The headline
In a large phase 3 trial called INTerpath-001, adding intismeran autogene, a personalised mRNA cancer vaccine developed by Moderna and Merck, to the immunotherapy drug Keytruda (pembrolizumab) reduced the risk of melanoma coming back or death by 42 percent, compared with Keytruda alone. The detailed results were presented at the ESMO Congress in October 2026 and have been accepted for publication in the New England Journal of Medicine, according to the companies.
It is the first phase 3 success for an individualised mRNA cancer vaccine, which makes it a significant milestone. It is not yet approved, and it is not a cure.
What the trial found
| Measure | Result (vaccine + Keytruda vs Keytruda alone) |
|---|---|
| Recurrence-free survival (cancer not returning, or death) | 42% lower risk (hazard ratio 0.58) |
| Distant metastasis-free survival (cancer not spreading elsewhere) | 38% lower risk (hazard ratio 0.62) |
| Overall survival | Not yet mature; a favourable trend was reported |
| Median follow-up | About 24.6 months |
| Patients | 1,137 people with high-risk stage IIB to IV melanoma, after surgery |
Patients were randomised two to one to receive the vaccine plus Keytruda, or Keytruda alone, for about a year. The companies reported that the benefit was similar between the groups for the first six months, during the vaccination course, and emerged after that.
What a 42 percent lower risk means: it is a relative figure. It means that, over the follow-up period, recurrence or death happened noticeably less often in the vaccine group. It does not mean 42 percent of patients were cured.
How a personalised mRNA cancer vaccine works
- The tumour removed in surgery is sequenced, along with a sample of the patient's normal cells.
- Software identifies mutations that produce abnormal proteins, called neoantigens, found only on the cancer cells.
- Moderna makes a custom mRNA vaccine encoding up to 34 of these neoantigens for that patient.
- The vaccine teaches the immune system to recognise cells carrying them.
- Keytruda, a checkpoint inhibitor, takes the brakes off the immune system so it can attack those cells more effectively.
Because each dose is made for one person, production takes several weeks and is far more complex than a standard drug.
Why the reaction was mixed
Early headlines about "cancer vaccines" raised expectations. When the detailed numbers came out, Moderna's share price fell and some coverage said the results did not live up to the hype. The main reasons:
- Overall survival is not yet known. Regulators and doctors want to see whether people live longer, not only whether the cancer comes back later.
- Cost and complexity. A personalised vaccine for every patient is expensive to make.
- Competition from other approaches. Some analysts noted that giving immunotherapy before surgery (neoadjuvant therapy) has shown strong results in some patients at lower cost.
- Only one cancer type so far. Trials in lung and other cancers are under way, but results are not in.
None of this changes the main finding: the combination worked better than the current standard treatment in the trial.
What happens next
- Regulatory review: the companies are expected to seek approval from regulators such as the US FDA and the European Medicines Agency. Approval is not guaranteed, and review takes months.
- Longer follow-up: overall survival data will be reported as they mature.
- Other cancers: intismeran is also being tested in non-small cell lung cancer and other tumour types.
What it means for patients
- If you have had melanoma removed, ask your oncologist whether you are eligible for any clinical trials, and what adjuvant treatment is recommended for your stage. Standard options such as immunotherapy remain the current treatment.
- Melanoma prevention still matters most: sun protection, avoiding sunburn and sunbeds, and checking your skin for changing moles. See a doctor about any mole that changes in size, shape or colour, bleeds or itches.
For other recent advances, see our roundup of medical breakthroughs in 2026 and CRISPR gene therapy trials.
Key takeaways
- Moderna and Merck's personalised mRNA vaccine plus Keytruda cut the risk of melanoma recurrence or death by 42 percent in phase 3.
- It treats people after surgery; it does not prevent cancer.
- It is not yet approved, and overall survival data are still maturing.
- Each vaccine is made for one patient from their own tumour's mutations.
This article is general information, not medical advice. It reflects results reported up to 24 October 2026. Speak to an oncologist about treatment options.