FDA Approves Keytruda (Pembrolizumab) for Any Tumor with Specific Genetic Change

The US Food and Drug Administration (FDA) has expanded the approval of the immunotherapy drug Keytruda (pembrolizumab) to include tumors with a specific genetic change regardless of cancer type. This is the first time the FDA has approved a drug based not on cancer type, but on the genetic change itself. The approval is for adults and children with advanced solid tumors that have certain gene changes – either high levels of microsatellite instability (MSI-H) or mismatch repair deficiency (dMMR) – and that are still growing despite prior treatment.

Microsatellite instability and mismatch repair deficiency are types of genetic changes to a cell that interfere with its ability to repair itself. This can lead to cancer cells that are very different from normal cells, which can make them more "visible" to the body’s immune system. Tumors with this type of genetic change are most commonly found in colorectal, endometrial, and gastrointestinal cancers.

Keytruda works by helping the body’s immune system recognize cancer cells and attack them. Keytruda had already been approved for treating people who had several types of cancer, including some types of lung, head and neck, bladder, and skin cancers, and Hodgkin lymphoma.

The FDA based its decision on 5 clinical trials that included 149 people who had a total of 15 different cancer types. Almost 40% saw their tumors shrink or disappear after they received Keytruda. For 78% of those people, the improvement lasted for at least 6 months.

Keytruda was approved for the new indication using accelerated approval and priority review, programs the FDA can use to speed up the availability of drugs to treat serious diseases. Under accelerated approval, the company that makes the drug must submit additional clinical information after approval, to demonstrate its benefit. Priority review means the FDA tries to make a decision within 6 months instead of the usual 10 months.

Keytruda is given as an infusion into the vein. The most common side effects are fatigue, cough, nausea, itchy skin, rash, decreased appetite, constipation, joint pain, and diarrhea. Less common but more serious side effects can include inflammation of the lung, colon, hormone-producing glands, liver, and other organs.

Keytruda is manufactured by Merck & Co.

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