Personalised Cancer Vaccine Reduces Melanoma Recurrence Risk

An experimental cancer vaccine developed by Moderna and Merck has significantly improved outcomes for patients with high-risk melanoma, reducing the relative risk of cancer recurrence or death by 42% when combined with an established immunotherapy drug.

Detailed findings released on October 22, 2026, from the international Phase 3 INTerpath-001 trial involved 1,137 patients whose skin cancers had been surgically removed.

After two years, 82.2% of patients receiving the personalised vaccine alongside pembrolizumab, marketed as Keytruda, remained alive without disease recurrence. The corresponding figure was 70% among patients receiving pembrolizumab alone.

The findings represent the first successful Phase 3 trial of an individualised mRNA cancer therapy, marking an important milestone in a field that has been investigated for decades.

A vaccine designed for one patient at a time

The experimental treatment, known as intismeran autogene, takes a different approach from conventional cancer drugs.

Rather than administering an identical formulation to every patient, researchers analyse genetic differences between a patient's tumour and healthy tissue.

The information is used to manufacture an individualised mRNA vaccine that instructs the immune system to recognise distinctive features of the cancer.

Each formulation can target up to 34 tumour-specific markers.

The vaccine is administered alongside pembrolizumab, which helps immune cells attack cancer by blocking a mechanism that tumours can exploit to evade immune detection.

Unlike preventive vaccines, intismeran is intended to treat patients who have already developed cancer. Its purpose in this trial was to reduce the likelihood of melanoma returning following surgery.

Results show a meaningful clinical benefit

The study followed patients for a median of 24.6 months.

Researchers reported a 42% relative reduction in the combined risk of recurrence or death and a 38% reduction in the risk of distant metastasis or death.

The absolute difference in two-year recurrence-free survival was 12.2 percentage points between the treatment groups.

A planned additional analysis indicated that the treatment's benefit became more pronounced after six months.

However, researchers have not yet established whether the combination significantly extends overall survival. That outcome remains under investigation as follow-up continues.

The results have been accepted for publication in The New England Journal of Medicine, and the findings are scheduled for presentation at the European Society for Medical Oncology Congress in Madrid on October 24.

Safety and treatment availability

The combination treatment was associated with more frequent side effects than pembrolizumab alone.

Treatment-related adverse events occurred in 95.8% of patients receiving both therapies, compared with 90% of patients receiving pembrolizumab alone.

Common reactions included fever, injection-site pain and fatigue. Severe treatment-related adverse events occurred in 14.2% and 13.4% of patients, respectively.

Investigators reported no unexpected new safety concerns.

Although the results are encouraging, the vaccine remains investigational and is not yet approved for routine clinical use.

Moderna and Merck are discussing the findings with regulatory authorities. Meanwhile, further clinical studies are examining the personalised mRNA approach in other cancers, including lung, kidney and bladder tumours.

The latest results establish important evidence for personalised cancer vaccines, but longer follow-up will be needed to determine their lasting benefits and whether similar outcomes can be achieved in other malignancies.