Moderna and Merck announced Thursday that their personalized mRNA cancer vaccine cut the risk of death or recurrence by 42 percent in patients with melanoma, the deadliest form of skin cancer. The result comes from a late-stage Phase 3 trial and marks the first time an mRNA-based cancer therapy has shown a clinically meaningful benefit at this stage of testing.
The two companies had already said in August that the trial met its goals, but held back the numbers until they could be presented at a scientific conference. Those data were due Saturday at the European Society of Medical Oncology in Madrid. After an oncology news site broke the embargo early, the companies released the top-line results, which have also been accepted for publication in the New England Journal of Medicine.
How the personalized mRNA vaccine works
The vaccine is called intismeran, or mRNA-4157. It carries synthetic mRNA encoding up to 34 mutations found in a patient's own tumor cells. To build it, researchers compare the genetic sequence of a patient's cancer cells with that of healthy cells, then select cancer-specific mutations that could train the immune system to attack the tumor selectively.
In the trial, 1,137 patients with stage IIB–IV melanoma that had been surgically removed were randomized 2-to-1. One group received the personalized mRNA vaccine combined with Merck's established monoclonal antibody treatment Keytruda; the other received Keytruda plus a placebo. Researchers measured recurrence-free survival (RFS) and distant metastasis-free survival (DMFS).
Phase 3 trial results: 42% reduction in recurrence or death
After two years, the intismeran-Keytruda group saw a 42 percent reduction in the risk of recurrence or death compared with the Keytruda-placebo group. In concrete terms, 82 percent of patients on the combination were still alive without recurrence, versus 70 percent on Keytruda alone.
