Training the Immune System to Remember Cancer
Commentary by Dr. Donald Greig
I recently read a fascinating article about what may prove to be a landmark moment in cancer treatment: a personalised cancer vaccine that has succeeded in a large late-stage trial for high-risk melanoma.
At first glance, the phrase “cancer vaccine” can be confusing. We usually think of vaccines as something given to prevent infections before they happen. This is different. This vaccine is being used after cancer has already been removed by surgery, with the aim of teaching the immune system to recognise and destroy any cancer cells that may remain.
The experimental vaccine, called intismeran autogene - also known as V940 or mRNA-4157 - has been developed by Moderna and Merck. It is designed individually for each patient, based on the unique mutations found in that person’s own tumour. In the phase 3 INTerpath-001 trial, it was tested alongside Keytruda, an established immunotherapy drug also known as pembrolizumab, in patients with completely resected stage IIB to IV melanoma. The trial met its primary endpoint of improving recurrence-free survival and a key secondary endpoint of improving distant metastasis-free survival.
Why Melanoma Matters
Melanoma is one of the most serious forms of skin cancer. When detected early and removed, outcomes can be good. But when melanoma is high-risk, or has already spread, the chance of recurrence remains a major concern.
This is why treatment after surgery, known as adjuvant therapy, is so important. The aim is to reduce the risk that microscopic cancer cells, too small to detect on scans, will later grow into recurrent or metastatic disease.
Keytruda has already changed the outlook for many patients by helping the immune system recognise and attack cancer. But the new trial suggests that adding a personalised vaccine may improve on that approach.
How a Personalised Cancer Vaccine Works
The science behind this treatment is both elegant and highly individualised.
After a patient’s melanoma is surgically removed, scientists analyse the tumour to identify mutations that are unique to that cancer. These mutations can create abnormal proteins known as neoantigens - molecular flags that may help the immune system distinguish cancer cells from normal healthy cells.
The vaccine uses mRNA technology, now widely recognised because of Covid vaccines. But here, instead of carrying instructions related to a virus, the mRNA carries instructions for selected tumour-specific neoantigens.
The aim is to train the patient’s own immune system, particularly cancer-killing T cells, to recognise those neoantigens and attack any remaining melanoma cells.
In simple terms, the vaccine is not “off the shelf.” It is made for one person, from one tumour, to help that person’s immune system target their own cancer.
Why the Phase 3 Result Is Important
The significance of this news is that the treatment has now shown success in a phase 3 trial - the large, final-stage type of study usually needed before regulators consider approval.
More than 1,000 patients with completely resected stage IIB to IV melanoma were enrolled in INTerpath-001. Patients were randomly assigned to receive intismeran plus Keytruda, or Keytruda alone, after surgery. The companies reported that the combination significantly improved the time patients remained free from recurrence and also reduced the risk of distant spread.
That matters because recurrence and distant metastasis are the outcomes patients fear most after high-risk melanoma surgery.
Earlier phase 2b follow-up data had already been encouraging. At around five years of follow-up, intismeran plus Keytruda reduced the risk of recurrence or death by 49% and reduced the risk of distant metastasis or death by 59% compared with Keytruda alone.
The phase 3 result now strengthens the case that personalised mRNA cancer vaccines may become a real part of oncology practice, not just a scientific aspiration.
What This Could Mean for Cancer Care
This research is exciting not only because of melanoma, but because of what it suggests for cancer treatment more broadly.
Cancer is not one disease. Even within the same cancer type, two patients’ tumours can behave very differently. Their mutations, immune visibility and response to treatment may vary considerably.
A personalised cancer vaccine fits into the broader direction of modern medicine: moving away from one-size-fits-all treatment and towards more precise, tailored care.
Moderna and Merck are already studying similar approaches in other cancers, including non-small cell lung cancer, bladder cancer and kidney cancer. Several phase 2 and phase 3 trials are underway across different tumour types.
If the technology proves effective beyond melanoma, this could represent a new treatment platform: using a patient’s own tumour biology to build a personalised immune strategy.
