Moderna shares fall about 25% intraday after reported cancer-vaccine data leak

Moderna shares fell about 25% intraday on October 22 after reports that partial trial data for its experimental melanoma vaccine, developed with Merck, had leaked. The data were scheduled for presentation this weekend at the European Society for Medical Oncology, or ESMO, conference; melanoma is a type of skin cancer.^[1][2]

The companies subsequently announced positive results from INTerpath-001, a Phase 3 trial—a late-stage study assessing treatment effectiveness and safety. It tests the personalized mRNA vaccine intismeran autogene alongside the immune-system treatment Keytruda. The vaccine is designed to help the immune system recognize features of an individual patient’s tumor. The companies described positive recurrence-free and distant metastasis-free survival results, measuring time without cancer returning or spreading to distant parts of the body.^[3]

The sell-off shows that expectations for the treatment’s commercial value came under pressure even as the companies assessed the clinical results positively. Coverage also reported that analysts considered the findings clinically meaningful. How the benefit measures up against investors’ earlier expectations therefore remains central to valuation.^[4][3]

For vaccine developers, the size and durability of any reduction in cancer recurrence or spread can influence future physician adoption and potential revenue. Partial data leave those commercial prospects uncertain. Investors also reassessed a rival developer: coverage reported that BioNTech shares dipped the same day.^[1][3][5]

Impact

What to watch next

• The ESMO presentation over the October 24–25 weekend: fuller efficacy and follow-up information will help assess whether the positive results described by the companies support expectations for the treatment’s commercial value.^[2][3]