Personalized mRNA Vaccine Lowers Melanoma Relapse Risk 42%
Two years after surgery, 82.2% of melanoma patients who received a personalized mRNA vaccine plus the immunotherapy drug pembrolizumab (sold as Keytruda) had no recurrence of their cancer. In the comparison group, which got a placebo plus pembrolizumab, the figure was 70.0%. Merck and Moderna announced the phase 3 results (the large, randomized stage that precedes any approval request) on October 22, 2026, and investigators presented them at the European Society for Medical Oncology (ESMO) Congress in Madrid.
The trial, called INTerpath-001, enrolled 1,137 patients whose stage IIB, IIC, III or IV skin melanoma had been completely removed by surgery and who had received no other drug treatment. Researchers assigned them at random, two to one, to the vaccine plus pembrolizumab (757 patients) or placebo plus pembrolizumab (380). Neither patients nor doctors knew who got which.
A vaccine built from each patient's tumor
The vaccine, intismeran autogene (also called V940 or mRNA-4157), is made one patient at a time. National Geographic describes the steps: sequence DNA from the tumor, compare it with the patient's healthy tissue to find mutations, use machine learning to predict which of the resulting abnormal proteins (neoantigens) matter for that tumor, then write instructions for those targets into messenger RNA (mRNA) wrapped in a fat-based nanoparticle. Each vaccine encodes up to 34 neoantigens.
Making a custom product for every patient worked at trial scale. Manufacturing succeeded for more than 99% of patients in the vaccine group, and 91% of randomized patients received the full set of 34 targets. The median time to a first vaccine dose was 64 days. Patients then got 1 mg every three weeks for up to nine doses, with pembrolizumab every six weeks.
What the trial found
The vaccine group had 136 recurrences or deaths (18.0% of 757 patients). The pembrolizumab-only group had 111 (29.2% of 380). That gives a hazard ratio of 0.58 (95% confidence interval 0.45 to 0.75), which means a 42% lower risk of recurrence or death at any given time in the vaccine group. The gap in two-year relapse-free survival is 12.2 percentage points (our arithmetic from the reported 82.2% and 70.0%). Median follow-up was 24.6 months, with data collected through June 30, 2026.
Distant metastasis-free survival (no spread to other organs, and no death) moved the same direction. The hazard ratio was 0.62 (95% CI 0.45 to 0.85), a 38% lower risk, with two-year rates of 88.5% against 80.2%.
The first six months look the same
In the first six months the two groups did not separate. The hazard ratio for recurrence-free survival was 0.99 (95% CI 0.66 to 1.49). After month six it was 0.42 (95% CI 0.30 to 0.58). Merck and Moderna list the post-six-month figure as a sensitivity analysis, not the primary result. OncLive's report links the early overlap to the wait for the first dose and the time T cells (immune cells that attack tumors) need to respond to the vaccine.
What remains open
Overall survival (how long patients live) is not settled. Its hazard ratio was 0.77 (95% CI 0.45 to 1.31; P = 0.33), which missed the trial's preset threshold for significance. Merck's release describes the survival data as immature and cites a favorable trend without statistics. Follow-up continues. The vaccine is investigational and not approved, and OncLive reports that the full results are slated for the New England Journal of Medicine on November 11, 2026.
📍 Multiple Perspectives on the Story
A benefit reported across stages and ages
The trial's target group is people whose melanoma has been removed but who face a risk of recurrence. CancerNetwork's report of the ESMO presentation shows the lower recurrence risk in both stage groups: hazard ratio 0.60 for stages IIB to IIIB and 0.57 for stages IIIC, IIID and IV. It also appeared in patients under 65 (0.65) and 65 and older (0.53).
