Leaked Moderna data showed a more modest result in its cancer trial

Detailed results from Moderna’s cancer-vaccine trial leaked two days before a scheduled presentation. The host said medical publication Oncology Central posted the data early, after which screenshots circulated on X. Moderna shares fell 26% intraday and closed down 18%.

The successful Phase 3 trial included 1,137 patients, but its results fell short of investor expectations: the relative reduction in the risk of cancer recurrence or death was 42%, compared with the 49% cited in earlier Phase 2 data. The host stressed that the trial had not failed; the results simply did not match elevated expectations. As described by the host, the treatment’s effect began to emerge after about six months, potentially making it less useful for fast-growing cancers.

Moderna’s approach involves sequencing a patient’s tumor, identifying its individual mutations, and making an mRNA vaccine that trains the immune system to recognize cancer cells. The vaccine is administered alongside Merck’s Keytruda, not as a standalone treatment. The combination aims to reduce the chance of cancer returning after surgery and may eventually be used against different cancer types. This is not a universal “cure for cancer”: the host said Moderna had been pursuing the personalized-drug idea since 2013, and CEO Stéphane Bancel had publicly discussed that direction.