BioNTech's cancer vaccine trial fails after rival's win

Personalized mRNA cancer vaccines are built from a patient's own tumor. They train the immune system to attack it. Last week, one version worked: Merck and Moderna's vaccine succeeded in a major melanoma trial. This week, a different version failed. BioNTech and Genentech stopped their Phase 2 colorectal cancer trial Friday. An independent board found survival numerically worse in vaccinated patients, not better.

BioNTech and its partner Genentech, part of Roche, didn't say the vaccine caused the imbalance directly. Their independent safety board found what it called a 'numerical imbalance' in survival between the two patient groups. It concluded more time wouldn't change the outcome. That's different from a straightforward safety alarm, but it's still a bad sign. The board first noticed the problem back in October 2025. Investors reacted fast: BioNTech's stock fell as much as 10% Friday.

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Does one failed trial mean personalized cancer vaccines don't work? Not necessarily. Merck and Moderna's success came in melanoma, a different cancer with its own biology, using a different vaccine design. But it's a reminder that this whole approach is still unproven outside the cases where it's already worked. The next real test is whether BioNTech's other cancer vaccine trials hold up better than this one did.