One trial in a larger program
A smaller phase 2b trial, KEYNOTE-942, reported five-year follow-up at the 2026 ASCO meeting, and OncLive cites hazard ratios of 0.510 for recurrence-free survival and 0.411 for distant metastasis-free survival from it. Merck's INTerpath program now includes nine phase 2 and phase 3 trials, among them three phase 3 trials in non-small cell lung cancer. Catherine Wu of Dana-Farber Cancer Institute, whose team demonstrated proof of concept for mRNA cancer vaccines in 2017, told National Geographic the odds are good that the approach works in other cancers. Her team's phase 1 ovarian cancer vaccine raised immune responses but was less effective at preventing relapse.
The personalization may not be the whole explanation
Inge Marie Svane, a cancer immunologist at Copenhagen University in Herlev, Denmark, called the results a significant moment for cancer vaccines. She also suggested to National Geographic that the mRNA or its nanoparticle carrier, rather than the patient-specific neoantigens, may explain part of the benefit. Because the comparison group received a placebo, the trial design does not test that (our reading). National Geographic reports that researchers do not fully understand why the vaccine worked.
From trial result to prescription
National Geographic reports that Merck and Moderna will seek approval from the U.S. Food and Drug Administration, and that Janice Mehnert of NYU Perlmutter Cancer Center, an investigator on the trial, said the team is prepared to scale up production if the agency finds the data convincing. Merck and Moderna's release says they are engaging with regulators and gives no filing timeline. A usable tumor sample is required: 302 of 1,749 people screened (17.3%) were excluded for lacking one. Price and insurance coverage are not addressed in the sources reviewed.
Company-reported results, with more side effects in the vaccine group
Merck and Moderna make the vaccine and issued the release that carries the headline numbers. Georgina Long of Melanoma Institute Australia presented the data and, per OncLive, has disclosed consulting or advisory roles with several companies, including Merck (MSD). Side effects ran higher with the vaccine: fever in 52.2% against 8.2%, injection-site pain in 51.0% against 9.5%, and influenza-like illness in 25.4% against 9.2%. Serious (grade 3 to 5) treatment-related events were similar, 14.2% against 13.4%. CancerNetwork reports that treatment-related events led to stopping a study drug in 14.0% of the vaccine group and 8.7% of the comparison group; OncLive's all-cause figures are 16.6% and 9.5%. Eight patients (1.1%) in the vaccine group had fatal adverse events and none in the comparison group. OncLive reports that none were judged related to the vaccine, and that two were attributed to pembrolizumab.
What This Does and Does Not Mean
The trial shows that in people with completely resected stage IIB to IV melanoma, adding the vaccine to pembrolizumab lowered the rate of recurrence or death at a median 24.6 months, with the benefit reported across the subgroups above. It has not shown a survival benefit, the reason the vaccine works, or results in any other cancer, since the other cancers in the program are still being studied. The next checkable points are the New England Journal of Medicine paper, further overall survival follow-up, and the regulators' decisions.
Frequently Asked Questions
What did the melanoma vaccine trial find?
In the phase 3 INTerpath-001 trial of 1,137 people with surgically removed stage IIB to IV melanoma, adding the personalized mRNA vaccine intismeran autogene to pembrolizumab lowered the risk of recurrence or death by 42% compared with placebo plus pembrolizumab. At two years, 82.2% of vaccine recipients had no recurrence, against 70.0% in the comparison group.
How is the vaccine personalized?
Doctors sequence DNA from the patient's tumor and healthy tissue to find mutations, and machine learning picks up to 34 abnormal proteins (neoantigens) to target. Those targets are written into mRNA, wrapped in a lipid nanoparticle and injected, according to National Geographic.
Is the melanoma vaccine approved?
No. Intismeran autogene is investigational. Merck and Moderna say they are engaging with regulators, and overall survival data from the trial are still immature.
Does the vaccine work for other cancers?
That is not yet known. The trial covered melanoma only. Similar vaccines are being tested in other cancers, including lung cancer, but no results have been reported. A phase 1 ovarian cancer vaccine from a different team raised immune responses but was less effective at preventing relapse.