Shares fell about 21%, with the steepest losses after what appeared to be early trial results were posted online and then taken down, Investing.com reported. Moderna declined to comment. The data had been scheduled for presentation on Saturday.
In August, Moderna and Merck told investors their personalized cancer vaccine had worked. They did not say by how much. On Thursday, with the detailed numbers not yet officially published, Moderna shareholders lost about $20 billion.
Moderna shares traded at about $193.65 at 3:16 p.m. Eastern, down 21.2% from Wednesday's close of $245.81, after touching $180.80. At that price the company was worth about $77.3 billion, roughly $20.2 billion less than a day earlier.
The steepest selling followed reports that results from INTerpath-001, the companies' Phase 3 trial of the vaccine with Merck's Keytruda in melanoma, had appeared early. What appeared to be the results showed up on the medical news website Oncology Central around 12:30 p.m. Eastern and were taken down shortly afterward, according to Investing.com. The posted material has not been confirmed by the companies. The data had been scheduled for presentation on Saturday at the European Society for Medical Oncology congress.
Moderna declined to comment. Merck, Oncology Central and the congress organizer did not immediately respond to requests for comment from The Wall Street Journal.
Two moves, not one
The decline began before the posting. Moderna was down about 9.7% at noon, on a day when the Invesco QQQ Trust was down about 2.6% in early afternoon and biotech indexes slipped: the SPDR S&P Biotech ETF was down about 1% and the iShares Biotechnology ETF about 1.3% by mid-afternoon. The stock had pared that loss to about 6% just before 12:30 p.m. It had also dropped about 9% on Oct. 16 without any new clinical news.
The sharp break came after 12:30 p.m. In the 15 minutes that followed, shares traded as high as $235 and as low as $204.70 on 3.6 million shares, the session's widest 15-minute price swing. Selling continued into the afternoon.
Merck fell as much as about 4% on the day after the posting and was down about 1.3% at $147.97 at 3:16 p.m. For Merck, worth about $366 billion and anchored by Keytruda, the stakes are proportionally smaller.
What the price had assumed
One reason the stock is so sensitive to any news on the trial is how far it had already run. Moderna closed 2025 at $29.49 and had more than doubled, to $62.96, by Aug. 18. On Aug. 19, the day the companies said the trial met its main goal, recurrence-free survival, and a key secondary goal, distant metastasis-free survival, at a planned interim analysis, the shares jumped 177%. They fell 23.5% the next day, then climbed back. By Wednesday they stood at $245.81, nearly four times their level on the eve of the result and about 733% above where they began the year.
Most of that gain came after a result without numbers. Analysts had set out what they needed to see. Goldman Sachs analyst Salveen Richter wrote on Oct. 15 that a hazard ratio for recurrence-free survival below 0.70 would be needed to support the shares, according to a summary of the note published by TipRanks. Before the topline, Citi said a ratio of 0.72 or lower would be positive and 0.65 or lower a clear win, Fierce Biotech reported. In the earlier Phase 2b study, five-year data presented at this year's ASCO meeting showed a hazard ratio of 0.51 for recurrence or death.
Even after Thursday's drop, the stock sits well above Goldman's $137 price target and more than twice Citi's $80 target, set when Citi downgraded the shares to Sell on Sept. 30.
Unwind or reset
One reading is that this is a positioning unwind into a binary event. The trial's success on its primary and key secondary endpoints is company-confirmed, the posted material is unconfirmed, the stock was falling before it appeared, and the complete dataset, with subgroups, durability and safety, is scheduled for Saturday.
The other reading is that the valuation had run ahead of what any result could deliver, and that a stock up nearly fourfold since August on a single program had little room for uncertainty of any kind. On that view, the official data are more likely to confirm the reset than reverse it.
Thursday's tape cannot separate the two. It does show how much of Moderna's value now depends on one set of numbers.
What to watch
The presentation, late-breaking abstract LBA1 in the congress's Presidential Symposium, is scheduled for Saturday, Oct. 24, at 10:30 a.m. Eastern, with Moderna's investor webcast at 1 p.m. Eastern. The hazard ratios and confidence intervals for both endpoints, the maturity of overall survival data and the safety profile will decide which reading holds. Monday, Oct. 26, is the first full trading session after the presentation. Any statement from Moderna, Merck, the congress or Oncology Central on the early posting, or any earlier official release of the data, would move that timetable up.