mRNA Vaccine Cuts Melanoma Recurrence Risk by 49% in Trial

A groundbreaking personalized mRNA cancer vaccine has demonstrated sustained effectiveness in preventing the recurrence of melanoma, the deadliest form of skin cancer, according to five-year data presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting. The results, published simultaneously in the Journal of Clinical Oncology, mark a pivotal moment for mRNA technology beyond COVID-19.

Developed by Moderna in collaboration with Merck, the vaccine — known as intismeran autogene (mRNA-4157/V940) — is personalized to each patient’s unique tumor. After five years of follow-up, 68.8% of patients who received the combination therapy remained cancer-free, compared with 49.1% of patients who received Merck’s immunotherapy Keytruda (pembrolizumab) alone — a 49% reduction in the risk of recurrence or death.

A Personalized Approach to Cancer

Unlike the COVID-19 mRNA vaccines, which delivered the same RNA fragment to everyone, this therapy is fundamentally different. Scientists sequence a patient’s surgically removed tumor to identify up to 34 unique molecular fingerprints called neoantigens, then encode them into a custom mRNA vaccine.

“The COVID vaccine was the same RNA fragment given to everybody. Whereas in this case, the antigen itself is not one virus, it’s [each] patient’s tumor,” explained Dr. Sarah Arron, a dermatologist and skin cancer surgeon who was not involved in the research, in an interview with NPR.

When injected, the vaccine trains T cells to recognize and target those specific neoantigens, giving the immune system a blueprint for attacking the cancer. No two vaccines are identical because each patient’s tumor informs the vaccine they receive.

Striking Five-Year Results

The Phase 2b KEYNOTE-942 trial enrolled 157 patients with high-risk stage III/IV melanoma who had undergone complete surgical resection. Patients were assigned 2:1 to receive the combination therapy or Keytruda alone.

According to Merck’s press release, the combination therapy also reduced the risk of distant metastasis or death by 59%. Perhaps most striking, 92% of patients who received the combination were alive at the five-year mark, compared with 71% of those who received Keytruda alone.

“I think this is strong evidence that this therapy, when used in combination with immunotherapy, can demonstrably reduce the risk of dying from this disease,” said Dr. Janice Mehnert, a melanoma specialist at NYU Langone Health and senior author of the study, as reported by NPR.

Safety and Tolerability

The safety profile remained favorable throughout the five-year follow-up period. The most common side effects were fatigue (59.6%), injection site pain (59.6%), and chills (51.0%). The vast majority of adverse events were mild to moderate, with no Grade 4 or 5 events attributed to the vaccine. Importantly, the combination did not result in a potentiation of immune-related adverse events compared to Keytruda alone.

Beyond Melanoma: A Platform for Cancer Treatment

The implications extend far beyond skin cancer. Moderna and Merck now have nine total Phase 2 and Phase 3 clinical trials underway investigating intismeran autogene across multiple tumor types, including non-small cell lung cancer, bladder cancer, and renal cell carcinoma.

A Phase 3 trial for adjuvant melanoma (INTerpath-001) is fully enrolled with nearly 1,000 patients, and results are expected in the coming months. If confirmed, the companies plan to seek FDA approval.

“These findings add to our confidence in the potentially transformative impact of this novel, personalized approach to cancer care made possible by mRNA technology,” said Dr. David Berman, Chief Development Officer of Moderna.

A Patient’s Story

Connie Franciosi, 80, was diagnosed with melanoma in 2020 and joined the trial after surgery. She remains cancer-free. “I am cancer-free. Life is good,” she told NPR. “I have a very satisfying life.”

What’s Next

While the results are encouraging, several questions remain. The Phase 3 trial will need to confirm these findings in a larger population. Cost and access are also significant considerations — personalized cancer vaccines are inherently expensive to manufacture, and questions remain about insurance coverage and Medicare reimbursement.

Additionally, researchers are investigating whether the approach will work as effectively for other cancer types. The ongoing clinical program will help answer whether this personalized mRNA platform can become a cornerstone of cancer treatment across multiple malignancies.

For now, the five-year data represent a landmark advance. As Dr. Arron put it: “I think this is a landmark advance in how we treat these very advanced, high-risk melanomas.”