NEW YORK – The US Food and Drug Administration on Wednesday granted accelerated approval to pembrolizumab (Merck's Keytruda) combined with trastuzumab (Genentech's Herceptin) and chemotherapy as a first-line treatment for patients with locally advanced or metastatic, HER2-positive gastric or gastroesophageal junction (GEJ) cancer.
The agency based its approval on an interim analysis from the Phase III Keynote-811 trial, in which 264 patients with HER2-positive gastric or GEJ cancer were randomized to receive either the trastuzumab-chemotherapy combination plus pembrolizumab or the combination plus a placebo. The overall response rate among patients treated in the pembrolizumab arm was 74 percent, versus 52 percent for those in the placebo arm. The median duration of response was 10.6 months with the pembrolizumab-containing regimen versus 9.5 months in the placebo arm.
Patients enrolled in the clinical trial had tumors that were HER2-positive defined as either immunohistochemistry (IHC) 3+ or 2+, and HER2-positive according to in situ hybridization (ISH) or fluorescent in situ hybridization (FISH).
The accelerated approval comes less than a week after the FDA's Oncologic Drugs Advisory Committee voted 6 to 2 against maintaining accelerated approval for pembrolizumab in PD-L1-positive gastric or GEJ cancer.
As a condition for accelerated approval, Merck may have to submit additional data confirming the benefit of this regimen in HER2-positive gastric cancer.