Moderna Shares Plunge 26% After Melanoma Vaccine Data Leak

Moderna shares plunged after Phase 3 results for the company's personalized melanoma vaccine surfaced ahead of a planned disclosure, as positive efficacy findings failed to prevent a sharp pullback in the stock.

Shares fell to an intraday low of $180.80, down 26.45% from the prior close, before rebounding to $202.63 at the end of the session. Moderna closed down 17.57%, with the low 28.95% below its Oct. 21 high of $254.48.

Moderna and Merck developed the treatment together. Trial results showed the combination lowered the risk of melanoma recurrence or death by 42%, and the risk of distant metastasis or death by 38%. Those are separate outcomes from the Phase 3 study of the personalized cancer vaccine.

Moderna's shares had advanced more than 500% this year before the retreat, and the $254.48 mark on Oct. 21 was the stock's recent high. Full disclosure of the trial results was scheduled for Oct. 24, the day after the results surfaced.