Moderna and Merck: personalized mRNA vaccine cut melanoma recurrence or death risk by 42%

US drugmakers Moderna and Merck have announced results from a Phase 3 clinical trial of a personalized mRNA cancer vaccine for melanoma, a malignant skin cancer. The vaccine, called intismeran (or mRNA-4157), was given together with the immunotherapy drug Keytruda. According to the companies, after two years the combination reduced the risk of cancer returning or of death by 42% compared with Keytruda plus a placebo. The trial involved patients whose melanoma had been surgically removed.

How the vaccine works

The vaccine uses a synthetic mRNA carrying the genetic code for up to 34 mutations found in a patient's own cancer cells. To make it, researchers compare the genetic sequences of the cancer cells with those of healthy cells and select cancer-specific mutations. These are meant to help the immune system target only the cancer cells.

Results

The trial measured recurrence-free survival, meaning time without the cancer returning, and distant metastasis-free survival, meaning time without the cancer returning in a different part of the body.

After two years, 82% of patients in the intismeran-Keytruda group were alive without recurrence, compared with 70% in the Keytruda-placebo group. The risk of distant metastasis or death was 38% lower. At the end of the trial, 88.5% of the vaccine group were alive without distant metastasis, against 80% in the placebo group.

The effect was weaker than in a five-year Phase 2 trial, which showed a 49% reduction in the risk of recurrence or death and a 59% reduction in the risk of distant metastasis or death.

Dean Li, president of Merck Research Laboratories, said in an announcement that this is the first Phase 3 study to show a clinically meaningful improvement over standard-of-care Keytruda in patients with resected melanoma.