A cancer shot custom-made from each patient’s tumor cut the risk of melanoma returning by 42% in a major trial, full results show, as Moderna and Merck prepare a launch

People whose high-risk melanoma had been removed by surgery were less likely to have the cancer come back when they got a personalized mRNA treatment along with the standard immunotherapy drug Keytruda, according to full results of a late-stage trial published Nov. 11 in the New England Journal of Medicine.

The treatment, intismeran autogene, is made separately for each patient from the genetic changes in their own tumor.  Moderna, which developed it with Keytruda maker Merck, said Nov. 12 that it is preparing to sell it if regulators approve it.  For now it is available only in clinical trials.

What the trial found

• Two years in, 82.2% of patients who got intismeran plus Keytruda were alive with no return of cancer, compared with 70.0% of those who got Keytruda alone.  That is a 42% lower risk of the cancer returning or death.
• The cancer spread to distant organs less often:  88.5% of patients on the combination were free of distant spread at two years, versus 80.2% on Keytruda alone.
• The benefit showed up after about six months, following the series of shots.  After that point the risk of return or death was 58% lower, Moderna said.
• Severe side effects (grade 3 or higher) of any cause occurred in 23.6% of patients on the combination and 20.3% on Keytruda alone.  The most common side effects of the combination were fever, pain where the shot was given and tiredness, Moderna said.

How a custom cancer shot works

As cancer cells multiply, they pick up genetic mistakes that make abnormal proteins, which the immune system can learn to attack.  For each patient, the company reads the DNA of a tumor sample and a blood sample, uses computer programs to choose up to 34 of those abnormal proteins and writes their recipes into an mRNA shot that trains immune cells to hunt them.  Keytruda, already the standard treatment after surgery for these patients, releases a natural brake on those immune cells.  Moderna said it made the custom shot for more than 99% of patients assigned to get it.

What comes next

Moderna said its factory in Marlborough, Mass., built for intismeran, is expected to become the treatment’s global supply site in 2027 and could eventually supply tens of thousands of patients a year.  Merck and Moderna plan to market it together in the U.S.  Moderna has pointed to a possible approval in 2027.  The companies are also testing the approach in other cancers, including three late-stage lung cancer trials.

About 112,000 Americans are expected to be diagnosed with melanoma, a skin cancer, in 2026, and 8,510 to die of it, according to the National Cancer Institute.  The trial enrolled patients with stage IIB to IV melanoma, meaning higher-risk disease that had been fully removed.  Patients in that situation can ask their cancer doctor about treatment after surgery and open clinical trials.

Source:  Intismeran Autogene plus Pembrolizumab for Resected Stage IIB to IV Melanoma, New England Journal of Medicine, Nov. 11, 2026.