Merck and Moderna reported Phase 3 success for their personalized neoantigen mRNA cancer vaccine, intismeran autogene, delivering randomized evidence of benefit in a late-stage melanoma setting. The company partners said adding the individualized vaccine to Merck’s Keytruda slowed recurrence and spread versus Keytruda alone, setting up an approval push. The trial is positioned as a pivotal test of whether neoantigen vaccines can deliver durable, clinically meaningful outcomes as an adjuvant strategy after surgery, rather than only earlier-phase signals. While detailed efficacy and safety numbers were not immediately released, the companies framed the readout as the first randomized Phase 3 trial designed to “definitively prove” benefit for this modality. Industry attention is likely to focus on durability of response, subgroup performance in biomarker-defined populations, and how the trial design and manufacturing workflow translate to broader clinical adoption. If regulators accept the totality of evidence, it would further validate personalized mRNA as an oncology platform beyond single-program updates.