Moderna, Merck say melanoma vaccine trial shows benefit

Moderna and Merck said Wednesday that an experimental personalized cancer vaccine used with the immunotherapy drug Keytruda helped keep high-risk melanoma from returning or spreading in a late-stage clinical trial, sending Moderna’s shares sharply higher.

The companies said the mRNA-based vaccine, called intismeran, was tested in people who had surgery to remove melanoma, one of the deadliest forms of skin cancer. The vaccine was given with Keytruda, Merck’s cancer immunotherapy, as an adjuvant treatment — therapy given after surgery to reduce the chance that cancer will come back.

The drugmakers have not published the new results in a peer-reviewed journal or released the full data. They said the findings will be presented at an upcoming international medical meeting and shared with regulators.

According to the companies’ announcement, interim results showed the vaccine-drug combination extended the time before cancer returned in high-risk patients. NBC News reported that the companies did not say how long that benefit lasted. CBS News reported that the treatment also helped prevent the cancer from spreading to other organs.

“Today’s results represent a landmark moment for adjuvant melanoma treatment,” Professor Georgina Long, the study’s principal investigator and chair of University of Sydney’s Melanoma Medical Oncology and Translational Research, said in a statement cited by CBS News. Long said the study was the first of its kind to show that treatment can “reduce the risk of recurrence or death in patients” with melanoma.

The companies described the Phase 3 findings as the first breakthrough of their kind and said the trial will continue to examine overall survival rates after treatment.

“These Phase 3 findings represent a pivotal moment for the field of cancer research,” Moderna CEO Stéphane Bancel said in the companies’ release. “For many years, the idea of creating an mRNA treatment designed specifically for an individual patient’s cancer was aspirational. We are now helping turn that vision into a reality.”

Merck and Moderna have been working on the melanoma vaccine for about a decade, NBC News reported. The treatment is designed to train the immune system to identify and kill cancer cells by targeting abnormal proteins called neoantigens that appear on the surface of those cells.

In June, the companies presented earlier research on the vaccine at the American Society of Clinical Oncology’s annual meeting, saying it halved the risk of melanoma returning after five years. Those findings were published in the Journal of Clinical Oncology.

“By intervening earlier in the course of disease, when many cancers are considered most treatable, the goal of adjuvant therapy given after surgery is to increase the possibility of cure for more patients,” Dr. Dean Y. Li, president of Merck Research Laboratories, said in a statement.

The announcement triggered a surge in Moderna’s stock. NBC News reported that shares rose as much as 106% in premarket trading, while CBS News reported that the stock later climbed $91.52, or 145%, to $154.48 in morning trading after touching an intraday high of $163. Merck shares also rose, with NBC News reporting a 7% gain and CBS News reporting a $14.35, or 10.6%, increase to $149.52.

CBS News reported that more than 8,500 people are expected to die from melanoma this year and that more than 234,680 cases will be diagnosed in the United States in 2026, citing the Skin Cancer Foundation. The Mayo Clinic describes melanoma as a cancer that starts in melanocytes, the cells that give skin its color, CBS News reported.

The future of mRNA research has faced uncertainty under the Trump administration, NBC News reported. Health Secretary Robert F. Kennedy Jr. has repeatedly criticized mRNA technology and cut $500 million in contracts last year for mRNA vaccine research and development. NBC News also reported that the Food and Drug Administration initially rejected Moderna’s mRNA-based flu vaccine under former vaccine chief Dr. Vinay Prasad before later reversing course.