The US Food and Drug Administration (FDA) has revised the gastric cancer indication for Merck’s immune checkpoint inhibitor, pembrolizumab (Keytruda), restricting its use to patients whose tumors express programmed death–ligand 1 (PD-L1), as determined by an FDA-approved companion diagnostic device.
That device, the PD-L1 IHC22Cs pharmDx (Agilent Technologies), was approved to identify patients with gastric or gastroesophageal junction adenocarcinoma who have tumors expressing PD-L1 with a combined positive score (CPS) ≥ 1.
Pembrolizumab remains approved under accelerated approval regulations for this updated indication. Previously, the agent was indicated for use with trastuzumab, fluoropyrimidine, and platinum-containing chemotherapy for first-line treatment of patients with locally advanced unresectable or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma, regardless of PD-L1 expression.
That approval, granted May 5, 2021, was based on interim findings from the KEYNOTE-811 trial showing improved objective response rate and duration of response with pembrolizumab vs placebo.
However, in a recent prespecified interim analysis, data in the subgroup of patients with PD-L1 CPS < 1 suggest that the overall survival and progression-free survival (PFS) benefits are limited. In this population, the hazard ratio for overall survival was 1.41 (95% CI, 0.90-2.20) and the hazard ratio for PFS was 1.03 (95% CI, 0.65-1.64).
The recommended pembrolizumab dose is 200 mg every 3 weeks or 400 mg every 6 weeks until disease progression, unacceptable toxicity, or up to 24 months. Pembrolizumab should be administered prior to trastuzumab and chemotherapy when given on the same day, according to prescribing information.
Sharon Worcester, MA, is an award-winning medical journalist based in Birmingham, Alabama, writing for Medscape, MDedge and other affiliate sites. She currently covers oncology, but she has also written on a variety of other medical specialties and healthcare topics. She can be reached at [email protected] or on Twitter: @SW_MedReporter .
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