How Moderna’s Personalised mRNA Cancer Vaccine Could Change Melanoma Treatment

Discover how Moderna and Merck’s personalised mRNA cancer vaccine works, why it is being tested for melanoma, and what the latest clinical results could mean for cancer treatment.

A new approach to treating cancer

Cancer treatment has traditionally relied on therapies designed to work broadly across groups of patients. A new generation of personalised cancer vaccines is taking a different approach by using information from an individual patient's tumour to help the immune system identify and attack cancer cells.

One of the most closely watched developments is a personalised mRNA cancer vaccine being developed by Moderna and Merck. Known as intismeran, the experimental treatment is being investigated in people with high-risk melanoma, an aggressive form of skin cancer.

Early clinical findings suggest that combining the personalised vaccine with an established immunotherapy can reduce the risk of melanoma returning after treatment. However, the vaccine remains an experimental treatment, and researchers are continuing to assess its long-term benefits.

What is a personalised mRNA cancer vaccine?

The basic idea is relatively straightforward, although the science behind it is highly sophisticated.

A tumour contains genetic changes that distinguish cancer cells from healthy cells. Some of these changes can result in abnormal proteins called neoantigens. These proteins may provide the immune system with clues that a cell is cancerous.

A personalised cancer vaccine is designed using information obtained from a patient's tumour. After the tumour is removed, scientists analyse its genetic characteristics and identify mutations that could produce useful neoantigens.

The selected targets are then incorporated into an mRNA vaccine.

Rather than delivering a traditional vaccine antigen, the mRNA provides temporary instructions that tell cells how to produce specific proteins. The aim is to expose the immune system to tumour-related targets so that immune cells, particularly T cells, can learn to recognise cancer cells carrying those characteristics.

In simple terms, the treatment is intended to give the immune system a more specific target.

How does the Moderna cancer vaccine work?

The process begins with tumour analysis.

Doctors obtain a sample of the patient's tumour, which is then genetically sequenced. Researchers look for mutations that could generate neoantigens likely to be recognised by the immune system.

A personalised vaccine is subsequently produced using selected targets from that individual tumour. According to information provided about the clinical programme, the vaccine can encode as many as 34 neoantigens.

Once administered, the mRNA delivers instructions that help the patient's cells temporarily produce the selected targets. The immune system can then respond to these targets and develop a stronger, more focused T-cell response.

The treatment is being used alongside pembrolizumab, an immunotherapy medicine sold under the brand name Keytruda.

The two treatments are intended to perform complementary roles. The personalised vaccine aims to help the immune system identify cancer cells, while pembrolizumab works by helping immune cells maintain their ability to attack cancer.

This combination is important because cancer can develop mechanisms that allow it to evade the immune system.

Why is melanoma an important target?

Melanoma develops from pigment-producing cells in the skin and can become particularly dangerous when it spreads to other parts of the body.

Although melanoma represents only part of the overall skin cancer burden, advanced melanoma can be difficult to treat. In the UK, thousands of people are diagnosed with melanoma each year, and the disease causes significant numbers of deaths.

The potential value of personalised immunotherapy is particularly relevant in melanoma because these tumours can contain numerous genetic mutations. Some of those mutations may create neoantigens that can potentially be recognised by the immune system.

The goal of the vaccine is therefore not simply to stimulate immunity in a general way. Instead, researchers are attempting to create an immune response tailored to the specific characteristics of a patient's cancer.

What have clinical trials shown?

A large phase three clinical trial has evaluated the personalised vaccine approach in more than 1,000 people with advanced melanoma.

Participants included patients with high-risk disease, including some whose cancer had involved other parts of the body. The vaccine was administered alongside pembrolizumab.

Early results have indicated that the combination can extend the period during which patients remain free of cancer compared with immunotherapy alone.

That finding is significant because preventing melanoma from returning after treatment is an important objective in cancer care.

However, early evidence should not be interpreted as proof that the vaccine is a cure. Researchers need longer follow-up to determine how much the treatment improves overall survival and how durable the benefit is.

The results also need to be considered alongside potential side effects, manufacturing challenges and the practicalities of producing an individualised treatment for every patient.

Could personalised mRNA vaccines treat other cancers?

Melanoma is not the only cancer being investigated.

Moderna and Merck are also studying personalised cancer vaccines in other tumour types, including lung, kidney and bladder cancers.

Clinical development is at different stages for these diseases. Some programmes have progressed further than others, reflecting the complexity of developing an effective vaccine for different types of cancer.

The underlying principle remains similar: identify genetic features of a patient's tumour, select potentially useful neoantigens and use an mRNA-based treatment to train the immune system to recognise them.

Whether this strategy can deliver meaningful benefits across a wide range of cancers remains an open scientific question.

What makes this approach different?

One of the most interesting aspects of personalised cancer vaccines is that they move away from the idea of giving every patient exactly the same treatment.

Cancer is not one single disease. Even two tumours originating in the same organ can have very different genetic characteristics.

A personalised vaccine attempts to account for those differences.

Dr Lennard Lee, a consultant medical oncologist at the University of Oxford, has described personalised cancer vaccines as a fundamentally different way of thinking about treatment because the therapy is designed around the genetic fingerprint of an individual's cancer.

This approach could eventually become part of a broader trend towards precision oncology, in which treatments are selected according to the molecular characteristics of a patient's tumour.

What happens next?

Despite the excitement surrounding mRNA cancer vaccines, there is still a significant amount of research to complete.

Scientists need to establish how long the immune response lasts, which patients are most likely to benefit and whether the treatment can improve long-term survival.

There are also practical considerations. Personalised vaccines require tumour sequencing, target selection and individual manufacturing, which can be more complicated than producing a standard medicine.

If future trials continue to produce positive results, however, personalised mRNA vaccines could become an important addition to the cancer treatment toolkit.

The technology could ultimately help doctors develop treatments that are more closely matched to the biology of an individual patient's cancer.

Final thoughts

The development of Moderna's personalised mRNA cancer vaccine represents an important step in the evolution of cancer immunotherapy.

Instead of simply trying to attack cancer directly, the strategy aims to teach the immune system what makes a particular tumour different and then strengthen the body's ability to respond.

The early results in high-risk melanoma are encouraging, but it is important to distinguish promising clinical research from an established treatment. The vaccine is still being evaluated, and longer-term evidence will be needed before its full potential can be understood.

If successful, personalised mRNA cancer vaccines could eventually extend beyond melanoma and become part of a new generation of precision cancer treatments.

Disclaimer: This article should not be considered medical advice, a diagnosis, or a substitute for guidance from a qualified healthcare professional. Medical research and clinical trial results can change as new evidence becomes available. Readers should consult their doctor or an appropriate medical professional for advice about cancer, treatment options, or individual health circumstances.