Merck Eyes Keytruda Indication Update with Phase III Gastric Cancer Data

Pictured: A sign with the Merck logo surrounded by yellow flowers in front of a glass building / iStock, hapabapa

Merck notched another success for Keytruda Friday, as the blockbuster drug met one of its primary endpoints in a Phase III trial for patients with a rare cancer of the esophagus. The results mark an important step toward full approval of the drug in this indication.

The FDA in May 2021 granted Keytruda, in combination with trastuzumab, fluoropyrimidine- and platinum-containing chemotherapy, accelerated approval for the first-line treatment of patients with locally advanced unresectable or metastatic HER2-positive gastric or gastroesophageal junction (GEJ) adenocarcinoma, based on tumor shrinkage data.

With Friday’s announcement of positive results from the KEYNOTE-811 trial, Merck is working with the FDA to update the current indication for Keytruda “to those patients whose tumors are PD-L1 positive,” Scot Ebbinghaus, vice president of global clinical development at Merck Research Laboratories, said in a statement.

In KEYNOTE-811, the anti-PD-1 therapy was used in combination with Roche’s Herceptin and chemotherapy to treat HER2-positive advanced gastric or GEJ adenocarcinoma. Compared with placebo, Keytruda showed statistically significant improvements in progression-free survival, according to the press release.

The improvement was in a subgroup of patients whose tumors were PD-L1 positive, which covered some 80% of those in the trial. There was also a trend toward improvement in overall survival, the trial’s other primary endpoint, but these results did not meet statistical significance. Overall survival will be tested at a subsequent analysis, the company stated, while the full data from the KEYNOTE-811 trial will be shared at an upcoming medical meeting.

Keytruda, which brought in $20.9 billion in sales last year, has gained several new indications since its original approval. Most recently, the FDA approved it as an adjuvant treatment for non-small cell lung cancer and in combination with Seagen’s Padcev in first-line bladder cancer. The drug is being tested in some 1,600 different trials across a range of cancers and treatment settings.

Stomach cancer is the fourth leading cause of cancer deaths worldwide, with only a 6% five-year survival rate at advanced stages. More than 70% of patients with this cancer type develop advanced-stage disease, according to Merck.

David Adam is a freelance science journalist based in the UK. Reach him at davidneiladam@gmail.com.