Moderna and Merck announced on August 19, 2026 that their Phase 3 INTerpath-001 trial met its main goal. A personalized mRNA vaccine called intismeran autogene, added to Merck's immunotherapy Keytruda, cut the risk of melanoma coming back after surgery.
The 1,137-patient study also met its key secondary endpoint, showing fewer cancers spreading to distant sites compared with Keytruda alone. The companies say they will engage with regulators about a submission for approval.
Patients had stage IIB to IV melanoma that had been fully removed. They were randomized 2:1 to receive up to nine doses of intismeran (1 mg every three weeks) plus Keytruda (400 mg every six weeks for up to nine cycles), or Keytruda on its own.
The primary endpoint was recurrence-free survival and the key secondary endpoint was distant metastasis-free survival. Both were met with what the companies called statistically significant and clinically meaningful improvements. Safety was consistent with earlier reports of the combination, with no new safety signals.
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How the personalized shot is built
Intismeran is not one shot for everyone. A sample of each patient's tumor is sequenced to identify its unique mutations. Those mutations are then used to design synthetic messenger RNA that encodes up to 34 neoantigens, the molecular flags sitting on the surface of that patient's cancer cells.
Once injected, the mRNA instructs the body to produce those flags so the immune system can recognize and attack cells carrying them. It is the same mRNA delivery approach Moderna scaled up for its COVID-19 vaccine, now aimed at cancer.
Dr. Ahmad Tarhini, a melanoma specialist at H. Lee Moffitt Cancer Center & Research Institute quoted by ABC News, described this class of therapy as individualized neoantigen therapy that starts with genetic sequencing of the tumor to define its unique mutational fingerprint.
Who might qualify
Melanoma is the deadliest form of skin cancer. Merck and Moderna estimate around 112,000 new melanoma cases and more than 8,500 deaths in the United States in 2026.
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Stage IIB to IV melanoma, the group studied here, covers patients whose tumors have deeper skin invasion or have already reached lymph nodes and, in some cases, distant sites. Recurrence risk after surgery is high in this population. Keytruda on its own is already used as add-on treatment after surgery for many of these patients, and the Phase 3 result suggests layering a custom mRNA vaccine on top could push that recurrence risk lower still.
Georgina Long, medical director of Melanoma Institute Australia and the trial's lead investigator, said in the joint announcement that "intismeran in combination with pembrolizumab has the potential to establish a new treatment paradigm in the adjuvant melanoma setting."
Full trial data are expected at an international medical meeting. Tarhini told ABC News that if regulators act on the filing, the treatment could reach patients around early 2027. Until then, intismeran remains investigational and is available only through clinical trials, so anyone being treated for high-risk melanoma who is curious about the option should raise it with their oncologist.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.