Merck and Moderna release melanoma vaccine Phase 3 results early after leak

After an embargo breach ahead of the 2026 ESMO Congress, Merck and Moderna released Phase 3 results early for their personalized melanoma vaccine, intismeran autogene (V940/mRNA-4157), given with Keytruda (pembrolizumab).

In the INTerpath-001 trial of 1,137 patients with high-risk melanoma removed by surgery, the combination reduced the risk of recurrence or death by 42% versus Keytruda alone (hazard ratio 0.58). At two years, 82.2% of patients in the combination group were recurrence-free, compared with 70.0% in the control group.

The combination also reduced the risk of distant metastasis or death by 38%. Overall-survival results are not yet mature, and the companies reported no new safety concerns.

The data had been scheduled for a Saturday ESMO presentation. After the results appeared prematurely online, ESMO confirmed an embargo breach and lifted the embargo; the presentation was still expected to proceed.

Investors reacted negatively despite the positive trial findings, with Moderna shares falling sharply and Merck shares also declining. Reports attributed the selloff partly to expectations that the Phase 3 benefit might match or exceed earlier Phase 2 results.