Merck and Moderna’s August 19, 2026, announcement that their personalized mRNA-4157 (intismeran autogene) neoantigen vaccine plus Keytruda met the primary recurrence-free survival and key secondary distant metastasis-free survival endpoints in the Phase 3 INTerpath-001 trial for resected high-risk melanoma has become the dominant driver of trader sentiment. The result marks the first positive late-stage readout for an individualized mRNA cancer therapy and has prompted the companies to schedule full data presentation at an upcoming medical meeting while initiating regulatory engagement on potential BLA filings. Traders are weighing the speed of FDA interactions, historical precedents for accelerated review in breakthrough-designated oncology assets, and the absence of any confirmed submission to date against the backdrop of ongoing trials in lung, bladder, and kidney cancers that could expand the program.