The European Commission (EC) has approved pembrolizumab, Merck’s anti-PD-1 therapy, in combination with trastuzumab, fluoropyrimidine- and platinum-containing chemotherapy, for the first-line treatment of locally advanced unresectable or metastatic human epidermal growth factor receptor 2 (HER2)-positive gastric or gastroesophageal junction (GEJ) adenocarcinoma in adults whose tumours express PD-L1 (Combined Positive Score [CPS] ≥1).

This approval by the EC follows the positive recommendation from the Committee for Medicinal Products for Human Use received in July 2023 and was based on results from the Phase 3 KEYNOTE-811 trial.

In the study, pembrolizumab plus trastuzumab and chemotherapy significantly improved progression-free survival (PFS), and objective response rate (ORR), compared to trastuzumab and chemotherapy alone in this patient population.

In the study, more than 80% of patients had tumours that were PD-L1 positive.

There was a trend toward improvement in overall survival (OS), the trial’s other primary endpoint, in the ITT population for patients who received the pembrolizumab combination versus placebo in combination with trastuzumab and chemotherapy; however, these results did not meet statistical significance per the pre-specified statistical analysis plan.

OS analysis for this trial is ongoing.

Results from KEYNOTE-811 will be presented at the upcoming 2023 European Society for Medical Oncology (ESMO) Annual Meeting.

“Patients in the EU diagnosed with HER2-positive advanced gastric cancer face an aggressive disease associated with a poor prognosis, underscoring the need for additional first-line treatment options for these patients,” said Dr. Scot Ebbinghaus, vice president, global clinical development, Merck Research Laboratories.

“With today’s approval of pembrolizumab, we’re proud that patients whose tumours express PD-L1 with a combined positive score ≥1 and healthcare providers in the EU will have an option that includes immunotherapy for this difficult-to-treat disease.”

This approval allows marketing of this pembrolizumab regimen in all 27 European Union (EU) member states plus Iceland, Lichtenstein, Norway and Northern Ireland.

In May 2021, pembrolizumab was approved in combination with trastuzumab, fluoropyrimidine- and platinum-containing chemotherapy for the first-line treatment of patients with locally advanced unresectable or metastatic HER2-positive gastric or GEJ adenocarcinoma in the U.S.

This indication was approved by the FDA under accelerated approval based on ORR data from KEYNOTE-811, and continued approval for this indication may be contingent upon verification and description of clinical benefit in the confirmatory trials.

Merck is working with the FDA to update this indication to patients whose tumours are PD-L1 positive.

Merck has an extensive clinical development program evaluating pembrolizumab in gastrointestinal cancers and is continuing to study pembrolizumab for multiple uses in gastric, hepatobiliary, oesophagal and colorectal cancers.

Source: Merck