Data Investigating KEYTRUDA, Merck's Anti-PD-1 Therapy, In Patients With Advanced Triple-Negative Breast Cancer Presented At 2014 San Antonio Breast Cancer Symposium

Merck

, known as MSD outside the United States and Canada, announced today early study findings demonstrating an overall response rate of 18.5 percent with KEYTRUDA, the company's anti-PD-1 therapy, as assessed by RECIST v1.1, central review (n=5/27), in PD-L1 positive, advanced triple-negative breast cancer – one of the most aggressive forms of breast cancer. At the time of analysis, the median duration of response had not been reached with three of five responders on therapy for 11 months or more (range, 15 to 40+ weeks). These early findings, from the ongoing Phase 1b KEYNOTE-012 study, were shared today for the first time as part of the official press program at the 2014 San Antonio Breast Cancer Symposium (SABCS) (ABSTRACT #S1-09) and will be presented in an oral session at 10:45 a.m. CST by Dr. Rita Nanda, the University of Chicago. “Metastatic, triple-negative breast cancer is an aggressive and often difficult to treat disease,” said Dr. Rita Nanda, associate director, breast medical oncology, the University of Chicago and principal investigator for the KEYTRUDA triple-negative breast cancer Phase 1b study cohort. “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.” “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,” said Dr. Alise Reicin, vice president, global clinical development, oncology, Merck Research Laboratories. “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. Our Phase 2 study planned for the first half of 2015 will be an important next step for our breast cancer clinical program.” Early Findings Evaluating KEYTRUDA in Advanced Triple-Negative Breast Cancer Data presented were from a cohort of the ongoing Phase 1b KEYNOTE-012 study which evaluated KEYTRUDA monotherapy at 10 mg/kg every two weeks in patients with advanced TNBC whose tumors were determined to be positive for PD-L1 expression (n=32). As measured by Merck's proprietary PD-L1 immunohistochemistry (IHC) clinical trial assay, tumors were considered to be PD-L1 positive if staining was present in the stroma or in greater than or equal to one percent of tumor cells. In the study, 58 percent of patients screened had tumors determined to be positive for PD-L1 expression. Most patients enrolled in this study had received two or more prior chemotherapies for metastatic disease and 87.5 percent had received prior neo-adjuvant or adjuvant therapy. Antitumor Activity with KEYTRUDA by Response Evaluation Criteria in Solid Tumors (RECIST) v1.1, Central Review* Patients Evaluable for Response (n=27)(a) Overall Response Rate (ORR), n (%) 5 (18.5%) Best Overall Response, n (%) Complete Responseb 1 (3.7%) Partial Responseb 4 (14.8%) Stable Disease 7 (25.9%) Progressive Disease 12 (44.4%) No Assessmentc 3 (11.1%) *Analysis cut-off as of: November 10, 2014. aIncludes patients with measurable disease at baseline who received ≥1 pembrolizumab dose and who had ≥1 post-baseline scan or discontinued therapy before the first scan due to progressive disease or a treatment-related AE. Five patients were excluded because they did not have any assessments per central review (n=2) or because they did not have measurable disease per central review at baseline (n=3). bConfirmed responses only. c“No assessment” signifies patients who discontinued therapy before the first post-baseline scan due to progressive disease or a treatment-related AE. The median time to response was 18 weeks (range, 7-32 weeks). In the study, 33 percent of patients with KEYTRUDA achieved tumor shrinkage. At six months, the progression-free survival rate with KEYTRUDA was 23.3 percent. Adverse events were consistent with previously reported safety data for KEYTRUDA. The most common treatment-related adverse events (occurring in greater than or equal to five percent of patients) included arthralgia (n=6), fatigue (n=6), myalgia (n=5), nausea (n=5), ALT increased (n=2), AST increased (n=2), diarrhea (n=2), erythema (n=2) and headache (n=2). Grade 3-5 treatment-related adverse events occurred in a total of five patients and included anemia, disseminated intravascular coagulation (DIC), headache, meningitis aseptic, decreased blood fibrinogen, and pyrexia. Two patients discontinued KEYTRUDA due to adverse events. One treatment-related death was reported in a patient with rapidly progressive disease and was due to DIC with thrombocytopenia and decreased blood fibrinogen.