Moderna and Merck cancer vaccine cuts recurrence risk by 42 percent

Moderna and Merck released detailed Phase 3 results for their personalised melanoma vaccine intismeran at the ESMO conference in Madrid on Thursday, showing a 42 percent reduction in the risk of disease recurrence compared with standard treatment.

Why it matters: The figures are the first detailed confirmation behind the companies' August claim that the trial met its endpoints, and they arrive hours after a reported leak of the data sent Moderna shares down 25 percent before either company had confirmed any number.

Data as of MarketWatch report of October 22, 2026, at 14:10 ET, and TipRanks report of October 22, 2026; Moderna gave no comment to MarketWatch at that time and neither company had then confirmed that the leaked material was the trial data. Update, October 22: STAT report from Madrid of October 22, 2026, read in its openly published portion (the remainder is subscriber-only), reporting the companies' release of the detailed results at ESMO and the 42 percent recurrence-risk figure. Developing item.

Latest: Moderna and Merck released the detailed results of their Phase 3 melanoma trial at the European Society for Medical Oncology conference in Madrid on Thursday. The personalised mRNA vaccine, intismeran autogene, reduced the risk of disease recurrence by 42 percent compared with standard treatment, and patients lived significantly longer without their cancer returning, STAT reported from Madrid. Oncologists cited by STAT called the results an important advance for melanoma treatment.

Moderna’s stock plunged 25 percent in Thursday afternoon trading, and was briefly halted for volatility, after data for the cancer vaccine it is developing with Merck was reportedly published by a cancer news site and then taken down, MarketWatch reported. Merck shares fell 1.4 percent. The vaccine, intismeran, is a personalised treatment made from a patient’s own DNA and given with Merck’s Keytruda, and the Phase 3 trial tested whether it prevents recurrence in melanoma patients.

The two companies said in August that the study met its primary and secondary endpoints but released no figures at the time. A Moderna spokesperson said the company had no comment on the reported leak, and spokespeople for Merck and the conference organiser did not immediately respond to requests for comment, MarketWatch reported.

Moderna and Merck cancer vaccine cuts recurrence risk by 42 percent

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