Merck and Moderna mRNA Melanoma Vaccine Cuts Recurrence Risk in Phase 3 Trial

Merck and Moderna announced Wednesday that a personalized mRNA-based cancer vaccine succeeded in a large, late-stage trial among high-risk patients with melanoma. The individualized vaccine, when paired with the existing immunotherapy, Keytruda, is the first and only combination regimen that demonstrated success in potentially extending melanoma patients' lifespans. In Phase 3 trials, the regimen significantly reduced the risk of cancer returning or spreading among patients whose high-risk melanoma had been surgically removed.

In Phase 2b trials, the treatment showed a 49% reduction of melanoma return after patients underwent surgery and a 59% reduction of metastasization of the cancer to distant organs. The vaccine uses genetic information from patients' individual tumors to identify and attack the cancer. "It's what we call individualized neoantigen therapy, where we take the cancer itself, we do genetic sequencing and try to define a unique mutational fingerprint of the cancer itself," said an oncologist at the H. Lee Moffitt Cancer Center & Research Institute.

The Food and Drug Administration has not yet approved the vaccine. The agency will review the full data once it has been collected and submitted. Merck and Moderna plan to present data at an upcoming international medical meeting where they hope to engage regulators on filing submissions for approval of the regimen, the companies said in a joint press release. The oncologist said he expects the treatment to be approved based on very positive trial results and made available to patients likely by early 2027.

The treatment is considered relatively safe, according to the companies. The most common side effects include fatigue, sore arm and chills. Melanoma is the deadliest form of skin cancer, with about 112,000 new cases expected in 2026, according to the American Cancer Society. Treatments utilizing mRNA technologies are being used in trials for other forms of cancer, including that of the bladder, kidney, lungs, stomach and pancreas, according to the oncologist. "I think it will certainly improve the outcome of our patients," he said. "We are, you know, excited about this development. My expectation is this will eventually change the standard care of our patients."