Personalised cancer vaccine cuts melanoma recurrence risk in trial

A personalised cancer vaccine has shown promising results in reducing the risk of melanoma returning or spreading after surgery.

This marks a potential breakthrough in the treatment of high-risk skin cancer.

The messenger ribonucleic acid (mRNA) based treatment, known as intismeran autogene, was tested in 1,137 patients with completely resected stage IIB to IV melanoma in the Phase 3 INTerpath-001 trial.

The vaccine, when combined with pembrolizumab (Keytruda), significantly improved recurrence-free survival and distant metastasis-free survival compared with Keytruda alone.

The results were announced by pharmaceutical companies Merck and Moderna, representing the first positive Phase 3 results for an individualised neoantigen therapy and an mRNA-based cancer treatment.

The study involved patients whose melanoma had been completely removed through surgery, but remained at risk of the cancer returning or spreading.

In the study, researchers said the findings could open a new chapter in personalised cancer treatment, particularly for patients with high-risk melanoma following surgery.

“This is the first Phase 3 study to show that intismeran, a treatment designed based on the unique mutational fingerprint of a patient's own tumour, given in combination with pembrolizumab can reduce the risk of recurrence or death,” said Professor Georgina Long, the study's principal investigator and medical director of Melanoma Institute Australia

The study is still ongoing to assess other important outcomes, including overall survival.

The companies plan to present detailed findings at an upcoming international medical meeting and engage regulatory authorities on applications for approval.

Unlike conventional vaccines, that are generally designed to prevent an infectious disease or stimulate protection against a common target, intismeran is a treatment given to people who already have cancer.

The vaccine is created specifically for an individual patient.

In administering the treatment, doctors first analyse the genetic mutations in a patient's tumour to identify abnormal proteins, known as neoantigens, that are unique to the cancer.

The patient's tumour information is then used to design an mRNA treatment intended to train the immune system to recognise those cancer-specific markers.

The aim is to enable the body's immune cells to identify and attack remaining cancer cells that may have escaped surgery.

The treatment is being evaluated in combination with Keytruda, an immunotherapy that works by helping the immune system attack cancer cells.

The combination is given after surgery as an adjuvant treatment, with the goal of eliminating residual cancer cells and reducing the likelihood of recurrence.

The companies reported that the safety profile of the combination in the Phase 3 trial was consistent with earlier studies, with no new safety concerns identified.

However, for Kenya, cancer specialists caution against interpreting the development as a vaccine that could prevent people from developing cancer.

Dr Catherine Nyongesa, a consultant clinical and radiation oncologist and Director of Medical Services at Kenyatta National Hospital (KNH), said the treatment was a therapeutic vaccine, meaning it is intended for patients who already have cancer rather than people seeking protection against developing the disease.

“It is a treatment vaccine, not a preventive vaccine, so it will not directly reduce the incidence of new cancer cases,” she said.

She said the development was nevertheless significant because of its potential to improve outcomes among patients with high-risk cancers after surgery.

“If the Phase III results are confirmed and the vaccine receives regulatory approval, some patients with high-risk melanoma after surgery may have a lower risk of the cancer returning or spreading compared with current treatment alone,” Dr Nyongesa said.

Melanoma is a form of skin cancer that develops in pigment-producing cells. Although it is less common than some other skin cancers, it can spread rapidly to other organs if not detected and treated early.

Access could be the bigger challenge

For countries such as Kenya, the breakthrough also raises questions about affordability and the capacity required to deliver highly personalised cancer treatments.

Dr Nyongesa said the development was unlikely to make cancer treatment cheaper immediately.

“This is a personalised treatment vaccine, made using information from an individual patient's tumour, and it is given together with immunotherapy such as Keytruda. Initially, this may actually be an expensive and technologically demanding treatment,” she said.

Unlike medicines manufactured in a standard form for large numbers of patients, an individualised neoantigen treatment requires information from the patient's own tumour to develop the therapy.

This means access could depend on the availability of sophisticated genomic testing, specialised laboratories, manufacturing capacity and trained personnel.

Regulatory approval and the eventual price of the treatment will also determine whether it becomes accessible beyond high-income health systems.

“For Kenya and other African countries, the key question will therefore be not only ‘Does it work?’ but also ‘Can our patients access and afford it?’” posed Dr Nyongesa.

She added that regulatory approval, pricing, genomic testing and laboratory capacity would all be important considerations.

The latest findings build on earlier results from the Phase 2b KEYNOTE-942/mRNA-4157-P201 trial.

Five-year follow-up data presented at the 2026 ASCO annual meeting showed that the combination reduced the risk of recurrence or death by 49 per cent compared with Keytruda alone.

It also reduced the risk of distant metastasis or death  by 59 per cent.

The Phase 3 findings now provide further evidence as researchers move to determine whether the approach can become part of standard treatment.

Merck and Moderna are currently evaluating intismeran in nine Phase 2 and Phase 3 trials across different cancers, including melanoma, non-small cell lung cancer, bladder cancer and kidney cancer.

Additional studies are investigating the treatment in pancreatic cancer, gastric cancer and lung cancer.

Merck Research Laboratories president Dr Dean Y Li said the findings demonstrated the potential of a more personalised approach to cancer treatment.

The companies are continuing to follow patients in the melanoma trial to determine whether the improvement in recurrence-free and distant metastasis-free survival will translate into longer overall survival.

For Kenya, cancer specialists say such advances should complement not replace, existing efforts to prevent cancer, including detecting it early and expanding access to effective treatment.

Cancer prevention, screening, early diagnosis and affordable treatment remain critical as the burden of cancer continues to grow in Kenya and globally.

Data from the Kenya National Cancer Institute shows that at least 35,867 new cancer cases are reported annually in Kenya, with 22,888 people dying from the disease each year.

About 76,165 people are estimated to be living with cancer within five years of diagnosis.

The leading cancers in Kenya include breast, cervical, prostate, oesophageal and colorectal cancers.

Experts note that the emergence of personalised cancer vaccines could eventually add another tool to the cancer treatment arsenal, but whether such technology can benefit patients in Africa will ultimately depend on its effectiveness, regulatory approval, affordability and the health systems' ability to deliver it.