These Melanoma Patients Got a Vaccine Made for Their Own Tumors. 2 Years Later, 82% Are Still Cancer-Free

A new era of cancer treatment seems to have begun in earnest. Merck and Moderna’s personalized therapeutic vaccine for advanced melanoma is working as intended and keeping people cancer-free years later, trial data released this week has shown.

On Thursday, the pharmaceutical companies released the full promising Phase III results of their mRNA-based vaccine, named intismeran autogene. People given intismeran in combination with a standard immunotherapy drug were substantially less likely to have their cancer return two years later and are likely living longer than those only given the drug, researchers found. Though longer-term data is still being collected, intismeran appears set to become the first next-generation cancer vaccine to garner regulatory approval in the near future.

These results are expected to be published in the New England Journal of Medicine, meaning they will undergo the typical peer-review process. However, the companies reportedly decided to release their findings ahead of schedule after a third party seemingly broke the embargo and leaked the data early.

The era of cancer vaccines

Vaccines are usually preventative—helping the body recognize threats like viruses before they arrive. Cancer vaccines, on the other hand, are typically therapeutic, meaning they’re intended to prevent future recurrences of a previously treated cancer. These vaccines, like intismeran, are often personalized to someone’s specific tumors.

Intismeran is specifically designed to train the body’s immune system to recognize up to 34 different neoantigens, the distinct proteins that cancer cells produce as they mutate. This newest trial, codenamed INTerpath-001, involved 1,137 patients with high-risk melanomas (stages 2B to 4) that were likely to recur. The patients first underwent surgery to remove any visible traces of their melanoma, then were randomized into two groups: People who were given Merck’s immunotherapy drug Keytruda (pembrolizumab) and people who were given Keytruda plus up to nine doses of intismeran, repeated every three weeks.

In August, the companies disclosed that intismeran met the primary goals of the trial. This week, they finally revealed the detailed primary findings of the trial.

Compared to Keytruda-only, the vaccine-drug combo reduced people’s risk of melanoma recurrence or death by 42% by the two-year mark. In absolute terms, 82.2% of vaccinated people were still cancer-free after two years, compared to 70% of Keytruda-only patients. The combination also reduced people’s risk of distant metastasis (cancer reappearing far away from the original site, which is more concerning) or death by 38%. And though it will take more time to know for sure, the companies stated there is early evidence suggesting that people on intismeran are living longer overall.

The treatment also appeared to be relatively safe and in line with earlier results, with no new safety signals seen in the trial. Most adverse events related to the treatment are likely to stem from Keytruda, which is known to commonly cause side effects like fatigue and muscle pain; it can also potentially cause severe complications like liver or lung inflammation.

The future of intismeran

The companies’ announcement Thursday drew a muted response from the financial sector, with their stock prices initially falling. On the science end of things, however, this seems very promising. Though there are some existing cancer vaccines available today, they’re generally modest in effectiveness. Personalized and other next-generation versions of these vaccines, like intismeran, are expected to significantly improve the field of cancer treatment moving forward. Merck and Moderna are already working on other late-stage trials testing intismeran plus immunotherapy for other types of tumors, including non-small cell lung cancer.

Intismeran’s approval would also bolster the reputation of mRNA vaccine technology, which has been under fire lately. Many supporters of the antivaccination movement, including the current secretary of the U.S. Department of Health and Human Services, Robert F. Kennedy Jr., are especially hostile to mRNA vaccines.