For patients whose melanoma has been cut out by surgery but still sits at high risk of returning, a personalized mRNA shot given alongside the immunotherapy Keytruda beat Keytruda alone in a large phase 3 trial. Moderna and Merck announced the topline result on August 19, 2026.
The 1,137-patient INTerpath-001 study met its primary endpoint of recurrence-free survival and its key secondary endpoint of distant metastasis-free survival, according to Merck's announcement. The companies described the readout as the first positive phase 3 result for an mRNA-based cancer therapy and for an individualized neoantigen therapy.
The trial enrolled adults with completely resected stage IIB through IV cutaneous melanoma, disease that has usually grown deep into the skin or spread to lymph nodes or distant sites. Even after surgery removes visible tumor, these patients face a meaningful risk that microscopic cancer left behind will regrow or spread.
Standard care in that setting is adjuvant immunotherapy, most often Keytruda, whose active ingredient is pembrolizumab, an antibody made by Merck that releases a brake on the immune system.
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How a personalized shot is built for one patient
The investigational vaccine is called intismeran autogene, also known as mRNA-4157 or V940. Each dose is manufactured for one person. Researchers sequence a piece of the patient's tumor to map its mutations, then encode up to 34 tumor-specific neoantigens into a single strand of messenger RNA.
The mRNA is wrapped in lipid nanoparticles, the same delivery technology behind the COVID-19 shots, and given as an intramuscular injection. Once inside the body, the mRNA instructs cells to display the tumor-specific markers, training T cells to recognize and attack cancer cells carrying those same mutations.
Keytruda works in parallel by keeping those T cells switched on. In the trial, patients received intismeran every three weeks for up to nine doses, together with Keytruda every six weeks for up to nine cycles, for about a year.
The exact effect size is still under wraps
The companies did not release precise numbers in the topline announcement, saying more details will be presented at an upcoming medical meeting. That leaves independent oncologists waiting for the full data before judging how large the benefit is and whether adding intismeran raises the rate of immune-related side effects.
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For context, the earlier phase 2b KEYNOTE-942 trial in a similar melanoma population produced striking longer-term follow-up numbers, with the combination cutting the risk of recurrence or death by 49 percent and the risk of distant metastasis or death by 59 percent compared with Keytruda alone.
Merck says safety in the phase 3 study was consistent with what was seen in those earlier studies, with no new safety signals.
What happens next
Georgina Long, principal investigator on INTerpath-001 and medical director of the Melanoma Institute Australia, said the phase 3 result marks the first time an individualized neoantigen therapy has reduced the risk of recurrence in this setting on top of Keytruda. Dean Y. Li, president of Merck Research Laboratories, said the companies are now moving toward regulatory submissions.
The vaccine is investigational. It is not approved by the Food and Drug Administration, and the trial is still following patients to see whether the combination extends overall survival.
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Merck and Moderna say the INTerpath program now spans nine phase 2 and phase 3 studies across melanoma, non-small cell lung cancer, bladder cancer and renal cell carcinoma. Patients treated for melanoma who have questions about their own recurrence risk or about clinical trials should raise them with their oncology team.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.