Archive · 20 Aug 2026
Cancer Vaccine Trial Sends Moderna Shares Soaring 177 Percent
Moderna and Merck are testing a personalized vaccine for some people with melanoma, a serious type of skin cancer.
The vaccine uses mRNA technology and is given with Merck’s Keytruda drug.
In a large Phase 3 trial, the treatment did better than Keytruda alone at keeping the cancer from returning.
It also lowered the chance that the cancer would spread to other parts of the body.
More than 1,100 people took part in the study.
The companies have not yet applied for approval in the United States.
They plan to study whether the treatment helps patients live longer overall.
The encouraging results made Moderna’s shares rise 177% and Merck’s shares rise 13%.
The vaccine is also being tested against several other cancers.
Moderna shares surged 177% on Wednesday, August 19, after positive initial results from a late-stage personalized cancer-vaccine trial.
The experimental mRNA vaccine is being developed with Merck and is combined with Merck’s Keytruda immunotherapy.
The Phase 3 trial involved more than 1,100 patients with higher-risk or advanced melanoma removed through surgery.
The combination extended the time patients lived without their melanoma returning and reduced the risk of cancer spreading.
Merck shares rose 13%, while both companies said additional survival data will be studied before seeking US regulatory approval.
- Who
- Moderna, Merck & Co., and more than 1,100 patients with higher-risk or advanced melanoma.
- What
- An experimental personalized mRNA cancer vaccine, used with Keytruda, met key goals in its first late-stage trial.
- When
- Wednesday, August 19; the companies said further data will be presented at an upcoming international medical meeting.
- Where
- The trial involved patients, and potential approval would be sought from the US drug regulator.
- Why
- The treatment extended the time without melanoma returning and reduced the risk of the cancer spreading compared with Keytruda alone.
- Moderna share move
- Shares rose 177% by the close of Wednesday’s session.
- Merck share move
- Shares climbed 13% on the news.
- Treatment
- A personalized mRNA vaccine combined with Merck’s Keytruda immunotherapy.
- Trial phase
- Phase 3, the first late-stage trial reported for the vaccine.
- Trial population
- More than 1,100 patients with higher-risk or advanced melanoma removed through surgery.
- Study result
- The combination extended recurrence-free time and reduced the risk of distant cancer spread.
- Regulatory timing
- Merck officials said an application could be submitted to US regulators in the next few months, though no specific timeline was given.