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The U.S. Food and Drug Administration has granted breakthrough therapy designation to Keytruda (pembrolizumab) for the treatment of patients with microsatellite instability high (MSI-H) metastatic colorectal cancer. Keytruda is a humanized monoclonal antibody that blocks the interaction between PD-1 and its ligands, PD-L1 and PD-L2.

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The breakthrough therapy designation, enacted as part of the FDA's 2012 Safety and Innovation Act, was created to expedite the development and review time of a potential new drug for serious or life-threatening disease where early clinical evidence suggests the drug may demonstrate substantial improvement compared with existing therapies.


Keytruda is currently approved for the treatment of patients with advanced or unresectable melanoma who are no longer responding to other drugs (OT 10/10/14 issue).


Keytruda has also previously received priority review designation for the first-line treatment of patients with unresectable or metastatic melanoma (OT 9/10/15 issue), as well as for the treatment of patients with advanced non-small cell lung cancer (NSCLC) whose disease has progressed on or after platinum-containing chemotherapy and an FDA-approved therapy for EGFR or ALK genomic tumor aberrations, if present (OT 6/25/15 issue).


And the drug also previously received breakthrough therapy designation for the treatment of patients with NSCLC that has progressed on or following platinum-based chemotherapy and that is also epidermal growth factor receptor (EGFR) mutation-negative and anaplastic lymphoma kinase (ALK) rearrangement-negative (OT 11/25/14 issue).


This latest FDA action for Keytruda for advanced colorectal cancer is based on data from a Phase II study evaluating the activity of Keytruda in cancers with microsatellite instability.


The data, presented at the American Society of Clinical Oncology Annual Meeting earlier this year, showed a response rate of more than 60 percent and a disease-control rate of more than 90 percent (OT 7/25/15 issue).


A Phase II registration study (KEYNOTE-164) to evaluate the efficacy and safety of Keytruda based on microsatellite instability status in patient with previously treated advanced colorectal cancers is currently ongoing, and a Phase III study (KEYNOTE-177) to evaluate the drug in a previously untreated patient population is also being planned, according to a news release from the drug's manufacturer, Merck.