“For the first time, the FDA has approved a drug for use in cancer—of any type—that harbors certain molecular features. Merck’s Keytruda, an immune oncology drug, may be prescribed for any resistant, metastatic tumor with microsatellite instability (MSI) or other evidence for defective DNA mismatch repair.
“This is good news for patients. Previously, Keytruda (pembrolizumab) was approved by the FDA for use in some forms of lung cancer, melanoma, head and neck cancer, and Hodgkin’s lymphoma. Now, patients can try this medication if they have advanced cancer of any form with pathological MSI or DNA mismatch repair defects. Microsatellite instability most often appears in colon cancers, affecting around 15% of cases. Variants of DNA mismatch repair genes are implicated in heritable cancer dispositions such as Lynch syndrome.”
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