Personalized mRNA Vaccine and Keytruda Cut Melanoma Recurrence Risk
A personalized mRNA vaccine combined with the immunotherapy drug Keytruda halved the risk of advanced melanoma returning or spreading after surgery, according to five-year clinical trial results announced in August 2026. The experimental treatment, developed by Moderna and Merck, builds on messenger RNA technology to train a patient’s immune system to target unique tumor mutations, offering a new approach for patients with high-risk skin cancer.
Five-Year Trial Results for Personalized Melanoma Vaccine
The long-term data were presented at the American Society of Clinical Oncology’s annual meeting and published in the Journal of Clinical Oncology, according to reporting by NBC News. The clinical trial tracked patients with at least Stage 3 melanoma, meaning the cancer had spread to nearby lymph nodes or skin and carried a high risk of recurrence even after surgical removal.
In the study, 50 patients received standard treatment consisting of surgery followed by pembrolizumab, which is marketed as Keytruda. Another 107 patients received the standard immunotherapy alongside a personalized mRNA vaccine tailored to their specific tumor profile. Five years later, nearly 70% of participants in the vaccine group remained cancer-free, compared to 49% of those who received standard treatment alone, according to NBC News data. Furthermore, adding the vaccine cut the risk of the cancer metastasizing by nearly 60%.
“The treatments we have are not perfect. People relapse,” said Dr. Janice Mehnert, director of the melanoma and cutaneous medical oncology program at NYU Langone Health in New York and senior trial investigator, as reported by NBC News.
How the Personalized mRNA Vaccine Targets Tumor Neoantigens
Surgery remains the first line of defense for melanoma to remove the primary tumor, but undetectable cancer cells frequently remain in the body. The personalized vaccine aims to clear those lingering cells by teaching the immune system to recognize unique targets.
According to NBC News, each vaccine is manufactured using genetic material sampled from the patient’s own tumor. Technicians sequence the cancer cells to identify DNA mutations that form unique proteins on the cell surface, known as neoantigens. The vaccine is designed to instruct immune T-cells to attack cells carrying these specific neoantigens.
Production of each custom vaccine takes approximately four to six weeks following surgery. Patients then receive up to nine doses spaced about three weeks apart, timed to align with their pembrolizumab treatments.
“It’s training the immune system to recognize the tumor signature long after the tumor is gone,” said Jeff Coller, a professor of RNA biology and therapeutics at Johns Hopkins University in Baltimore, who was not involved in the research, as quoted by NBC News.
Regulatory Steps and Broader Cancer Research
The treatment, referred to as intismeran, relies on the same underlying mRNA technology utilized in certain Covid-19 vaccines and emerging influenza shots, according to reporting by Smithsonian Magazine.
Moderna and Merck announced further trial developments involving a larger cohort of 1,137 patients who had their advanced melanoma surgically removed, as reported by Smithsonian Magazine. In that trial, participants were given either pembrolizumab combined with intismeran or pembrolizumab with a placebo. While detailed data from that larger cohort remain pending upcoming medical meetings, drugmakers described the results as clinically meaningful, moving the therapy closer to regulatory review.
“This is a new chapter in cancer care,” Stéphane Bancel, chief executive officer of Moderna, told CNN in remarks cited by Smithsonian Magazine.
Researchers are also evaluating similar personalized mRNA approaches for other difficult malignancies, including pancreatic cancer, where early-stage trials indicate potential in reducing recurrence rates. Meanwhile, Dr. Mehnert and her coinvestigators are finalizing data from a broader phase 3 trial encompassing 1,000 patients across multiple countries to further establish the efficacy of combining personalized vaccines with standard immunotherapy.