Personalized mRNA vaccine cuts melanoma recurrence risk by 42% in phase III trial
Phase III trial of intismeran with pembrolizumab in 1,137 melanoma patients cut death or recurrence risk by 42%, with experts seeking longer-term survival data.
The story in focus
A phase III trial of the personalized mRNA vaccine intismeran given with pembrolizumab cut the risk of death or melanoma recurrence by 42% in 1,137 patients followed for about 25 months, according to results released by Merck and Moderna ahead of the 24 October European Society for Medical Oncology meeting in Madrid.
- The intismeran-plus-pembrolizumab group saw a 42% lower risk of death or melanoma return than pembrolizumab plus placebo.
- The combination also reduced the risk of melanoma spreading by 38% over two years, and investigators reported no major harmful side effects.
- Independent experts called the result impressive but said longer follow-up is needed to show whether the vaccine improves overall survival.
What the trial measured
The trial enrolled 1,137 adults with moderate to advanced melanoma at 157 centres who had surgery to remove tumours. Participants were randomly assigned to receive pembrolizumab, an established immunotherapy, with either the personalized vaccine intismeran or an inactive placebo. Roughly two-thirds received the vaccine. Intismeran is built from each patient's tumour DNA: researchers sequenced mutations to identify neoantigens that distinguish cancer cells from healthy tissue, then used mRNA to train the immune system to target them if cancer returns. The vaccine is designed to prevent recurrence, not to prevent melanoma from developing.
Results and limits
Two years after starting treatment, the vaccine group was 42% less likely to die or have melanoma return, and 38% less likely to see it spread. Trial leader Georgina Long said participants have been followed for around 25 months and will continue to be monitored for several years to determine any effect on overall survival. She reported no major harmful side effects. Merck and Moderna said the approach is also being tested in kidney, bladder and lung cancers, and that they are engaging with regulators, suggesting a possible approval filing as soon as next year. Independent experts noted that some patients did not respond and that cancer cells can adapt, so longer-term data are needed.
Did the trial show that the vaccine helps patients live longer?
Not yet. The 42% figure covers death or melanoma recurrence over about 25 months. Investigators say participants will be monitored for several years to establish whether intismeran improves overall survival.
Sources & further reading
- First personalised cancer vaccine stops disease returning in major trial ↗BBC
- Moderna mRNA vaccine almost halves the risk of skin cancer returning ↗Nature
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