mRNA Melanoma Vaccine Cuts Recurrence Risk 42% in Trial
Merck and Moderna's personalized mRNA therapy, intismeran, cut melanoma recurrence or death by 42% in a Phase 3 trial. What the data show and what's next.
The short answer
In a Phase 3 trial of 1,137 people whose high-risk melanoma had been surgically removed, adding Merck and Moderna's personalized mRNA therapy intismeran autogene to the immunotherapy Keytruda cut the risk of the cancer returning or death by 42% compared with Keytruda alone, after a median 24.6 months of follow-up. Two-year recurrence-free survival was 82.2% versus 70.0%. Overall survival data are not yet mature, and the treatment is not approved; the companies say they are talking to regulators.
Key takeaways
- Trial: INTerpath-001, a randomized, double-blind Phase 3 study in 1,137 patients with resected stage IIB-IV melanoma.
- Main result: 42% lower risk of recurrence or death (hazard ratio 0.58) with intismeran plus Keytruda vs. Keytruda alone.
- Two-year recurrence-free survival: 82.2% vs. 70.0%.
- Not yet known: whether it helps people live longer; overall survival data are immature.
- Status: investigational, not FDA-approved. Merck and Moderna say they are engaging with regulators.
In this article
A personalized cancer therapy built on mRNA, the technology Moderna is best known for, has produced one of the most closely watched results in oncology this year. On Oct. 22, 2026, Merck and Moderna reported that their investigational therapy intismeran autogene (also called V940 or mRNA-4157), given alongside Merck's immunotherapy Keytruda (pembrolizumab), cut the risk of melanoma returning or death by 42% in a large Phase 3 trial. The data were scheduled for presentation at the European Society for Medical Oncology (ESMO) congress in Madrid on Oct. 24, and the trial ran at 157 centers, Nature reported. Here is what the trial found, what it did not show, and what comes next.
Health information, not medical advice. This article summarizes trial results reported by the companies and independent coverage. Talk with a doctor about any treatment decision.
What we know: the INTerpath-001 results
According to Merck's announcement, INTerpath-001 is a randomized, double-blind, placebo-controlled trial (ClinicalTrials.gov NCT05933577) in 1,137 adults with high-risk stage IIB to IV cutaneous melanoma that had been completely removed by surgery. Patients were assigned 2-to-1 to intismeran plus Keytruda or placebo plus Keytruda for about a year.
| Measure (median follow-up 24.6 months) | Intismeran + Keytruda | Keytruda alone |
|---|---|---|
| Risk of recurrence or death | 42% lower (hazard ratio 0.58) | Comparison |
| Risk of distant spread or death | 38% lower (hazard ratio 0.62) | Comparison |
| Recurrence-free at 2 years | 82.2% | 70.0% |
| Free of distant spread at 2 years | 88.5% | 80.2% |
| Grade 3-5 treatment-related side effects | 14.2% | 13.4% |
Source: Merck press release, Oct. 22, 2026.
How to read a hazard ratio: a hazard ratio of 0.58 means that, over the follow-up period, patients on the combination had their cancer return (or died) at about 58% of the rate seen with Keytruda alone, which is where the "42% lower risk" figure comes from.
The benefit appeared after six months
One detail stood out to researchers. In the first six months, while patients were still receiving the vaccine doses, results in the two groups were about the same. After that point, a pre-specified analysis showed the combination cut the risk of recurrence or death by 58% compared with Keytruda alone, Merck said. That pattern fits the idea that the therapy needs time to train the immune system.
What it is and is not
Intismeran is not a preventive vaccine. As Nature explains, it is designed to stop melanoma from coming back in people who have already had tumors removed. To make each dose, researchers sequence DNA from a patient's tumor and from healthy tissue, identify mutations unique to the cancer and build an mRNA molecule that codes for up to 34 of those "neoantigens", according to Merck. Once injected, the instructions prompt the body to display those cancer-specific markers so T cells can recognize and attack cancer cells.
What we don't know yet
- Survival. Merck said overall survival data are "not yet mature," though a favorable trend has been observed. The study continues, and trial leader Georgina Long of Melanoma Institute Australia told Nature that patients will be followed for several years.
