Moderna stock plunged 18% after cancer vaccine data leak
Dubai: Moderna shares plunged 18 per cent on Thursday after full results from its personalised melanoma vaccine trial leaked online before the official release. Shares of Merck, its development partner, fell 1.8 per cent. The data confirmed the vaccine works, however, investors were expecting far more. The leak was first tracked on X, when unverified accounts posted details of the vaccine, known…
Moderna's shares dropped 18% on Thursday following the leak of full results from its personalized melanoma vaccine trial ahead of the official release. Merck, the company's development partner, saw a 1.8% decline in its shares. The data revealed that the vaccine, named intismeran autogene (mRNA-4157 or V940), proved effective; however, investors were anticipating even more significant results.
The leak was initially detected on X, where unverified accounts shared details of the vaccine, which remains unverified. The pharmaceutical companies involved were planning to present the full results at the European Society for Medical Oncology meeting in Madrid on October 24. Nevertheless, Moderna had already released the report on October 22, 2026.
The trial tested an individually tailored vaccine, administered alongside Merck's Keytruda, the company's top-selling drug. The final-stage study involved over 1,100 patients at high risk of recurrence after melanoma surgery. A control group received Keytruda alone. The results showed that the vaccine reduced the risk of cancer recurrence by 42% and decreased the chance of metastasis by 38%. This marks the first positive final-stage trial for any mRNA-based cancer therapy.
Despite the positive trial results, shares fell due to investors' expectations of even greater outcomes. In August, both companies announced a substantial and clinically meaningful decrease in tumor recurrence. While no figures were provided for comparison, investors were optimistic about the results, causing a significant increase in Moderna and Merck shares.
Moderna's stock trades more than 200% above its price before the August announcement, even after the recent sell-off. An earlier study set the benchmark, showing a 49% reduction in recurrence or death risk and a 59% reduction in distant spread or death risk. Analysts compared the new numbers against these results. Wall Street treated the melanoma shot as a test case for Moderna's broader oncology franchise built on the same technology. The companies are running trials in lung cancer, bladder cancer, and other tumor types.
Stéphane Bancel, Moderna's CEO, expressed his belief that mRNA technology could revolutionize cancer treatment by enabling personalized therapies. The INTerpath-001 results mark a defining moment for this vision, demonstrating what is possible through innovative medicine-making approaches. The CEO emphasized that these results reinforce Moderna's confidence in the potential of mRNA to fundamentally change cancer treatment.
The next test lies in ongoing trials for kidney and bladder cancer, which will determine the extent of the breakthrough's impact.
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