BioNTech Misses BNT113 Phase 3 PFS Endpoint, Leaving Overall Survival As Its Remaining Path

BioNTech’s mRNA cancer immunotherapy BNT113 missed one of its two primary endpoints in the phase 3 portion of Ahead-Merit, failing to show a statistically significant progression-free survival benefit when added to Keytruda versus Keytruda alone. The company is continuing the trial in metastatic head and neck cancer because overall survival data remain immature and the study’s statistical design still allows an overall survival win to define the trial as positive.

The miss is a setback for a program that had been moving in a more favorable market narrative for mRNA cancer vaccines. In August, Merck & Co. and Moderna’s phase 3 data had raised expectations for the field, and Fierce Biotech reported BioNTech’s share price had risen 20% on the strength of that external readthrough. On Tuesday, that optimism reversed: BioNTech’s stock fell 5% to $91.32 in premarket trading from a Monday close of $95.84, while Moderna also dipped 3%.

The data

Ahead-Merit is an open-label study testing whether BNT113 plus Keytruda can outperform Merck’s checkpoint inhibitor used as a monotherapy in patients with HPV16-positive head and neck squamous cell carcinoma. BioNTech said the combination was statistically no better than single-agent Keytruda on progression-free survival, triggering the primary-endpoint miss.

The independent data monitoring committee nevertheless recommended that the trial continue as planned to assess overall survival, the other primary endpoint. That matters because BioNTech is arguing the mechanism may work on a delayed timetable. BNT113 is designed to trigger immune responses against the HPV16 oncoproteins E6 and E7 and to boost pre-existing T-cell immunity, a profile the company says could complement the T-cell responses induced by Keytruda.

Chief Medical Officer Özlem Türeci said the phase 3 data show BNT113 “is engaging its intended therapeutic mechanism” and argued that immune-mediated antitumor effects can build and deepen over time. That is the core case for staying in the study despite the PFS failure: a therapy that does not delay progression early enough to move that endpoint could still produce more durable benefit later.

What The Miss Means

That explanation is plausible, but it is no longer the favored interpretation. BMO Capital Markets said it is plausible that the immune response triggered by BNT113 takes time to fully deepen, leaving the door open to an overall survival improvement, while also saying the PFS miss makes the firm “significantly” less confident that BNT113 will extend overall survival.

There is precedent for that pattern in immuno-oncology. Fierce Biotech noted that a phase 3 Keytruda trial in head and neck squamous cell carcinoma missed progression-free survival but later showed an overall survival benefit that persisted across five years of follow-up. But that precedent does not remove the broader risk: many oncology trials that miss PFS also go on to fail on overall survival.

For BioNTech, the readout does more than hurt one asset. BNT113 differs from Moderna’s personalized intismeran autogene because it encodes a fixed set of antigens rather than antigens tailored to each patient’s tumor mutations. A positive overall survival result would support the idea that fixed-antigen mRNA immunotherapy can still compete in cancer. A failure would make that claim materially harder to finance and defend.