Moderna ascends more than 175% from cancer vaccine breakthrough

It marks the first successful Phase 3 trial for an mRNA-based cancer therapy

Rowan Dunne

Published

2 hours ago

Investors were ecstatic this week as a long-sought breakthrough in cancer care finally came. Markets reacted with intensity when Moderna Inc (NASDAQ: MRNA) (ETR: 0QF) and Merck & Co Inc (NYSE: MRK) revealed that their experimental personalised skin cancer vaccine treatment had succeeded in a large final-stage study.

Moderna’s shares skyrocketed by as much as 177 per cent, while Merck posted a more modest gain of around 12 per cent. The jump reflected both the scale of the result and renewed confidence in a technology many had started to question after the Covid era.

The trial involved 1,137 patients whose high-risk melanoma had been fully removed by surgery. Participants received either the personalised vaccine together with Merck’s established drug Keytruda, or Keytruda alone, for about a year. The combination clearly extended the time patients stayed free of cancer returning and also reduced the chance of the disease spreading to other parts of the body.

This is the first successful final-stage result for any personalised cancer vaccine of this type and for any mRNA-based cancer treatment. Full details will appear at a future medical meeting and longer-term survival data is still being collected. Side effects matched those seen in earlier studies, with nothing new or unexpected.

Moderna’s billionaire chief executive Stéphane Bancel described the day as an extraordinary milestone, while Merck said it would start talks with regulators in the coming months.

Some experts urged caution though. The exact scale of the benefit remains unclear because detailed numbers have not yet been released. Others noted the practical challenge of making a unique vaccine for every patient. Political criticism of mRNA technology continues due to lingering pessimism over several adverse reactions from recipients during the pandemic-era, the ongoing Fauci scandal and condemnation from U.S. Health Secretary Robert F. Kennedy Jr.

Absolutely insane. Major breakthrough today

Moderna used AI to design an mRNA cancer vaccine that succeeded in a phase 3 trial

It's not approved yet and it's just a treatment, but it's a step towards AI eventually curing cancer

It's incredibly sad people are trying to stop… pic.twitter.com/6ZNgcTjBo7

— Alex Finn (@AlexFinn) August 19, 2026

Already ahead of the pack

Even before this week’s news, the Moderna–Merck programme ranked as the world’s most advanced cancer vaccine effort. Earlier mid-stage results had already shown it could cut the risk of cancer returning, and the large final-stage trial was fully under way.

BioNTech SE ADR (NASDAQ: BNTX) (FRA: 22UA) and Roche Holdings’ (OTCMKTS: RHHBY) similar personalised mRNA vaccine stands as the clear second-strongest contender. The main difference is progress: Moderna and Merck have stronger evidence from a proper head-to-head trial and a fully enrolled late-stage study. BioNTech’s most encouraging signs came from smaller, earlier tests, including lasting immune responses and hopeful survival results in a group of pancreatic cancer patients.

This announcement arrives alongside other global momentum. Russian scientists are running early tests of personalised vaccines for melanoma and bowel cancer while Cuba’s CIMAvax-EGF shot has already shown survival benefits in lung cancer and gained approval in several countries. Promising research on an mRNA injection for lung cancer also emerged in Iran last September.

Together they show a field that is steadily turning long-held hopes into real progress for patients in need, though challenges remain.

I have to say, when Merck called me last night with the mRNA cancer vaccine news (embargoed, of course), I literally yelped in reaction.

Consider this: Between this spring's Revolution Medicines success with a KRAS-targeted drug and now Merck and Moderna's success with an mRNA…

— Adam Feuerstein ✡️ (@adamfeuerstein) August 19, 2026