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mRNA Cancer Vaccine Improves Survival Rates in Melanoma

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A new personalized cancer vaccine has demonstrated efficacy against melanoma in a Phase IIb clinical trial.

Personalized cancer vaccines

As tumor cells are genetically unstable, they often express abnormal proteins that are not present on healthy cells, which can be a target for therapeutics. Personalized vaccines are developed by using this information to generate a T cell-response that is specific to the unique genetic signature of a patient’s tumor.

The biopharmaceutical companies Merck and Moderna have announced Phase IIb trial results of a mRNA-based cancer vaccine – mRNA-4157/V940 – used in combination with the antibody therapy KEYTRUDA for the treatment of melanoma. mRNA-4157/V940 consists of a single synthetic mRNA that can code for up to 35 neoantigens that are designed and produced using the mutational signature of the patient’s tumor. Once administered, the RNA sequences are translated within the patient’s cell, triggering an immune response that targets and kills cancer cells.


KEYTRUDA is a humanized antibody therapy that can be used to treat a variety of cancers, including melanoma, lung cancer and stomach cancer, among others. It was first approved by the US Food and Drug Administration in 2014, and is now included in the World Health Organization’s “List of Essential Medicines”.

The trial, called KEYNOTE, is an ongoing, randomized and open-label clinical study that has enrolled 157 participants with stage III/IV melanoma. Patients have been randomized to receive either 9 doses of mRNA-4157/V940 and KEYTRUDA (200 mg every 3 weeks for up to 18 rounds of treatment), or KEYTRUDA alone, for approximately 1 year. 

Merck and Moderna are measuring recurrence-free survival as the primary endpoint of the trial, and distant metastasis-free survival and safety as the secondary endpoints.

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Significant improvement in recurrence-free survival

The Phase IIb trial data shared by the companies demonstrate a significant improvement in recurrence-free survival when using mRNA-4157/V940 and KEYTRUDA versus KEYTRUDA treatment alone. Similarly, the risk of recurrence or death was reduced by 44% when using the combination therapy versus just administering KEYTRUDA.

“The results of this randomized Phase IIb trial are exciting for the field. These data provide the first evidence that we can improve on the rates of recurrence-free survival achieved by PD-1 blockade in resected high-risk melanoma,” says Dr. Jeffrey S. Weber, principal investigator of the study and deputy director of the Perlmutter Cancer Center at NYU Langone. “These findings also provide the first randomized evidence that a personalized neoantigen approach may be beneficial in melanoma.”

The safety profile of mRNA-4157/V940 and KEYTRUDA was consistent with previous reports from a Phase I trial. Serious treatment-related adverse events were experienced by 14.4% of patients that received the combined treatment, versus 10% in patients receiving KEYTRUDA alone.

“Today’s results are highly encouraging for the field of cancer treatment. mRNA has been transformative for COVID-19, and now, for the first time ever, we have demonstrated the potential for mRNA to have an impact on outcomes in a randomized clinical trial in melanoma,” says Stéphane Bancel, Moderna’s chief executive officer. “We will begin additional studies in melanoma and other forms of cancer with the goal of bringing truly individualized cancer treatments to patients. We look forward to publishing the full data set and sharing the results at an upcoming oncology medical conference, as well as with health authorities.”

According to the press release, a Phase III trial is in discussion and set to begin in 2023.

This article is a rework of a press release issued by Merck. Material has been edited for length and content.