Moderna and Merck's personalized cancer vaccine, used alongside Keytruda, significantly extended recurrence-free time for melanoma patients in its first late-stage trial, according to CNBC. Moderna's stock climbed sharply on the news.
Key facts
- The Moderna-Merck combination regimen significantly extended the time patients lived without their melanoma returning, compared with Keytruda alone.
- The result came from the first late-stage trial of the personalized cancer vaccine.
- Moderna's stock rose 177% during the trading day, according to CNBC.
- Merck's shares jumped 12% following the announcement.
- The news was reported by CNBC on August 19, 2026.
A personalized cancer vaccine developed by Moderna and Merck has shown promise in its first late-stage clinical trial for melanoma, according to CNBC. The combination regimen significantly extended the time patients lived without their melanoma returning, when compared with Merck’s cancer drug Keytruda used alone.
The findings mark an early but closely watched milestone for the two companies, which have been developing the personalized vaccine to be used in combination with Keytruda. CNBC reported that the regimen delivered a significant improvement in recurrence-free time for patients in the study.
Investors reacted strongly to the results. Moderna’s stock climbed dramatically over the course of the trading day on August 19, 2026, with CNBC’s reporting reflecting successive gains that reached 177% by late afternoon. Merck’s shares rose 12% on the same day, according to CNBC.
The rapid rise in Moderna’s share price was reflected across multiple updates from CNBC through the day, which tracked the stock’s climb as the market absorbed the trial data. The scale of the move underscored the significance investors attached to the late-stage results.
The trial focused on melanoma, a form of skin cancer, and measured how long patients went without their cancer returning. According to CNBC, the vaccine plus Keytruda combination outperformed Keytruda on its own on this measure.
CNBC’s coverage did not detail additional trial figures beyond the reported outcome and the movements in the companies’ share prices.
Why it matters
Personalized cancer vaccines represent a new approach to treating cancer, tailoring therapy to individual patients, and a positive late-stage result could signal progress toward wider availability. The sharp market reaction reflects the potential commercial and medical stakes for both Moderna and Merck.
Frequently asked questions
What did the Moderna-Merck cancer vaccine trial show?
According to CNBC, the combination of the personalized vaccine and Keytruda significantly extended the time melanoma patients lived without their cancer returning, compared with Keytruda alone.
How did the companies' stocks react?
CNBC reported that Moderna's stock rose 177% during the trading day on August 19, 2026, while Merck's shares jumped 12%.
What type of cancer was studied?
The trial studied melanoma, and measured the time patients lived without their melanoma returning.