On Nov. 13, 2020, Merck announced that the U.S. Food and Drug Administration (FDA) had approved KEYTRUDA, Merck’s anti-PD-1 therapy, in combination with chemotherapy for treatment of patients with locally recurrent unresectable or metastatic triple-negative breast cancer (TNBC) whose tumors express PD-L1 (Combined Positive Score [CPS] =10) as determined by an FDA-approved test. The approval was based on results from the Phase 3 KEYNOTE-355 trial, where KEYTRUDA in combination with chemotherapy – paclitaxel (pac), paclitaxel protein-bound (commonly known as nab-paclitaxel) or gemcitabine (gem) and carboplatin (carbo) – significantly reduced the risk of disease progression or death by 35% for patients whose tumors express PD-L1 (CPS ≥10) versus the same chemotherapy regimens alone.

Immune-mediated adverse reactions, which may be severe or fatal, can occur with KEYTRUDA, including pneumonitis, colitis, hepatitis, endocrinopathies, nephritis, severe skin reactions, solid organ transplant rejection, and complications of allogeneic hematopoietic stem cell transplantation. Based on the severity of the adverse reaction, KEYTRUDA should be withheld or discontinued and corticosteroids administered if appropriate. KEYTRUDA can also cause severe or life-threatening infusion-related reactions. Based on its mechanism of action, KEYTRUDA can cause fetal harm when administered to a pregnant woman.

Triple-negative breast cancer 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 receptors, progesterone receptors or overexpression of human epidermal growth factor receptor 2 (HER2), TNBC tests negative for all three. Approximately 15-20% of patients with breast cancer are diagnosed with TNBC.