Melanoma Vaccine Shows 42% Cut in Death or Relapse, Firms Seek Approval

Patients with advanced melanoma who received a bespoke mRNA vaccine alongside standard care had a 42 percent lower risk of dying or seeing their cancer come back than those on standard treatment alone, according to results released Thursday by Merck and Moderna. The two companies said they are already in talks with regulators about securing approval for the shot, which would put a new kind of cancer medicine in front of people facing one of the most aggressive forms of skin cancer.

The trial enrolled 1,137 people whose stage IIB to IV melanoma had been surgically removed before they joined. Participants were assigned 2-to-1 to get either the personalized vaccine paired with Merck's established antibody drug Keytruda, or Keytruda on its own. The companies reported the vaccine met its goal in August but kept details under wraps pending a scientific meeting.

That meeting, the European Society of Medical Oncology congress, opened this week in Madrid. The data had been slated for a Saturday presentation, but an oncology news outlet published the figures ahead of schedule, prompting the firms to release the top-line numbers early. The full results have been accepted for publication in the New England Journal of Medicine.

The work stems from a push by both companies to turn the mRNA platform behind COVID-19 shots toward oncology. Moderna chief executive Stéphane Bancel said in a statement that the program was built on the idea that mRNA could generate treatments matched to each person'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."

Bancel added that the findings "reinforce our conviction that mRNA has the potential to fundamentally change how we treat cancer." Melanoma remains the deadliest form of skin cancer, and cutting the odds of recurrence or death by nearly half would represent a meaningful shift in how the disease is managed if regulators agree.

For now, the path forward runs through regulatory submissions and the publication of the complete dataset. Any approval would mark the first personalized cancer vaccine of its kind to reach the market, a signal to investors that mRNA technology can extend well beyond infectious disease and into areas where patient needs and drug spending are both large.