A New Personalized Cancer Vaccine Could Keep Skin Cancer From Coming Back, Drugmakers Say

The results, announced this week by Moderna and Merck, could pave the way for a new generation of treatments tailored to individual tumors

Sarah Kuta | Daily Correspondent

August 21, 2026 2:16 p.m.

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A personalized cancer vaccine, used in combination with an existing treatment, helped prevent the return and spread of melanoma in a late-stage clinical trial, Moderna and Merck, the companies developing the drug, announced this week. The results bring the vaccine, called intismeran, one step closer to regulatory approval and potentially wider use.

“This is a new chapter in cancer care,” Stephane Bancel, chief executive officer of Moderna, tells CNN’s Meg Tirrell and Jamie Gumbrecht.

Intismeran is a personalized cancer vaccine, also known as an individualized neoantigen therapy. The vaccine isn’t designed to stop cancer from occurring in the first place. Rather, it aims to keep the disease from returning in patients who have already had it. It relies on the same mRNA, or messenger RNA, technology as many Covid-19 vaccines and a new mRNA flu shot. While those vaccines target viruses, intismeran uses a similar approach to fight cancer.

For this trial, a version of intismeran was created exclusively for each patient, a process that took about six weeks. Researchers made each personalized treatment by sampling the patient’s cancer tumor, then genetically sequencing the cells to identify unique mutations. Because of these mutations, tumor cells produce proteins called neoantigens, which sit on the cells’ surface. Once injected, the personalized vaccine helps train the immune system to recognize and attack cancer cells that carry these neoantigens.

Researchers recruited 1,137 patients whose advanced melanoma had been surgically removed but was considered likely to return. All participants received pembrolizumab, an immunotherapy cancer treatment drug also made by Moderna and Merck and sold under the brand name Keytruda. In addition to pembrolizumab, about half of the patients were also given intismeran; the other half were given a placebo. Neither the participants nor their doctors knew who received the cancer vaccine.

According to Merck and Moderna, participants who were given both intismeran and pembrolizumab lived longer without their cancer coming back than those who only took pembrolizumab. Similarly, patients who took both intismeran and pembrolizumab went longer without developing new lesions outside the original site of the cancer.

The drugmakers did not release detailed trial data but described the results as “clinically meaningful” in a statement. They say they plan to present the findings at an upcoming international medical meeting and share them with regulatory authorities.

Earlier this year, Moderna and Merck shared the results of a mid-stage trial of intismeran and pembrolizumab. The combination of the drugs, they said, reduced the risk of melanoma’s recurrence or spread by 49 percent after five years compared to pembrolizumab alone.

Melanoma is the deadliest form of skin cancer, responsible for an estimated 8,510 deaths per year in the United States. If detected early, melanoma is highly treatable, and most patients have a good chance of surviving. However, advanced melanoma can be difficult to treat, as it has often spread deeper into the skin or to other parts of the body.

Outside experts are awaiting the data. However, they say the results seem promising and align with the findings of other small studies conducted in recent years.

“This is really an important achievement,” Jedd Wolchok, the director of the Meyer Cancer Center at Weill Cornell Medicine who was not involved with the trial, tells STAT’s Matthew Herper and Angus Chen. “It tells us what might have been considered science fiction 15 or 20 years ago—that we can produce a personalized vaccine based on sequencing from a tumor from a pathology specimen—could be used to delay progression of melanoma. It really establishes personalized cancer vaccines as being a new addition to standard cancer therapy.”

The trial only included people with melanoma, but experts say the results suggest the same treatment approach could potentially be applied more broady—to other types of cancer, as well as rare conditions caused by genetic mutations, per Nature’s Rachel Fieldhouse and Mohana Basu.

Personalized mRNA vaccines are being developed for pancreatic, stomach, kidney, bladder, colon and lung cancers.

“We should be hearing results from multiple studies over the next few years and there’s every reason to hope now, with this news, that ​many of them will be positive,” Robert Vonderheide, director of Penn Medicine's Abramson Cancer Center and president-elect of the American Association for Cancer Research, tells Reuters’ Julie Steenhuysen.

Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.