Moderna and Merck sustain 49% risk reduction in milestone five-year cancer vaccine study

Moderna (NASDAQ:MRNA) and Merck (NYSE:MRK) announced Tuesday that their individualized neoantigen therapy continues to show dramatic long-term benefits, providing the strongest evidence to date that mRNA technology can be harnessed to treat established cancer.

New data from the Phase 2b KEYNOTE-942/mRNA-4157-P201 study, representing a median five-year follow-up, revealed that the combination of intismeran autogene (mRNA-4157) and Keytruda reduced the risk of recurrence or death by 49% compared to Keytruda alone in patients with resected high-risk stage III/IV melanoma.

The results are particularly significant as they demonstrate that the "immune training" provided by the vaccine is durable, with a hazard ratio of 0.510 that has remained remarkably stable since earlier readouts.

Patients in the study received the personalized vaccine—which is custom-manufactured to target up to 34 unique mutations identified in a specific patient's tumor—alongside Merck’s blockbuster immunotherapy.

The safety profile remained consistent with prior reports, with no new safety signals emerging over the extended follow-up period.

The companies are now aggressively pursuing a broader clinical program, with enrollment continuing across eight Phase 2 and 3 studies in various tumor types.

Notably, the pivotal Phase 3 adjuvant melanoma trial is now fully enrolled, setting the stage for a potential regulatory filing that could transform the standard of care for skin cancer.

The partnership represents a critical test for Moderna as it seeks to diversify its revenue beyond its COVID-19 franchise.

For Merck, the success of the combination therapy provides a potential lifecycle extension for Keytruda, which faces patent expiration later this decade.

The companies plan to present additional data from the study at upcoming medical congresses.