KEYTRUDA Approved for Advanced Unresectable or Metastatic HER2-negative Gastric Cancer in Adults

Health Canada has approved KEYTRUDA® (pembrolizumab), an anti-PD-1 therapy developed by Merck & Co., for the first-line treatment of adult patients with advanced gastric or gastroesophageal junction (GEJ) adenocarcinoma that cannot be removed through surgery and is HER2-negative. The approval follows the positive outcomes of the Phase 3 KEYNOTE-859 clinical trial, which showed significant improvements in overall survival (OS), progression-free survival (PFS), and objective response rate (ORR) when KEYTRUDA® was used in combination with specific chemotherapy treatments, as opposed to chemotherapy with a placebo.
Merck Canada's Executive Director & Vice President of the Oncology Business Unit, André Galarneau, PhD, expressed pride in the expansion of KEYTRUDA®'s application to gastric cancers, which are often detected late and carry a poor prognosis. He emphasized Merck's dedication to enhancing patient outcomes through effective treatment options.
The KEYNOTE-859 trial was a randomized, double-blind, placebo-controlled study that involved 1579 patients who had not previously received treatment for metastatic disease. Participants were evenly divided to receive either pembrolizumab with chemotherapy or a placebo with chemotherapy. The study's primary endpoint was OS, with PFS and ORR as secondary endpoints. The results indicated a 22% reduction in the risk of death for patients treated with pembrolizumab and chemotherapy compared to chemotherapy alone. The median OS for this group was 12.9 months, compared to 11.5 months for the chemotherapy-only group.
The study also revealed a correlation between the PD-L1 CPS score and the extent of treatment benefit. The most common side effects associated with pembrolizumab and chemotherapy were nausea, diarrhea, anemia, vomiting, decreased platelet and neutrophil counts, palmar-plantar erythrodysesthesia syndrome, loss of appetite, and fatigue.
Gastric cancer is typically slow-developing and symptomless in its early stages, leading to late diagnoses and high mortality rates. In Canada, it accounted for roughly 4,100 cases and 2,000 deaths in 2023. KEYTRUDA® works by enhancing the immune system's ability to detect and combat tumor cells, and it has been approved for various cancer types since its initial approval in Canada in 2015.
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