A personalized cancer vaccine developed by Merck and Moderna has delivered strong results over a five-year period, significantly reducing the recurrence of melanoma in high-risk patients.

The injectable therapy, known as intismeran autogene, works in combination with KEYTRUDA, an immunotherapy drug also known as pembrolizumab.

Researchers shared the latest results from the phase 2b KEYNOTE-942 trial during the American Society of Clinical Oncology Annual Meeting held in Chicago on May 27.

After approximately five years of follow-up, the study found that the combination therapy cut the risk of melanoma returning or causing death by 49% compared to those treated with KEYTRUDA alone.

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The trial examined data from 157 patients who had undergone surgery for stage 3 or 4 melanoma.

They were divided into two groups, with one receiving the experimental vaccine alongside KEYTRUDA and the other taking pembrolizumab by itself.

According to investigators, patients who received the combination treatment experienced results that were “sustained and durable over time.”

Intismeran autogene is custom-built for each patient by using mutations from their own tumor. The vaccine is meant to train the immune system to recognize and attack the cancer if it reappears.

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Researchers reported that the vaccine was “well-tolerated” and had a “manageable” safety profile during the study.

Common side effects included fatigue, pain at the injection site, chills, fever, and headache. The research team found no new safety concerns or serious vaccine-related adverse events in the long-term data.

The combination therapy is already being tested in a larger phase 3 trial to confirm its effectiveness and safety on a broader scale.

Kyle Holen, MD, Moderna’s senior vice president and head of development for oncology and therapeutics, said in a January press release that the findings show the “potential of a prolonged benefit … in patients with resected high-risk melanoma.”

He added that Moderna plans to continue investing in oncology and developing its mRNA platform because of the encouraging outcomes seen so far.

Dr. Marjorie Green, senior vice president and head of oncology at Merck Research Laboratories, said that high-risk patients continue to face a “significant risk of recurrence” even after surgical treatment.

“For many of these patients, demonstrating the longer-term potential of intismeran autogene and KEYTRUDA to reduce that risk is a meaningful milestone,” Green stated.

Both companies emphasized that the promising five-year data reflect a step forward for mRNA-based therapies in cancer treatment.

Merck also pointed to upcoming results from its late-stage INTerpath trials, which will explore the vaccine’s effectiveness in other hard-to-treat cancers in partnership with Moderna.

As the phase 3 research continues, experts at the oncology meeting noted that this new direction in personalized cancer immunotherapy could redefine treatment expectations for certain melanoma patients.