Personalized mRNA Therapy Potentially Marks Major Step Forward in Preventing Melanoma’s Return

Patients with stage 3 or metastatic melanoma who have already undergone surgery but still face a high risk of recurrence now have encouraging news. New clinical trial results show that adding a personalized Moderna–Merck vaccine—called intismeran autogene (mRNA‑4157 or V940)—to the immunotherapy drug pembrolizumab (Keytruda) cut the risk of recurrence or death by nearly 50% over five years compared to using Keytruda alone.

Dr. George Ansstas, medical oncologist at Siteman Cancer Center at Barnes-Jewish Hospital and WashU Medicine, says the early data suggest that adding this personalized mRNA vaccine to Keytruda could meaningfully improve long‑term outcomes for stage 3 and 4 melanoma patients who remain at high risk even after surgery.

Dr. Anna Pavlick is a medical oncologist at Weill Cornell Medicine and Professor of Medicine in the Division of Hematology & Medical Oncology. While hopeful, she remains “cautiously optimistic” about the overall patient survival the personalized vaccine, coupled with immunotherapy, will have.

“The randomized Phase III trial results are due out soon and will hopefully confirm these findings and demonstrate a survival benefit by the addition of this vaccine,” Dr. Pavick told SurvivorNet.

“This combination reduced the risk of recurrence or death by 49% compared with Keytruda alone, highlighting its potential to significantly improve long‑term outcomes for patients with high unmet needs after surgery,” Dr. Ansstas tells SurvivorNet.

The Phase 2b KEYNOTE‑942 trial

The Phase 2b KEYNOTE‑942 trial enrolled 157 patients with high-risk stage 3 or 4 melanoma. After complete surgical removal of their tumors, participants were randomized 2:1 to receive the personalized vaccine plus Keytruda or Keytruda alone. The vaccine was given at 1 mg every three weeks for nine weeks, while Keytruda was administered every three weeks for up to 18 cycles (about one year). The control group received Keytruda alone for the same duration unless recurrence or treatment toxicity occurred.

The study’s primary endpoint was recurrence-free survival (RFS)—the time from the first Keytruda dose until recurrence, a new melanoma, or death. Secondary endpoints included distant metastasis-free survival and safety, with exploratory analyses examining tumor mutational burden (TMB) and its relationship to outcomes.

According to Merck, the combination therapy continued to show “sustained and clinically meaningful improvement” in RFS, reducing the risk of recurrence or death by 49% (HR 0.510; 95% CI 0.294–0.887). The company says it will provide additional follow-up data at an upcoming medical meeting.

Dr. Ansstas noted that the results suggest personalized mRNA immunotherapy can enhance PD‑1 blockade without adding significant toxicity. “The safety profile remained consistent with earlier analyses, supporting its potential integration into standard practice for patients who are disease-free after surgery but still at high risk,” he told SurvivorNet.

Dr. Ansstas added that these early results show this personalized mRNA vaccine could meaningfully strengthen immunotherapy for melanoma—and possibly other cancers—and that larger ongoing trials will help determine which patients benefit most.

“Ongoing Phase 3 and Phase 2 studies in melanoma, lung, bladder, and renal cancers will further clarify its role in routine oncology practice, including which patient populations derive the greatest benefit and how personalized mRNA therapies may be incorporated into future treatment paradigms,” Dr. Ansstas said.

Moderna’s mRNA technology gained global recognition during the COVID-19 pandemic—and now appears poised to play a growing role in cancer treatment as well.