Personalized Melanoma Vaccine Shows 42% Reduction in Recurrence, Death Risk

New phase 3 trial results show further promise in helping prevent melanoma recurrence or spread after surgery.  

Intismeran, a personalized mRNA cancer vaccine, combined with Keytruda (pembrolizumab), reduced the risk of recurrence or death by 42% compared with Keytruda alone, according to Moderna and Merck.  

The findings from the trial will be presented at the European Society for Medical Oncology (ESMO) Congress 2026 Presidential Symposium.  

The results of this phase 3 trial are consistent with the prior phase 2 study results and are highly likely to impact the standard of care pending reviews and approvals by the FDA and other regulatory agencies.

Ahmad Tarhini, MD, PhD

“The results of this phase 3 trial are consistent with the prior phase 2 study results and are highly likely to impact the standard of care pending reviews and approvals by the FDA and other regulatory agencies,” said Ahmad Tarhini, MD, PhD, Moffitt Cancer Center’s Cutaneous Clinical and Translational Research director.   

Moffitt Cancer Center was among the participating research sites in the trial, which enrolled 1,137 patients with high-risk melanoma following surgery. Tarhini served as Moffitt’s site principal investigator and has led several studies in adjuvant therapy over several years.   

How It Works  

Intismeran is designed and produced using genetic information from a patient’s own tumor.  

After a piece of the patient’s tumor is removed, it is analyzed in a lab to identify unique mutations. That information is used to develop the mRNA vaccine, which delivers synthetic mRNA into cells.  

Melanoma is among the deadliest forms of skin cancer because it can spread to other parts of the body.

Keytruda is an immunotherapy drug widely used to reduce the risk of melanoma recurrence. While Keytruda helps the immune system recognize and fight cancer, the personalized vaccine helps train the immune system to attack cancer cells.  

In the phase 3 trial, researchers found that the combination treatment could provide additional protection against melanoma returning or spreading to other parts of the body.  

These results build on earlier findings from a phase 2 trial, which showed that patients receiving intismeran with Keytruda had approximately half the risk of melanoma recurrence or death after five years compared with patients receiving Keytruda alone. Those findings were presented at the 2026 American Society of Clinical Oncology Annual Meeting this summer.  

Potential Impact on Melanoma Treatment  

The phase 3 results could represent an important step toward expanding personalized cancer vaccine approaches for patients with melanoma. Merck and Moderna say they are engaging with regulatory authorities following the results.  

Melanoma is among the deadliest forms of skin cancer because it can spread to other parts of the body. The American Cancer Society estimates that 112,000 new cases of melanoma will be diagnosed in the United States in 2026.  

The personalized mRNA vaccine approach is also being tested to prevent the recurrence of lung and other cancers, offering hope for new treatment options that could help prevent cancer from returning.