Moderna shares plunge on apparent cancer vaccine data leak

Moderna's shares experienced a significant drop of over 25% on Thursday following what seemed to be an unauthorized release of clinical trial results for their experimental cancer vaccine. The news appeared on Oncology Central at around 12:30 p.m. ET but was removed shortly thereafter. The trial data was initially set to be presented at the ESMO Congress the following day.

According to the prematurely published report, when combined with Merck's Keytruda, the personalized mRNA cancer vaccine showed a 42% reduction in the risk of melanoma recurrence or death compared to Keytruda alone. After two years, 82.2% of patients receiving the vaccine-therapy combination were alive and cancer-free, compared to 70% of patients receiving Keytruda alone.

The Phase 3 clinical trial included 1,137 participants. Both Moderna and Merck are working together to develop this vaccine, known as intismeran autogene, a personalized treatment designed to help the immune system recognize and combat cancer cells post-surgery. Earlier in August, the companies had confirmed that the trial had met its primary objectives, but had not released any further details. When contacted, Moderna declined to provide any comment on the matter.