Moderna Short Sellers Hit With $4.8 Billion Loss as Stock Soars

Moderna Inc. short sellers suffered an estimated $4.8 billion in mark-to-market losses on Wednesday as the biotech company’s shares more than doubled following encouraging results from a late-stage cancer therapy trial.

According to data analytics firm ORTEX, Moderna stock climbed to $159, putting investors betting against the company down nearly $100 per shorted share compared with the previous closing price of $62.96. Shares briefly reached a high of $163 before retreating to around $148.30.

The dramatic Moderna stock surge has increased the possibility of a short squeeze, as bearish investors may be forced to buy shares to close their positions and limit further losses.

Peter Hillerberg, co-founder of ORTEX, said the scale of losses facing short sellers could create significant pressure to cover positions. While the rally is supported by a substantial clinical catalyst, he noted that short covering could add momentum and push Moderna shares even higher.

ORTEX estimated that short interest represented approximately 13.5% of Moderna’s free float as of Wednesday. That level places the biotechnology company among the most heavily shorted large-cap stocks and leaves a sizable group of investors exposed to further losses if the rally continues.

The sharp rise in Moderna shares followed positive results involving the company’s personalized mRNA cancer therapy, which is being developed in partnership with Merck & Co. The treatment was tested alongside Merck’s cancer drug Keytruda in a late-stage clinical trial.

Moderna reported that the combination reduced the risk of skin cancer recurrence and the disease spreading, strengthening investor optimism over the potential of personalized mRNA technology beyond the company’s established vaccine business.

The clinical trial results triggered an extraordinary wave of buying in Moderna stock, while short sellers rushing to exit bearish positions may have intensified the move.

With shares posting a triple-digit percentage increase at their intraday peak, Moderna was on course to record its largest one-day percentage gain, marking a dramatic reversal for one of the market’s most heavily shorted biotech stocks.