Personalized mRNA Cancer Therapy Lowers Melanoma Recurrence Risk in Phase 3 Trial

Removing melanoma with surgery doesn’t always mean the cancer is gone for good. People with higher-stage disease face a real risk of the cancer returning, most often within two years. New results from a large phase 3 trial suggest that a personalized therapy made from each patient’s own tumor may help lower that risk.

The INTerpath-001 trial tested intismeran autogene, an investigational mRNA-based therapy developed by Merck and Moderna, together with the immunotherapy pembrolizumab (Keytruda). The results were presented at the European Society for Medical Oncology (ESMO) Congress 2026 and have been accepted for publication in The New England Journal of Medicine.

A treatment designed around each patient’s tumor

Every tumor carries its own set of genetic mutations. To make intismeran, researchers analyze a sample of the patient’s tumor along with normal DNA to find neoantigens, which are markers found only on that person’s cancer cells. They then build a custom mRNA treatment that codes for up to 34 of these markers.

Once the mRNA is in the body, it teaches the immune system to recognize those markers and go after cancer cells that carry them. Pembrolizumab, which is already a standard treatment after melanoma surgery, works by releasing a brake on the immune system so it can fight cancer more effectively.

“For decades, cancer treatment has largely been defined by where a tumor originates in the body,” said Georgina Long, MBBS, Ph.D., the study’s principal investigator and medical director of Melanoma Institute Australia, in a statement. “The INTerpath-001 findings support a fundamentally new and individualized approach to treating resected melanoma in the adjuvant setting, one that tailors treatment to the unique mutational signature of a patient’s tumor to enhance an anti-tumor immune response.”

More patients stayed cancer-free after two years

The trial enrolled 1,137 people with stage IIB to IV melanoma that had been completely removed with surgery. Two out of 3 received intismeran plus pembrolizumab, and the rest received a placebo plus pembrolizumab, for about one year.

After a median follow-up of about two years, the combination lowered the risk of the cancer coming back or death by 42% compared with pembrolizumab alone. At two years, 82.2% of patients on the combination had no recurrence, compared with 70% of those on pembrolizumab alone.

The combination also lowered the risk of the cancer spreading to distant parts of the body, or death, by 38%. That matters because melanoma that spreads to organs such as the lungs, liver or brain is much harder to treat.

Benefits appeared after the first six months

During the first six months, both groups did about the same. After patients finished the intismeran doses, the benefit grew. From that point on, the combination lowered the risk of recurrence or death by 58% compared with pembrolizumab alone, according to a planned additional analysis.

That timing makes sense with how the therapy works, since the immune system needs time to learn to recognize the cancer.

Side effects were mostly mild

The most common side effects with the combination were fever (52.2%), pain at the injection site (51%) and fatigue (38.5%). Serious side effects occurred at similar rates in both groups: 14.2% with the combination and 13.4% with pembrolizumab alone. No new safety concerns were found.

Not yet available to patients

Intismeran is still investigational and has not been approved. Merck said it is in discussions with regulators. Researchers are also still collecting data on whether the combination helps people live longer, although early signs are favorable.

Other trials are testing the approach in additional cancers, including non-small cell lung cancer. Long noted that the melanoma results “will help inform our understanding of intismeran as clinical research continues into other tumor types and across settings.”

People with melanoma who are interested in newer treatment options can ask their oncologist whether a clinical trial might be right for them.