By Tristan Manalac

Pictured: Merck Research Laboratories building in California
The FDA on Thursday approved Merck’s anti-PD-1 blockbuster Keytruda (pembrolizumab) for the first-line treatment of adult patients with locally advanced unresectable or metastatic gastric or gastroesophageal junction adenocarcinoma.
Thursday’s label expansion is Keytruda’s seventh approval in gastrointestinal cancer and its 38th indication overall in the U.S., according to Merck’s announcement. This latest approval covers patients with HER2-negative cancers and authorizes the use of the PD-1 blocker in combination with fluoropyrimidine- and platinum-containing chemotherapy.
Previously, Keytruda was indicated for gastric cancer only in patients who had progressed after at least two prior lines of systemic therapy, including fluoropyrimidine- and platinum-containing chemotherapy.
Marjorie Green, senior vice president and head of late-stage oncology, global clinical development at Merck Research Laboratories, in a statement called Keytruda’s label expansion an “important milestone” in the care of gastric or gastroesophageal junction adenocarcinoma.
Data from the Phase III KEYNOTE-859 study supported the FDA’s approval on Thursday. The randomized and double-blinded study enrolled 1,579 patients who had not yet received systemic therapies. The results demonstrated that the Keytruda-based regimen cut the risk of death by 22% versus chemotherapy alone. Median survival was also slightly longer in the Keytruda arm.
Keytruda is a monoclonal antibody that targets the PD-1 receptor, disrupting its downstream signaling and boosting the immune system’s cancer-killing activity. It is Merck’s most widely applied oncology asset, with more than 1,600 trials across a variety of cancers and treatment settings.
In its third-quarter earnings report, Merck reported $6.3 billion in sales for Keytruda, representing a 17% increase from the same period last year. During the first nine months of 2022, Keytruda brought in more than $18.4 billion. Much of this growth, according to the company, can be attributed to continued strong demand in metastatic care as well as higher uptake in earlier-stage settings.
In October 2023, Merck was able to push Keytruda into the perioperative setting for non-small cell lung cancer. The FDA’s approval allowed the PD-1 blocker to be administered as a neoadjuvant treatment when used in combination with platinum-based chemotherapy, and then continued as an adjuvant monotherapy after surgery.
Earlier this month, Merck secured another label expansion for Keytruda, this time in biliary tract cancer as part of a combo regimen with gemcitabine and cisplatin chemotherapy.