Moderna-Merck mRNA vaccine plus Keytruda lowers melanoma recurrence in 1137-patient phase 3 trial

Moderna and Merck announced results from a randomized phase 3 trial of 1137 patients with stage III/IV melanoma who underwent resection. Participants received either the individualized neoantigen mRNA vaccine plus pembrolizumab or pembrolizumab monotherapy. The combination arm showed lower rates of recurrence or distant metastasis, though exact hazard ratios, absolute risk reductions, and confidence intervals were not disclosed. The companies indicated plans to present full data at a medical meeting and submit to regulators.

This builds on earlier phase 2 data and Catherine Wu's 2017 proof-of-concept work demonstrating neoantigen vaccines could elicit T-cell responses in small melanoma cohorts. The mRNA platform enables rapid manufacturing of patient-specific constructs encoding up to 34 neoantigens, addressing tumor heterogeneity more effectively than off-the-shelf approaches. Melanoma's high mutational burden makes it particularly responsive, explaining why this indication leads broader testing in lung, pancreatic, and renal cancers.

The announcement remains preliminary without peer-reviewed publication or independent verification. Regulatory decisions will hinge on mature overall survival data and manufacturing scalability for individualized therapies. Ongoing trials in additional tumor types will test whether the approach generalizes beyond immunogenic cancers like melanoma.

Next steps include full dataset release and expansion of manufacturing capacity to support potential approval and broader application across solid tumors.