An experimental vaccine kept melanoma from returning or spreading in people at high risk of the skin cancer coming back, drugmakers Moderna and Merck announced Wednesday.
The vaccine is built for one patient at a time. It is designed to match the genetics of that person’s own tumor and to teach the immune system to find and attack any cancer cells left behind after surgery, reports The New York Times.
In the late-stage trial, 1,137 people with high-risk melanoma had surgery to remove their cancer.
Those who then received an investigational vaccine — called intismeran — along with the immunotherapy drug Keytruda were less likely to have their cancer return or spread than those who received Keytruda alone, according to The Times.
“It’s a big deal,” said Dr. Elias Sayour, a pediatric oncologist at the University of Florida who was not involved in the trial.
The findings “could help usher a whole new wave of new therapeutic treatments for cancer,” he told The Times.
The pharmaceutical companies shared only a broad outline of the results.
They have not said how much the vaccine lowered the risk of recurrence, and outside scientists have not yet reviewed the findings. They should be considered preliminary until published in a peer-reviewed journal.
Merck and Moderna said they plan to present the full data at an international medical meeting and share it with regulators.
Cancer vaccines have been a long-sought goal — the idea of turning a person’s own immune system against their tumor. They have been studied for many years.
What changed here is the use of mRNA, the same technology used to build COVID-19 vaccines quickly. It allows scientists to make a custom vaccine for each patient rather than one product for everyone, reports The Times.
“It is certainly gratifying to see these exciting results — to come full circle, from our early proof-of-concept results to now,” Dr. Catherine Wu, a professor of medicine at Harvard Medical School and the Dana-Farber Cancer Institute, wrote in an email to The Times.
Wu’s lab showed the promise for custom cancer vaccines in 2017 in studies involving fewer than 20 patients. The next hurdle, she said, is making the approach work for other cancers that may be even more challenging to treat than melanoma.
Melanoma is one of the deadliest skin cancers. It begins in the cells that give skin its color.
About 112,000 new cases are expected in the United States this year, along with more than 8,500 deaths, Merck and Moderna said.
Even after surgery, the cancer can return, most often within the first two years.
Personalized vaccines are now being tested against lung, bladder, kidney and pancreatic cancers as well.
“Folks like myself in the community have been waiting for this,” Sayour said, adding that there is “tremendous capacity for enhancing these approaches.”
More information
Visit the U.S. National Cancer Institute for more information about melanoma treatment.
SOURCES: The New York Times, Aug. 19, 2026; Merck & Co. and Moderna, Inc., company announcement, Aug. 19, 2026
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