Merck and Moderna announced that their personalized mRNA neoantigen vaccine, intismeran autogene, met a key Phase 3 endpoint in high-risk melanoma, supporting the combination with Keytruda (pembrolizumab) in the adjuvant setting. The companies said the regimen improved recurrence-free survival and also demonstrated an improvement in distant metastasis-free survival at an interim analysis. The trial enrolled surgically resected patients with stage IIB to IV cutaneous melanoma, randomizing them to Keytruda plus placebo versus Keytruda plus the individualized mRNA therapy. Merck and Moderna did not release full numerical results in the announcement, but characterized the improvement as statistically significant and clinically meaningful. Market reaction was immediate, with coverage noting Moderna’s market value jump tied to the data disclosure and rising expectations for broader impact if efficacy translates beyond melanoma. The companies have framed the result as a potentially defining proof-of-concept for personalized neoantigen vaccines. If the final results hold up, the companies are positioned for regulatory conversations about accelerated pathways in adjuvant melanoma, with follow-on efforts likely to test similar approaches in additional solid tumor settings.