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Jump to Key Points Adding the personalized mRNA-based cancer vaccine intismeran autogene to pembrolizumab significantly reduced the risk for recurrence or death by 42% in patients with high-risk melanoma who had undergone complete surgical resection.
At 2 years, recurrence-free survival (RFS) was 82.2% with intismeran autogene plus pembrolizumab, compared with 70% with pembrolizumab alone, in the phase 3 INTerpath-001 trial. The combination also reduced the risk for distant metastasis or death by 38%, without a substantial increase in severe treatment-related adverse events.
“INTerpath-001 sets a new benchmark for adjuvant therapy in melanoma and establishes intismeran as a landmark advance in personalized cancer medicine,” said lead investigator Georgina V. Long, MD, PhD, medical director of Melanoma Institute Australia, while presenting the results at the European Society for Medical Oncology (ESMO) Congress 2026 in Madrid.
Results of the trial will be published in The New England Journal of Medicine, with a target publication date in mid-November.
- Intismeran autogene + pembrolizumab ↓ recurrence/death risk 42% in resected high-risk melanoma.
- 2-year RFS: 82.2% vs 70% with pembrolizumab alone; median RFS not reached.
- DMFS also improved: HR 0.62; 2-year rates 88.5% vs 80.2%.
- Benefit emerged after 6 months; early RFS similar, later HR 0.42.
- Severe TRAEs similar: 14.2% vs 13.4%; no new safety signals.
Study discussant Inge Marie Svane, MD, PhD, of Copenhagen University Hospital in Herlev, Denmark, described the results, which drew sustained applause from the audience, as “compelling” and marking “a crucial moment for personalized cancer vaccines.”
On the other hand, she said important questions remain, including whether the benefits will translate into longer overall survival and whether the individualized therapy can be manufactured and delivered on a large scale.
First Phase 3 Success for Personalized Cancer Vaccine
Despite advances with adjuvant PD-1 inhibitors, many patients with high-risk melanoma experience recurrence, including distant metastatic disease. Several phase 3 trials testing combination immunotherapy in the adjuvant setting have failed to improve outcomes over PD-1 monotherapy.
Intismeran (Moderna/Merck) is an individualized mRNA-based therapy developed using genetic information from a patient’s tumor. It encodes up to 34 patient-specific neoantigens designed to stimulate T-cell responses against the cancer, complementing the activity of pembrolizumab. The vaccine takes approximately 6-8 weeks to manufacture for each patient.
Positive results for intismeran plus pembrolizumab were reported in the proof-of-concept phase 2b KEYNOTE-942 trial in patients with resected melanoma, as reported by Medscape Medical News.
That led to the phase 3 INTerpath-001 trial — a global, double-blind trial of 1137 adults with high-risk (stage IIB-IV) resected cutaneous melanoma who had not received prior systemic therapy. Patients were required to have tumor tissue suitable for next-generation sequencing and manufacturing of the individualized therapy.
Patients were randomly assigned (2:1) to receive intismeran (1 mg intramuscularly every 3 weeks) for up to nine doses plus pembrolizumab (400 mg IV every 6 weeks) for up to nine cycles, or placebo plus pembrolizumab. Treatment continued for about 1 year unless disease recurrence or unacceptable toxicity occurred.
After a median follow-up of 24.6 months, the combination significantly improved recurrence-free survival (RFS) in the intention-to-treat population, the primary endpoint (hazard ratio [HR], 0.58; P < .001).
The estimated 2-year RFS rates were 82.2% with intismeran plus pembrolizumab and 70% with pembrolizumab alone. Median RFS was not reached in either group.
The combination also significantly reduced the risk for distant metastasis-free survival (DMFS) by 38% (HR, 0.62; P = .002). At 2 years, DMFS rates were 88.5% and 80.2%, respectively. Median DMFS was not reached in either group.
The benefits of the combination on both endpoints were generally consistent across prespecified patient subgroups.
Benefit Emerges After 6 Months
Long noted that the treatment benefit of the vaccine emerged after the first 6 months, an anticipated pattern based on the earlier phase 2 trial and the mechanism of action of the individualized therapy.
In a prespecified piecewise sensitivity analysis examining outcomes after 6 months, intismeran plus pembrolizumab reduced the risk for recurrence or death by 58% (HR, 0.42), while the RFS was similar between groups during the first 6 months (HR, 0.99).
A similar pattern emerged for DMFS. There was essentially no difference during the first 6 months (HR, 1.01), but after 6 months, the combination reduced the risk for distant metastasis or death by 50% (HR, 0.50).
Long explained that the delayed benefit was expected because intismeran requires individualized manufacturing and was administered a median of 9 weeks after pembrolizumab initiation. The therapy also “works at the initiation of the immune response, so it takes time,” she noted.
Overall survival (OS) data remain immature, but a favorable trend in OS with intismeran has been observed, Merck and Moderna said in a press release.
The safety profile of intismeran plus pembrolizumab was generally consistent with previous experience, with no new safety signals identified. Long reported “no potentiation of pembrolizumab-associated adverse events” with the combination.
The most common all-cause adverse events with the combination were fever, injection-site pain, and fatigue. Grade 3-5 treatment-related adverse events occurred in 14.2% of patients receiving the combination and 13.4% receiving pembrolizumab alone. Rates of serious adverse events (17.6% vs 15.8%) and treatment discontinuation of both agents due to serious adverse events (6.5% vs 5.3%) were also similar between groups.
Important Questions Remain
Looking ahead, Svane said an important question is how the combination should be positioned relative to neoadjuvant ipilimumab plus nivolumab for patients with macroscopic, resectable stage III/IV melanoma. No direct comparison between the strategies is available, and “further insight into predictive markers and mode of action” is needed to guide treatment selection, she said.
Svane also highlighted practical hurdles, including the “complex and time-consuming” manufacturing process, the need for adequate tumor tissue, and questions about cost and access. In INTerpath-001, roughly 17% of screened patients had inadequate tissue for vaccine development, she noted.
Other experts echoed both the excitement and the caution surrounding the findings in comments to the UK nonprofit Science Media Centre.
"These are very impressive results. It is an important proof of principle for the field, although we shouldn’t get ahead of the evidence," said Alan Melcher, MD, PhD, professor of translational immunotherapy at The Institute of Cancer Research, London.
"We can’t assume from one melanoma trial that the same approach will work across all cancers, and longer follow-up will be important to understand the effect on overall survival,” Melcher added.
Lennard Lee, MD, PhD, associate professor of AI and cancer vaccine research at the University of Oxford, UK, highlighted the challenge of making personalized vaccines accessible on a large scale.
“One of the greatest challenges is manufacturing,” Lee said. “We have demonstrated what is scientifically possible. The next challenge is to make it practically achievable and affordable for everyone affected by cancer, wherever they live.”
The INTerpath-001 trial was sponsored by Merck and Moderna. Long reported consulting or advisory relationships with MSD and several other pharmaceutical companies. Svane disclosed consulting, speaking, or advisory relationships with multiple companies, including MSD and Bristol Myers Squibb, and is a co-founder and shareholder of IO Biotech. Melcher and Lee reported no relevant financial relationships.
