Moderna and Merck treatment cuts melanoma recurrence or death risk by 42% in Phase 3
Key Facts
A prespecified interim analysis of a Phase 3 trial showed that the experimental treatment intismeran autogene, developed by Moderna and Merck, cut the risk of melanoma recurrence or death by 42% when added to pembrolizumab, marketed as Keytruda, compared with pembrolizumab alone. The results included patients who had undergone complete resection of stage IIB to IV melanoma tumors. The companies said the reduction was achieved on the study’s specified measure, the risk of recurrence or death. The full announcement came after some data were made public on Thursday evening, accelerating disclosure ahead of the scientific presentation scheduled for the end of the week, according to the Associated Press. The results highlight a treatment that adds a personalized messenger RNA-based vaccine to immunotherapy after surgery.
Intismeran autogene uses a personalized vaccine design for each patient, formulated to match mutations in the patient’s tumor, according to the Associated Press. The treatment is given after surgical removal of the tumor, alongside pembrolizumab, an immunotherapy drug used alone in the comparison group. This means the trial evaluated adding the vaccine to an existing treatment, not the vaccine as a substitute for surgery or immunotherapy. The study compared outcomes between the combination treatment and pembrolizumab alone in patients whose melanoma had been completely resected. The prespecified interim analysis showed a 42% relative reduction in the risk of recurrence or death, according to the companies’ announcement.
The results do not yet establish the treatment’s effect on overall survival: the companies said data for that measure remain immature and that the study is continuing to assess it. This sets a clear limit on what can be inferred from the current announcement: the reported measure is recurrence-free survival, not proof of extended life. Moderna and Merck said they are in discussions with regulators about next steps. The next milestone therefore centers on completing patient follow-up and evaluating regulatory data, while the study continues. The companies did not specify in their statement a final date for when overall survival data would be ready.
The Phase 3 result follows five years of follow-up in the Phase 2 KEYNOTE-942 trial, in which the companies showed a 49% reduction in the risk of recurrence or death and a 59% reduction in the risk of distant metastasis or death, compared with KEYTRUDA alone. The follow-up data were presented at the 2026 American Society of Clinical Oncology meeting, according to Merck’s announcement. Those earlier results provide context for the program’s development, but relate to a Phase 2 trial, its measures and follow-up period, while the Phase 3 announcement concerns a prespecified interim analysis. Merck also said its INTerpath program includes 9 Phase 2 and Phase 3 clinical trials covering multiple tumor types and different stages of disease. The companies announced in August that they would engage with regulators on filing applications.
Meeting the announced target did not prevent both shares from falling after the results were leaked. Reuters reported that Moderna shares closed down more than 17% on Thursday, October 22, while Merck shares fell about 1.8% in the same session. The full announcement came after some data were published on Thursday evening, according to the Associated Press, and ahead of the scientific presentation scheduled for the end of the week. The following day, Moderna shares closed at $200.1, according to EL7 data. The market reaction in August was different: Moderna shares rose more than 120% to $140.12 in the August 19 session, while Merck shares gained about 11%, after the preliminary results were announced. The companies said the next steps include reviewing the complete data and regulatory discussions.