Merck–Moderna Cancer-Vaccine Trial Win Sends Stocks Higher

Merck and Moderna said their personalized mRNA cancer vaccine, intismeran autogene, met the primary endpoint in the Phase 3 INTerpath-001 trial for high-risk melanoma.

Used alongside Merck’s Keytruda, the vaccine significantly improved recurrence-free survival versus Keytruda alone and also reduced the risk of cancer spreading to distant organs.

The trial enrolled 1,137 patients with stage IIB–IV melanoma whose tumors had been surgically removed. No new safety concerns were reported, and the study will continue tracking overall survival.

The result is being described as the first positive Phase 3 readout for an individualized neoantigen or mRNA cancer vaccine, and the first late-stage trial to demonstrate a meaningful improvement over Keytruda alone in this setting.

Moderna’s shares surged—at points more than doubling—while Merck gained roughly 10%–12%, adding tens of billions of dollars to Moderna’s market value.

Investors and analysts are now debating whether intismeran could eventually become as broadly useful as Keytruda. Analysts estimate the initial adjuvant-melanoma market could generate more than $2 billion to $3 billion annually, but broader success across other cancers is needed to justify the companies’ sharply higher valuations.

The companies plan to use the data in regulatory filings, though detailed efficacy figures and longer-term survival results are still pending.