Cancer Vaccine Cuts Melanoma Risk, Trial Shows

Merck and Moderna said Thursday that a personalized vaccine designed to fight melanoma lowered the chance of death or cancer returning by 42 percent when added to a standard therapy, compared with the standard therapy alone. The companies released the results after an oncology news site reported them ahead of schedule, ahead of a scheduled presentation at a medical conference in Madrid.

The trial enrolled 1,137 patients whose stage IIB to IV melanoma had already been removed through surgery. Participants were assigned at a 2-to-1 ratio to receive either the vaccine alongside Merck's monoclonal antibody treatment Keytruda, or Keytruda alone. The study is a Phase 3 trial, the final stage before a medicine is typically reviewed for approval by regulators.

Melanoma is the most lethal form of skin cancer. The companies said they are in discussions with regulators about seeking approval for the vaccine. The full results have been accepted for publication in the New England Journal of Medicine.

Moderna chief executive Stéphane Bancel said in a statement that the company had set out to build cancer treatments matched to each patient's tumor. The trial results, he said, "mark a defining moment for that vision and show what's possible when we rethink how medicines are made." He added that the findings "reinforce our conviction that mRNA has the potential to fundamentally change how we treat cancer."

The companies had said in August that the vaccine met its goal in the trial but withheld details pending a scientific conference. The data was slated for presentation Saturday at the European Society of Medical Oncology meeting in Madrid. After an oncology news site reported the findings, breaking the embargo, the companies released the top-line results early.

The broader interest in the work rests on the approach itself. The vaccine is built to match an individual patient's tumor, a strategy that could in principle be applied beyond melanoma. The companies' statement framed the results as evidence that mRNA technology, which gained wide attention through COVID-19 vaccines, can be turned toward cancer treatment.

Questions remain before any approval decision. The data presented so far is top-line, and the full study has yet to be published. Regulators will review the complete findings before determining whether the vaccine can be marketed.

Melanoma patients who have had surgery face the risk that the disease will return, and treatments that lower that risk are closely watched in oncology. Standard care has centered on immunotherapy drugs such as Keytruda, which works by helping the immune system recognize and attack cancer cells. Any addition to that regimen would be weighed against its side effects and cost.

The trial's design placed the vaccine alongside Keytruda rather than in place of it, meaning the reported 42 percent figure reflects the combination compared with Keytruda alone. The companies are now turning to regulators, and to the full publication of the data, as the next steps in the process.