Moderna and Merck's Personalized mRNA Vaccine Significantly Reduces Melanoma Recurrence and Mortality

Image: Ars Technica · Source

A Phase 3 trial shows a personalized mRNA cancer vaccine combined with Keytruda reduces risk of death or recurrence by 42% in melanoma patients, marking a major advancement in cancer treatment.

Moderna and Merck have announced promising results from a Phase 3 clinical trial testing their personalized mRNA cancer vaccine, intismeran (mRNA-4157), in patients with melanoma, the deadliest form of skin cancer. The study demonstrated that combining the vaccine with Merck's standard monoclonal antibody therapy, Keytruda, reduced the risk of death or cancer recurrence by 42 percent compared to Keytruda alone. This data represents a significant advance in melanoma treatment and supports the potential of personalized mRNA therapies in oncology.

The trial involved 1,137 patients with stage IIB to IV melanoma who had undergone surgical removal of tumors prior to enrollment. Participants were randomized in a 2:1 ratio to receive either the personalized vaccine with Keytruda or Keytruda with a placebo. Intismeran is a synthetic mRNA vaccine designed to encode up to 34 unique cancer mutations identified from each patient’s tumor, enabling an immune response tailored specifically to malignant cells.

After two years, 82 percent of patients in the vaccine plus Keytruda group were alive without recurrence, compared to 70 percent in the Keytruda-placebo group. Regarding distant metastasis-free survival, the combination therapy reduced risk by 38 percent, with 88.5 percent of treated patients surviving without metastasis at locations distant from the original tumor site compared to 80 percent in the control group.

While slightly less pronounced than outcomes observed in a prior Phase 2 trial, these results establish the vaccine’s efficacy in a larger population. According to Merck and Moderna, these findings could set a new standard of care for melanoma in the adjuvant setting, heralding a shift toward individualized mRNA cancer treatments. Both companies are now engaging regulatory authorities to seek vaccine approval.

Moderna's CEO Stéphane Bancel highlighted the results as a defining moment for personalized mRNA medicines, reinforcing the technology’s transformative potential in cancer care. The detailed data is slated for presentation at the European Society for Medical Oncology conference and publication in the New England Journal of Medicine. This breakthrough underscores the broader potential for mRNA platforms beyond infectious diseases, extending into highly targeted cancer immunotherapies.