mRNA Vaccine Shows High Effectiveness at Preventing Melanoma Recurrence

You've probably heard mRNA mentioned a lot since the COVID-19 vaccine rollout. Well, that same technology is now showing serious promise in a completely different fight — stopping skin cancer from coming back.

A new study published in the Journal of Clinical Oncology, and presented this week at the American Society of Clinical Oncology's annual conference, found that a personalized mRNA vaccine dramatically reduced the chances of melanoma returning in high-risk patients. Melanoma is the deadliest form of skin cancer. To put the stakes in perspective: there are approximately 112,000 melanoma diagnoses in the U.S. every year, and about 8,500 people die from it.

Here's the setup. The trial focused on patients who had already had surgery to remove their melanoma, but were considered at high risk for recurrence — meaning the cancer could come back, potentially somewhere much harder to treat, like the lungs, liver, or brain. Half the patients got the standard treatment: an immunotherapy drug called Keytruda (technically called pembrolizumab), which helps the immune system fight cancer. The other half got Keytruda plus the new mRNA vaccine, called intismeran — developed jointly by Moderna and Merck.

What makes this vaccine genuinely different from anything you've had before is that it's built specifically for each patient. Scientists sequence a patient's tumor to identify up to 34 unique molecular fingerprints — called neoantigens — that are specific to their cancer cells. Those fingerprints get encoded into a custom mRNA vaccine. Essentially, it hands your immune system a wanted poster tailored to your own tumor.

The results, after five years of follow-up, are hard to ignore. Nearly 69% of patients who got the combination therapy remained cancer-free, compared to just 49% of those who only received Keytruda — that works out to a 49% reduction in the risk of cancer returning or dying. And on the survival side: 92% of combination-therapy patients were still alive at the five-year mark, versus 71% in the Keytruda-only group. As one outside expert — a dermatologist not involved in the research — put it, this is "a landmark advance in how we treat these very advanced, high-risk melanomas."

Side effects appear manageable. People in the trial reported flu-like symptoms — chills, headaches — similar to what many experienced with mRNA COVID vaccines, and they only lasted a couple of days.

So where does this go from here? A much larger Phase 3 trial — about 1,000 patients, expanded to Europe — has already finished enrolling, and results are expected in the coming months. If those hold up, Moderna plans to seek FDA approval. Researchers are also exploring whether the same mRNA approach could work against other cancers, including lung cancer and pancreatic cancer.

The bottom line: this isn't approved yet, and the current study is mid-stage (Phase 2b) with a relatively small group. But the five-year durability of these results — and the fact that the 49% risk reduction has held steady from the three-year mark to the five-year mark — is what's getting oncologists genuinely excited. Keep an eye on those Phase 3 results.