Moderna and Merck announced promising results from a Phase 2b trial showing their personalized mRNA cancer vaccine reduced melanoma recurrence risk by 44% when combined with Merck's checkpoint inhibitor Keytruda. The companies tested the vaccine on 557 patients with high-risk stage 3 or 4 melanoma who had surgery to remove their tumors.
Researchers customized each vaccine to target mutations unique to individual patients' cancer cells. The approach trains the immune system to recognize and attack melanoma-specific proteins before the cancer can return. Patients received either the vaccine plus Keytruda or Keytruda alone. After two years, 44% fewer patients who received the combination developed recurrent or metastatic melanoma compared to those on Keytruda alone.
The findings represent a shift in cancer treatment strategy. Rather than attacking existing tumors, this therapeutic vaccine works as a preventive tool for patients at high risk of recurrence. The personalized nature addresses why cancers often resist standard treatments. Each tumor carries its own mutations, so a one-size-fits-all vaccine struggles to work effectively. By sequencing individual tumors and encoding their specific mutations into an mRNA vaccine, Moderna and Merck tailored protection to each patient's biology.
Keytruda, an immunotherapy drug, primes the immune system to recognize cancer cells. The vaccine then teaches immune cells which melanoma-specific targets to attack. This combination approach appears more effective than either treatment alone.
The FDA granted the combined therapy Breakthrough Therapy designation in 2023, recognizing its potential to address an unmet medical need. Melanoma affects roughly 100,000 Americans annually, and stage 3 or 4 disease carries a significant recurrence risk even after surgery.
Moderna and Merck plan to seek regulatory approval based on these results.