Merck and Moderna’s investigational mRNA vaccine, used with Keytruda, significantly reduced the risk of melanoma recurrence in a Phase 3 trial.

An experimental personalized cancer vaccine from Merck and Moderna has cleared a major clinical milestone, sending Moderna’s stock soaring approximately 177% following positive results from the therapy’s first Phase 3 trial.

The investigational mRNA-based treatment, intismeran autogene, is being studied in combination with Merck’s Keytruda (pembrolizumab) for patients with high-risk melanoma whose detectable cancer had been completely removed through surgery.

The Phase 3 study enrolled more than 1,100 patients and met its primary endpoint, showing that the combination significantly extended the amount of time patients remained free of recurrent melanoma compared with Keytruda alone. The treatment also reduced the risk of the cancer spreading to distant parts of the body.

The results triggered a dramatic market response. Moderna shares jumped about 177%, while Merck shares rose more than 12% following the announcement. The magnitude of Moderna’s move reflects investor expectations that the cancer vaccine could become an important part of the company’s strategy to build a business beyond its COVID-19 vaccine franchise.

Despite the surge, Moderna’s shares remain well below their 2021 peak. The latest results, however, have renewed enthusiasm around the company’s oncology pipeline and the potential for its mRNA technology to extend into cancer treatment.

A Personalized Approach to Cancer

The Merck-Moderna vaccine is designed differently from traditional vaccines. Rather than targeting a common disease-causing organism or a shared cancer marker, the treatment is customized based on the unique mutations found in an individual patient’s tumor.

The goal is to use those tumor-specific mutations to train the patient’s immune system to identify and attack cancer cells. When combined with Keytruda, which helps activate and sustain the immune system’s anti-cancer response, the approach is intended to create a more targeted defense against remaining cancer cells following surgery.

The strategy is particularly relevant in melanoma, where patients can face the possibility of recurrence even after surgeons have successfully removed all detectable disease.

Beyond Melanoma

The positive results could have implications well beyond the current melanoma program. Merck and Moderna are evaluating their personalized cancer vaccine approach in several other cancers, including non-small cell lung cancer, bladder cancer, and renal cell carcinoma.

Success across multiple tumor types could significantly expand the potential market for the technology and provide Moderna with an opportunity to establish a new growth driver outside its COVID-19 business.

The companies’ latest findings also provide clinical validation for the broader concept of personalized mRNA cancer vaccines, an area researchers have been pursuing for years.

Regulatory Path Still Ahead

While the Phase 3 trial achieved its primary endpoint, the study remains ongoing, with researchers continuing to evaluate outcomes including overall survival. Merck and Moderna plan to present additional data at an upcoming medical meeting.

The companies have not yet disclosed when they will seek U.S. regulatory approval for the treatment, although discussions with regulators are expected to begin in the coming months.

For now, the results represent a significant milestone for both companies—and a potentially important development for personalized oncology. If longer-term data and additional studies confirm the benefit, individualized mRNA vaccines could eventually become part of a new generation of cancer treatments designed around the molecular profile of each patient’s disease.