Personalized mRNA Melanoma Vaccine Lowers Recurrence Risk 42% at Two Years
A personalized mRNA melanoma vaccine cut recurrence risk by 42% at two years, and regulatory discussions are ongoing.
Event / Science
Moderna-Merck Melanoma Vaccine Trial
On 22 October 2026, Moderna and Merck released full results of a late-stage international trial of intismeran, a personalized mRNA cancer vaccine, in over 1,100 high-risk melanoma patients. Adding the vaccine to standard Keytruda treatment reduced the risk of recurrence by 42% at two years. Side effects were mainly injection-site soreness and fatigue. The companies are discussing regulatory steps, and results will be presented at the European Society of Medical Oncology meeting in Madrid.
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2026-10-24 to 2026-10-24 · UTC publication dates
Coverage begins 24 Oct, 04:04 UTC
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What happened
Moderna and Merck are in discussions with regulators on next steps toward approval of intismeran
Moderna and Merck are discussing next steps for seeking regulatory approval of intismeran with regulatory authorities. The cost of the vaccine has not been disclosed.
Moderna and Merck announced in August that the intismeran late-stage trial was successful
In August, Moderna and Merck announced that the late-stage trial of intismeran had met its goal, before releasing detailed results later in October.
Other personalized mRNA cancer vaccines are being tested against lung, kidney, and pancreatic cancers
Experimental personalized cancer vaccines using mRNA and other approaches are being tested against lung, kidney, and pancreatic cancers in addition to melanoma.
Moderna and Merck release results of late-stage trial of personalized mRNA cancer vaccine intismeran in melanoma
Moderna and Merck released detailed results of a major late-stage international trial of intismeran, a personalized mRNA cancer vaccine, for patients with melanoma. The results showed a reduction in the risk of melanoma recurrence.
Intismeran is a custom vaccine targeting neoantigens unique to each patient's tumor
Intismeran is individually produced for each patient based on gene mutations unique to that patient's tumor, which create proteins that appear only in cancer cells. The vaccine is given as nine doses spaced three weeks apart to train the immune system to attack these neoantigens.
Trial enrolls more than 1,100 patients with surgically removed high-risk melanoma
The randomized trial included more than 1,100 patients with high-risk melanoma that had been surgically removed. All participants received Merck's immunotherapy Keytruda as standard follow-up, and were randomly assigned to also receive either the custom vaccine or a placebo.
Patient Tony Hout, 62, remains cancer-free after joining the intismeran trial in 2024
Tony Hout, 62, joined the intismeran trial at MD Anderson Cancer Center in Houston in 2024, after melanoma was found on his ear and surgery revealed it had begun to spread. Scans in the week of the results showed he remained cancer-free. He has since moved to Cayuga, Indiana, and returns to Houston every few months for study check-ups.
Moderna manufacturing facility in Massachusetts supplies doses for thousands of patients in international studies
Moderna's specialized cancer vaccine manufacturing facility in Massachusetts is producing doses for thousands of people enrolled in multiple cancer vaccine studies underway internationally.
82% of vaccine-group patients remain recurrence-free at two years versus 70% on Keytruda alone
Two years after surgery, 82% of patients who received intismeran with Keytruda were still living without a melanoma recurrence, compared with 70% of patients who received Keytruda alone. The trial continues to track longer-term outcomes.
Full trial results released early after partial data was leaked, ahead of Madrid oncology meeting
Some trial data became public through a leak late Thursday, prompting Moderna and Merck to release full results ahead of a scheduled presentation at the European Society of Medical Oncology meeting in Madrid on Saturday.
Moderna shares fall 18% after full trial results are released
Moderna shares fell 18% on Thursday after the full results of the intismeran trial were made public. The shares remained more than 200% above their late-August level, before the initial trial results were announced.
Reported side effects of intismeran are mainly sore arm and fatigue
The main side effects of intismeran were sore arm, fatigue, and other reactions typical of mRNA COVID-19 vaccination, according to the trial's lead researcher at MD Anderson Cancer Center.
Intismeran plus Keytruda reduces melanoma recurrence risk by 42% two years after surgery
In the trial, adding intismeran to the standard post-surgery treatment Keytruda reduced the risk of melanoma returning by 42% two years after surgery compared with Keytruda alone.
Custom vaccine production takes about six weeks from tumor analysis to finished dose
Producing an individual intismeran dose takes a few days of brewing, but the full process, beginning with analysis of tumor genetics to design each patient's vaccine, can take roughly six weeks or longer. Patients in the trial began standard Keytruda treatment while their vaccine was being prepared.
Intismeran uses the mRNA technology behind COVID-19 vaccines
Intismeran is built on the same mRNA technology used in COVID-19 vaccines, for which the underlying science received the Nobel Prize.
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