Five years after surgery to remove their melanomas, nearly seven in ten patients who received a personalized vaccine alongside standard immunotherapy remained cancer-free—a striking testament to a new two-pronged approach that is reshaping how doctors fight one of the skin's deadliest forms of cancer.
The breakthrough comes from a Phase IIb clinical trial called KEYNOTE-942, led by researchers at NYU Langone Health's Perlmutter Cancer Center. The study tested whether intismeran, a personalized mRNA vaccine developed from each patient's individual tumor, could enhance the effects of pembrolizumab—a widely used immunotherapy drug also known as Keytruda. The results, presented at the 2026 American Society of Clinical Oncology annual meeting in Chicago and published simultaneously in the Journal of Clinical Oncology, show a 49% reduction in the risk of cancer recurrence or death when the vaccine and immunotherapy were combined.
The trial enrolled 107 patients randomly selected after melanoma surgery to receive the combination therapy, and compared their outcomes to 50 patients who received pembrolizumab alone—the current standard of care. After five years, 68.8% of patients in the combination group had no signs of cancer, while only 49.1% of those receiving immunotherapy alone remained cancer-free. The vaccine's impact extended beyond recurrence prevention: it reduced the risk of distant metastasis—when cancer spreads to other parts of the body—by 59%. Overall survival rates told an equally compelling story. Among patients who received both the vaccine and immunotherapy, 92.2% were alive five years later, compared to 71.3% in the immunotherapy-alone group.
What makes intismeran distinctive is its personalized design. Because patients had their tumors surgically removed, researchers could analyze each one and identify up to 34 neoantigens—abnormal proteins unique to that individual's cancer. The mRNA vaccine was then custom-made to teach each patient's immune system to recognize and attack those specific cancer proteins, effectively turning the body's own T cells into precision-guided hunters.
Dr. Janice Mehnert, senior investigator and professor in the Department of Medicine at NYU Grossman School of Medicine, emphasized the trial's significance: "Our study offers strong evidence to melanoma patients that intismeran vaccine therapy, when used in combination with immunotherapy, can demonstrably reduce their risk of having their cancer return and improve clinical outcomes."
The two-drug approach targets cancer through complementary mechanisms. Pembrolizumab works by blocking the PD-1 checkpoint, a molecular "off switch" that cancer cells exploit to hide from the immune system. By removing this cloak of invisibility, the drug makes tumors vulnerable to immune attack. Intismeran amplifies this vulnerability by actively training T cells to recognize melanoma's distinctive neoantigens, creating a coordinated assault that melanoma cells struggle to evade.
Melanoma has long posed a challenge because its cells are notoriously skilled at dodging immune responses. Many patients become resistant to immunotherapy alone. This trial demonstrates that adding a vaccine can overcome that resistance, at least in the five-year window studied so far.
Dr. Mehnert sees implications beyond melanoma: "Our findings also serve as encouragement to cancer researchers globally that mRNA vaccines like intismeran could work well in combination with immunotherapy for other cancers whose high rates of mutations have proven difficult to target." The success of this personalized approach opens a new chapter in cancer treatment—one where patients' own immune systems, properly educated and unleashed, become their most powerful allies.