A personalized cancer vaccine built from the mutations in each patient's own tumor has cut the risk of melanoma returning by 42 percent in a large Phase 3 trial — the first time an individualized vaccine of this kind has succeeded at this stage of testing.
The detailed results of the INTerpath-001 trial, announced by Merck and Moderna on October 22 and being presented this weekend at the European Society for Medical Oncology (ESMO) Congress 2026 in Madrid, tested intismeran autogene — an mRNA therapy also known as V940 or mRNA-4157 — combined with Merck's immunotherapy Keytruda (pembrolizumab), in 1,137 patients whose high-risk stage IIB-IV melanoma had been completely removed by surgery but remained likely to return.
At a median follow-up of 24.6 months, patients who received the vaccine plus Keytruda had a 42 percent lower risk of recurrence or death than those on Keytruda alone, with two-year recurrence-free survival of 82.2 percent against 70.0 percent. The risk of distant metastasis or death fell by 38 percent (88.5 percent versus 80.2 percent at two years). A pre-specified sensitivity analysis suggested the benefit grows after the first six months. Overall survival data are not yet mature, though the companies report a favourable trend, and no new safety concerns emerged.
A treatment made for exactly one person
Intismeran is not a drug pulled from a shelf. A sample of the patient's tumor and healthy tissue is sequenced, software selects up to 34 "neoantigens" — protein fragments unique to that cancer — and their genetic code is written into a single messenger RNA molecule, the same platform Moderna used for its COVID-19 vaccine. Injected into the patient, the mRNA teaches the immune system to recognise those fragments, while Keytruda releases a brake on the T cells doing the attacking. Every dose is unique to one patient.
"The transformative INTerpath-001 results have the potential to make a foundational shift in how we treat patients with earlier-stage melanoma in the adjuvant setting," said the study's principal investigator, Professor Georgina Long of Melanoma Institute Australia. The results have been accepted for publication in The New England Journal of Medicine. They build on the earlier Phase 2b KEYNOTE-942 trial, whose five-year follow-up found the combination reduced the risk of recurrence or death by 49 percent.
Why it matters, and what happens next
Cancer vaccines were one of oncology's most persistent disappointments for decades; this is both the first positive Phase 3 readout for an individualized neoantigen therapy and the first for an mRNA-based cancer therapy. The treatment is not approved anywhere yet, and the companies say they are now engaging with regulators. The wider INTerpath programme spans nine trials, including three Phase 3 studies in non-small cell lung cancer — the real test of whether a vaccine built for one patient at a time can become a practical model for treating cancer at scale.
*Reporting based on Merck and Moderna's INTerpath-001 announcement and The American Journal of Managed Care's coverage of the results.*