A cancer vaccine developed by Moderna and Merck has cut the risk of melanoma recurrence or death by nearly 50% over five years, marking a significant advance in the race to harness mRNA technology against the disease.
The personalised vaccine mRNA-4157/V940, given alongside the immunotherapy drug Keytruda, maintained its benefit long-term in Phase 2 trials—a critical benchmark in oncology, the companies announced last week.
The finding comes as around 50 mRNA cancer vaccine studies run globally, with pharmaceutical firms leveraging infrastructure built during the COVID-19 pandemic to target various cancer types.
Kyle Holen, senior vice president at Moderna, said the data “capture the potential of mRNA in treating cancer”. The company continues “to invest in our oncology platform thanks to such encouraging results”, he added.
Pandemic expertise drives cancer research
Pharmaceutical companies are fully exploiting the infrastructure and know-how they acquired during the pandemic. Scientists rely on the principle of activating the immune system, as with classic vaccines, but pursue targeted results against specific cancer types.
Melanoma, the most serious form of skin cancer, is considered a suitable first target. Experts say it presents a high number of genetic mutations, giving the immune system more points to recognise and attack.
Speaking to Phileleftheros, Christos Petrou, professor at the University of Nicosia’s Pharmacy Department, said the announcement updates the same study after five years of participant follow-up, following last year’s results.
“The extension of follow-up time shows that the clinical benefit appears maintained long-term and this is particularly important,” he said. “Personalised therapies with mRNA-based neoantigens constitute one of the most interesting developments in immuno-oncology.”
How the treatment works
Combination with immunotherapy plays a central role, Petrou explained. Drugs like Keytruda target the PD-1 protein, which tumours use to “deactivate” immune cells and escape immune surveillance. The mRNA vaccine “shows” the immune system what it must recognise.
The technology works as an “instruction carrier” to the human organism. It delivers information to cells for producing specific proteins that correspond to cancer cell characteristics. The immune system learns to recognise these as foreign and fight them.
But Petrou stressed these treatments do not replace existing therapies. “For patients and the general public, it’s important to clarify that mRNA anticancer ‘vaccines’ do not replace existing therapies. This specific practice is part of a broader trend toward more personalised and targeted therapy, during which specialised drugs will be developed for each patient.”
Realistic expectations needed
He emphasised the need for realistic interpretation of the data. “Although the results are very encouraging, this is a mid-phase study with a relatively small sample. Larger clinical trials are required before definitive conclusions can be drawn about long-term clinical impact.”
Despite being frequently called “vaccines”, mRNA cancer therapies are not vaccines in the classic sense. They are not intended for prevention, nor are they given to healthy people. Instead, they are therapeutic preparations for patients with already diagnosed disease, usually after surgical tumour removal, aiming to reduce recurrence or progression risk.
The international scientific community prefers the term “therapeutic vaccines” to avoid confusion with preventive vaccines against infectious diseases.
Multiple trials underway
The Moderna-Merck vaccine is not the only one being studied. Similar mRNA vaccines for high-risk melanoma are being developed by BioNTech and Roche, all in early clinical trials.
Similar mRNA-based therapies are being tested in lung, bladder, kidney and pancreatic cancer. In some cases early data are encouraging, whilst in others studies have not delivered expected results or have been suspended.
Cost poses access challenge
The development of mRNA therapies comes with practical challenges. A therapeutic vaccine cannot simply be copied and adapted to other cancer types, demonstrating the difficulty of rapid study expansion. Each cancer form requires a different approach and analysis of tumours. This is why in many cases development is personalised.
This process leads to very high cost. The major challenge is ensuring patient access to therapeutic vaccines, given the need for increased expenditure from national health systems.
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