Moderna and Merck mRNA Cancer Vaccine Succeeds in Phase 3 Melanoma Trial

Moderna and Merck announced in August 2026 that their personalized mRNA cancer vaccine, intismeran, succeeded in a Phase 3 clinical trial for patients with surgically removed melanoma. The results mark the first time an mRNA-based cancer treatment has met its goals in a late-stage study.

The trial, called INTerpath-001, enrolled 1,137 patients who had undergone complete surgical removal of stage IIB through IV cutaneous melanoma. Participants were randomized to receive either intismeran combined with Merck's immunotherapy drug Keytruda, or Keytruda alone, for approximately one year.

The combination therapy met the trial's primary endpoint of recurrence-free survival and a key secondary endpoint of distant metastasis-free survival. Both improvements were statistically significant compared to Keytruda alone. No new safety signals were observed during the trial.

Intismeran is an individualized therapy. Researchers sequence a patient's tumor and healthy cells to identify up to 34 patient-specific mutations. The vaccine uses synthetic mRNA to encode those mutations, priming the immune system to recognize and attack the cancer.

The Phase 3 results build on earlier Phase 2b data, which showed a 49 percent reduction in the risk of recurrence or death and a 59 percent reduction in the risk of distant metastasis or death when using the combination therapy.

Moderna and Merck said they plan to present detailed data at an upcoming international medical conference and will engage with regulatory authorities about potential filing submissions. The trial will continue to track overall survival as a secondary endpoint.

The companies have not announced a timeline for a regulatory submission.