Merck and Moderna Set to Reveal Full Melanoma Vaccine Trial Data at ESMO 2026

Merck and Moderna are presenting the first full set of Phase 3 trial results for their jointly developed personalized melanoma vaccine at the European Society for Medical Oncology (ESMO) Congress 2026, taking place October 23 to 27 in Madrid, Spain, according to Merck's own announcement of its ESMO program.

What is scheduled at ESMO

The detailed data from the trial, called INTerpath-001, are due to be presented during the Presidential Symposium I session, listed as late-breaking abstract LBA1, on October 24, 2026, by principal investigator Professor Georgina V. Long, according to Merck's press materials. Merck senior vice president Dr. Marjorie Green said in the company's statement that this marks the first time Phase 3 data for the therapy, known as intismeran autogene, have been shared.

What Merck and Moderna already announced in August

On August 19, 2026, Merck and Moderna reported topline results showing that INTerpath-001 had met its primary endpoint of recurrence-free survival and its key secondary endpoint of distant metastasis-free survival, according to the companies' joint press release posted on Merck.com. The Phase 3 trial randomized 1,137 patients with completely resected stage IIB-IV cutaneous melanoma in a 2:1 ratio to receive intismeran autogene plus Merck's immunotherapy Keytruda (pembrolizumab), or Keytruda alone.

The release stated the improvements were statistically significant, and that no new safety signals had emerged at the pre-specified interim analysis. Overall survival, a secondary endpoint, was still being evaluated and had not matured enough for reporting, the companies said. Merck executive Dean Y. Li and Moderna chief executive Stéphane Bancel both described the result as an early step toward a more personalized approach to cancer treatment, per the same release.

Earlier Phase 2b data set expectations

Before the Phase 3 trial, a smaller Phase 2b study called KEYNOTE-942 tested the same combination in 157 resected stage III/IV melanoma patients. Merck's own 3-year data release reported that after a median follow-up of 34.9 months, the combination reduced the risk of recurrence or death by 49% versus Keytruda alone (hazard ratio 0.510, 95% CI 0.288–0.906, p=0.019), and reduced the risk of distant metastasis or death by 62% (hazard ratio 0.384, 95% CI 0.172–0.858, p=0.015).

These Phase 2b figures involved far fewer patients than the 1,137-person Phase 3 trial, and Merck's August statement did not disclose equivalent hazard ratios for INTerpath-001 itself. As of October 22, 2026, those exact Phase 3 numbers were expected to be unveiled only at the October 24 ESMO session, according to reporting previewing the conference.

How the vaccine is made, and the manufacturing bottleneck

Intismeran autogene is manufactured individually for each patient. After a tumor is surgically removed, it is sequenced, and software is used to predict which of the tumor's mutations are most likely to trigger an immune response; up to 34 of these targets are then encoded into a single mRNA formulation unique to that patient, according to background summarized from the English-language Wikipedia entry on the therapy.

That personalization creates a production challenge: Moderna's current process, from biopsy to a completed, patient-specific dose, takes roughly four to eight weeks, a report on the company's manufacturing operations summarized. The report described this turnaround — not the underlying science — as the larger obstacle to scaling the therapy beyond a clinical-trial population, noting that melanoma alone accounts for an estimated 112,000 new diagnoses a year in the United States.

Known and unknown so far

• Known: INTerpath-001 enrolled 1,137 patients with resected stage IIB-IV melanoma and met its primary and key secondary endpoints, per Merck's August 2026 statement.
• Known: Full data are scheduled for ESMO's Presidential Symposium on October 24, 2026, presented by Prof. Georgina Long.
• Known: Phase 2b data (157 patients) showed a 49% reduction in recurrence/death risk and a 62% reduction in distant-metastasis risk versus Keytruda alone.
• Unknown: The exact Phase 3 hazard ratios and percentage risk reductions had not been disclosed publicly as of October 22, 2026.
• Unknown: Overall survival results, which Merck said remained immature in the Phase 3 trial as of August.
• Unknown: Timing of any regulatory filing or approval decision.

Why it matters

Cancer is the second leading cause of death in the United States after heart disease, according to a syndicated health-news summary circulated by RealClearHealth. A personalized mRNA vaccine that reaches Phase 3 is notable because, according to the Wikipedia summary of the drug's development, intismeran autogene is among only a small number of neoantigen cancer vaccines worldwide to advance that far, after Moderna began developing the approach in 2017 and partnered with Merck (known outside the U.S. and Canada as MSD) in 2018.