Earlier this month, the U.S. Food and Drug Administration (FDA) announced that it had approved the use of the immunotherapeutic pembrolizumab (Keytruda) for treating certain patients with head and neck squamous cell carcinoma (HNSCC), which is the most common type of head and neck cancer diagnosed in the United States. Specifically, it is approved for treating patients with recurrent or metastatic HNSCC whose disease has progressed despite treatment with a platinum-containing chemotherapeutic.
The National Cancer Institute estimates that head and neck cancer accounts for about 3 percent of all new cases of cancer diagnosed each year. In 2016, this is predicted to translate into about 50,000 new cases of head and neck cancer. Patients with recurrent or metastatic head and neck squamous cell carcinoma have a particularly poor prognosis and new treatment options are urgently needed.
According to the company that manufactures pembrolizumab, Merck, the approval of the immunotherapeutic for HNSCC was based on results from the phase Ib clinical trial KEYNOTE-012. In short, 16 percent of the 174 patients who received pembrolizumab had a partial or complete response. In its announcement, the FDA noted that so many of the responses were ongoing at the time of data analysis that the median time of duration of response has not yet been determined. It also highlighted that 82 percent of the responses had lasted at least six months.
Given that the approval centered on response data, rather than overall survival, Merck is required by the FDA to conduct a study to confirm that pembrolizumab improves survival for patients with HNSCC. The ongoing phase III KEYNOTE-040 clinical trial is designed to address this issue by comparing median overall survival among patients with recurrent or metastatic HNSCC treated with pembrolizumab and those treated with standard chemotherapy.
Pembrolizumab works by releasing the PD-1/PD-L1 brake on cancer-fighting immune cells called T cells. With this FDA decision, it is now approved for treating three different types of cancer. As highlighted on this blog, it was first approved in September 2014 for treating certain patients with advanced melanoma. Then, in October 2015, it was approved for use in treating patients who have non–small cell lung cancer that tests positive for PD-L1 using the PD-L1 IHC 22C3 pharmDx test.
Promising early results reported from clinical trials testing pembrolizumab as a potential treatment for certain patients with colorectal cancer and Hodgkin lymphoma have earned the immunotherapeutic breakthrough therapy designation from the FDA for use in these indications. Since this designation is intended to expedite regulatory assessment of new agents and it is only granted to those agents that show substantial improvement over available treatments in early clinical trials, it is hoped that more patients will have pembrolizumab as a treatment option in the near future.
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