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Merck Nets Two Keytruda Approvals in Japan for TNBC, Colon Cancer

NEW YORK – Merck said on Thursday that Japanese regulators have approved the firm's anti-PD-1 agent pembrolizumab (Keytruda) for two new indications: PD-L1-positive triple-negative breast cancer (TNBC) and microsatellite instability (MSI)-high colorectal cancer.

The Japan Pharmaceuticals and Medical Devices Agency (PMDA) has approved pembrolizumab combined with chemotherapy for patients with inoperable or recurrent, PD-L1-positive, hormone receptor-negative, HER2-negative breast cancer and pembrolizumab monotherapy for unresectable, advanced, or recurrent, MSI-high colorectal cancer.

To approve the TNBC indication, the PDMA reviewed results from the Phase III KEYNOTE-355 trial, in which pembrolizumab plus chemotherapy improved progression-free survival versus chemotherapy alone for patients whose tumors expressed PD-L1 with a combined positive score of at least 10. The median progression-free survival time in this trial was 9.7 months with the immunotherapy combo compared to 5.6 months with chemo alone. According to Merck, overall survival results from KEYNOTE-355 will be presented at an upcoming medical meeting.

The PDMA approved the colorectal cancer indication based on the results of the KEYNOTE-177 trial, in which pembrolizumab reduced the risk of disease progression or death by 40 percent versus standard-of-care chemotherapy. Median progression-free survival for patients treated with the checkpoint inhibitor was 16.5 months compared to 8.2 months among patients who received standard-of-care chemo.

These approvals in Japan come after the US Food and Drug Administration last month converted its prior accelerated approval of the PD-L1-positive, advanced TNBC indication into full approval, and approved pembrolizumab last year as a first-line treatment for MSI-high or mismatch repair deficient metastatic colorectal cancer.