What happened
On October 22, Merck and Moderna released the results of the INTerpath-001 trial, which will be presented in full on Saturday, October 24, at the European Society for Medical Oncology (ESMO) Congress in Madrid. It is the first phase 3 study, the last stage before seeking approval, to show a benefit from a personalized mRNA cancer therapy. Principal investigator Georgina Long, from Sydney, will present the data, and the paper has been accepted by The New England Journal of Medicine.
The trial enrolled 1,137 people whose stage IIB to IV melanoma had been surgically removed, meaning a high risk of it returning. For one year, two out of three received the experimental therapy, called intismeran autogene, together with the immunotherapy drug pembrolizumab; the rest received pembrolizumab with a placebo.
The results
- 42% lower risk of relapse or death with the combination (hazard ratio 0.58), after a median follow-up of 24.6 months.
- At two years, 82.2% of patients on the combination were relapse-free, compared with 70.0% on pembrolizumab alone.
- 38% lower risk of distant metastasis or death (hazard ratio 0.62).
- Serious side effects were similar in both groups (14.2% vs 13.4%). The most common with the therapy were fever, injection-site pain and fatigue.
How it works
Although it is often called a vaccine, it does not prevent cancer: it is given after surgery to stop the disease from coming back. A sample of each patient's tumor is analyzed, its unique mutations are identified, and an mRNA molecule is made with instructions for up to 34 of them. This teaches the immune system to recognize cells carrying those markers. It is the same technology as the mRNA COVID vaccines, aimed at one specific tumor.
What we don't know yet
This is good news, not a cure, and it is worth telling the whole story:
- It is not yet known whether it extends life: overall survival data are not mature. The companies report a favorable trend.
- It is not approved. Merck and Moderna say they will engage with regulators.
- The result was somewhat below what analysts had hoped for, as they had in mind the 49% from a smaller earlier phase 2 trial. Cost, and how it compares with immunotherapy given before surgery, are still open questions.
- It has only been shown in melanoma. Other trials are under way in lung, bladder and kidney cancer.
Why it is good news
For decades, most therapeutic cancer vaccines failed in large trials. This is the first personalized mRNA therapy to succeed in phase 3 and to improve on the immunotherapy that is today's standard treatment. For people who have had a high-risk melanoma removed, keeping the cancer from coming back is exactly what matters.
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Sources
- Merck, Moderna Cancer Vaccine Cuts Melanoma Recurrence Risk by 42%. AJMC (The American Journal of Managed Care), .
- Merck and Moderna Announce Phase 3 INTerpath-001 Trial of Intismeran Autogene Plus KEYTRUDA Met Endpoints of Recurrence-Free Survival (RFS) and Distant Metastasis-Free Survival (DMFS). Merck (nota de prensa conjunta con Moderna), .
- ESMO 2026: Merck, Moderna shares fall as cancer vaccine disappoints after data leak. BioSpace, .
- ESMO Congress 2026. European Society for Medical Oncology (ESMO).
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