A personalized mRNA cancer vaccine cut the risk of melanoma recurrence or death by 42 percent compared with standard treatment in a Phase 3 clinical trial, Moderna and Merck announced Thursday — a result that could usher in a new wave of cancer therapies, as The Washington Post’s Daniel Wu reports.
The drug, intismeran autogene, is built from scratch for each patient. Researchers analyze tissue from a patient’s tumor, then use mRNA — the same platform behind the leading covid-19 vaccines — to deliver a customized vaccine alongside an existing immunotherapy. It also lowered the risk of the cancer spreading or death by 38 percent, though overall survival data isn’t in yet.
“It was really creative science,” said Janice Mehnert, associate director for clinical research at NYU Langone Health’s Pearlmutter Cancer Center and a lead investigator in the trial, who called intismeran a “first in class technology.”
Melanoma, the deadliest form of skin cancer, will account for more than 100,000 new U.S. cases this year, according to the National Cancer Institute, and it often returns even after a tumor is surgically removed. Side effects — fatigue, chills, injection-site pain — matched those seen in earlier studies.
Full results were slated for October 24, 2026, at the European Society for Medical Oncology’s congress in Madrid, but the data leaked early. Moderna shares fell about 25 percent, a drop some analysts blamed on inflated expectations rather than the numbers themselves.
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The companies say they are “engaging with regulatory authorities,” though the road ahead is uncharted. “This is going to be new territory for the FDA,” said Karen Knudsen, CEO of the Parker Institute, a nonprofit for cancer therapeutic research and development.
Not every mRNA cancer vaccine is hitting its marks: BioNTech’s head and neck cancer candidate missed a survival target this month. Still, trials targeting pancreatic, lung and breast cancer are underway. “This is, I do think, a whole new frontier,” Knudsen said.
