A phase III trial of pembrolizumab for second- or third-line treatment of metastatic triple-negative breast cancer has failed to demonstrate superior overall survival compared to chemotherapy, manufacturer Merck has announced.

The pre-specified primary endpoint of superior overall survival compared to chemotherapy (capecitabine, eribulin, gemcitabine or vinorelbine) was not met in the phase III KEYNOTE-119 trial.

“Metastatic triple-negative breast cancer is an aggressive and challenging disease to treat, especially after progression on initial standard-of-care treatment,” said Dr Roy Baynes, senior vice-president and head of global clinical development, chief medical officer, at Merck Research Laboratories in the US.

“While we are disappointed by the outcome of this monotherapy trial, we are continuing to study Keytruda (pembrolizumab) in earlier stages of the disease and in combination with chemotherapy to address the unmet medical need of patients with triple negative breast cancer.