Moderna shares plunge after apparent leak of cancer-vaccine trial data

Illustration of a gloved hand holding a cancer-vaccine vial beside Moderna branding and stock-market graphics. — MarketWatch photo illustration/iStock

Summary

Moderna shares fell more than 24% Thursday after an apparent early release of Phase 3 data for its experimental melanoma treatment with Merck.
The report appeared on Oncology Central around 12:30 p.m. ET and was removed; Merck declined to comment to Investing.com.
The reported figures showed benefit versus Keytruda alone, but companies had not confirmed them and the full results were still scheduled for presentation at ESMO.

Shares slide after apparent early release

Moderna shares fell more than 24% Thursday after a report containing purported results for its experimental cancer vaccine appeared online ahead of a scheduled medical-conference presentation. Investor’s Business Daily reported the shares at $186.75, while Investing.com put the decline at more than 25% during the session. Merck shares also fell, with Investing.com reporting a drop of more than 3%. The outlets’ figures differ, but both described a sharp selloff tied to the apparent release.^{[1] [2]}

Investing.com said the report briefly appeared on medical news site Oncology Central at about 12:30 p.m. ET and was removed shortly afterward. The findings were due to be presented at the European Society for Medical Oncology Congress. Merck declined to comment to Investing.com; Investor’s Business Daily said representatives of both companies had not immediately returned its requests for comment. Neither company had publicly confirmed the leaked details in those reports.^{[1] [2] [4]}

What the reported figures said

According to Investing.com’s account of the briefly published report, the personalized mRNA treatment intismeran autogene, given with Merck’s immunotherapy Keytruda, reduced the risk of melanoma recurrence or death by 42% compared with Keytruda alone. It reported that 82.2% of patients receiving the combination were alive and cancer-free at two years, versus 70% of those receiving Keytruda alone. The Phase 3 trial enrolled 1,137 patients. Those figures remain attributed to the temporary report, not to a company-confirmed release.^{[1] [3]}

Merck and Moderna had announced in August that the trial met its primary endpoint of recurrence-free survival and a key secondary endpoint of distant metastasis-free survival. Their announcement described the results as statistically significant and clinically meaningful but did not publish effect sizes. The companies said the study would continue to assess other endpoints, including overall survival. The later ESMO presentation was expected to provide the fuller data.^{[3] [4]}

Why the reaction is not yet clear

The available reporting establishes the timing of the selloff and the apparent leak, but not a definitive explanation for why investors sold so aggressively. The reported efficacy figures were favorable against Keytruda alone; they do not, by themselves, establish that investors judged the treatment unsuccessful. Investor’s Business Daily characterized the leaked data as mixed but did not provide further trial details in its accessible report. Without confirmed results or company comment, the market’s interpretation remains uncertain.^{[1] [2]}

Intismeran is tailored to mutations in an individual patient’s tumor and is being developed jointly by Moderna and Merck. The treatment is investigational, and the Phase 3 study tested it after surgery in patients with resected stage IIB-IV melanoma. Until the companies release or present the complete data, the leak’s accuracy, the full benefit-risk picture and the implications for the program remain unresolved.^{[3] [4]}

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