In May 2021, the FDA accelerated the approval of a new indication for the immunotherapy Keytruda (pembrolizumab; from Merck & Co), a PD-1 inhibitor, in combination with Herceptin plus fluoropyrimidine- and platinum-containing chemotherapy, for the first-line treatment of patients with locally advanced unresectable (can’t be removed by surgery) or metastatic, HER2-positive gastric or gastroesophageal junction (GEJ) adenocarcinoma. Keytruda has previously been approved for many types of cancer but not for gastric cancer.
Keytruda is the second immunotherapy to be approved by the FDA as the first-line therapy for some patients with gastric cancer. Keytruda has previously been approved for many types of cancer.
This new approval was based on findings from the interim analysis of 264 patients with advanced unresectable or metastatic HER2-positive gastric or GEJ adenocarcinoma who had not received systemic therapy for metastatic disease. Patients received either Keytruda or placebo, both in combination with Herceptin plus chemotherapy.
The overall response rate was 74% in the patients who received Keytruda versus 52% in the patients who received placebo. The average duration of response was 10.6 months in the Keytruda group compared with 9.5 months in the placebo group.
The side effects reported in this study for Keytruda were consistent with the known side effects for this immunotherapy.