The Role of mRNA After the Pandemic
One of the wider lessons from this story is how quickly scientific tools can be redirected.
The Covid pandemic brought mRNA technology into public awareness. But mRNA research did not begin with Covid, and its potential was never limited to infectious disease.
In cancer, mRNA offers a way to rapidly encode personalised tumour targets and deliver them to the immune system. That flexibility is central to why this platform is so attractive.
The same broad technology that helped accelerate vaccine development during the pandemic is now being tested against some of the most challenging cancers.
That does not mean the treatments are the same. A Covid vaccine is designed to help prevent infection. A personalised cancer vaccine is designed to help treat an existing disease by improving immune recognition after cancer surgery.
But the technological connection is important. It shows how investment in one area of medicine can create momentum in another.
Important Questions Still Remain
As promising as this news is, caution is still needed.
The detailed phase 3 results have not yet been fully presented or peer reviewed in the same way as a completed journal publication. Researchers will want to see the size of the benefit, subgroup results, safety data, durability of response and, eventually, whether the treatment improves overall survival.
There are also practical questions.
A personalised vaccine must be manufactured for each individual patient. That requires tumour sequencing, data analysis, vaccine design, production, quality control and delivery - all within a clinically useful timeframe. Moderna has said manufacturing takes several weeks, and patients can begin Keytruda while the vaccine is being prepared.
Cost and access will also matter. Highly personalised treatments can be complex and expensive. If approved, health systems will need to decide which patients benefit most and how to deliver the treatment fairly.
And as with all immunotherapy, side-effects require careful monitoring. Stimulating the immune system can be powerful, but it must be done safely.
What Should Patients Take From This?
For patients, the most important message is hope, but measured hope.
This is not a general cancer vaccine that prevents all cancer. It is not a replacement for surgery, immunotherapy, targeted therapy, radiotherapy or careful follow-up. It is not yet a routine treatment.
But it is a significant step towards a future in which cancer treatment is increasingly personalised.
For someone with high-risk melanoma, the idea that doctors could remove the tumour, analyse its unique mutations, manufacture a vaccine from that information and use it to train the immune system to prevent recurrence is genuinely remarkable.
It represents a shift from treating cancer only after it returns, to trying to prevent recurrence by anticipating what the cancer looks like at a molecular level.
A Broader Reflection
This story speaks to a theme that runs through much of modern medicine: precision with purpose.
The goal is not simply to make treatment more sophisticated. It is to make treatment more effective, more targeted and, where possible, less wasteful.
Cancer care has already moved a long way from the era when treatment was based mainly on where a tumour started in the body. Increasingly, we look at the molecular features of the cancer, the immune environment around it, the patient’s risk of recurrence and the treatments most likely to help.
Personalised cancer vaccines take that logic one step further.
They ask: can we turn the tumour’s own mutations into a treatment map? Can we teach the immune system to recognise the cancer more clearly? Can we reduce the chance of recurrence before it becomes visible again?
The answer is not complete yet. But this trial suggests that the answer may be yes.
For patients, that is an important and hopeful development.
For medicine, it may be the beginning of a new chapter, one in which vaccines are not only tools for preventing infection, but personalised instruments for helping the immune system keep cancer from coming back.
Disclaimer: This newsletter is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider for any medical concerns.
Landmark vaccine stops cancer returning in trial
By Rhys Blakely
A cancer vaccine personalised for each patient has succeeded in a large final-stage trial, raising hopes that a new generation of tailor-made treatments could benefit thousands of people.
The experimental vaccine, developed by Moderna and Merck, was given to patients with high-risk melanoma, a type of skin cancer, after they had surgery. The vaccine, named Intismeran, was accompanied by Keytruda, an immunotherapy drug already prescribed by the NHS for a dozen types of cancer.
The companies said the combination, compared with Keytruda alone, significantly extended the time patients remained free of cancer and also reduced the risk of the disease spreading to other organs.
Moderna and Merck are testing similar personalised vaccines for lung, bladder and kidney cancers. Lung cancer trials have reached the final stage 3 phase, while kidney and bladder studies are in phase 2. The hope is that the technology can work across many tumour types.
