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FDA Approves Merck's Keytruda for MSI-H, dMMR Endometrial Cancer With Roche CDx

NEW YORK – The US Food and Drug Administration on Monday approved Merck's PD-1 inhibitor Keytruda (pembrolizumab) for advanced, previously treated endometrial cancer patients whose tumors express high microsatellite instability (MSI) or harbor DNA mismatch repair deficiencies (dMMR).

The agency approved the drug for patients whose cancers have progressed on systemic therapy in any setting and who are not candidates for surgery or radiation. The FDA also approved Roche's Ventana MMR RxDx Panel as an immunohistochemistry-based companion diagnostic to select patients with dMMR tumors for Keytruda treatment.

Keytruda has been approved in the US since 2017 as a last-line treatment option for adult and pediatric patients with any type of unresectable, metastatic cancer that is MSI-high or dMMR. The agency previously approved Foundation Medicine's FoundationOne CDx next-generation sequencing panel to select patients with MSI-H solid tumors.

In approving Keytruda's latest endometrial cancer indication, the FDA reviewed data from the multi-cohort KEYNOTE-158 trial. In cohorts D and K, the objective response rate was 46 percent among Keytruda-treated patients. After a median of 16 months follow-up, 12 percent of patients experienced a complete response and 33 percent had a partial response. Among responding patients, 68 percent benefited for more than a year and 44 percent had responses lasting over two years.

Merck's blockbuster checkpoint inhibitor, when combined with Eisai's Lenvima (lenvatinib), is already approved in the US for advanced endometrial cancer patients who have progressed on systemic therapy, are not candidates for surgery or radiation, and don't have MSI-high status or dMMR.