Moderna shares fell 25.2 percent to $183.88 on Thursday, erasing roughly $24 billion of market value in the steepest single-day percentage drop on record for the company. The slide coincided with the release of detailed results from a late-stage melanoma study that had been posted early on an oncology website, forcing Moderna and partner Merck to publish ahead of a planned weekend presentation. Merck shares slipped about 1 percent.
The data and the leak
The trial, which enrolled more than 1,100 high-risk melanoma patients, showed that the experimental vaccine intismeran combined with Keytruda reduced the risk of recurrence or death by 42 percent versus Keytruda alone. The risk of distant metastasis or death fell 38 percent. Overall survival data are not yet mature, though the companies described the trend as favorable and said they are engaging with regulators. The findings cover the first two years after treatment and were slated for formal discussion at a European oncology meeting in Madrid on Saturday.
Valuation ran ahead of the readout
Shares had surged more than 500 percent this year before Thursday, a rally analysts attributed to bullish commentary from the companies themselves. William Blair's Myles Minter called the numbers "great" but said the reversal looked like a classic sell-the-news move. TD Cowen placed the 42 percent recurrence reduction in the "exceptional range" defined by medical experts.
The next question is breadth
Investors are now asking whether the benefit will translate to other tumor types at a valuation that prices in broad applicability. Regulatory conversations are underway, but the market's reaction suggests the bar for the next data set has moved higher.