Merck and Moderna said on August 19, 2026 that their personalized mRNA cancer therapy had beaten the standard of care in a Phase 3 melanoma trial. No individualized neoantigen therapy had won at this stage before, and neither had any cancer treatment built on mRNA.
The trial, INTerpath-001, enrolled 1,137 patients with stage IIB to IV cutaneous melanoma whose tumors had been fully removed, randomized 2:1 after surgery. One arm received the experimental therapy, intismeran autogene, together with Merck’s Keytruda (pembrolizumab). The other received Keytruda alone for about a year. At a planned interim look, the combination improved recurrence-free survival, the primary endpoint, and distant metastasis-free survival, a key secondary one. Safety looked consistent with earlier studies, with no new signals.
The treatment is built per patient. A sample of the tumor is read for its mutational signature, and each dose carries up to 34 neoantigens, written into synthetic mRNA and chosen from that tumor’s biology. The aim is to train the immune system to find and attack cancer cells that surgery may have missed. The dosing: 1 mg of intismeran every three weeks, up to nine doses, with 400 mg of Keytruda each six weeks across as many as nine cycles.
The numbers arrive
The August announcement gave no effect size. The detailed results came in a later release, ahead of a presentation at the ESMO Congress 2026. Median follow-up was 24.6 months. By then the pairing had cut relapse or death risk 42% (HR=0.58; two-sided p<0.001), and the chance of distant spread or death by 38% (HR=0.62; p=0.002), against Keytruda alone.
The benefit grew after the first six months, once the intismeran immunization regimen was done. A sensitivity analysis set in advance put the drop in recurrence or death risk at 58% past that point. During the first six months, the two arms were comparable (HR=0.99). Overall survival data are not yet mature, though the companies report a favorable trend.
“Today’s results represent a landmark moment for adjuvant melanoma treatment,” said Professor Georgina Long, who led the study and directs medical work at Melanoma Institute Australia. Stéphane Bancel, Moderna’s CEO, called the findings “a pivotal moment for the field of cancer research.”
The result follows a Phase 2b study, KEYNOTE-942, whose five-year follow-up presented at ASCO’s 2026 annual meeting, showed risk of recurrence or death falling 49%. Merck and Moderna are engaging with regulators, and the paper has been accepted by the New England Journal.
Sources
- Merck and Moderna Announce Phase 3 INTerpath-001 Trial of Intismeran Autogene Plus KEYTRUDA Met Endpoints of RFS and DMFS
- Merck and Moderna’s Intismeran Autogene Plus Keytruda Meets Phase 3 RFS and DMFS Endpoints in Resected Melanoma
- Merck and Moderna Will Present Results From Landmark Phase 3 INTerpath-001 Trial at ESMO 2026
