Moderna, Merck treatment cuts risk of melanoma recurrence or death by 42%
Key Facts
Merck said adding intismeran autogene, the experimental treatment it is developing with Moderna, to Keytruda reduced the risk of melanoma recurrence or death by 42% compared with Keytruda alone, in results made public following a leak on October 22. This relative reduction pertains to the primary analysis of the trial testing the combination treatment after surgical removal of the tumor, with a group receiving Keytruda alone serving as the comparator. According to Merck's statement, two-year recurrence-free survival was 82.2% among patients receiving the combination treatment, versus 70.0% in the comparator group. The analysis also showed a 38% reduction in the risk of distant metastasis or death, an endpoint covering the spread of cancer to distant sites or the patient's death. The company said adding the experimental treatment "reduced the risk of recurrence or death by 42%." The details follow the companies' announcement in August that the trial had met its primary endpoint of recurrence-free survival and a key secondary endpoint of distant metastasis-free survival.
The trial enrolled 1,137 patients who had undergone complete surgical resection of melanoma, according to Merck and Moderna's announcement, to evaluate adding the experimental treatment to Keytruda after surgery. The comparison pits the two treatments together against Keytruda alone to measure the effect of the addition on recurrence or death and on distant metastasis or death. Intismeran is designed using a sample taken from the patient's own tumor, according to Merck's description of how the treatment is prepared. The sample is used to identify the mutational signature of the patient's cancer, which the company described as the tumor's "unique fingerprint." The aim of this design is to generate an antitumor immune response based on that patient-specific signature. The combination treatment thus brings together intismeran, designed using the tumor sample, and Keytruda, in a trial whose primary endpoint measures continued recurrence-free survival after resection.
The current trial was preceded by a phase 2b study, for which the companies announced a follow-up update in June 2026 that also showed a benefit from adding intismeran to Keytruda. In that earlier study, the reduction in the risk of recurrence or death was 49% compared with Keytruda alone, according to Merck. The reduction in the risk of distant metastasis or death was 59% in the same study update, compared with the comparator group receiving Keytruda alone. The two reductions reported in the current trial were smaller than those recorded in the earlier study, with each result remaining specific to the trial in which it was obtained. In the market, Reuters reported that Moderna shares fell more than 20% during trading on October 22 following the leak of the results. Bloomberg reported that the magnitude of the benefit fell short of market expectations, while an analyst described the result for preventing distant spread as less exceptional. Investing described the disclosure as an "early and unauthorized publication of embargoed results."
On safety, Merck and Moderna said in their announcement of preliminary results in August that the trial had identified no new safety signals. They added in the same announcement that they would engage with regulators on registration submissions for intismeran autogene in combination with Keytruda. The companies said they "will engage with regulators on registration submissions," the next regulatory step for the combination treatment after announcing that the trial had met both endpoints. In parallel, the study continues to evaluate overall survival, an endpoint for which follow-up remains ongoing, according to Merck. The company described the results for this endpoint as "not yet mature," while the trial continues to follow patients to assess it.