Moderna-Merck personalised cancer vaccine takes step closer to market after trial success, could be available next year

A personalised mRNA cancer vaccine developed by Moderna and Merck has cleared a major hurdle, reporting positive results from a late-stage clinical trial in high-risk melanoma, the first time an individualised mRNA cancer vaccine has met its goals at this stage of testing.

The vaccine, known as antisera, was tested in combination with Merck's established immunotherapy drug Keytruda. The trial enrolled 1,137 patients with high-risk stage IIB to IV melanoma whose tumours had already been surgically removed. Half received Keytruda combined with the personalised vaccine; the other half received Keytruda alone, for approximately one year.

The combination met both the trial's primary goal, reducing the risk of cancer returning after surgery, and a secondary goal of reducing the risk of the cancer spreading to other parts of the body. The companies reported no new safety signals from the trial. Full detailed data are expected to be presented at an upcoming medical conference.

How the vaccine works

Unlike vaccines designed to prevent infections, this one is built around a patient's own tumour. After surgery, the tumour's genetic mutations are analysed to identify markers that may help the immune system recognise any remaining cancer cells. Moderna's mRNA technology is then used to instruct the immune system to target those specific mutations, essentially giving the body a personalised blueprint for identifying and attacking cancer cells before they can grow or spread.

Building on earlier results

The Phase 3 findings build on earlier data reported in January, when Moderna and Merck shared five-year results from a smaller study showing the combination reduced the risk of recurrence or death by 49 per cent compared with Keytruda alone. That earlier signal gave the companies, and the oncology community, reason to believe a larger trial would hold up, and it has.

Karen Knudsen, CEO of the Parker Institute for Cancer Immunotherapy, said the findings could mark the beginning of a new phase in immunotherapy for solid tumours.

Moderna President Stephen Hoge confirmed that the companies are already in discussions with regulators. Because the treatment holds breakthrough therapy designation, he indicated it could potentially become available as early as next year, subject to regulatory approval.

What remains unknown

Overall survival data, which indicate whether the treatment actually helps patients live longer, are still pending. The companies have also not yet published the full trial dataset. Questions around manufacturing complexity, scalability and cost remain significant, given that each vaccine is individually tailored to a specific patient's tumour.

What it could mean beyond melanoma

The implications reach further than skin cancer. Researchers are already investigating whether similar personalised mRNA vaccines can be effective against lung, breast and pancreatic cancers. The broader ambition is a model of cancer treatment increasingly shaped by the genetic fingerprint of each patient's tumour rather than a one-size-fits-all approach.

For Moderna, the results carry strategic weight as the company works to establish its mRNA platform in areas beyond COVID-19. For Merck, adding a personalised vaccine to Keytruda's profile could extend the drug's clinical reach as it approaches patent challenges later this decade.