Researchers reported encouraging early results from the first phase 3 trial of the personalised melanoma vaccine developed by Moderna and Merck, bringing the treatment a step closer to potential regulatory approval.
The companies said the mRNA-based vaccine, used alongside Merck's Keytruda immunotherapy, met the study's primary endpoints in more than 1,100 patients with high-risk or advanced melanoma whose visible tumours had been completely removed through surgery.
Reduced risk of recurrence
According to preliminary data, the combination therapy significantly extended the period patients remained free of disease recurrence compared with treatment using Keytruda alone.
It also reduced the risk of the cancer spreading to distant parts of the body, reinforcing positive findings from an earlier phase 2 trial.
"This is an important moment for medicine and for patients," Moderna chief executive Stéphane Bancel said.
Moderna’s mRNA vaccine combined with Merck’s immunotherapy Keytruda succeeded in a late-stage trial for skin cancer, the companies said, sending shares of the vaccine maker up 60% in premarket trading. https://t.co/AbE55DcOOj pic.twitter.com/qP9KEh1ECg
— CNN (@CNN) August 19, 2026
Survival benefit still under review
The phase 3 study will continue to assess whether the treatment improves overall survival.
Full results are expected to be presented at a forthcoming international medical conference, while the two companies plan to begin discussions with regulators in the coming months on submitting approval applications.
Aggressive form of skin cancer
Melanoma accounts for around 1% of all skin cancers, but is responsible for the vast majority of deaths linked to the disease.
Most recurrences occur within the first two to three years after initial treatment and tumour removal.
Dr Jane Healy, head of early oncology development at Merck, described the benefits of the vaccine-Keytruda combination as "clinically meaningful".
She added that the treatment was generally well tolerated, with side effects similar to those associated with other established vaccines.
How the vaccine works
The vaccine uses mRNA technology and is customised for each patient.
Because every tumour contains different genetic mutations, the treatment is designed to target the unique characteristics of an individual's cancer, training the immune system to recognise and destroy cancer cells.
Its effect is reinforced by Keytruda, which helps the immune system mount a stronger response against tumours.
Moderna stock rockets more than 90% after cancer vaccine succeeds in late-stage trial.
— CTech (@Calcalistech) August 19, 2026
Moderna's personalized mRNA vaccine, combined with Merck's Keytruda, reduced melanoma recurrence and met a secondary goal for preventing the disease from spreading.https://t.co/KRXsy5szwy
Potential beyond melanoma
The companies said the results have implications beyond melanoma and strengthen the case for personalised cancer vaccines more broadly.
Clinical trials are already under way to evaluate the approach in other cancers, including:
- Non-small-cell lung cancer
- Bladder cancer
- Kidney cancer
Shares surge
The announcement also had an immediate impact on financial markets.
Moderna shares rose by about 90% in pre-market trading on Wall Street, while Merck shares gained more than 8%, reflecting investor optimism about the treatment's potential as a new option for tackling the deadliest form of skin cancer.
Source: CNBC, via LiFO
