Phase III KEYNOTE-859 trial met primary endpoint of overall survival in patients with HER2-negative gastric or gastroesophageal junction adenocarcinoma

Keytruda in combination with chemotherapy showed a statistically significant and clinically meaningful improvement in the trial’s primary endpoint of overall survival (OS) versus chemotherapy alone in the all-randomized patient population at a pre-specified interim analysis conducted by an independent Data Monitoring Committee. Statistically significant and clinically meaningful improvements in progression-free survival (PFS) and overall response rate (ORR) were also observed in the all-randomized patient population.

The safety profile of Keytruda in this trial was consistent with that observed in previously reported studies; no new safety signals were identified. Results will be presented at an upcoming medical meeting and will be submitted to regulatory authorities.

“Despite improvements in cancer care, advanced gastric cancer continues to have one of the lowest five-year survival rates, and new interventions are urgently needed. The results from KEYNOTE-859 show the potential of Keytruda plus chemotherapy to improve survival beyond chemotherapy alone for patients with HER2-negative locally advanced unresectable or metastatic gastric or gastroesophageal junction adenocarcinoma, regardless of PD-L1 expression,” said Dr. Eliav Barr, senior vice president and head of global clinical development, chief medical officer, Merck Research Laboratories. “We are excited by these new results that demonstrate our commitment to exploring new treatment options for patients fighting gastrointestinal cancers with Keytruda and thank all investigators and patients who participated in this trial.”

Merck has an extensive clinical development program evaluating Keytruda in gastrointestinal cancers, which includes KEYNOTE-811 in first-line advanced HER2-positive gastric cancer, KEYNOTE-585 in early-stage gastric cancer, and further exploration in advanced/metastatic gastric cancer in LEAP-015. Merck is continuing to study Keytruda for multiple uses in hepatobiliary, esophageal, pancreatic and colorectal cancers.

About KEYNOTE-859: KEYNOTE-859 is a randomized, double-blind Phase III trial (ClinicalTrials.gov, NCT03675737) evaluating Keytruda in combination with chemotherapy compared to placebo in combination with chemotherapy for the first-line treatment of patients with HER2-negative locally advanced unresectable or metastatic gastric or GEJ adenocarcinoma. The primary endpoint is OS, and secondary endpoints include PFS, ORR, duration of response and safety. The trial enrolled 1,579 patients who were randomized to receive Keytruda (200 mg every three weeks for up to approximately two years) in combination with fluoropyrimidine- and platinum-containing chemotherapy, or placebo in combination with chemotherapy.