Moderna and Merck’s intismeran autogene, an mRNA vaccine designed individually from each patient’s tumour, reduced the risk of melanoma recurrence by 42% when added to the immunotherapy drug pembrolizumab, according to phase 3 results released on 22 October. It is the first phase 3 success for an individualised neoantigen vaccine, though survival data are not yet mature.
For decades, cancer vaccines were one of oncology’s most persistent disappointments. On 22 October, detailed results from the phase 3 INTerpath-001 trial suggested that a new approach, building a bespoke vaccine from the mutations in each patient’s own tumour, can make a measurable difference.
The trial tested intismeran autogene (also known as V940 or mRNA-4157), developed by Moderna and Merck, in patients whose melanoma had been surgically removed but who were at high risk of it returning. The results have been accepted for publication in the New England Journal of Medicine and will be presented on Saturday 24 October as the first late-breaking abstract (LBA1) in the Presidential Symposium of the ESMO Congress 2026 in Madrid, according to CancerNetwork.
How a personalised vaccine is made
Every tumour carries mutations that alter its proteins. Some of those altered fragments, known as neoantigens, are absent from healthy cells and can be recognised by the immune system as foreign. To make intismeran, a sample of the patient’s tumour and a sample of normal tissue are sequenced. Software then selects up to 34 neoantigens most likely to provoke an immune response, and their genetic code is written into a single messenger RNA molecule, the same platform used in Moderna’s COVID-19 vaccine.
Injected into the patient, the mRNA instructs cells to produce those neoantigens, training T cells to recognise and attack any remaining cancer cells that carry them. The vaccine is combined with pembrolizumab (Keytruda), a checkpoint inhibitor that releases a brake on T cells. Each patient’s vaccine is unique.
What the trial found
INTerpath-001 enrolled 1,137 patients with completely resected stage IIB, IIC, III or IV cutaneous melanoma who had not received previous systemic treatment. They were randomised two to one to receive intismeran (1 mg every three weeks, up to nine doses) plus pembrolizumab, or placebo plus pembrolizumab, for about a year.
At a median follow-up of 24.6 months, the results were:
- Recurrence-free survival: hazard ratio 0.58 (95% CI 0.45–0.75; P<0.001), a 42% reduction in the risk of recurrence or death
- Two-year recurrence-free survival: 82.2% with the vaccine against 70.0% with pembrolizumab alone
- Distant-metastasis-free survival: hazard ratio 0.62 (95% CI 0.45–0.85), a 38% reduction; two-year rates 88.5% against 80.2%
- Overall survival: not yet mature, with what investigators described as a favourable trend
A pattern in the timing is instructive. In the first six months there was no difference between the groups (hazard ratio 0.99). After six months, in a prespecified sensitivity analysis, the hazard ratio for recurrence fell to 0.42. That is consistent with how a vaccine should work: the personalised vaccine takes about six weeks to manufacture, and the immune response takes time to build.
The comparison is a demanding one. Pembrolizumab on its own is already a standard adjuvant treatment for high-risk resected melanoma, so the trial measured what the vaccine adds to an effective therapy rather than to placebo alone. A 12-percentage-point gain in two-year recurrence-free survival on top of an active standard is a substantial effect in this setting. In a modified analysis that excluded patients who never received a planned dose, the hazard ratio was 0.51.
Safety
Treatment-related side-effects were common in both groups, reported in 95.8% of patients receiving the vaccine and 90.0% of those on pembrolizumab alone. Serious (grade 3–5) treatment-related events were similar, at 14.2% and 13.4%. The most frequent side-effects with the vaccine were fever (52.2%), injection-site pain (51.0%) and fatigue (38.5%). No new safety signals were reported.
“INTerpath-001 is the first [phase 3] study to demonstrate a clinically meaningful improvement in RFS and DMFS,” said Dean Li, president of Merck Research Laboratories. The study’s principal investigator is Professor Georgina Long of Melanoma Institute Australia and the University of Sydney.
Why this is a milestone, and its limits
The result builds on a randomised phase 2b trial, KEYNOTE-942, which reported a similar reduction in recurrence in 2022–23 but was too small to be conclusive. A phase 3 confirmation in more than 1,100 patients is a different order of evidence, and it opens a path to regulatory applications; the companies say they are already talking to regulators.
Caution is still warranted on several fronts:
- Survival. Recurrence-free survival is an accepted endpoint in adjuvant melanoma, but regulators and patients will want to know whether the vaccine helps people live longer.
- Sponsor data. The trial was run by the manufacturers. Independent scrutiny will come at ESMO and in the NEJM paper.
- Practicality. Each vaccine requires tumour sequencing, bespoke design and individual manufacture within weeks. Cost and logistics, not just efficacy, will determine who can receive it.
What it means for India
Melanoma is relatively uncommon in India compared with Australia, Europe or North America, so the direct benefit to Indian patients from this particular product will be limited. The significance lies in the platform. If individualised neoantigen vaccines work in melanoma, trials in lung, kidney, bladder and other cancers, several already under way, become more promising.
For India, that raises questions of capacity: tumour sequencing at scale, bioinformatics, and regulatory pathways for products that differ for every patient. India’s mRNA manufacturing base, built partly during the pandemic, and its expanding genomic infrastructure would both be relevant. Affordability will be the decisive issue, as it has been for CAR-T cell therapy, where Indian developers have sharply reduced costs.
What happens next
The full data will be presented on 24 October and published in NEJM. Overall-survival results will follow as the trial matures. Regulatory filings in the United States and Europe are likely to be the next commercial milestone.
