Landmark Melanoma Vaccine Is Right Around the Corner

An individualized melanoma vaccine may be available to late-stage skin cancer patients in just two years.

Melanoma is the deadliest type of skin cancer, as it spreads very quickly if left untreated. It is estimated there will be nearly 100,000 new melanoma diagnoses and almost 8,000 deaths resulting from the disease in the United States in 2023.

The Phase 2b clinical trial, KEYNOTE-942, evaluated experimental neoantigen therapy (INT), mRNA-4157, developed by Merck and Moderna, in combination with KEYTRUDA, a type of immunotherapy used to treat breast, lung, and other cancers.

The trial enrolled 157 patients with high-risk stage III/IV melanoma. After undergoing complete surgical resection, the patients were assigned to receive either mRNA-4157 in combination with KEYTRUDA or KEYTRUDA alone for about one year.

During the average follow-up of three years, the combined therapy reduced the risk of cancer recurrence or death by 49% compared with KEYTRUDA alone. Patients on the experimental treatment were also at a 62% lower risk of distant metastasis than those taking KEYTRUDA only.

"We are committed to driving research forward for innovative modalities in earlier stages of cancer, where we can make the most meaningful impact for patients, by combining Merck's expertise in immuno-oncology with Moderna's innovative mRNA technology," said Dr. Marjorie Green, senior vice president and head of late-stage oncology, global clinical development, Merck Research Laboratories, in a statement.

In the trial, 25% of patients on the experimental treatment reported adverse events, with fatigue, pain in the injection site, and chills being the most common.

The U.S. Food and Drug Administration (FDA) has granted mRNA-4157 a breakthrough therapy designation to accelerate its approval in February.

Moderna CEO Stephane Bancel told AFP that the vaccine could be available to patients in as little as two years, and the company is already building a new factory in Massachusetts to ensure the supply.

"We think that in some countries, the product could be launched under accelerated approval by 2025," he said.

How does the therapy work?

The mRNA-4157 therapy is based on messenger RNA (mRNA), the technology used for developing COVID-19 vaccines.

Individualized neoantigen therapies, such as mRNA-4157, are designed to train and activate an antitumor immune response by generating specific T-cell responses based on the unique mutational signature of a patient's tumor.

Meanwhile, KEYTRUDA works by strengthening the immune system's ability to help detect and fight tumor cells.

Dr. Alan Melcher, professor of Translational Immunotherapy at the Institute of Cancer Research, says the results are very exciting and show the feasibility of making and delivering personalized vaccines for cancer treatment.

He said, "However, these are still early results and we have not seen the full data yet. The trial is relatively small and the benefits of vaccines against melanoma and potentially other cancers need to be further tested in larger trials and other cancer types. It will also be important to see if the vaccine did indeed generate an immune response against the tumor, which I anticipate will be tested using tissue and blood collected from patients in this study."