Merck Shares Significant Keytruda Breast Cancer Results

Keytruda plus chemotherapy reduces the risk of death by 27% in patients with triple-negative breast cancer.

Merck’s Keytruda/chemotherapy combo treatment demonstrates a statistically significant and clinically meaningful improvement in overall survival (OS) for patients with triple-negative breast cancer (mTNBC), according to recent data.

The phase 3 KEYNOTE-355 study of Keytruda (pembrolizumab) in combination with chemotherapy (paclitaxel, nab-paclitaxel or gemcitabine/carboplatin) reduced the risk of death by 27% in patients with mTNBC whose tumors expressed PD-L1 compared with chemotherapy alone, Merck said in a news release.

There was an increase of 6.9 months in median overall survival with Keytruda plus chemotherapy compared with chemotherapy alone (23 months versus 16 months). The increase in overall survival was observed across the three chemotherapy choices.

The data was presented at the European Society for Medical Oncology (ESMO) Congress 2021.

Keytruda is currently approved under accelerated approval in the United States in combination with chemotherapy for the treatment of patients with locally recurrent unresectable or metastatic TNBC whose tumors express PD-L1.

“Metastatic TNBC has the worst survival prognosis among breast cancer subtypes, and there is an urgent need for treatment options that improve survival,” Hope Rugo, M.D., director, Breast Oncology and Clinical Trials Education, University of California San Francisco (UCSF) Helen Diller Family Comprehensive Cancer Center, said in a statement. “I am very encouraged to see these new overall survival data for the Keytruda combination.”

“With these new data, KEYNOTE-355 has now met both primary endpoints, improving progression-free and overall survival for the approximately 40% of patients from this trial with metastatic TNBC whose tumors expressed PD-L1,” Vicki Goodman, M.D., vice president, clinical research, Merck Research Laboratories, said in a statement.

The incidence of treatment-related adverse events was similar among patients in the two treatment groups, with Grade 3 to 5 adverse events occurring in 68% of patients in the Keytruda plus chemotherapy arm and nearly 67% of patients in the chemotherapy arm. Treatment-related adverse events led to discontinuation in 18.3% of patients in the Keytruda plus chemotherapy arm and 11% of patients in the chemotherapy arm.

Triple-negative breast cancer is a type of breast cancer that tests negative for estrogen hormone receptors, progesterone hormone receptors, and overexpression of human epidermal growth factor receptor 2. It is an aggressive type of breast cancer that characteristically has a high recurrence rate within the first five years after diagnosis. About 10% to 15% of patients with breast cancer are diagnosed with TNBC, which tends to be more common in people who are younger than 40 years of age, who are African American, or who have a BRCA1 mutation.