A melanoma vaccine tailored to one person’s tumor takes about two months to make—and, when paired with immunotherapy, it lowered the risk of cancer returning or death by 42% in a clinical trial. For Dr. Craig Slingluff, a cancer vaccine researcher at UVA Health in Charlottesville, the result points to a promising new path for treating melanoma and possibly other cancers.
Melanoma can return even after surgery removes all known signs of the disease. Patients at high risk of recurrence are often given pembrolizumab, an immunotherapy drug, or a similar medicine called nivolumab. Both help the immune system recognize and attack cancer. The trial tested whether adding a personalized vaccine could improve on that standard care. Merck and Moderna announced the results last week.
The vaccine, called intismeran, uses mRNA technology, the same broad platform that helped make COVID-19 vaccines. But its aim is different from that of most vaccines against infectious diseases. Instead of mainly prompting the body to make antibodies against a virus, a cancer vaccine seeks to train immune cells to attack cancer cells.
To personalize the treatment, researchers sequence DNA from a patient’s melanoma biopsy and compare it with DNA from normal tissue, such as blood cells. They look for mutations found in the tumor and choose up to 34 targets that the immune system may recognize. The vaccine’s RNA carries instructions for those targets, packaged in tiny particles for delivery. Making an individual vaccine took about two months on average.
The study included people whose melanoma had been removed surgically but who remained at high risk of its return. They had thick tumors without known spread, melanoma in nearby lymph nodes, or cancer that had spread to distant sites and was then removed. Slingluff said the benefit was seen across these groups, suggesting the approach could be relevant to a broad range of patients with high-risk melanoma.
The 42% figure describes the relative reduction in the risk of recurrence or death compared with immunotherapy alone; it does not mean that 42% more patients were cured. Still, Slingluff called the results significant: he said this was the first randomized trial of a personalized mRNA cancer vaccine to show a meaningful benefit for patients. He also noted that side effects were very tolerable, making the balance between benefit and risk encouraging.
For now, the goal is to stop melanoma from returning or spreading after treatment, not to vaccinate healthy people against cancer. Slingluff said the results could help guide efforts to develop personalized vaccines for other cancers, though more research will be needed to establish where else the approach works. After decades spent studying cancer vaccines, he sees a reason for optimism: a treatment designed around the specific changes in a patient’s tumor has now shown a measurable benefit in a major trial.