Moderna and Merck say their personalized mRNA cancer vaccine, used together with Keytruda, lowered the risk of melanoma returning or causing death by 44% compared with Keytruda alone in a phase 3 trial. The companies described the result as a significant step for an experimental approach designed to help the immune system recognize and attack tumor cells.

The late-stage study focused on patients with melanoma, one of the most aggressive forms of skin cancer. According to the announcement, the vaccine was tailored to each patient’s tumor profile, reflecting a growing push toward precision medicine in oncology.

While the findings are encouraging, the treatment still needs additional review before it can move toward broader use. Regulators and medical experts typically examine safety, durability of benefit, and how new therapies perform across larger and more diverse patient groups.

If confirmed in follow-up analysis, the result could strengthen interest in mRNA-based cancer treatments beyond infectious disease applications. Researchers have been working for years to adapt the technology to target tumors more precisely and improve outcomes for patients with limited options.