Moderna and Merck reported that a personalized mRNA vaccine, intismeran, given with Merck’s Keytruda significantly reduced melanoma recurrence and prevented spread to other organs in a large Phase 3 trial of 1,137 high‑risk patients. The vaccine is tailored to mutations found in each patient’s tumor. Full trial data have not yet been released; the companies plan to present detailed results to regulators and at an international medical meeting. Earlier mid‑stage results showed a 49% reduction in recurrence or death when intismeran was added to Keytruda.
Moderna and Merck Report Positive Phase 3 Results: Personalized mRNA Vaccine Cuts Melanoma Recurrence
An employee works in a lab focused on cancer vaccine research at the Moderna headquarters in Cambridge, Massachusetts. | Credit: Adam Glanzman / Bloomberg via Getty Images
Moderna and Merck announced Wednesday that their experimental personalized mRNA vaccine, intismeran, combined with Merck’s immunotherapy Keytruda (pembrolizumab), significantly reduced melanoma recurrence and prevented the cancer from spreading to other organs in a large clinical trial.
Trial Overview
The ongoing Phase 3 study enrolled 1,137 high‑risk melanoma patients whose tumors were surgically removed and genetically sequenced. Each patient received a bespoke intismeran vaccine designed to target mutations found in their own tumor, together with standard Keytruda therapy.
Key Findings and Context
Moderna and Merck said the combination reduced recurrence and inhibited metastasis in the trial population. The companies have not yet released full, detailed data publicly; they said they will present the results to regulators and at an international medical meeting. An earlier mid‑stage trial had shown that adding intismeran to Keytruda reduced the risk of melanoma recurrence or death by 49% compared with Keytruda alone.
“The results mark the first successful late‑stage trial for a personalized mRNA cancer therapy, validating decades of research and paving the way for a potentially new life‑extending treatment,” The Wall Street Journal reported.
What This Means
Researchers and investors are watching closely: the announcement marks a potentially important milestone for personalized cancer vaccines, but independent review of the full trial data is needed to confirm effectiveness, safety and broader applicability. Moderna’s shares surged following the announcement.
Important note: While the headline results are promising, regulators and the scientific community will evaluate detailed efficacy and tolerability data before drawing definitive conclusions about clinical use.
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