Detailed phase 3 data confirm Moderna–Merck mRNA cancer vaccine cuts melanoma recurrence by 42%
Full trial results presented at ESMO 2026 show intismeran combined with pembrolizumab reduced disease recurrence significantly versus standard treatment alone in resected high-risk melanoma.
Moderna and Merck have released detailed phase 3 trial data for their personalised mRNA cancer vaccine, intismeran (previously called mRNA-4157/V940), showing a 42% reduction in the risk of melanoma recurrence when combined with the checkpoint inhibitor pembrolizumab (Keytruda), compared with pembrolizumab alone. The results were presented at the European Society for Medical Oncology (ESMO) 2026 annual congress and confirm the primary endpoint that had been signalled in earlier interim analyses.
The vaccine is designed for individual patients: tumour tissue is sequenced to identify neoantigens — protein fragments unique to each person's cancer — and an mRNA construct encoding up to 34 of those targets is manufactured and administered alongside pembrolizumab. This personalised approach is intended to prime the immune system to recognise residual tumour cells following surgical resection.
The ESMO presentation marks a significant milestone for the neoantigen vaccine field, providing the first phase 3 evidence that a personalised mRNA cancer vaccine can meet a pre-specified efficacy endpoint in a randomised controlled trial. Cancer Research UK's experts noted the results at ESMO as among the most anticipated data of the conference.
The combination is not yet approved for routine use; regulatory submissions have not been publicly announced at the time of publication. Researchers and oncologists will be examining the full dataset — including durability of response and subgroup analyses — as it becomes available in peer-reviewed form.
Plain-language version
For patients, families, and general readers. Educational only — not medical advice.
Researchers at Moderna and Merck have shared detailed results from a large clinical trial of a personalised cancer vaccine designed for people with melanoma (a type of skin cancer). The vaccine is made individually for each patient by reading the DNA of their tumour to find targets — called neoantigens — that are unique to that person's cancer. An mRNA molecule (similar technology to some COVID-19 vaccines) is then made to teach the immune system to attack any remaining cancer cells after surgery. In the trial, people who received the vaccine alongside an existing cancer medicine called pembrolizumab were 42% less likely to see their melanoma return compared with those who had pembrolizumab alone. These results were presented at Europe's biggest cancer conference, ESMO 2026, and represent the first time a personalised mRNA cancer vaccine has met its main goal in a large randomised trial. The vaccine is not yet approved for standard use, and researchers are continuing to study how long the benefit lasts. This is an educational summary, not medical advice. If anything here raises questions for you, please speak with your GP or a clinical professional.
Sources
Read the original reporting — these are the public sources this summary draws from.
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Primary source Stat News · 2026-10-22STAT+: Detailed data confirm Moderna and Merck cancer vaccine met key endpoints in melanoma trial
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Cancer Research UK · 2026-10-23ESMO 2026: First phase 3 trial results for a personalised cancer vaccine
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Stat News · 2026-10-22STAT+: What to expect from the Moderna-Merck cancer vaccine data reveal