Merck (NYSE: MRK), known as MSD outside the United States and Canada, today announced that the U.S. Food and Drug Administration (FDA) has approved KEYTRUDA, Merck’s anti-PD-1 therapy, in combination with chemotherapy for the 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 is 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 (HR=0.65 [95% CI, 0.49, 0.86]; p=0.0012). Events were observed in 62% (n=136/220) of these patients receiving KEYTRUDA in combination with pac, nab-paclitaxel or gem/carbo versus 77% (n=79/103) with the same chemotherapy regimens alone. In the trial, 38% of patients had tumors expressing PD-L1 with CPS ≥10. This indication is approved under accelerated approval based on progression-free survival (PFS); continued approval for this indication may be contingent upon verification and description of clinical benefit in the confirmatory trials.
“Approximately 15-20% of patients with breast cancer are diagnosed with triple-negative breast cancer, which is a difficult-to-treat and aggressive cancer,” said Dr. Hope Rugo, director of Breast Oncology and Clinical Trials Education, University of California San Francisco (UCSF) Helen Diller Family Comprehensive Cancer Center. “Notably, in KEYNOTE-355, KEYTRUDA was combined with three different chemotherapy regimens: paclitaxel, nab-paclitaxel or gemcitabine and carboplatin. The approval of KEYTRUDA in combination with chemotherapy gives physicians an important new option for appropriate patients.”
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. For more information, see “Selected Important Safety Information” below.
“Today’s approval is a significant milestone, as it represents the first approval for KEYTRUDA in the breast cancer setting,” said Dr. Roy Baynes, senior vice president and head of global clinical development, chief medical officer, Merck Research Laboratories. “In the study supporting this approval, KEYTRUDA in combination with paclitaxel, nab-paclitaxel or gemcitabine and carboplatin significantly improved progression-free survival for patients with advanced triple-negative breast cancer whose tumors express PD-L1 with CPS greater than or equal to 10 compared with the same chemotherapy regimens alone.”
Data Supporting the Approval
The accelerated approval was based on data from KEYNOTE-355 (ClinicalTrials.gov, NCT02819518), a multicenter, double-blind, randomized, placebo-controlled trial conducted in 847 patients with locally recurrent unresectable or metastatic TNBC, regardless of tumor PD-L1 expression, who had not been previously treated with chemotherapy in the metastatic setting. Patients were randomized (2:1) to receive either KEYTRUDA (200 mg on Day 1 every three weeks) or placebo (on Day 1 every three weeks) in combination with the following chemotherapy; all medications were administered via intravenous infusion:
- Pac (90 mg/m2 on Days 1, 8 and 15 every 28 days); or
- Nab-paclitaxel (100 mg/m2 on Days 1, 8 and 15 every 28 days); or
- Gem/carbo (1,000 mg/m2 and AUC 2 mg/mL/min, respectively, on Days 1 and 8 every 21 days).
Randomization was stratified by chemotherapy treatment (pac or nab-paclitaxel vs. gem and carbo), tumor PD-L1 expression (CPS ≥1 vs. CPS <1) according to the PD-L1 IHC 22C3 pharmDx kit and prior treatment with the same class of chemotherapy in the neoadjuvant setting (yes vs. no). Assessment of tumor status was performed at Weeks 8, 16 and 24, then every nine weeks for the first year and every 12 weeks thereafter. The main efficacy outcome measure was PFS as assessed by blinded independent central review (BICR) according to RECIST v1.1, modified to follow a maximum of 10 target lesions and a maximum of five target lesions per organ tested in the subgroup of patients with CPS ≥10. Additional efficacy outcome measures were overall survival, as well as objective response rate (ORR) and duration of response (DOR) as assessed by BICR.
The study population characteristics were: median age of 53 years (range, 22 to 85), 21% age 65 or older; 100% female; 68% White, 21% Asian and 4% Black; 60% ECOG PS of 0 and 40% ECOG PS of 1; and 68% were post-menopausal. Seventy-five percent of patients had tumor PD-L1 expression CPS ≥1 and 38% had tumor PD‑L1 expression CPS ≥10.
In KEYNOTE-355, efficacy results were in patients who were PD‑L1 positive with a CPS ≥10 (n=323) and randomized to receive KEYTRUDA in combination with pac, nab-paclitaxel or gem/carbo compared with the same chemotherapy regimens alone. KEYTRUDA in combination with pac, nab-paclitaxel or gem/carbo (n=220) reduced the risk of disease progression or death by 35% (HR=0.65 [95% CI, 0.49, 0.86]; p=0.0012), with a median PFS of 9.7 months (95% CI, 7.6, 11.3) versus 5.6 months (95% CI, 5.3, 7.5) with the same chemotherapy regimens alone (n=103). For PFS, 62% (n=136) of patients experienced an event with KEYTRUDA in combination with pac, nab-paclitaxel or gem/carbo versus 77% (n=79) with the same chemotherapy regimens alone. For patients who received KEYTRUDA in combination with pac, nab-paclitaxel or gem/carbo, the ORR was 53% (95% CI, 46, 60), with a complete response rate of 17% and a partial response rate of 36%. For patients treated with the same chemotherapy regimens alone, the ORR was 40% (95% CI, 30, 50), with a complete response rate of 13% and a partial response rate of 27%. Median DOR was 19.3 months (95% CI, 9.9, 29.8) with KEYTRUDA in combination with pac, nab-paclitaxel or gem/carbo versus 7.3 months (95% CI, 5.3, 15.8) with the same chemotherapy regimens alone.
In the study, the median duration of exposure to KEYTRUDA was 5.7 months (range, 1 day to 33.0 months). Fatal adverse reactions occurred in 2.5% of patients (n=596) receiving KEYTRUDA in combination with chemotherapy, including cardio-respiratory arrest (0.7%) and septic shock (0.3%). Serious adverse reactions occurred in 30% of patients receiving KEYTRUDA in combination with pac, nab-paclitaxel, or gem/carbo. Serious adverse reactions observed in ≥2% of patients were pneumonia (2.9%), anemia (2.2%), and thrombocytopenia (2%). KEYTRUDA was discontinued for adverse reactions in 11% of patients. The most common adverse reactions resulting in permanent discontinuation of KEYTRUDA (≥1%) were increased alanine aminotransferase (ALT) (2.2%), increased aspartate aminotransferase (AST) (1.5%), and pneumonitis (1.2%). Adverse reactions leading to the interruption of KEYTRUDA occurred in 50% of patients. The most common adverse reactions leading to interruption of KEYTRUDA (≥2%) were neutropenia (22%), thrombocytopenia (14%), anemia (7%), increased ALT (6%), leukopenia (5%), decreased white blood cell count (3.9%), and diarrhea (2%). The most common adverse reactions (all grades ≥20%) for KEYTRUDA in combination with pac, nab-paclitaxel or gem/carbo were: fatigue (48%), nausea (44%), alopecia (34%), diarrhea and constipation (28% each), vomiting and rash (26% each), cough (23%), decreased appetite (21%), and headache (20%).
About Triple-Negative Breast Cancer (TNBC)
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.
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.
Merck has the industry’s largest immuno-oncology clinical research program. There are currently more than 1,300 trials studying KEYTRUDA across a wide variety of cancers and treatment settings. The KEYTRUDA clinical program seeks to understand the role of KEYTRUDA across cancers and the factors that may predict a patient’s likelihood of benefitting from treatment with KEYTRUDA, including exploring several different biomarkers.