Personalized mRNA Vaccine Cuts Melanoma Recurrence Risk by Nearly Half at Five Years

A personalized mRNA cancer vaccine reduced the risk of melanoma coming back - or killing patients - by 49 percent over five years when added to standard immunotherapy, according to trial data presented this week at the American Society of Clinical Oncology annual meeting in Chicago.

The results come from the KEYNOTE-942 phase 2b trial, a collaboration between Moderna and Merck. Researchers followed 157 patients with high-risk stage 3 and stage 4 melanoma who had already undergone surgery to remove their tumors. According to reporting by BioSpace on the ASCO presentation, the combination regimen of intismeran autogene - the personalized mRNA vaccine - plus pembrolizumab (Keytruda) also reduced the risk of distant metastasis or death by 59 percent compared with pembrolizumab alone, and boosted overall survival by 53 percent in an exploratory analysis.

The trial was not designed to be the definitive test of this approach. Patients were enrolled at cancer centers in Australia and the United States between 2019 and 2021, and the study assigned 107 patients to the combination arm versus 50 to pembrolizumab monotherapy - the current standard of care after melanoma surgery, as reported by The Dermatology Digest in its coverage of the ASCO data. That 2:1 randomization reflects a relatively small cohort for claims of this magnitude, a point researchers themselves acknowledge.

What makes intismeran autogene different from a conventional vaccine is how it is made. According to coverage in The Dermatology Digest, the shot is built using genetic information drawn from each patient's individual tumor, prompting the immune system to produce T cells that target proteins unique to that person's cancer. Each dose is, in effect, a one-of-a-kind drug. That manufacturing complexity is part of why the path from a promising phase 2 signal to routine clinical use will take time.

The principal investigator for the study, Dr. Janice Mehnert of NYU Langone Health's Perlmutter Cancer Center, said in a statement reviewed by Clinical Trials Arena that the results serve "as encouragement to cancer researchers globally that mRNA vaccines like intismeran could work well in combination with immunotherapy for other cancers" with high mutation rates. Her team is testing that hypothesis directly: the vaccine is already in trials for lung cancer and several other tumor types, according to The Dermatology Digest.

A phase 3 trial called INTerpath-001 is the real test. According to NBC News, that study enrolled roughly 1,000 patients and expanded enrollment to Europe. Interim data are expected next year. Until those results arrive, clinicians treating patients with resected high-risk melanoma are watching the phase 3 readout, not changing their practice based on a 157-person phase 2 study - however consistent the signal looks after five years of follow-up.

The trial was funded by Moderna and a subsidiary of Merck, the maker of Keytruda, as noted by NBC News. That funding relationship does not invalidate the findings, but oncologists weighing the data for their patients will want the independent, larger-scale confirmation that only INTerpath-001 can provide.

For patients sitting across from a surgical oncologist after a stage 3 melanoma resection, the conversation is not yet "you can get this vaccine." It is still "we wait and we watch." What the KEYNOTE-942 five-year data do is make that phase 3 trial feel less like a long shot and more like a genuinely consequential question the field is close to answering.

Sources cited:
- BioSpace (ASCO 2026 coverage) (https://www.biospace.com/drug-development/asco-modernas-mrna-based-melanoma-vaccine-shows-encouraging-5-year-survival)
- The Dermatology Digest (ASCO 2026 KEYNOTE-942) (https://thedermdigest.com/asco-2026-news-personalized-mrna-based-melanoma-vaccine-plus-immunotherapy-slashes-risk-of-recurrence-and-death/)
- NBC News (https://www.nbcnews.com/health/cancer/personalized-vaccine-melanoma-cut-risk-cancer-returning-five-years-rcna347424)
- Clinical Trials Arena (ASCO 2026) (https://www.clinicaltrialsarena.com/news/asco26-cancer-vaccines-and-at-home-injectable-drugs-continue-to-show-promise/)
- CancerNetwork (KEYNOTE-942 five-year data) (https://www.cancernetwork.com/view/mrna-vaccine-pembrolizumab-shows-sustained-5-year-rfs-in-high-risk-melanoma)