Merck & Co.'s Keytruda misses main goal in late-stage trial of previously treated patients with triple-negative breast cancer

Merck & Co. announced Monday that Keytruda (pembrolizumab) monotherapy failed to significantly prolong overall survival (OS) in the Phase III KEYNOTE-119 trial versus chemotherapy when used in the second- or third-line treatment of patients with metastatic triple-negative breast cancer (TNBC). Roy Baynes, chief medical officer at Merck Research Laboratories, said "while we are disappointed by the outcome of this monotherapy trial, we are continuing to study Keytruda in earlier stages of the disease and in combination with chemotherapy to address the unmet medical need of patients with [TNBC]."

The trial involved 622 patients who were randomly assigned to treatment with Keytruda every three weeks for up to 24 months or physician's choice of single-agent chemotherapy, consisting of capecitabine, eribulin, gemcitabine or vinorelbine. The primary endpoint of the study was OS, while secondary goals included progression-free survival, duration of response, overall response rate and disease control rate.

Merck noted that secondary endpoints were not formally tested because the primary endpoint of OS was missed. The drugmaker said the safety profile of its PD-1 inhibitor in the KEYNOTE-119 trial was "consistent" with previous findings of Keytruda monotherapy, with no new safety signals identified. Data from the study will be presented at a future research conference.

The company added that the KEYNOTE-355, KEYNOTE-242 and KEYNOTE-522 registration-enabling studies in TNBC for Keytruda are ongoing. Last month, Merck said Keytruda also failed to improve survival versus chemotherapy in first-line gastric cancer in the Phase III KEYNOTE-062 trial.

Sales of Keytruda, which recently saw its first-line non-small-cell lung cancer label expanded in the US, jumped 55 percent in the first quarter to $2.3 billion (for related analysis, see ViewPoints: Key takeaways from Merck & Co.'s Q1 earnings and investor call).

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