New Immunotherapy Combination Approved for Some Gastrointestinal Cancers  

The FDA has granted accelerated approval to an immunotherapeutic to be used in combination with a targeted therapeutic and chemotherapy to treat certain patients with gastric or gastroesophageal junction adenocarcinomas. 

The U.S. Food and Drug Administration (FDA) recently granted accelerated approval to the checkpoint inhibitor pembrolizumab (Keytruda) in combination with the molecularly targeted agent trastuzumab (Herceptin) and chemotherapy as a first-line treatment for patients with locally advanced unresectable or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma.  

Pembrolizumab releases the brakes on T cells, a type of immune cell, so they can mount an effective immune attack on cancer cells. Trastuzumab targets the HER2 protein, which is expressed at high levels on the surface of some cancer cells.   

The data demonstrating the efficacy of adding pembrolizumab to trastuzumab and chemotherapy stem from 264 patients who had not received any prior systemic therapy for metastatic disease. The study was a multicenter, randomized, double‑blind, placebo‑controlled trial in which one group of patients received pembrolizumab along with trastuzumab and a chemotherapy agent and the other group received a placebo along with trastuzumab and a chemotherapy agent. 

The overall response rate for patients in the pembrolizumab arm of the study was 74 percent, compared with 52 percent for the group of patients that received the placebo. The median duration of response was 10.6 months for the patients treated with pembrolizumab and the other two treatments versus 9.5 months for those who received the placebo and the other two therapies. 

Gastric or stomach cancer begins in the mucosal layer of the stomach and then spreads to cells in the outer linings. Gastroesophageal junction adenocarcinoma is a rare type of esophageal cancer which affects cells that produce mucus and starts in the area where the esophagus joins the stomach. According to federal statistics, it was estimated that there would be over 26,000 new cases of stomach cancer diagnosed in the U.S. in 2021 and over 19,000 new cases of esophageal cancer.  

The accelerated approval for this treatment was rendered by the FDA on May 5, 2021. Accelerated approval means continued approval may be contingent upon a confirmatory trial.