Merck and Moderna's mRNA cancer therapy cuts melanoma recurrence risk by 42% in Phase 3

Merck and Moderna released the full Phase 3 INTerpath-001 results for their individualised mRNA cancer therapy intismeran autogene on 22 October 2026, two days before the planned ESMO 2026 presentation, after the data were leaked ¹². Added to Keytruda after surgery for stage IIB to IV melanoma, intismeran cut the risk of recurrence or death by 42% against Keytruda alone ¹.

What the trial found

INTerpath-001 is a randomised, double-blind global trial of 1,137 patients with completely resected high-risk cutaneous melanoma, allocated 2:1 to intismeran plus Keytruda or placebo plus Keytruda for roughly one year ¹. Intismeran is given at 1 mg every three weeks for up to nine doses ¹.

At a median follow-up of 24.6 months, the hazard ratio for recurrence-free survival, the primary endpoint, was 0.58 (95% CI 0.45 to 0.75) ¹. Two-year recurrence-free survival was 82.2% with the combination and 70.0% with Keytruda alone ¹. For distant metastasis-free survival the hazard ratio was 0.62, with two-year rates of 88.5% and 80.2% ¹.

The effect was not visible early. In the first six months the two arms performed alike (hazard ratio 0.99 for recurrence or death) ¹. From six months, once the immunisation course was complete, a pre-specified sensitivity analysis gave a hazard ratio of 0.42 for recurrence or death and 0.50 for distant metastasis or death ¹. Overall survival is not yet mature, though the companies report a favourable trend ¹.

Treatment-related adverse events affected 95.8% of patients on the combination and 90.0% on Keytruda alone; grade 3 to 5 events were 14.2% and 13.4% ¹. Fever (52.2%), injection site pain (51.0%) and fatigue (38.5%) were the most frequent ¹. The companies said there were no new safety signals ¹.

What it means for the market

This is the first Phase 3 evidence for a tumour-specific, mRNA-made therapy, and Merck and Moderna say they are now in talks with regulators ¹. For oncology developers it sets a benchmark: a manufactured-per-patient product has beaten an established checkpoint inhibitor in the adjuvant setting ¹. The INTerpath programme already runs nine Phase 2 and 3 trials, three of them Phase 3 studies in non-small cell lung cancer, so the melanoma result will shape how investors and competitors read those ¹.

Investors were less certain. Fierce Biotech reports that the recurrence result sat near the range analysts expected, with some having predicted a hazard ratio as low as 0.5, but that the metastasis result disappointed ². The Phase 2 trial had shown a 65% reduction in distant metastasis or death, against 38% here ². Shares in both companies fell after the release, Moderna more sharply than Merck ². Analysts at TD Cowen noted that Moderna executives had treated metastasis-free survival as an especially meaningful measure in melanoma ².

ESMO's press office confirmed an embargo breach after an oncology news site published some of the data early, which forced the companies to move the release forward ².

Caveats

All the efficacy figures come from the companies' release, and the survival data are immature ¹. The benefit appeared only after six months of treatment, and median recurrence-free survival was not reached in either arm ¹. The results apply to resected cutaneous melanoma, and the principal investigator, Professor Georgina Long, said they are in that population only and will inform research in other tumour types ¹.

The results have been accepted by The New England Journal of Medicine, and the presentation at ESMO in Madrid goes ahead on Saturday as planned ¹².