Moderna’s mRNA Cancer Treatment Shows Major Phase 3 Success Against Melanoma

Moderna’s personalized mRNA cancer treatment combined with Merck’s immunotherapy Keytruda succeeded in a late-stage trial for skin cancer, the companies said Wednesday. The Phase 3 INTerpath-001 study tested the combination in patients with high-risk melanoma whose tumors had been completely removed through surgery, marking an important milestone for personalized mRNA technology in cancer treatment.

The combination significantly improved recurrence-free survival compared with Keytruda alone, meaning patients went longer without their melanoma returning or dying. It also significantly improved distant metastasis-free survival, which measures how long patients remain alive without the cancer spreading to distant parts of the body. The companies have not yet disclosed the detailed Phase 3 results.

The results represent the first positive Phase 3 trial for an individualized neoantigen therapy and an mRNA-based cancer treatment, according to Moderna and Merck. The milestone extends the potential use of mRNA technology beyond infectious diseases, providing late-stage clinical evidence that a treatment customized around the characteristics of an individual patient’s tumor can improve outcomes in melanoma.

The experimental treatment, called intismeran autogene, is individually designed using a sample of each patient’s tumor. Researchers identify mutations specific to that cancer and create an mRNA treatment based on its unique characteristics. The objective is to train the patient’s immune system to recognize those characteristics and more effectively identify and attack remaining cancer cells.

Each personalized intismeran treatment can contain mRNA encoding as many as 34 cancer-specific targets. Keytruda works differently, blocking the PD-1 pathway that can prevent immune cells from effectively attacking tumors. By combining the treatments, researchers aim to help the immune system recognize cancer more precisely while strengthening its ability to attack cells carrying those tumor-specific characteristics.

The Phase 3 trial enrolled 1,137 patients with stage IIB through stage IV cutaneous melanoma who had undergone surgery to completely remove their cancer. Participants received either intismeran combined with Keytruda or Keytruda alone. Treatment continued for approximately one year unless the melanoma returned, unacceptable side effects developed or the planned treatment period was completed.

The Phase 3 success follows encouraging results from an earlier Phase 2b study. After five years of follow-up, the combination reduced the risk of melanoma recurrence or death by 49% compared with Keytruda alone. It also reduced the risk of distant metastasis or death by 59%, providing earlier evidence supporting the larger late-stage trial.

Moderna and Merck said the safety profiles observed with intismeran and Keytruda were consistent with those previously reported for the combination. No new safety signals were identified during the Phase 3 trial. The study is continuing as researchers evaluate additional measures, including overall survival, which will determine whether the combination ultimately helps patients live longer.

Melanoma remains one of the deadliest forms of skin cancer, and patients can face the possibility of recurrence even after their tumors are completely removed. Recurrences most commonly occur within the first two years and are more often metastatic than localized. About 112,000 new melanoma cases and more than 8,500 deaths are expected in the United States in 2026.

Keytruda is already approved as an additional treatment after surgery for certain patients with stage IIB, IIC or III melanoma. The Phase 3 trial therefore tested whether adding Moderna’s personalized mRNA approach could improve outcomes beyond an established immunotherapy. The positive results showed a clinically meaningful improvement over Keytruda alone in patients with completely resected high-risk melanoma.

Moderna and Merck plan to present detailed Phase 3 data at an upcoming international medical meeting and share the results with regulatory authorities. Moderna CEO Stéphane Bancel called the findings «a pivotal moment for the field of cancer research». The companies will now engage with regulators over potential submissions for intismeran combined with Keytruda.