Merck Posts Keytruda Data In Triple Negative Breast Cancer

Merck presented early-study data for Keytruda (pembrolizumab) in the treatment of advanced triple-negative breast cancer at the 2014 San Antonio Breast Cancer Symposium (SABCS) held this week.

Keytruda is an anti-PD-1 human monoclonal antibody (mAb) designed to stop PD-1 from interacting with its ligands PD-L1 and PD-L2. In turn, the drug keeps PD-1 from blocking the immune system. Pembrolizumab has scored an accelerated FDA approval this year for the treatment of melanoma and is undergoing several clinical trials for a number of cancers, including gastric and bladder cancer, as well as relapsed/refractory classical Hodgkin Lymphoma (cHL).

The company reported new findings from the ongoing, non-randomized, Phase 1B KEYNOTE-012 study investigating pembrolizumab as monotherapy in patients with advanced triple-negative breast cancer (TNBC) whose tumors were verified to be positive with PD-L1 expression. Results show that Keytruda achieved an overall response rate of 18.5 percent among patients. The median time to response was 18 weeks and progression-free survival (PFS) was reported to be 23.3 percent. Thirty-three percent of patients who took pembrolizumab in the study experienced shrinkage of their tumor.

Forbes noted that although the study yielded a low overall response rate (a mere 5 among 27 patients available for evaluation), the results still drew attention because TNBC is no walk in the park to treat. Breast cancer in itself is a major cause of cancer-related death, ranking fifth in the world. An estimated 15 to 20 percent of patients with breast cancer are diagnosed with TNBC, in which cancer cells do not have sufficient estrogen or progesterone receptors as well as the growth-promoting HER2 protein, which are usual therapeutic targets for treatment.

“Metastatic, triple-negative breast cancer is an aggressive and often difficult to treat disease. The results presented at this year’s SABCS, while early, show encouraging anti-tumor activity in these patients, most of whom had received multiple prior chemotherapies,” said Dr. Rita Nanda, principal investigator for the Keytruda Phase 1b study cohort.

Dr. Alise Reicin, VP of global clinical development, oncology, Merck Research Laboratories, said, “This year, Merck has significantly advanced our immuno-oncology development program and new data for Keytruda have been presented in seven different cancers, including these first findings in triple-negative breast cancer. These early data with Keytruda show responses in patients with one of the most aggressive forms of breast cancer and further our understanding of the PD-1 pathway’s role in this disease.”

Dr. Reicin added that the company plans to launch a Phase 2 study for pembrolizumab in breast cancer in the first half of 2015.