Merck and Moderna reported positive results from a Phase 3 trial testing their personalized mRNA cancer vaccine, intismeran autogene, in adjuvant melanoma. The program combines intismeran autogene, which is individualized to each patient’s tumor neoantigens, with Merck’s Keytruda (pembrolizumab) after surgical removal of high-risk skin cancer. The companies said the combination met its primary endpoint of improved recurrence-free survival at an interim analysis and showed a statistically significant, clinically meaningful improvement versus Keytruda plus placebo. They also reported benefit across a secondary endpoint, including distant metastasis-free survival. Merck and Moderna did not release full trial details in the announcement. The companies characterize the Phase 3 readout as a first for randomized testing of personalized neoantigen mRNA vaccines in melanoma. Regulators will still need to review the data before any potential approval path, and the trial is continuing on additional endpoints such as overall survival. Investor interest has sharpened around the prospect that personalized mRNA can move beyond early proof-of-concept into registrational-grade outcomes, particularly as questions linger about manufacturing complexity and durability of response in broader patient populations.