- Long-term durability. Cancer geneticist Jessamy Tiffen of Sydney's Centenary Institute told Nature the results are exciting but "only time will tell" how effective the treatment is beyond two years, and noted that some patients did not respond.
- Who benefits most. Long said her team will run analyses to identify which patients are most likely to benefit. Results were "generally consistent" across pre-specified subgroups, per Merck.
Side effects
Treatment-related side effects of any grade were common in both groups: 95.8% with the combination and 90.0% with Keytruda alone. Serious (grade 3 to 5) side effects were similar, at 14.2% versus 13.4%. The most common side effects with the combination were fever (52.2%), injection-site pain (51.0%) and fatigue (38.5%). The companies said no new safety signals were seen.
Why this story is trending
Melanoma is one of the deadliest forms of skin cancer and accounts for most skin cancer deaths in the U.S., according to Merck's release, which cites estimates of about 112,000 new U.S. cases and more than 8,500 deaths in 2026. Experts quoted by Nature called the size of the effect remarkable: a risk reduction of 10% is regarded as substantial in oncology, one immunotherapy researcher said. The story also moved markets. Nature reported that the key data leaked online on Oct. 22, prompting the early release, and that Moderna's stock fell about 25% after the leak, which one analyst attributed to inflated expectations rather than doubts about efficacy. Moderna's shares and its ticker, MRNA, appeared among U.S. Google search trends the same day.
What's next
- Regulators. Merck said that "based on these data, we are engaging with regulatory authorities." No application timeline or approval date has been announced.
- Publication. The results have been accepted for publication in The New England Journal of Medicine, according to Merck.
- Other cancers. The INTerpath program includes nine Phase 2 and Phase 3 trials, including three Phase 3 trials in non-small cell lung cancer, with smaller studies in pancreatic and gastric cancers.
If you or a family member has melanoma
The therapy is available only in clinical trials. The National Cancer Institute's melanoma treatment overview explains current, approved options, and ClinicalTrials.gov lists studies along with their recruiting status. Your oncologist can tell you whether any trial fits your situation.
The bottom line
A personalized mRNA therapy added to standard immunotherapy lowered the chance of melanoma returning by 42% over about two years in a large, rigorous trial, with side effects similar to immunotherapy alone. It is not yet approved, and whether it helps people live longer is still unknown. For more of this week's major stories, see our coverage of the record Four Corners flooding and the toothpaste recall affecting kids' brands.
Frequently asked questions
- Is the mRNA melanoma vaccine approved or available?
- No. Intismeran autogene is an investigational therapy. Merck and Moderna said on Oct. 22, 2026, that they are engaging with regulatory authorities based on the Phase 3 data. It is not available outside clinical trials. Patients should talk with their oncologist about trial options.
- Does the vaccine prevent skin cancer?
- No. It is not a preventive vaccine. It is designed for people whose melanoma has already been surgically removed, to lower the chance that the cancer comes back. Each dose is made for one patient from the genetic signature of that person's tumor.
- How effective was intismeran in the trial?
- After a median follow-up of 24.6 months, adding intismeran to Keytruda reduced the risk of recurrence or death by 42% compared with Keytruda alone. Two years after starting treatment, 82.2% of patients on the combination had no recurrence, compared with 70.0% on Keytruda alone, according to Merck.
- What side effects were reported?
- Merck reported serious (grade 3 to 5) treatment-related side effects in 14.2% of patients on the combination and 13.4% on Keytruda alone. The most common side effects with the combination were fever, injection-site pain and fatigue. No new safety signals were observed.
Sources
- Merck and Moderna Will Present Results From Landmark Phase 3 INTerpath-001 Trial for Intismeran Autogene Plus KEYTRUDA · Merck (press release), Oct. 22, 2026
- Moderna mRNA vaccine almost halves the risk of skin cancer returning · Nature, Oct. 23, 2026
- Recapping the Phase 3 INTerpath-001 Results · Moderna
- INTerpath-001 (NCT05933577) study record · ClinicalTrials.gov, U.S. National Library of Medicine
- Melanoma Treatment (PDQ) – Patient Version · National Cancer Institute
About the author
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Spotted an error? Read our corrections policy or contact us. Last reviewed October 26, 2026.
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