Key Highlights

● Moderna closed at $202.63 on October 22 after trading around $183 at its low.

● About $24 billion in market value was erased.

● The Phase 3 trial enrolled more than 1,100 patients and showed a 0.58 hazard ratio.

● Moderna's shares had climbed more than sixfold this year.

Shares of Moderna (NASDAQ:MRNA) fell hard on Thursday, October 22, 2026, closing at $202.63 and finishing as one of the weakest performers in the S&P 500, after late-stage data for its experimental melanoma vaccine appeared before its scheduled presentation. The slide made Moderna one of the standout losers on the Nasdaq-100 on a day already dominated by a tech selloff.

The decline was dramatic even by biotech standards. At its intraday low, around $183, the stock was down so sharply that it would have marked its steepest one-day drop on record. Shares recovered some ground into the close, but about $24 billion in market value was erased. Reports differed on the size of the closing move.

What the data showed

The results come from INTerpath-001, a Phase 3 trial of intismeran, Moderna's individualized cancer vaccine, given alongside Merck (NYSE:MRK)'s immunotherapy Keytruda in patients with high-risk melanoma. The study enrolled more than 1,100 patients.

According to the data that reportedly leaked, the combination reduced the risk of cancer recurrence or death, with a hazard ratio of 0.58, and also cut the risk of distant metastasis or death. However, the benefit on recurrence was smaller than the one seen in the earlier Phase 2b trial, and that comparison appeared to weigh on sentiment.

Full results are due on Saturday at the European Society for Medical Oncology congress in Madrid.

Analysts liked the data, the market did not

Wall Street analysts were broadly positive about the science. A UBS analyst described the results as "solid data" and characterized the reaction as a "sell the news" event. A William Blair analyst similarly called the data great while describing the move as sell-the-news. TD Cowen called the results compelling.

Those analysts framed the gap between their views and the stock's reaction as a sell-the-news response. Moderna's shares had climbed more than sixfold this year before Thursday's session began.

Merck, Moderna's partner on the program, also fell, closing at $147.24. Market reports described its move, too, as a sell-the-news reaction to the same data.

A strong day for health care otherwise

Moderna's slide was an outlier. The S&P 500 health care sector hit a record high despite its drop, as investors rotated into defensive stocks. Johnson & Johnson (NYSE:JNJ) and Amgen (NASDAQ:AMGN) both rose.

The broader market was split. The Nasdaq Composite fell 694.00 points to 26,008.86, its steepest drop since June 5, as AI and chip stocks were hammered after heavy spending plans from Meta Platforms (NASDAQ:META) and cautious guidance from Lam Research (NASDAQ:LRCX). The Nasdaq-100 lost about $1.32 trillion in market value.

Beneath that, about two of every three S&P 500 stocks rose, according to market reports. Consumer staples had their best day since April 2025, Treasuries rallied, and the Dow Jones Industrial Average edged up 11.89 points to 52,867.98.

Moderna Faces Monday After the Full Presentation

The key event is Saturday's full presentation at ESMO in Madrid. Investors will look for detail on the durability of the benefit, how different patient groups responded, and how the Phase 3 results compare with the earlier trial once fully laid out. Any comment from Moderna or Merck on regulatory plans could also move the shares. Because the data appeared before the scheduled presentation, Monday's trading will be the first chance for the market to react to the complete picture.