Moderna Shares Sink About 25% After Cancer-Vaccine Data Leaks Early

what happened

Moderna shares dropped about 25% after details of a tightly held mRNA cancer-vaccine study appeared on social media. According to the Wall Street Journal, the decline puts the Cambridge, Mass., biotech on course for its steepest fall since its initial public offering.

In August, Moderna and partner Merck said the vaccine had kept melanoma from coming back or spreading. The result was called remarkable, but experts stressed the need to review the full study details. The data was scheduled for release on Saturday at the European Society for Medical Oncology conference. Screenshots posted on X suggest the cancer website OncologyCentral published some of the results on Thursday.

Shares of Merck, which co-develops the vaccine with Moderna, fell 1.5%. Moderna declined to comment, Merck did not immediately respond, and representatives for OncologyCentral and the ESMO conference did not immediately respond to requests for comment.

why it matters

The key issue for markets is timing as well as the drug itself. An early leak deprives investors of a full look at the data at the planned presentation, so the share move reflects uncertainty until official results are published.

market impact

Moderna and Merck shares: early data leak pressures stock until full results are released

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