Researchers will want to see a more detailed breakdown of the results. Shares in Moderna, which are traded on Wall Street’s Nasdaq exchange, closed $111.42, or 177 per cent, higher at $174.38, their biggest one day jump on record, valuing the business at $70 billion.
Stéphane Bancel, the Moderna chief executive, said that the latest results marked “a pivotal moment for the field of cancer research”.
He added: “For many years, the idea of creating an mRNA treatment designed specifically for an individual patient’s cancer was aspirational. We are now helping turn that vision into a reality.”
Professor Marco Gerlinger, of the Barts Cancer Institute, said: “I think it is fair to call it a breakthrough as it is the first phase 3 study that shows that a vaccine can protect against recurrences of one of the deadliest cancer types. 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.”
NHS data for England suggests that if melanoma reaches stage 4, meaning it has spread, only about a quarter of patients survive for five years. However, those figures do not fully reflect new treatments that have improved outcomes. The disease claims about 2,600 lives in total each year.
More than 1,000 patients took part in the phase 3 trial after having melanomas surgically removed. The patients had high-risk stage 2, 3 or 4 melanoma, meaning they ranged from having large but localised tumours to cancers that had spread to other parts of the body.
Although the companies have not released detailed results, they said the study met both its principal goal of improving recurrence-free survival and an important secondary goal of preventing the cancer from spreading.
The vaccine uses mRNA, a technology that became well known through Covid vaccines. Unlike conventional vaccines, which are usually designed to prevent infection, the treatment is made individually for each patient. After surgery, scientists analyse a sample of the tumour to identify mutations unique to its cancer cells.
They then encode selected targets into strands of mRNA, producing a vaccine designed to teach the immune system — particularly cancer-killing T cells — to recognise and attack any tumour cells that remain. Manufacturing each dose takes about six weeks. Patients begin treatment with Keytruda while their personalised vaccine is prepared.
Earlier results from a smaller study found that the combination reduced the risk of melanoma returning or patients dying by 49 per cent and cut the risk of the cancer spreading to other parts of the body or the patient dying by 59 per cent compared with Keytruda alone.
Important questions remain, including the size of the benefit, side-effects and the cost and complexity of manufacturing a bespoke vaccine for every patient.
Nevertheless, the trial appears to represent a milestone. If regulators approve the treatment, Moderna has said it hopes it could reach patients as early as next year.
Moderna and Merck will provide more details at a medical conference later this year. High costs could limit the drug’s accessibility if it is eventually approved by regulators.
Professor Georgina Long of the University of Sydney, who is the study’s principal investigator and also medical director of the Melanoma Institute Australia, said the results represented “a landmark moment”.
She added that the combination of Intismeran and Keytruda “has the potential to establish a new treatment paradigm” that would help patients remain cancer-free for longer.
Dr Lennard Lee of the University of Oxford, a consultant oncologist who is advising the NHS and the government on cancer vaccines, said that it was an “important moment that scientists have been working towards for many years”.
He added: “There is also a wider story here about what happened after the pandemic. In 2020, enormous global investment accelerated mRNA technology, vaccine science and manufacturing, and it started in the United Kingdom. The question afterwards was whether that capability could be redirected towards other major diseases.
“In 2022, the UK made an early strategic decision to pursue that opportunity in cancer, launching a national cancer vaccine advance to accelerate clinical trials of mRNA cancer vaccines. Since then, the UK has developed into one of the world’s leading environments for cancer vaccine trials.”
One mRNA vaccine trial now active in the UK involves patients with high-risk stage 2 or stage 3 colon or rectal cancer whose tumours have been surgically removed, but who still have traces of tumour DNA detectable in their blood, suggesting a high chance that the cancer could return. BioNTech developed that treatment.
The first English patient received the vaccine in Birmingham in 2024 through the Cancer Vaccine Launch Pad, a scheme for connecting eligible NHS cancer patients with clinical trials of new cancer vaccines. British patients are also involved in personalised vaccine trials for pancreatic cancer, being run by BioNTech and Genentech.
Disclaimer: This newsletter is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider for any medical concerns.
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