Merck and Moderna melanoma vaccine cuts the risk of recurrence or death by 42%, but Moderna shares drop after a data leak
The New York Times reported on Oct. 22 that Merck and Moderna said their personalized cancer vaccine, intismeran autogene, given with Merck's Keytruda cut the risk of melanoma recurrence compared with Keytruda alone. AJMC reported that the combination reduced the risk of recurrence or death by 42% in patients with completely resected stage IIB to IV melanoma. CNBC reported that partial data appeared online early and that Moderna shares plunged. MarketWatch reported that Moderna's stock tumbled after a reported leak of the data. The Boston Globe reported that Moderna stock plummeted even after the data confirmed that the vaccine met key endpoints in the trial. The Financial Times reported that Moderna shares sank after the leaked data missed expectations. CNBC reported that the full presentation is scheduled for Oct. 24.
A personalized mRNA vaccine is built from the genetic profile of a patient's own tumor, so each dose is made for one person. A Phase 3 trial is the large final-stage test regulators weigh before deciding on approval. Stock prices reflect expectations, so a positive result can still lead to a drop when investors hoped for a larger benefit.
Melanoma that has been surgically removed can return, so patients and doctors look for treatments that lower the chance of recurrence. This result applies to a specific group, people with completely resected stage IIB to IV melanoma who take Keytruda. Anyone with a melanoma diagnosis can ask an oncologist whether a trial or an approved option fits their stage.
The result is a milestone for supporters of the approach. The New York Times headline said the vaccine cuts the risk of melanoma recurrence, and The Boston Globe reported that the data confirmed the trial met its key endpoints, which supports moving toward filings with regulators.
Investors read the numbers as short of what they wanted. The Financial Times reported that the leaked data missed expectations, and MarketWatch and CNBC reported that Moderna's stock fell sharply, which on this view shows the market had priced in a bigger benefit.
Confirmed: the vaccine plus Keytruda lowered the risk of recurrence or death by 42% versus Keytruda alone, and Moderna shares fell after the leak. Not confirmed: how the early data reached the public, and overall survival, which has not been reported. Watch the full presentation scheduled for Oct. 24 and any plans for a regulatory filing.
DailyDrop U.S. No. 19 · October 23, 2026