Keytruda + trastuzumab + chemotherapy met primary endpoint of progression-free survival as first-line treatment of HER2-positive advanced gastric or gastroesophageal junction (GEJ) adenocarcinoma.- Merck Inc.,

At a pre-specified interim analysis conducted by an independent Data Monitoring Committee, Keytruda in combination with trastuzumab and chemotherapy demonstrated a statistically significant improvement in PFS compared to placebo in combination with trastuzumab and chemotherapy in the intention-to-treat (ITT) study population.

Based on a pre-specified subgroup analysis by PD-L1 expression , the improvement in PFS observed in the ITT population was limited to patients whose tumors were PD-L1 positive (Combined Positive Score [CPS] greater than 1) . In the study, more than 80% of patients had tumors that were PD-L1 positive. Merck has discussed these findings with the FDA and is working with the FDA to update the current indication for Keytruda in HER2-positive gastric or GEJ adenocarcinoma to those patients whose tumors are PD-L1 positive. In addition, these results will be presented at an upcoming medical meeting and shared with regulatory authorities worldwide.

In May 2021, Keytruda was approved in combination with trastuzumab, fluoropyrimidine- and platinum-containing chemotherapy for the first-line treatment of patients with locally advanced unresectable or metastatic .

A trend toward improvement in overall survival (OS), the trial’s other primary endpoint, was observed in the ITT population for patients who received the Keytruda combination versus placebo in combination with trastuzumab and chemotherapy; however, these results did not meet statistical significance per the pre-specified statistical analysis plan. Overall survival will be tested at a subsequent analysis. The safety profile of Keytruda was consistent with that observed in previously reported studies.

“These new data from KEYNOTE-811, demonstrating a significant improvement in progression-free survival, are meaningful and build on the earlier insights from this study that supported the accelerated approval of this Keytruda combination in the U.S. for certain patients with HER2-positive gastric or GEJ adenocarcinoma,” said Dr. Scot Ebbinghaus, vice president, global clinical development, Merck Research Laboratories. “We look forward to sharing these results with the medical community and regulatory authorities to ensure this Keytruda-based regimen is available to appropriate patients, and we are working with the FDA to update the current indication for Keytruda to those patients whose tumors are PD-L1 positive.”