Personalised cancer vaccine cuts melanoma recurrence risk by 42% in landmark trial

A new personalised cancer treatment could offer hope to people at high risk of melanoma returning after surgery, following international clinical trial results showing a 42% reduction in the risk of recurrence or death.

The treatment, known as intismeran, uses mRNA technology to help the immune system recognise and attack cancer cells based on the unique characteristics of an individual patient’s tumour.

Results from the phase 3 INTerpath-001 trial, involving 1,137 patients, mark a significant development in cancer research. The study found that combining the experimental vaccine with pembrolizumab, an established immunotherapy, was more effective at reducing the risk of melanoma returning or death than pembrolizumab alone.

Although the findings have generated excitement in the medical community, the treatment remains investigational and is not yet available to patients.

How does the personalised cancer vaccine work?

Unlike conventional vaccines designed to prevent infections, intismeran is a therapeutic cancer vaccine intended for people who have already been diagnosed with cancer.

It is designed around the unique molecular features of each patient’s tumour, allowing the immune system to learn what specific cancer cells look like.

Researchers analyse a tumour sample to identify abnormal proteins known as neoantigens. These act like a biological fingerprint, helping distinguish cancer cells from healthy tissue.

Using mRNA technology, the vaccine delivers instructions that help the body’s cells present these tumour-specific features to the immune system.

The aim is to train immune cells to recognise and destroy any remaining cancer cells after surgery, potentially lowering the likelihood of the disease returning.

The treatment is being developed by pharmaceutical companies MSD and Moderna.

What the clinical trial found

The international INTerpath-001 study included 1,137 people with high-risk melanoma, ranging from stage IIB to stage IV, whose tumours had been surgically removed.

Participants received either the personalised vaccine alongside pembrolizumab or pembrolizumab alone.

The results showed that patients receiving the combination experienced a 42% reduction in the risk of melanoma recurrence or death compared with those receiving immunotherapy alone.

Among patients who remained free of recurrence for more than six months after starting treatment, the reduction in risk was reported to be even greater, at 58%.

Researchers also reported that adding the vaccine did not increase pembrolizumab-related side effects. The vaccine was generally well tolerated, with reported short-term side effects including injection-site pain, headaches and chills.

However, the findings relate to a reduction in relative risk. They do not mean that 42% more patients were cured, nor do they establish that the treatment will prevent melanoma from returning in every patient.

Why this could change cancer treatment

Professor Georgina Long, medical director of Melanoma Institute Australia and the trial’s global principal investigator, described the findings as a major shift towards more personalised cancer treatment.

The approach combines two different strategies: teaching the immune system to recognise an individual’s cancer and helping immune cells overcome mechanisms that tumours use to evade detection.

Pembrolizumab works by blocking a pathway that cancer can exploit to suppress immune responses. The personalised vaccine adds another layer by helping the immune system identify the particular tumour it needs to target.

Researchers believe this combination could eventually inform treatments for other cancers, although further studies will be needed to establish whether the approach works in different tumour types.

What the findings mean for South African patients

Melanoma is a serious form of skin cancer that can spread to other parts of the body. Although it is often associated with prolonged exposure to ultraviolet radiation, it can affect people with different skin tones.

For South Africans, awareness of changing moles, unusual skin growths and other suspicious skin changes remains important. Any concerning changes should be assessed by a healthcare professional.

The latest findings are encouraging, particularly for people whose melanoma has been removed but who remain at high risk of recurrence.

However, the personalised vaccine is not yet available for routine treatment. The results must go through regulatory review, and the time required for approval will vary between countries.

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