A personalized mRNA-based cancer vaccine developed by Moderna and Merck has demonstrated encouraging long-term results in patients with advanced melanoma, significantly reducing the chances of the disease returning or leading to death over a five-year period.

The experimental treatment, known as intismeran autogene, is being tested in combination with KEYTRUDA (pembrolizumab), a widely used immunotherapy drug. New findings from the phase 2b KEYNOTE-942 trial were unveiled at the American Society of Clinical Oncology’s annual meeting in Chicago on May 27.

Researchers reported that patients who received the vaccine-immunotherapy combination experienced a 49% lower risk of melanoma recurrence or death compared with those treated with pembrolizumab alone after nearly five years of follow-up.

The study included 157 individuals with high-risk stage 3 and stage 4 melanoma whose tumors had been surgically removed. Participants were divided into two groups, with one receiving both intismeran autogene and KEYTRUDA, while the other received only KEYTRUDA.

According to investigators, the benefits seen in the combination-treatment group continued over time and remained durable throughout the follow-up period.

The vaccine is tailored to each individual patient. Scientists identify specific mutations within a patient’s tumor and use that information to create a personalized mRNA therapy designed to train the immune system to recognize and attack cancer cells if they return.

Researchers said the treatment has thus far demonstrated a favorable safety profile and has generally been well tolerated by patients.

Among the most frequently reported side effects were fatigue, pain at the injection site, chills, fever, and headaches. Investigators said they observed no new long-term safety issues and no serious adverse events directly linked to the vaccine.

The treatment has now advanced to a phase 3 clinical trial, the final stage typically required before regulatory approval can be considered.

In comments released by Merck in January, Kyle Holen, MD, Moderna’s senior vice president and head of development, oncology and therapeutics, said the findings underscore the “potential of a prolonged benefit … in patients with resected high-risk melanoma.”

“We continue to invest in our platform in oncology because of encouraging outcomes like these, which illustrate mRNA’s potential in cancer care,” he said.

Dr. Marjorie Green, senior vice president and head of oncology, global clinical development at Merck Research Laboratories, noted that many patients with advanced melanoma remain vulnerable to the disease returning even after surgery.

“As such, demonstrating the longer-term potential of intismeran autogene and KEYTRUDA to reduce the risk of recurrence for certain patients with melanoma is a meaningful milestone,” she said.

Merck also highlighted the positive long-term data while pointing to upcoming results from the late-stage INTerpath clinical program being conducted with Moderna in several cancers that have traditionally been difficult to treat.