A clinical trial of Merck & Co.’s flagship oncology drug in a form of breast cancer has failed. However, the company is also running additional trials designed to enable Food and Drug Administration approval of the drug, Keytruda (pembrolizumab).

The Kenilworth, New Jersey-based company said Monday that the Phase III KEYNOTE-119 study of Keytruda as a monotherapy in second- and third-line triple-negative breast cancer (TNBC) failed to extend overall survival in patients. The trial enrolled 622 patients, who were randomized to receive either Keytruda or one of four chemotherapy drugs used to treat TNBC.

Shares of Merck, which trade on the New York Stock Exchange, were unaffected by the news.

Other registration-directed trials of Keytruda in TNBC include KEYNOTE-355, randomizing 882 patients to receive either Keytruda with any of four chemotherapy drugs or chemotherapy and saline solution, and KEYNOTE-522, comparing Keytruda with chemotherapy or placebo and chemotherapy in 1,174 patients. Keytruda is an immunotherapy drug known as a PD-1 checkpoint inhibitor.

The news comes just two months after the FDA granted accelerated approval to a drug with a similar mechanism of action to Keytruda, Swiss drugmaker Roche’s PD-L1 checkpoint inhibitor Tecentriq (atezolizumab), combined with Celgene’s chemotherapy drug Abraxane (nab-paclitaxel). Abraxane is among the drugs being combined with Keytruda in the KEYNOTE-355 study.

Roche’s accelerated approval was based on data from the Phase III IMpassion130 showing a benefit of 2.6 months in progression-free survival, meaning the amount of time patients live without their disease worsening. Overall survival data were not mature, but Tecentriq’s full approval is contingent on Impassion130 showing a confirmation of benefit, which would likely mean a benefit in overall survival. However, Merck said that because the overall survival primary endpoint was not met in KEYNOTE-119, other endpoints were not formally tested as per the trial’s protocol.

According to a 2016 Harvard Medical School study of 197 patients with TNBC, 26 percent of cases were shown to express PD-L1. Tecentriq’s approval is only for patients shown by a diagnostic test to express PD-L1. Another study, of resected tumors from 55 TNBC patients, found high levels of PD-1 in 20 percent of the 54 that were evaluable, while PD-L1 was highly expressed in 37 percent. TNBC is breast cancer that does not express estrogen receptor, progesterone receptor or HER2, making it especially difficult to treat due to the general dearth of targeted therapies.

Photo: nopparit, Getty Images



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