Merck and Moderna Release Data on Personalized Melanoma Vaccine Trial
Newly released details from a late-stage study show the experimental treatment reduced death or recurrence risk for patients compared to standard care.
By Natalia Campos ·
A 42 percent reduction in death or recurrence is the figure that pharmaceutical companies Merck and Moderna are presenting regarding their experimental cancer vaccine for melanoma. The companies made this data available on October 22, 2026, concerning a treatment designed to address the deadliest form of skin cancer. This specific metric compares patients who received the personalized vaccine alongside a standard treatment against those who received only the standard care.
The timeline of this data release is marked by an unexpected disruption. In August 2026, Merck and Moderna confirmed that the vaccine had succeeded in its trial but withheld specific numbers. They planned to release the details at the European Society of Medical Oncology conference in Madrid, Spain, where the data was scheduled for presentation on Saturday. However, the companies released the top-line results early because an oncology news site reported the results before the scheduled time. The full data has been accepted for publication in the New England Journal of Medicine.
The trial, known as a Phase 3 study, involved 1,137 patients. These participants had stage IIB through IV melanoma that had been surgically removed before they entered the study. The design of the trial randomized patients two-to-one. One group received the personalized mRNA vaccine combined with a standard treatment, while the other received the standard treatment alone. The standard treatment used in this study was Keytruda, a monoclonal antibody cancer treatment already established by Merck.
Regulatory authorities are currently being engaged regarding the vaccine. Merck and Moderna are pursuing approval to make the treatment available. Stéphane Bancel, the CEO of Moderna, stated that from the start, the company believed mRNA technology could enable the creation of cancer treatments uniquely matched to each patient's tumor. Bancel described the trial results as a defining moment for that vision.
The release of these results suggests that mRNA vaccines and individualized cancer-targeting medicines may offer a different approach to cancer therapies. The data is intended to show what is possible when the manufacturing of medicines is rethought. Bancel also stated that the results reinforce the company's conviction that mRNA has the potential to change the treatment of cancer.
The involvement of Keytruda as the standard treatment in the combination arm of the trial is a detail that warrants attention. Keytruda is an established monoclonal antibody cancer treatment provided by Merck. The study compared a combination of the personalized vaccine and this established treatment against the established treatment alone. The 42 percent figure reflects the difference between these two specific regimens.
The trial data was scheduled for presentation at the European Society of Medical Oncology conference in Madrid on Saturday, October 24, 2026. The early release occurred because an oncology news site published the results prior to this scheduled presentation. The full set of data has been accepted for publication in the New England Journal of Medicine.
Source: Ars Technica
