On May 5, the U.S. Food and Drug Administration (FDA) granted accelerated approval to pembrolizumab (Keytruda) in combination with trastuzumab plus fluoropyrimidine- and platinum-containing chemotherapy for the first-line treatment of patients with locally advanced unresectable or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma.
Approval was based on the prespecified interim analysis of the first 264 patients of the ongoing KEYNOTE-811 trial, a multicenter, randomized, double‑blind, placebo‑controlled trial in patients with HER2‑positive advanced gastric or gastroesophageal junction adenocarcinoma who had not previously received systemic therapy for metastatic disease. Patients were randomly assigned 1:1 to receive pembrolizumab at 200 mg or placebo every 3 weeks in combination with trastuzumab and either fluorouracil plus cisplatin or capecitabine plus oxaliplatin.
The main efficacy measure for this analysis was overall response rate assessed by blinded independent review committee. The overall response rate was 74% (95% confidence interval [CI] = 66%–82%) in the pembrolizumab arm and 52% (95% CI = 43%–61%) in the placebo arm (one-sided P value < .0001, statistically significant).
The median duration of response was 10.6 months (range = 1.1+ to 16.5+) for patients treated with pembrolizumab and 9.5 months (range = 1.4+ to 15.4+) for those in the placebo arm.
The adverse reaction profile observed in patients receiving pembrolizumab in KEYNOTE-811 is consistent with the known pembrolizumab safety profile.
The recommended pembrolizumab dose for adult patients with locally advanced unresectable or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma in combination with trastuzumab and chemotherapy is 200 mg every 3 weeks or 400 mg every 6 weeks.