Merck announced positive interim results from the phase 3 KEYNOTE-355 trial evaluaitng Keytruda in combination with chemotherapy in patients with metastatic triple-negative breast cancer (mTNBC) whose tumors expressed PD-L1. The trial met one of its dual primary endpoints, progression-free survival (PFS). Based on the recommendation of the independent data monitoring committee, the trial will continue without changes to evaluate the other dual primary endpoint of overall survival (OS).
KEYNOTE-355 is a randomized, two-part trial evaluating Keytruda in combination with one of three different chemotherapies (investigator’s choice of either nab-paclitaxel, paclitaxel or gemcitabine/carboplatin) compared with placebo plus one of the three chemotherapy regimens for the treatment of locally recurrent inoperable or mTNBC that has not been previously treated with chemotherapy in the metastatic setting. Part 1 of the study was open-label and evaluated the safety and tolerability of Keytruda in combination with chemotherapy in 30 patients. Part 2 of KEYNOTE-355 was double-blinded, with dual primary endpoints of OS and PFS in all participants and in participants whose tumors expressed PD-L1 (CPS ≥1 and CPS ≥10). Part 2 of KEYNOTE-355 enrolled 847 patients who were randomized to receive Keytruda plus chemotherapy.
Based on an interim analysis conducted by an independent Data Monitoring Committee (DMC), first-line treatment with Keytruda in combination with chemotherapy (nab-paclitaxel, paclitaxel or gemcitabine/carboplatin) demonstrated a statistically significant and clinically meaningful improvement in PFS compared to chemotherapy alone in these patients. The safety profile of Keytruda in this trial was consistent with that observed in previously reported studies; no new safety signals were identified.
About Triple-Negative Breast Cancer (TNBC)
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 (HER2), 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 15-20% of patients with breast cancer are diagnosed with TNBC.
About Keytruda (pembrolizumab) Injection, 100 mg
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 humanized 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.