A First: Cancer Drug Is Approved on Genetic Basis, Not Tumor Location

Until now, cancer drugs were approved based on where the cancer originated. A drug might be approved to treat breast cancer or lung cancer, and might even be approved to treat both, but each approval was tied to location.

Now, the FDA has approved pembrolizumab (Keytruda, from Merck) to treat solid cancers that have a specific genetic feature, the microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR). Cancers containing this biomarker have abnormalities that change how well DNA is repaired inside tumor cells, according to an FDA statement. MSI-H and dMMR tumors are most commonly found in colorectal, endometrial, and gastrointestinal cancers, but can also appear in cancers found in the breast, prostate, bladder, thyroid, and other organs. About 5% of patients with metastatic colorectal cancer have MSI-H or dMMR tumors. The drug works by targeting the PD-1/PD-L1 cellular pathway which helps the immune system fight cancer cells.

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“This is an important first for the cancer community,” said Richard Pazdur, MD, Acting Director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research. “We have now approved a drug based on a tumor’s biomarker without regard to the tumor’s original location.”

Pembrolizumab received this new approval under an accelerated pathway. This approval is for use in patients with no alternatives after tumors have progressed after previous treatment and patients with colorectal cancer that has progressed after treatment with certain chemotherapy drugs. The manufacturer will be required to conduct further study to verify the clinical benefits of pembrolizumab.

The drug was first approved for use in treating melanoma in 2014, and had received previous FDA approvals for treating metastatic non-small-cell lung cancer, recurrent or metastatic head and neck cancer, refractory classical Hodgkin lymphoma, and urothelial carcinoma.