NEW YORK (GenomeWeb) – The US Food and Drug Administration has for the first time approved a drug to be given based on the genomic features in cancer patients' tumors, instead of where the tumor occurs in their bodies.
The agency today granted accelerated approval to Merck's PD-1/PD-L1 inhibitor Keytruda (pembrolizumab) for patients with unresectable or metastatic solid tumors with microstatellite instability-high (MSI-H) or mismatch repair deficiency (dMMR).
Tumor cells with MSI-H and dMMR have impaired DNA repair capabilities that drive cancer progression, and these features are common in colorectal, endometrial, and gastrointestinal cancers. They also occur in cancers of the breast, prostate, bladder, thyroid gland, and other areas, though less frequently. Around 5 percent of colorectal cancer patients have MSI-H or dMMR tumors.
The latest approval didn't come with a simultaneous approval for a complementary or companion diagnostic. However, testing will be necessary to define MSI-H or dMMR status in cancer patients.
"This is an important first for the cancer community," Richard Pazdur, acting director of the Office of Hematology and Oncology Products within the FDA's drug division, said in a statement. "Until now, the FDA has approved cancer treatments based on where in the body the cancer started — for example, lung or breast cancers. We have now approved a drug based on a tumor's biomarker without regard to the tumor's original location."
In order receive Keytruda in this manner, patients with solid tumors must have progressed on treatment and be without alternatives, and colorectal cancer patients must have progressed on certain chemotherapies.
Merck submitted data on the safety and efficacy of Keytruda in patients with MSI-H or dMMR solid tumors who were enrolled in one of five single-armed studies. In these studies, there were 149 patients with 15 cancer types characterized by MSI-H or dMMR who received Keytruda. Among these patients, 39.6 percent had a complete or partial response, and in 78 percent the response lasted for six months or more. In clinical trials, Keytruda has caused common side effects such as fatigue, itchy skin, and diarrhea, and serious conditions such as inflammation of healthy organs.
The agency clarified in an e-mail that the identification of MSI-H or dMMR tumor status for the majority of patients (135 out of 149) in the five studies was determined prospectively using local, laboratory-developed PCR testing for MSI-H and immunohistochemistry for dMMR, or both. The rest of the patients had their MSI-H status determined retrospectively using PCR within a central lab.
Because the drug was approved at an accelerated clip, Merck will have to submit data from additional studies, demonstrating Keytruda's safety and efficacy in cancer patients with MSI-H or dMMR tumors. The FDA has also approved Keytruda for the treatment of metastatic melanoma, metastatic non-small cell lung cancer, recurrent or metastatic head and neck cancer, refractory classical Hodgkin lymphoma, and urothelial carcinoma.