Moderna, Merck unveil mRNA-based cancer vaccine that cuts spread

August 19, 2026 - 19:43

A new mRNA-based cancer vaccine developed by Moderna and Merck has shown significant promise in reducing the spread of melanoma, according to late-stage trial data. The treatment, known as Intismeran, was tested in patients with high-risk melanoma that had already been surgically removed. The results indicate that the vaccine, when combined with Merck's immunotherapy drug Keytruda, lowered the risk of cancer recurrence or death by a notable margin compared to Keytruda alone.

The vaccine works by teaching the immune system to recognize specific mutations found in a patient's tumor. Unlike traditional vaccines that prevent infectious diseases, this one is personalized for each individual, targeting the unique genetic markers of their cancer. In the trial, patients who received the combination therapy saw a longer period without the disease returning, and the cancer was less likely to spread to other parts of the body.

These findings build on earlier phase 2 data that already showed promise. The new results come from a larger phase 3 study, which is a critical step before seeking regulatory approval. Moderna and Merck plan to discuss the data with health authorities in the coming months. If approved, Intismeran would be one of the first personalized mRNA cancer treatments available, marking a major shift in how certain cancers are managed. The companies also noted that side effects were manageable, with most patients experiencing mild to moderate reactions like fatigue or injection-site pain. Further studies are planned to test the vaccine in other cancer types, including lung and head and neck cancers.