mRNA Cancer Vaccine Slashes Melanoma Recurrence by 49%

A personalized mRNA cancer vaccine developed by Moderna in collaboration with Merck has delivered sustained and durable results against advanced melanoma, reducing the risk of recurrence or death by 49% over a five-year follow-up period, according to data presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago.

The findings, drawn from the Phase 2b KEYNOTE-942/mRNA-4157-P201 study and published simultaneously in ASCO’s Journal of Clinical Oncology, represent a significant milestone in the fight against melanoma, the deadliest form of skin cancer.

A Personalized Approach to Cancer Treatment

The investigational therapy, known as intismeran autogene (formerly mRNA-4157/V940), is an mRNA-based individualized neoantigen therapy designed using mutations identified in a patient’s own tumor. It consists of synthetic mRNA coding for up to 34 neoantigens that teach the immune system to recognize and attack cancer cells. When combined with KEYTRUDA® (pembrolizumab), Merck’s anti-PD-1 immunotherapy, the treatment activates T lymphocytes to mount a targeted immune response.

Five-Year Data Shows Sustained Benefit

The randomized, open-label study enrolled 157 patients with high-risk stage III/IV melanoma following complete surgical resection. Patients were assigned 2:1 to receive intismeran autogene plus KEYTRUDA or KEYTRUDA alone. With a median follow-up of 60.3 months, the results demonstrated:

• 49% reduction in the risk of recurrence or death (HR=0.51; 95% CI, 0.294–0.887)
• 59% reduction in the risk of distant metastasis or death (HR=0.411; 95% CI, 0.200–0.843)
• 53% reduction in overall survival risk in an exploratory analysis (HR=0.471; 95% CI, 0.165–1.345)

Jefferies analysts called the survival figures “encouraging” and noted that the readout “helps instill confidence in pivotal Phase III data in 2026.”

Safety Profile Remains Manageable

The combination therapy was well-tolerated, with safety consistent with prior analyses. The most common adverse events attributed to intismeran autogene were fatigue (59.6%), injection site pain (59.6%), and chills (51.0%). The majority of events were Grade 1 (31.7%) or Grade 2 (51.9%), with fatigue being the most common Grade 3 event (4.8%). No Grade 4–5 events were attributed to the vaccine. Immune-related adverse events occurred at similar rates in both the combination group (45.2%) and the KEYTRUDA-alone group (44%).

Expert Reactions

“With each year of continued follow-up of our Phase 2b study, we gain a more complete picture of the durability of intismeran autogene in combination with KEYTRUDA,” said David Berman, M.D., Ph.D., Chief Development Officer of Moderna, in the joint press release. “Now, with a median follow-up of five years, the sustained recurrence-free survival and distant metastasis-free survival demonstrate the potential long-term benefit.”

Dr. Marjorie Green, Senior Vice President and Head of Oncology, Global Clinical Development at Merck Research Laboratories, added that the risk of disease recurrence remains high for patients with stage III/IV melanoma following surgery, making these long-term findings particularly meaningful.

Broader Implications for mRNA Cancer Therapy

The success of intismeran autogene represents a validation of mRNA technology for personalized cancer treatment beyond infectious disease. Moderna and Merck have nine ongoing Phase 2 and Phase 3 clinical trials investigating the therapy across multiple tumor types, including non-small cell lung cancer, bladder cancer, and renal cell carcinoma.

The Phase 3 INTerpath-001 trial for adjuvant melanoma is fully enrolled and expected to release interim data next year. Jefferies analysts expect the vaccine to enter the market in 2027, with more meaningful sales contributions anticipated in 2028 due to the 50-50 profit-sharing agreement between Moderna and Merck. Adjuvant melanoma alone represents a “multi-billion dollar peak sales” opportunity for Moderna.

What’s Next

While the five-year data is highly encouraging, the results come from a Phase 2b study with a relatively small sample size of 157 patients, and the overall survival data remains exploratory with wide confidence intervals. Confirmation from the ongoing Phase 3 trials will be critical to establishing intismeran autogene as a new standard of care for high-risk melanoma.

Fox News reported that the combination therapy is currently being evaluated in a Phase 3 study, the final confirmation stage before potential regulatory approval. If confirmed, this personalized approach could transform the treatment landscape for melanoma and potentially many other cancers.