Merck and Moderna’s
success with a personalized cancer vaccine designed to
keep melanoma at bay opens a new avenue of treatment that
doctors hope will work against many types of tumors.
Unlike chemotherapy, which kills both healthy and cancerous
cells, or immunotherapy, which revs up the immune system,
personalized cancer vaccines train the immune system to
specifically target mutations found only on a person’s tumor.
Merck and Moderna said on Wednesday their vaccine helped prevent
the return and spread of disease in a large trial involving more
than 1,000 melanoma patients. They had localized tumors that
were removed surgically, but had a high risk of recurrence.
Moderna expects that thousands of melanoma patients could
benefit within the first few years of approval.
“It is a big deal for the field in general,” said Dr. Ryan
Sullivan, director of the Center for Melanoma at Mass General
Brigham Cancer Institute. “With this positive study, there is
hope (and likely investment to follow) that these approaches
may change the way we treat cancer more broadly.”
The trial result is “a monumental leap forward,” validating
mRNA technology as a cancer treatment, said Dr. Julie Gralow,
chief medical officer of the American Society of Clinical
Oncology.
Beyond melanoma, personalized cancer vaccines are in
late-stage development for a host of tumor types. Merck and
Moderna have several large trials under way in non-small cell
lung cancers that have been surgically removed.
They are also studying the combination in mid-stage trials
in patients with bladder and kidney cancers as well as in
early-stage trials in pancreatic and stomach cancers, with
numerous trial results expected in the next year or two, Moderna
President Stephen Hoge told Reuters.
Roche and BioNTech, whose mRNA
technology was used in the Pfizer COVID vaccines, are
testing a similar treatment called autogene cevumeran in
mid-stage studies in colon and pancreatic cancer patients who
have undergone surgery.
Results of the colon cancer trial are expected in 2027, with
pancreatic trial results to follow in 2031.
“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,” said Dr. Robert
Vonderheide, director of Penn Medicine’s Abramson Cancer Center
and president-elect of the American Association for Cancer
Research.
Merck and Moderna’s treatment, known as intismeran autogene,
involves activating the immune system with up to nine doses of
Merck’s immunotherapy drug Keytruda, infused every six weeks,
plus up to nine doses of a customized mRNA vaccine that
instructs the immune system to attack the patient’s specific
cancer cells.
When used alone after surgery to reduce the risk that
melanoma returns, Keytruda is given every three to six weeks for
up to a year.
In melanoma patients, Keytruda treatment can result in
fatigue, diarrhea, rash and inflammation of joints and muscles,
as well as of healthy organs in some cases. The companies said
they saw no new side effects with the addition of the vaccine.
The trial is ongoing and the companies have not released
full results. They will continue to follow volunteers to
determine whether the drug extends overall survival.
Five-year data from a previous mid-stage trial presented in
June showed the vaccine had cut the risk that the cancer would
return by half, and reduced the risk that it would spread to new
locations by 59% compared with Keytruda alone.
In that trial, the addition of an mRNA vaccine also showed
no new increase in the rate of serious side effects.
“What we saw in the (mid-stage trial) were the kinds of
reactions people were having when they got a flu or COVID shot
or any other vaccine,” Hoge said.
Dr. Elizabeth Buchbinder, a melanoma specialist at the Mass
General Brigham Cancer Institute, said doctors treating patients
whose cancer has been surgically removed often weigh the
benefits of treating with Keytruda against the risk of side
effects, especially for patients with only a 20% risk of cancer
recurrence.
The added benefit of the vaccine, however, “may change that
math,” she said.
Buchbinder said a key reason to select melanoma to test in
combination with Keytruda was that it is a tumor that produces a
lot of mutations, making it easier for the immune system to
spot.
Many other cancer types also produce multiple mutations, she
said, suggesting it may have broad applicability.
“We’ll see, but it’s definitely an area that is going to be
exploding, especially with these results coming out,” she
said.
Published on August 20, 2026
