Moderna (NASDAQ:MRNA), an mRNA medicines and preventive vaccine developer, closed at $202.63, down 17.57%. Reports of a possible leak of late-stage personalized melanoma vaccine data sent shares lower today. Investors are waiting for the planned full Phase 3 presentation and Oct. 24 ESMO (European Society for Medical Oncology) data. Trading volume reached 49.3M shares, coming in about 148% above its three-month average of 19.9M shares. Moderna IPO’d in 2018 and has grown 989% since going public.
How the markets moved today
The S&P 500 (SNPINDEX:^GSPC) fell 1.22% to 7,663, and the Nasdaq Composite (NASDAQINDEX:^IXIC) lost 2.60% to 26,009. Among biotechnology peers, BioNTech (NASDAQ:BNTX) closed at $89.67, down 1.77%, while Novavax (NASDAQ:NVAX) closed at $9.99, down 9.26%.
What this means for investors
Trading in MRNA shares was briefly halted today after reports of a partial data leak involving its personalized cancer vaccine hit the market. The leaked data supposedly showed that Moderna’s intismeran autogene, when paired with Merck’s (NYSE:MRK) immunotherapy Keytruda, “reduced the risk of recurrence or death in certain melanoma patients by 42% compared with Keytruda alone.” This figure was lower than the Phase II results, which showed a 49% decline.
The full Phase III results weren’t supposed to be released in detail until this Saturday, and MRNA stock’s drop today suggests the leaked statistics fell short of the market’s sky-high expectations for the company. Even after today’s decline, Moderna shares have risen more than sixfold in 2026, as the company’s breakthrough cancer vaccine naturally offers immense upside if it can prove to be helpful in cases outside of melanoma as well.
I’m in no rush to add to (or sell) any of my MRNA position after this news. It seems like expectations were borderline staggering for Moderna after its stock rose roughly 600% this year, and the leak showed (supposed) figures that weren’t absolutely perfect. The long-term potential of Moderna’s personalized cancer vaccines is obviously immense (albeit perhaps high-risk, high-reward), but I’ll just be patient with this one.
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