Merck and Moderna on Wednesday reported positive late-stage trial results for an experimental mRNA cancer vaccine, demonstrating a 59% reduction in the risk of melanoma recurrence compared with Merck’s immunotherapy Keytruda alone. The trial, which enrolled more than 1,000 patients with localized tumors at high risk of relapse, also showed the vaccine cut the risk of cancer spreading to new sites by 59%, based on five-year follow-up data presented in June.
The treatment regimen combined up to nine doses of Keytruda—administered every six weeks—with a customized mRNA vaccine. By comparison, Keytruda alone is typically given every three to six weeks for up to a year post-surgery. Researchers noted that the added benefit of the vaccine could influence clinical decisions for patients with lower recurrence risks, such as those with a 20% chance of relapse, where Keytruda’s side effects may outweigh its advantages.
The trial marks a significant milestone in oncology, validating mRNA technology beyond infectious diseases. Dr. Julie Gralow, chief medical officer of the American Society of Clinical Oncology, described the results as a "monumental leap forward," while Dr. Ryan Sullivan, director of the Center for Melanoma at Mass General Brigham Cancer Institute, called it "a big deal for the field in general."
Moderna President Stephen Hoge emphasized the broader implications, stating that numerous mid-stage and early-stage trial results are expected within the next one to two years. He noted that side effects observed in earlier trials were comparable to those of standard vaccines, such as flu or COVID-19 shots. Dr. Robert Vonderheide, director of Penn Medicine’s Abramson Cancer Center, echoed this optimism, predicting that "multiple studies" over the next few years could yield positive outcomes.
Beyond melanoma, the mRNA vaccine approach is being tested in late-stage trials for non-small cell lung cancer, mid-stage trials for bladder and kidney cancers, and early-stage trials for pancreatic and stomach cancers. Roche and BioNTech are also advancing their own mRNA cancer vaccine, autogene cevumeran, with colon cancer data expected in 2027 and pancreatic cancer results anticipated in 2031.
