WASHINGTON – An experimental treatment created individually for people with high-risk melanoma reduced the risk of the cancer returning or patients dying by 42% when added to standard immunotherapy after surgery, according to detailed results from a large Phase 3 trial.
At two years, 82% of patients who received the personalized mRNA treatment plus pembrolizumab, sold as Keytruda, were alive without a recurrence. That compared with 70% of patients who received Keytruda alone, Moderna and Merck reported Thursday.
The result is an important advance for individualized cancer treatment, but it does not mean that a broadly available vaccine can prevent melanoma. The product, called intismeran autogene, is made separately from each patient’s surgically removed tumor and is intended to help keep an existing cancer from returning.
Intismeran remains investigational and has not been approved by the U.S. Food and Drug Administration. Overall-survival data are not yet mature, so researchers cannot say whether the combination helps patients live longer. The companies reported a favorable early trend and said the trial will continue following participants.
The international INTerpath-001 study enrolled 1,137 people with stage IIB through stage IV cutaneous melanoma whose tumors had been completely removed. Participants had not previously received systemic treatment for the cancer.
Patients were randomly assigned in a 2-to-1 ratio to receive either intismeran and Keytruda or a placebo and Keytruda. Keytruda is a checkpoint inhibitor that helps immune cells recognize and attack cancer by blocking the PD-1 pathway, which tumors can use to evade an immune response.
The personalized component begins with genetic sequencing of a patient’s tumor. Researchers identify mutations that produce abnormal proteins, known as neoantigens, which can distinguish cancer cells from healthy tissue. A custom strand of messenger RNA is then designed to carry instructions for as many as 34 of those targets.
Once injected, the mRNA instructs cells to display the selected targets so the immune system can learn to recognize them. Patients in the study could receive up to nine doses of intismeran, spaced three weeks apart, along with Keytruda for about one year.
Creating the treatment can take roughly six weeks from the start of tumor analysis, Moderna President Stephen Hoge told The Associated Press. Patients can begin standard Keytruda treatment while the personalized product is being prepared.
The trial also found a 38% reduction in the risk of melanoma spreading to a distant part of the body or death among patients receiving the combination, according to results reported by The Washington Post. Researchers are continuing to evaluate overall survival, safety, quality of life and other outcomes.
Reported side effects were consistent with earlier studies. Investigators said common reactions included fatigue, chills, a sore arm and pain at the injection site. The companies reported no new safety signal, though regulators will review the full benefit-and-risk profile rather than relying only on the topline findings.
Moderna and Merck first announced in August that the study had met its main goals without releasing the numerical results. The fuller data were released Thursday after some information became public ahead of a scheduled presentation at the European Society for Medical Oncology meeting in Madrid.
The findings do not establish that mRNA treatments will work against every cancer. Personalized vaccines are being studied for lung, kidney, bladder, pancreatic and other cancers, and results have varied across diseases and treatment settings. Each approach requires separate clinical trials.
Melanoma develops in cells that produce skin pigment and can spread rapidly if it is not detected and treated. More than 100,000 new U.S. cases are expected this year. Even after a tumor is removed, people with high-risk disease can face recurrence, often within the first two years.
Moderna and Merck said they are discussing the results with regulators, but they have not announced an FDA decision date or a price. Personalized medicines can be costly to produce, and the companies have not said what intismeran would cost if approved.
Patients should not change treatment based on a trial announcement. Surgery, immunotherapy, targeted therapy and clinical trials are selected according to cancer stage, tumor characteristics and a patient’s overall health. People diagnosed with melanoma should discuss approved options and research studies with an oncologist.
Source: The Washington Post, published Oct. 22, 2026. Additional reporting and verification: The Associated Press, Merck and Moderna’s INTerpath-001 results, and ClinicalTrials.gov.
