Merck, Moderna vaccine reduces melanoma recurrence by 34% in phase III trial

Merck & Co. and Moderna announced on Monday that a late‑stage, phase‑III trial of their investigational cancer vaccine, designed to prevent recurrence of melanoma, has met its primary endpoint in both the overall study population and a pre‑planned high‑risk subgroup. The 1,200‑patient study, which began enrollment in 2021, compared the vaccine given in combination with standard adjuvant therapy to standard therapy alone. At the two‑year follow‑up, recurrence rates were 12.3 % in the vaccine arm versus 18.7 % in the control arm, a 34 % relative risk reduction that met the study’s predefined statistical thresholds. Both companies said the results support continued development toward regulatory approval in the United States and other major markets.

Merck, headquartered in Rahway, New Jersey, is the world’s fifth‑largest biomedical company by revenue. In 2024, nearly half of its sales – $29.5 billion – came from the oncology drug Keytruda (pembrolizumab), a PD‑1 inhibitor that has become a cornerstone of many cancer treatment regimens. The company also generates significant revenue from the HPV vaccine Gardasil and animal‑health products. Moderna, best known for its mRNA COVID‑19 vaccine, has been expanding into oncology, leveraging its platform to deliver personalized cancer vaccines that stimulate the immune system to target tumor‑associated antigens. The collaboration between the two firms combines Merck’s oncology expertise and market reach with Moderna’s mRNA technology and manufacturing capabilities.

The vaccine studied, a multivalent mRNA formulation encoding several melanoma‑associated antigens, is administered as a series of injections after standard surgical resection and adjuvant therapy. Its mechanism relies on priming the patient’s T‑cell repertoire to recognize and destroy residual malignant cells that may remain after surgery. Earlier phase studies suggested that the vaccine could enhance long‑term immune surveillance, but the late‑stage data are the first to demonstrate a clinically meaningful reduction in recurrence, particularly among patients who had high‑stage disease or positive lymph nodes at diagnosis.

If approved, the vaccine could represent a paradigm shift in melanoma care. Currently, adjuvant therapy for high‑risk melanoma often involves checkpoint inhibitors, which can be costly and associated with immune‑related adverse events. A vaccine that reduces recurrence risk could offer a complementary or alternative strategy, potentially improving survival while mitigating side effects. The oncology market already faces intense competition, with several companies developing peptide‑based, viral vector–based, and neo‑antigen vaccines. Merck’s entry into this space would add a significant new player with a robust commercial infrastructure.

Regulatory agencies are likely to scrutinize the trial’s safety profile, which was reported as acceptable, with most adverse events being mild to moderate injection‑site reactions. The companies have indicated plans to submit a Biologics License Application (BLA) to the U.S. Food and Drug Administration (FDA) in the third quarter of 2026, with parallel filings in the European Union and other key markets. If cleared, the vaccine would join a growing roster of immuno‑therapeutic agents that could transform the standard of care for melanoma and possibly other solid tumours.

For Taiwan, the announcement has several implications. The island’s pharmaceutical sector is a major contributor to the national economy, with a strong focus on biopharmaceutical development and manufacturing. A new, globally competitive melanoma vaccine would create opportunities for Taiwanese biotech firms to partner in production or supply chain logistics, potentially boosting local employment and export revenue. Moreover, Taiwan’s public health system, which has already adopted several of Merck’s oncology drugs, could benefit from an additional therapeutic option that might reduce recurrence rates and associated treatment costs. On a regional scale, the success of mRNA‑based vaccines beyond infectious disease underscores the strategic importance of advanced biotechnology for maintaining health security and economic resilience in East Asia.