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Moderna Sinks 17.6% Despite Melanoma Win

Moderna and Merck's personalised melanoma vaccine cut the risk of recurrence or death by 42% in a Phase 3 trial, yet the shares fell sharply after the data leaked online ahead of release.

Moderna (NASDAQ: MRNA) shares fell 17.6% on Thursday after data from its personalised melanoma vaccine trial leaked online hours before the official release. The mRNA medicines maker develops the vaccine with Merck. The results reportedly appeared first on Oncology Central, then on unverified X accounts, at about 5.30pm UK time.

Moderna closed at $202.63, down from $245.81 on Wednesday, after falling as much as 25% during the session. Volume reached 49.9m shares against 16.0m the day before.

MRNA.US

The two companies published the results just before 8pm UK time. Added to Keytruda, the vaccine cut the risk of recurrence or death by 42% (hazard ratio 0.58, 95% confidence interval 0.45 to 0.75) against Keytruda alone, in 1,137 patients with resected, or surgically removed, stage IIB to IV melanoma. The risk of distant spread or death fell 38%.

Two years on, 82.2% of vaccine patients were free of recurrence against 70.0% on Keytruda alone, and 88.5% were free of distant spread against 80.2%. Serious treatment-related side effects (grades 3 to 5) were 14.2% against 13.4%, with no new safety signals. Median follow-up was 24.6 months and overall survival data are immature.

Line chart of Moderna daily closing share price from July to October 2026, jumping in August and falling on 22 October
Moderna daily close, 20 July to 22 October 2026, US dollars.

The shares had risen almost fourfold from $62.96 on the 18th of August to Wednesday’s close, so a clearly positive result looked short of what was priced in. UBS called it “overall a strong data set”. BMO’s Evan Seigerman put the fall down to expectations:

Such a [stock] reaction likely reflects inflated expectations into the full data release, rather than a true indictment on the efficacy of the combo therapy.

Evan Seigerman, BMO

That is analyst opinion, and the effect of the leak cannot be separated from a sell-the-news reaction. The full data go to the ESMO cancer congress in Madrid on Saturday, in its Presidential Symposium, and the New England Journal of Medicine has accepted the paper. US trading resumes on Monday.

Asktraders News Team
Asktraders News Team
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The AskTraders Analyst Team features experts in technical and fundamental analysis, as well as traders specializing in stocks, forex, and cryptocurrency.

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