The study included 1,137 participants who were randomly assigned to receive either the combination of intismeran and Keytruda or Keytruda alone. Intismeran is designed to target specific mutations in each patient's tumor by training the immune system to recognize unique cancer markers. Keytruda works by unveiling cancer cells that often hide from the immune system.

Stéphane Bancel said that for many years, the idea of creating an mRNA treatment designed specifically for an individual patient’s cancer was aspirational. He added that they are now helping turn that vision into reality.

Dr. Jane Healy, Merck's head of oncology early development, described the therapy as leading to a clinically meaningful improvement over Keytruda. Healy noted that side effects were similar to other vaccines typically administered for other diseases. Professor Georgina Long stated that the study is the first of its kind to show that treatment can reduce the risk of recurrence or death in patients with melanoma.

Long said in a statement that today's results represent a landmark moment for adjuvant melanoma treatment. Long is the study principal investigator and chair of University of Sydney's Melanoma Medical Oncology and Translational Research. The companies did not release detailed data or specific recurrence and survival rates, stating the results would be presented at an upcoming international medical meeting.

Additional reported data indicated a 59% reduction in the risk of distant metastasis or death with the combination therapy compared to KEYTRUDA alone. In January, the companies announced results of a mid-stage trial of the treatment showing that it reduced the risk of recurrence or death by 49% after five years. More than 234,680 cases of melanoma are expected to be diagnosed in the U.S. in 2026, according to the Skin Cancer Foundation. More than 8,500 people are expected to die from melanoma in the U.S. this year.

Why It Matters

The success of intismeran in the Phase 3 INTerpath-001 trial marks a development in personalized cancer treatment, demonstrating that an mRNA-based vaccine can reduce recurrence risk when combined with standard immunotherapy. With more than 234,680 cases of melanoma expected to be diagnosed in the U.S. in 2026 and more than 8,500 deaths projected, the therapy addresses a substantial public health burden. The trial results support the expansion of mRNA technology beyond infectious diseases into oncology, a field where targeted therapies have shown promise but face challenges in broad application.

Timeline

On January 1, 2026, more than 234,680 cases of melanoma were expected to be diagnosed in the U.S. in 2026, according to the Skin Cancer Foundation. Also on January 1, 2026, more than 8,500 people were expected to die from melanoma in the U.S. this year. On August 19, 2026, Merck and Moderna announced that a personalized mRNA cancer vaccine, intismeran, succeeded in a late-stage clinical trial for melanoma.

On August 19, 2026, Stéphane Bancel said in a news release that these Phase 3 findings represent a pivotal moment for the field of cancer research. On the same day, he said that for many years, the idea of creating an mRNA treatment designed specifically for an individual patient’s cancer was aspirational. Also on August 19, 2026, he said they are now helping turn that vision into reality. On August 19, 2026, Professor Georgina he said in a statement that today's results represent a landmark moment for adjuvant melanoma treatment.

What's New

Later reporting included statements from company executives and additional context on the drug's mechanism. He said these Phase 3 findings represent a pivotal moment for the field of cancer research. Moderna CEO Stéphane Bancel showed that intismeran represents the first mRNA-based therapeutic vaccine designed to train the immune system to recognize tumor-specific mutations, a concept previously considered aspirational in cancer research. He also said that for many years, the idea of creating an mRNA treatment designed specifically for an individual patient’s cancer was aspirational, and added that they are now helping turn that vision into reality.

Additional background information noted that Merck and Moderna have nine Phase 2 and Phase 3 clinical trials underway investigating intismeran across multiple tumor types, including non-small cell lung cancer (NSCLC), bladder cancer, and renal cell carcinoma, beyond melanoma. Historical records show that research titled Merck KGaA has announced the approval of cetuximab [Erbitux] was published in 2006 in Inpharma Weekly, and research titled Merck KGaA has announced that the first patient has been enrolled for EXPAND,* was published in 2008 in Inpharma Weekly.