22 May 2019 - - The Phase 3 KEYNOTE-119 trial evaluating Keytruda, US-based pharmaceutical company Merck's (NYSE: MRK) anti-PD-1 therapy, as monotherapy for the second- or third-line treatment of patients with metastatic triple-negative breast cancer did not meet its pre-specified primary endpoint of superior overall survival compared to chemotherapy (capecitabine, eribulin, gemcitabine or vinorelbine), the company said.

Other endpoints were not formally tested per the study protocol because the primary endpoint of OS was not met.

The safety profile of Keytruda in this trial was consistent with that observed in previously reported studies involving patients treated with Keytruda monotherapy; no new safety concerns were identified. Results will be presented at an upcoming medical meeting.

The Keytruda breast cancer clinical development program encompasses several internal and external collaborative studies, including three ongoing registration-enabling studies in TNBC (KEYNOTE-355, KEYNOTE-242, and KEYNOTE-522).

KEYNOTE-119 is a Phase 3 randomised trial (ClinicalTrials.gov, NCT02555657) evaluating Keytruda monotherapy compared to single-agent physician's choice chemotherapy in metastatic TNBC.

The primary endpoint is OS and the secondary endpoints include progression-free survival, overall response rate, disease control rate and duration of response.

The study randomised 622 patients to receive either Keytruda as monotherapy (200 mg fixed dose every three weeks for up to 24 months) or physician's choice of single-agent chemotherapy (capecitabine, eribulin, gemcitabine or vinorelbine) at a ratio of 1: 1.

TNBC is an aggressive type of breast cancer that characteristically has a high recurrence rate within the first five years after diagnosis.

While some breast cancers may test positive for estrogen receptor, progesterone receptor or human epidermal growth factor receptor 2, TNBC tests negative for all three.

As a result, TNBC does not respond to therapies targeting these markers, making it more difficult to treat. Approximately 10-20% of patients with breast cancer are diagnosed with TNBC.

Keytruda is an anti-PD-1 therapy that works by increasing the ability of the body's immune system to help detect and fight tumor cells.

Keytruda is a humanised monoclonal antibody that blocks the interaction between PD-1 and its ligands, PD-L1 and PD-L2, thereby activating T lymphocytes which may affect both tumor cells and healthy cells.

There are currently more than 1,000 trials studying Keytruda across a range of cancers and treatment settings.

The Keytruda clinical programme seeks to understand the role of Keytruda across cancers and the factors that may predict a patient's likelihood of benefitting from treatment with Keytruda, including exploring several different biomarkers.