Cancer breakthrough as personalised mRNA vaccine stops melanoma returning
An mRNA vaccine built from patients’ own tumours has reportedly kept melanoma from returning, in a late-stage trial.
- 20 August 2026
- 5 min read
- by Priya Joi
At a glance
- A personalised mRNA vaccine, given with the immunotherapy drug Keytruda, extended the time patients with high-risk melanoma stayed cancer-free after surgery.
- This is the first late-stage randomised trial of a personalised cancer vaccine to succeed, however detailed findings have not yet been released or peer reviewed.
- The finding comes as mRNA vaccines are showing promise in other cancers too, including a vaccine that triggered lasting immune responses in pancreatic cancer patients, one of the hardest cancers to treat.
A new cancer vaccine given in combination with an immunotherapy drug has reportedly stopped skin cancer returning in a clinical trial.
Patients were given a combination of Intismeran, a vaccine that uses the patient’s own tumour in a novel 'personalised' approach, and an immunotherapy drug called Keytruda following surgery to remove high-risk melanoma, the deadliest form of skin cancer.
Those given this combination stayed cancer-free for longer than those given Keytruda alone. They were also less likely to see the disease reach other organs.
Detailed results have yet to be peer reviewed or published by the two companies behind it, Moderna and Merck & Co, and it’s unclear as yet how long the benefit from the vaccine lasts.
The findings comes on the back of progress in other personalised mRNA vaccines against other cancers like pancreatic cancer.
Prof Marco Gerlinger, Professor of Gastrointestinal Cancer Medicine and Consultant Medical Oncologist, Barts Cancer Institute, St Bartholomew’s Hospital, called it a “breakthrough in the development of new cancer immunotherapies”.
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“It is the first Phase 3 study that shows that a vaccine can protect against recurrences of one of the deadliest cancer types,” said Professor Gerlinger. “This is certainly good news for patients with melanoma, but the study has much wider implications. It provides proof of principle that personalised cancer vaccines work.”
Larger-scale trial
The Phase 3 trial enrolled over 1,000 people with stage two, three or four melanoma: a range that spans from sizeable tumours confined to one site to disease that spread to other parts of the body. Participants were assigned at random to either the combination or to Keytruda by itself, for roughly a year.
This builds on a smaller study of the same combination of vaccine and immunotherapy. In June, MSD and Moderna presented five-year results from a mid-stage trial of 157 patients at the American Society of Clinical Oncology annual meeting, reporting that the vaccine and drug together halved the risk of melanoma returning compared with the drug alone. Those findings were published in the Journal of Clinical Oncology.
Personalising the vaccine
These kinds of vaccines are unique to the person receiving it, using the patient’s own tumour to create it.
A fragment of the tumour is taken and its genetic code read to pinpoint the mutations carried by that particular cancer. Those mutations produce proteins known as neoantigens, which the immune system is capable of treating as foreign, but which typically slip past unnoticed.
Moderna’s manufacturing process then builds an mRNA vaccine carrying the code for as many as 34 of those neoantigens, tailored to that one patient. Once injected, it teaches the immune system what the remaining cancer cells look like.
Keytruda acts to dismantle the molecular camouflage that tumours rely on to escape notice: cancer cells display a protein that switches off approaching immune cells and Keytruda blocks that signal so those cells remain active and can attack the tumour.
While mRNA vaccines came to public attention during the COVID-19 pandemic, researchers were pursuing mRNA as a cancer therapy long before this, and Moderna won US approval for an mRNA influenza vaccine earlier this month.
Early signals in pancreatic cancer
Earlier this year the same technology produced long-lived immune responses against pancreatic cancer, a disease that kills roughly seven in eight patients within five years and that has repeatedly defeated immunotherapy.
Sixteen patients took part in a Phase 1 trial of autogene cevumeran, a vaccine from BioNTech and Genentech, led by Vinod Balachandran at Memorial Sloan Kettering Cancer Center in New York.
Each received chemotherapy and an immunotherapy drug alongside a vaccine carrying up to 20 neoantigens drawn from their own tumour.
Half of them showed a detectable immune response. Follow-up figures presented at the American Association for Cancer Research meeting this year showed seven of those eight patients alive between four and six years on from their operation.
Of the eight whose immune systems did not react, six had died, and the median survival across that group was 3.4 years. Among the responders, the tumour-killing T cells generated by the vaccine were still in circulation six years later.
“Personalised cancer vaccines are a fundamentally different way of thinking about cancer treatment,” said Dr Lennard Lee, Consultant Medical Oncologist, Associate Professor and Senior National Clinical Adviser on Cancer Vaccines, University of Oxford.
He called the melanoma vaccine results “an important moment for a field that scientists have been working towards for many years. Within six years of the pandemic, we have mRNA vaccines to treat cancer.”
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