Moderna plunges 25% as leaked cancer vaccine data falls short of lofty expectations

Moderna lost a quarter of its market value in trading on Thursday before paring some of the loss to close down 17.6%. Investors dumped the stock after trial results for the cancer vaccine it is developing with Merck were released ahead of schedule, even though the results themselves were positive, CNBC reported. Merck shares ended the day down 1.8%.

In August, the two drugmakers announced that the phase III trial had met its main goals but did not disclose details. The full data was scheduled to be presented on Saturday at the European Society for Medical Oncology (ESMO) conference in Madrid. On Thursday, however, details about the vaccine began circulating on X from unverified sources. One account posted a report attributed to Oncology Central, an industry news source, detailing the findings, though the accompanying web link was not live, as Bloomberg reported. ESMO confirmed the leak, stating that the publication embargo had been breached.

The new data showed that the companies’ treatment, called intismeran, combined with Merck’s cancer drug Keytruda, reduced the risk of melanoma recurrence or death by 42% versus Keytruda alone, CNBC reported.

The experimental vaccine uses messenger RNA to help the immune system recognize and attack cancer cells. It is customized for each patient based on the tumor’s genetic profile: after the melanoma is removed, scientists identify mutations specific to the cancer cells and encode them in mRNA. The process takes about six weeks, but Merck CEO Robert Davis told CNBC last week that he expects the companies to shorten that timeline, potentially allowing the vaccine to reach more patients more quickly.

The data was better than some analysts had expected, Barron’s noted. UBS analyst Michael Yee had previously suggested that Moderna stock could rally 10-20% if the reduction in the risk of melanoma recurrence or death reached 35%. Leerink Partners analyst Daina Graybosch had indicated that a result roughly in line with what Moderna achieved could potentially transform treatment.

Even so, investors may have been disappointed by individual trial findings, Barron’s explained. The combination therapy reduced the risk of cancer spreading to distant organs or tissues or death by 38%. TD Cowen analyst Tyler Van Buren said that figure fell short of Wall Street’s elevated expectations, the Wall Street Journal reported.

“There appears to be a sell-the-news reaction playing out here,” William Blair analyst Myles Minter wrote, noting that Moderna shares remained up more than 500% this year, even after Thursday’s plunge.

Moderna has been one of the top performers in the S&P 500 this year, driven by successful cancer vaccine trial results. On August 19, when the company announced the preliminary findings, its stock jumped 120%. Merck shares have also repeatedly hit all-time highs since the results were announced, MarketWatch reported.