Moderna and Merck have reported a major breakthrough with their AI-guided personalized mRNA cancer vaccine, saying the experimental treatment significantly reduced the risk of melanoma returning or spreading in a late-stage clinical trial.

The treatment, called intismeran (also known as intismeran autogene or mRNA-4157), combines a personalized mRNA vaccine developed by Moderna with Merck’s widely used immunotherapy Keytruda.

The vaccine is created specifically for each patient: after sequencing the tumor, artificial intelligence algorithms analyze the genetic mutations and predict which ones are most likely to trigger a strong immune response.

These AI models then select and rank up to 34 of the highest-priority neoantigens, which are encoded into a custom mRNA sequence that trains the immune system to recognize and attack remaining cancer cells.

The Phase 3 trial involved 1,137 patients with high-risk stage IIB to IV melanoma whose tumors had been surgically removed. Participants received either Keytruda combined with the personalized vaccine or Keytruda alone for about a year.

Interim results showed that the combination met its primary goal of reducing cancer recurrence and also achieved a secondary goal of reducing the risk of the cancer spreading to other parts of the body.

The companies have not yet released detailed figures from the trial and said overall-survival data are still being collected.The results mark the first positive late-stage trial for an individualized mRNA cancer vaccine and highlight how AI-driven neoantigen selection is making true personalization scalable. Earlier mid-stage research also produced encouraging results.

In a five-year follow-up, the treatment reduced the risk of recurrence or death by 49% compared with Keytruda alone.The companies said no new safety concerns have emerged. Previously reported side effects included fatigue, injection-site pain and chills.Moderna and Merck are now discussing the treatment with regulators and plan to seek approval. Moderna has suggested the therapy could potentially become available as early as 2027 if approved.

The announcement sent Moderna shares sharply higher, underscoring investor optimism that AI-enabled cancer treatments could become an important new growth area for the company beyond its Covid-19 vaccine.

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