The annual meeting of the American Association for Cancer Research (AACR) kicked off this past weekend in Orlando, FL. One talk from Sunday’s program, entitled “A personalized cancer vaccine, mRNA-4157, combined with pembrolizumab in patients with resected high-risk melanoma: Efficacy and safety results from the randomized, open-label Phase IIb mRNA-4157-P201/Keynote-942 trial” made a splash. The findings presented suggest that the combination of an experimental mRNA vaccine with an immunotherapy reduced the likelihood of melanoma recurring or causing death by 44% when compared to immunotherapy alone.

Led by researchers at NYU Langone Health’s Perlmutter Cancer Center, the randomized Phase IIb trial involved men and women who had surgery to remove melanoma from lymph nodes or other organs and were at high risk of the disease returning in sites distant from the original cancer. About 1.3 million Americans are currently diagnosed with some form of melanoma.

Among 107 study subjects who were injected with both the experimental vaccine, mRNA-4157/V940, and the immunotherapy pembrolizumab, the cancer returned in 24 subjects (22.4%) within two years of follow-up, compared with 20 out of 50 (40%) who received only pembrolizumab.

“Our Phase IIb study shows that a neoantigen mRNA vaccine, when used in combination with pembrolizumab, resulted in prolonged time without recurrence or death compared with pembrolizumab alone,” said Jeffrey Weber, MD, PhD, deputy director of the Perlmutter Cancer Center.

Phase III trials of the combination of the mRNA-4157/V940 vaccine with pembrolizumab versus pembrolizumab alone are already planned at NYU Langone and a number of other medical centers globally, said Weber. mRNA-4157/V940 is being jointly developed and commercialized by Moderna and Merck—the manufacturer of pembrolizumab.

The FDA granted Breakthrough Therapy Designation to mRNA-4157/V940 in combination with pembrolizumab earlier this year.

In designing a vaccine against melanoma, researchers attempted to trigger an immune response to specific abnormal proteins—neoantigens—made by cancer cells. Because the study volunteers all had their tumors removed, researchers were able to analyze their cells for neoantigens that were specific to each melanoma and create a “personalized” vaccine for each patient. As a result, T cells were produced specific to the neoantigen proteins encoded by the mRNA. Those T cells could then attack any melanoma cells trying to grow or spread.

Scientists involved in the study say that the personalized mRNA-4157/V940 vaccine took about six to eight weeks to develop for each patient and could recognize as many as 34 neoantigens. Severe side effects were similar between the two arms of the study, they said, with fatigue being the most common side effect specific to the vaccine reported by patients.

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