Moderna and Merck's personalized cancer vaccine cuts melanoma death or recurrence risk 42%

Trial results

Moderna and Merck said on Thursday, 22 October, that their personalised mRNA vaccine, intismeran, cut the risk of melanoma recurrence or death by 42% when given with Merck's immunotherapy Keytruda, compared with standard treatment. The Phase 3 trial enrolled 1,137 patients whose stage IIB-IV melanoma had been surgically removed, and patients were randomised 2-1 to receive either the combination or Keytruda alone. The companies also reported a 38% lower risk that the cancer spreads or that the patient dies. After two years, 82.2% of patients on the combination remained cancer-free, compared with 70% of those on Keytruda alone. Longer-term survival data were not yet available, although the companies said investigators had seen a "favourable trend". Side effects matched earlier studies and included fatigue, chills and pain at the injection site.

Vaccine plus Keytruda82.2%

Keytruda alone70%

Vaccine plus Keytruda

82.2 %

Keytruda alone

70 %

Data from the article text

How the results reached the public

Moderna and Merck reported in August that the trial had succeeded but gave no details, saying the data would be presented at the European Society for Medical Oncology (ESMO) congress in Madrid. On Thursday, screenshots circulating on X showed that the website OncologyCentral had published part of the results ahead of the scheduled presentation. ESMO said on X that the embargo had been breached, so the society published the information itself and lifted the embargo on the full dataset. The companies then released top-line results, and the complete data is due to be presented on Saturday, 24 October, in Madrid.

Market reaction

Moderna shares closed more than 17% lower on Thursday after the findings leaked, according to The Independent, even though the stock had nearly quadrupled between August and Wednesday's close. Handelsblatt reported a steeper intraday fall of up to 25%, to $181, after the shares had traded at about $63 before the August announcement and climbed to around $245 in the weeks that followed. Merck shares fell about 1.8%. Several Wall Street analysts had hoped for a cut in recurrence risk of 40% or more, so the reported 42% reduction sits just above that expectation.

Expert and company reactions

Moderna CEO Stéphane Bancel said in a statement that the company has long believed the technology could produce treatments tailored to each patient's tumour.

“From the beginning, we believed mRNA technology could make it possible to develop cancer treatments uniquely matched to each patient's tumor.”

Bancel said the companies are preparing to file for US regulatory approval and expect to launch the vaccine in 2027. Hussein Tawbi, a melanoma expert and trial investigator at the University of Texas MD Anderson Cancer Center, addressed the statistics directly.

“This is highly statistically significant. It is not by chance.”

Robert Vonderheide, president-elect of the American Association for Cancer Research, said the response among patients and clinicians was one of hope.

“Everyone is very hopeful that this will be a new way to treat patients with melanoma.”

What comes next

The full dataset covering the first two years after treatment is scheduled for presentation at ESMO on 24 October, and its publication in the New England Journal of Medicine has been accepted. According to The Independent, the findings are the first data showing that a custom vaccine paired with an immune-boosting drug can halt the disease. The companies are preparing US regulatory filings, with a launch expected in 2027. Longer-term survival data are still pending.