$MRNA: Up 6x This Year, Down 18% on Good News. What the Leaked Cancer Vaccine Data Actually Says
Moderna fell 17.6% after its Phase 3 melanoma vaccine data leaked early: a 42% recurrence-risk reduction against a 49% anchor the market had priced for. The trial-design detail the sellers skipped, the 50/50 Merck math, and the scenario zones into Saturday's ESMO presentation.
Moderna (NASDAQ: MRNA) closed Thursday at $202.63, down 17.6% on the day, after a late-stage trial report for its personalized cancer vaccine appeared online two days before its scheduled unveiling, then vanished. The data was good. The stock fell anyway, and it traded lower again in Friday's premarket, around $195. To understand why a positive readout erased roughly $17 billion of market value in a session, you need two numbers: 42 and 49. And one more for context: 697. That last one is Moderna's percentage gain this year before Thursday's drop, from $30.86 on January 2 to a closing high of $245.81 on Wednesday. This was the most crowded comeback trade in biotech, priced for perfection, and the leak delivered something slightly south of perfect.
The product is intismeran autogene, formerly mRNA-4157, a vaccine built individually for each patient from the mutations in their own resected tumor, given alongside Merck's Keytruda to prevent melanoma from coming back after surgery. The Phase 3 trial, INTerpath-001, is the first late-stage success for any individualized neoantigen therapy, a category the industry has chased for a decade. Topline success was announced in August, and the stock nearly doubled on the news, kicking off the vertical leg of the run from the mid-$50s. What the market was waiting for was the magnitude, scheduled for the European Society for Medical Oncology congress this Saturday, October 24, in a Presidential Symposium slot with simultaneous publication in the New England Journal of Medicine. That is the most prestigious stage in oncology, reserved for data meant to change practice.
Instead, the numbers escaped early. On Thursday a report containing the results was briefly posted online and quickly pulled, and Merck and Moderna then released the full dataset ahead of the congress. The headline: a 42% reduction in the risk of melanoma recurrence or death versus Keytruda alone. The anchor in every investor's head: 49%, the figure from the earlier Phase 2b study at three years of follow-up. The stock was priced off 49 and got 42, and sellers did not wait for the footnotes.
The footnotes, as it happens, are where the actual investment case lives. Whether 42 versus 49 is a disappointment or a statistical mirage depends on trial design details most of the stream has not read, and whether a $80.9 billion market cap survives contact with them depends on an approval clock and a cash runway that have hard dates attached. This briefing walks through all of it.
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The rest of this briefing is for paid members: what the leaked data actually shows once you adjust for who was enrolled, the landmark analysis that reads very differently from the headline, the 50/50 Merck economics and what intismeran is realistically worth, Moderna's cash clock against a commercial launch that has not been filed yet, and scenario-by-scenario price zones into Saturday's ESMO presentation and the November 6 earnings print.
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