Merck and Moderna reported Phase 3 results for the personalized mRNA vaccine intismeran autogene combined with Keytruda (pembrolizumab) in high-risk melanoma after surgery, showing a 42% reduction in the risk of recurrence or death versus Keytruda alone at a median follow-up of about two years. The dual approach also reduced the risk of distant spread or death by 38%. Regulators are now on the companies’ path toward review and potential approval, with overall survival still immature. The companies described data accepted for publication in the New England Journal of Medicine and said they are engaging with regulatory authorities. Market reaction has been volatile amid an early leak of top-line results ahead of planned conference presentation timing. For clinicians and biotech partners, the readout is a step change in personalized cancer vaccination delivery—pairing an individualized mRNA component with an approved PD-1 inhibitor—while also raising practical questions around manufacturing workflows and adoption pathways as regulators review the evidence base.