Moderna’s Personalized mRNA Cancer Vaccine Succeeds in Landmark Phase 3 Melanoma Trial

Moderna's new mRNA cancer treatment combined with Merck's immunotherapy Keytruda succeeded in a late-stage trial for skin cancer, the companies said Wednesday, marking an important milestone for the use of personalized mRNA technology against cancer. The Phase 3 INTerpath-001 study evaluated the combination in patients with high-risk melanoma whose tumors had been completely removed through surgery. The treatment significantly improved the amount of time patients remained alive without their cancer returning compared with Keytruda alone. It also significantly improved the amount of time patients lived without the melanoma spreading to distant parts of the body. The companies described the results as the first positive Phase 3 trial for an individualized mRNA-based cancer therapy.

The experimental treatment, called intismeran autogene, is designed individually for each patient rather than being manufactured as an identical therapy for everyone. After a patient's melanoma is removed, researchers use a sample of the tumor to identify mutations unique to that person's cancer. Moderna then creates an mRNA treatment carrying instructions based on those specific characteristics, with the objective of teaching the patient's immune system to recognize and attack cancer cells carrying them. Each individualized treatment can contain mRNA encoding as many as 34 cancer-specific targets. Keytruda, meanwhile, works differently by removing a biological barrier that can prevent immune cells from effectively attacking tumors. Combining the two approaches is intended to help the immune system identify the cancer and strengthen its ability to fight it.

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 were randomly assigned to receive either the personalized mRNA treatment alongside Keytruda or Keytruda alone, with treatment continuing for approximately one year unless the cancer returned or side effects required it to stop. Moderna and Merck said the combination achieved both the study's primary goal of improving recurrence-free survival and a key secondary goal measuring whether cancer spread to distant areas of the body. The companies have not yet released detailed Phase 3 figures showing the magnitude of the improvement and plan to present the full results at an upcoming international medical meeting. The study will continue to determine whether the combination also improves overall survival.

The Phase 3 success follows encouraging results from an earlier study of the same combination in melanoma patients. In the Phase 2b trial, patients receiving intismeran together with Keytruda had a 49% lower risk of their cancer returning or dying compared with those receiving Keytruda alone after five years of follow-up. The combination also reduced the risk of the melanoma spreading to distant parts of the body or death by 59%. Those earlier findings helped support the decision to advance the personalized treatment into the much larger Phase 3 trial. Importantly, Moderna and Merck said no new safety concerns emerged in the latest study, with the safety profiles remaining consistent with what researchers had previously observed with the combination.

The results are particularly significant because melanoma can return even after doctors successfully remove the visible cancer through surgery. The disease is one of the deadliest forms of skin cancer, and recurrence frequently happens within the first two years after treatment. When melanoma returns, it is more likely to have spread elsewhere in the body rather than remain confined to its original location, making preventing recurrence an important part of treatment for patients considered at high risk. In the United States, approximately 112,000 new melanoma cases and more than 8,500 deaths from the disease are expected in 2026. Keytruda is already approved as an additional treatment following surgery for certain patients with stage IIB, IIC or III melanoma, making the Phase 3 comparison an important test of whether adding Moderna's personalized approach can improve on an established treatment.

The companies now plan to present the complete Phase 3 results at an international medical meeting and share the findings with regulatory authorities as they discuss potential applications for approval of the combination. Moderna CEO Stéphane Bancel called the results a major development for personalized cancer treatment, saying: «These Phase 3 findings represent a pivotal moment for the field of cancer research. For many years, the idea of creating an mRNA treatment designed specifically for an individual patient's cancer was aspirational. We are now helping turn that vision into a reality.» The trial is continuing while researchers evaluate additional measures, including whether the treatment ultimately helps patients live longer. Until those results and the detailed Phase 3 data are available, the companies' announcement establishes that the trial met its predefined goals but does not yet show the precise size of the benefit.

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