Moderna Shares Recover From 10% Slide as Cancer Vaccine Data Fails to Top Sky-High Expectations

Moderna shares fell as much as 10% in premarket trading on October 26, extending a selloff that began October 22 when Phase 3 trial data for its personalized melanoma vaccine, intismeran autogene, leaked ahead of a scheduled presentation at the ESMO 2026 Presidential Symposium. At its worst point during that initial session, the stock dropped roughly 25% intraday before recovering some ground. By October 26 the stock was still down around 7% in premarket, with BioNTech falling about 3% in sympathy and Pfizer holding steady.

The Phase 3 INTerpath-001 trial, conducted with Merck, showed that intismeran autogene combined with Merck's immunotherapy Keytruda reduced the risk of melanoma recurrence or death by 42% compared to Keytruda alone in patients with completely resected higher-risk or advanced melanoma, a result that was statistically significant. When measured after six months, once patients had completed the immunization regimen, the risk reduction reached 58%. The data were positive and the treatment is widely considered likely to win regulatory approval.

The selloff reflects a gap between clinical success and investor expectations. Moderna had rallied more than 530% in 2026 ahead of the data release, and analysts noted that expectations were "incredibly high" heading into the Phase 3 readout. Critics noted the Phase 3 results did not meaningfully improve on earlier Phase 2b findings, and skeptics questioned whether the personalized, mRNA-based vaccine would prove to be the best available option once on the market. Oncologists, by contrast, have called the data a major clinical advancement in melanoma, a cancer that accounts for only about 1% of skin cancers but causes the large majority of skin-cancer deaths. The stock partially recovered from its 10% dive on October 26 as investors digested the nuances of the data, though muted commercial expectations continued to weigh on the shares.