drugs have typically been approved and used to treat cancer based on the body location the cancer originates. The FDA’s approval of Keytruda based on genetics signifies a major paradigm shift in cancer treatment.
What does this mean for patients?
In five clinical trials, nearly 150 patients whose tumors had the MSI-H or the dMMR genetic defect were studied. Nearly 40% of the patients studied experienced significant tumor shrinkage. More than half of the participating patients were diagnosed with colorectal cancer while the others had 14 different cancer types. Based on these results, Keytruda received a priority review designation, which means the FDA sped the review process to six months from the usual 10 months. The new FDA approval allows Keytruda to be used in tumors with the genetic defect that have progressed following prior treatment with other drugs, and have no satisfactory alternative treatment options.
Tumors with the biomarker MSI-H or dMMR are present in an estimated 4% of cancers.[ii] Most commonly found in colorectal, endometrial and gastrointestinal cancers, this genetic defect has also been present in some breast, prostate, bladder, thyroid as well as other cancers.
The FDA’s approval of Keytruda based on genetic defect is great news for patients— especially those whose tumors might not benefit from standard treatments approved for specific tumor sites as it will enable patients to receive the most promising treatments for their disease as quickly as possible.