Merck and Moderna Report a 42% Lower Risk of Melanoma's Return in a Phase 3 Trial

Merck and Moderna released detailed results on Oct. 22, 2026, from INTerpath-001, a phase 3 trial of an mRNA therapy made individually for each patient and given with the immunotherapy pembrolizumab after melanoma surgery. In the sponsors' primary pre-specified analysis, adding the therapy lowered the risk of the cancer returning or of death by 42% compared with pembrolizumab alone.

The companies describe the treatment, intismeran autogene, as built from a sample of the patient's own tumor: its mutations are read, and a synthetic mRNA is made that the body turns into markers unique to that tumor and shows to the immune system, which can then attack cells carrying them. It is given after surgery, to keep the disease from coming back.

Merck and Moderna report in their joint release that the trial enrolled 1,137 patients whose high-risk melanoma had been completely removed, and followed them for a median of 24.6 months. The companies also report that the two groups looked alike for the first six months, while the course of injections was still being given, and that a pre-specified further analysis measuring from six months onward put the reduction in risk at 58%. By the sponsors' account, the most common side effects in the combination group were fever, injection-site pain and fatigue.

The sponsors say it is too early to tell whether patients live longer; the trial is still running. The therapy is investigational, and the companies say they are in discussions with regulators; none has approved it. The results were presented at the European Society for Medical Oncology Congress, and the companies add that The New England Journal of Medicine has accepted a paper that has not yet appeared. The figures are therefore the sponsors' own, with no independent analysis published.

Georgina Long, the study's principal investigator and medical director of Melanoma Institute Australia, said in the release: "For decades, cancer treatment has largely been defined by where a tumor originates in the body."

Merck and Moderna said in August 2026 that the trial had met its main goal, without giving the size of the effect.