mRNA Vaccine Cuts Melanoma Recurrence Risk in Phase 3 Trial

Patients with high-risk melanoma now face a narrower window before cancer returns after surgery. A personalized mRNA vaccine developed by Moderna and Merck, given with the immunotherapy Keytruda, lengthened the time those patients stayed cancer-free compared with Keytruda alone.

The phase 3 trial enrolled more than 1,000 people with stage II to IV melanoma. After tumor removal, participants received either the combination or Keytruda by itself. The companies reported that the vaccine reduced recurrence risk and lowered the chance of spread to distant organs, though they released no hazard ratios or median durations. The vaccine, called Intismeran, is built by sequencing DNA from each patient’s tumor and using mRNA to train the immune system against remaining cancer cells.

Full data have not been published or peer-reviewed. Regulators must still review any eventual application, and separate health-technology assessments would determine availability through systems such as the NHS. Prof Peter Johnson, NHS England’s National Clinical Director for Cancer, described the approach as directing the immune system “very specifically” rather than broadly activating it. Dr Talisia Quallo of Cancer Research UK called the interim findings promising but stressed the need for complete review.

Moderna chief executive Stephane Bancel termed the results a “pivotal moment.” Shares in both companies rose after the announcement. The firms are running similar trials in lung, bladder, and kidney cancers. More detailed results are scheduled for presentation at a medical meeting in October.