Stock Market Today, Oct. 22: Moderna Stock Plummets 18% on Melanoma Vaccine Data Leak Reports
Personalized cancer vaccine material allegedly circulated online ahead of formal Phase 3 results, today, Oct. 22, 2026.
On October 22, Moderna's stock plummeted 18% following reports of a potential leak regarding its personalized melanoma vaccine data. The company's shares fell to $202.63 from $202.63. The leak reportedly indicated that Moderna's intismeran autogene, when combined with Merck's Keytruda, reduced the risk of recurrence or death in certain melanoma patients by 42% compared to Keytruda alone.
This figure was lower than the 49% decline observed in Phase II trials. Trading volume surged to 49.3 million shares, about 148% above the three-month average of 19.9 million shares. While Moderna's stock has risen over sixfold in 2026, the leak has raised doubts among investors about the company's prospects.
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