Merck, Moderna Vaccine Combo Cuts Melanoma Relapse or Death Risk 42%

A personalized mRNA cancer vaccine from Merck and Moderna lowered the risk of melanoma coming back or death by 42% in a Phase 3 trial. The companies released detailed results on Oct. 22. The data, from the INTerpath-001 study, are set to be presented at Presidential Symposium I of the ESMO Congress 2026.

What happened

The trial enrolled 1,137 people whose stage IIB to IV melanoma had been fully removed by surgery. They were randomized 2:1 to intismeran autogene plus Keytruda or to Keytruda alone.

The companies reported these results at a median follow-up of 24.6 months:

• Recurrence-free survival: a hazard ratio of 0.58, or a 42% lower risk of recurrence or death.
• Two-year rate: 82.2% of patients on the combination were alive without recurrence, compared with 70.0% on Keytruda alone.
• Distant spread: a hazard ratio of 0.62, or a 38% lower risk of distant metastasis or death.
• Overall survival: not yet mature, though the companies said the trend was favourable.

The companies said results in the first six months were comparable with Keytruda alone, with a hazard ratio of 0.99. A prespecified sensitivity analysis found a hazard ratio of 0.42 after six months.

Grade 3 to 5 treatment-related side effects occurred in 14.2% of patients on the combination and 13.4% on Keytruda alone. Fever, injection site pain and fatigue were the most common events with the combination. BioPharma Dive reported that about 7% of vaccine patients stopped treatment because of a side effect, compared with 5% in the comparator group.

The results were accepted for publication in The New England Journal of Medicine, the companies said.

Why it matters

Intismeran is built for each patient. It uses mRNA to help the immune system recognize up to 34 neoantigens found in that person's tumour. A win here supports the idea that individualized mRNA treatments can add to a standard checkpoint drug after surgery.

Investors had hoped for more. BioSpace reported that the data leaked online on Thursday morning, before Merck issued its release. RBC Capital Markets pointed to a Phase 2 hazard ratio of 0.51. Investors had hoped for a Phase 3 result between 0.50 and 0.59, which put 0.58 at the low end, BioSpace said.

Moderna shares fell 21% to $193.65 and Merck shares fell just over 1%, according to BioSpace. Still, RBC called the data clinically meaningful and likely approvable. BioSpace said an FDA approval could come in 2027.

Jane Healy, Merck's head of oncology early clinical development, told BioSpace the benefit was "not a subtle benefit."

What it means for people in the industry

Merck and Moderna said they are engaging with regulators on the results. The INTerpath program covers nine Phase 2 and Phase 3 trials, including three ongoing Phase 3 trials in non-small cell lung cancer.

The next test is kidney cancer. Interim results from a mid-stage trial there could arrive later this year or in the first half of 2027, BioPharma Dive reported, citing RBC analyst Trung Huynh. The field is not a sure bet: BioNTech recently said its own personalized vaccine failed a mid-stage trial in colorectal cancer.

For teams in oncology, mRNA and cell and gene therapy, the filings and the kidney readout are the next markers to watch.

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Sources

• Merck and Moderna Will Present Results From Landmark Phase 3 INTerpath-001 Trial for Intismeran Autogene Plus KEYTRUDA® (pembrolizumab) at ESMO 2026 Presidential Symposium, Merck
• ESMO 2026: Merck, Moderna shares fall as cancer vaccine disappoints after data leak, BioSpace
• Moderna, Merck shares fall on eagerly anticipated cancer vaccine results, BioPharma Dive