Medication first to aim at cancer biomarker

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Food and Drug Administration approved the first medication that’s designed to treat cancer patients whose cancer has a specific genetic feature, or biomarker, rather than being based on the location where a tumor was found.

Pembrolizumab, which is marketed as Keytruda by Merck, had been approved to treat several cancers, such as melanoma, lung cancer, and head and neck cancer. Now the medication may be used in the treatment of any cancer that has a biomarker that’s known as microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR). These biomarkers are common in colorectal, endometrial and gastrointestinal cancers and are less common in bladder, breast, prostate and thyroid cancers. (We reported on this medication in “Medical Breakthroughs & New Frontiers 2015.”)

Pembrolizumab works by targeting proteins that are found on the body’s immune cells and on some cancer cells. It’s believed that by blocking these proteins’ pathway, the medication helps the body’s immune system to fight the cancer cells.

Common side effects include fatigue, itchy skin (pruritus), diarrhea, decreased appetite, rash, fever, cough, difficulty breathing, musculoskeletal pain, constipation and nausea. More-serious side effects include inflammation of healthy organs and even death in patients who have allogenic hematopoietic stem cell transplantation.

FDA says patients who experience severe or life-threatening reactions should stop taking the medication. Women who are pregnant or breastfeeding should not take the medication.