For years, cancer vaccines have been touted as a breakthrough with transformative potential—a promise that always seemed to lie beyond some distant horizon. In 2023, however, the results of two clinical trials hinted that the breakthrough might be near.
The first report came in April, at the annual conference of the American Association for Cancer Research (ASCO). It concerned melanoma, the most deadly form of skin cancer. In patients whose tumors had been surgically removed, researchers showed, an experimental therapeutic vaccine cut the risk of recurrence by 44 percent compared to the immunotherapy drug pembrolizumab alone—the standard treatment in such cases.
These findings have “definitely revived the cancer vaccine field,” said lead author Jeffrey Weber, deputy director of NYU Langone’s Laura and Isaac Perlmutter Cancer Center, at the ASCO conference. “I say that as a genuine skeptic who has put many patients on previous trials and seen no benefit until now.”
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What are the Advancements in Cancer Vaccines?
The jab that changed Weber’s mind comes from a new generation of cancer vaccines. Previous approaches attempted to train the immune system to recognize a protein normally overexpressed by a given type of cancer, although that antigen may also exist in normal cells. The experimental shot, developed by the pharma company Moderna and Merck, targets neoantigens—proteins expressed by an individual’s unique cancer, but not by normal cells. This personalized shot, based on the same mRNA platform as Moderna’s COVID-19 vaccine, can target up to 34 neoantigens simultaneously.
In the phase 2 trial, 107 subjects who had undergone surgery to remove melanoma from lymph nodes or other organs received both the vaccine and pembrolizumab, which protects T cells—the immune system’s infantryman—from being shut down by cancer cells. Another 50 received only pembrolizumab. Among the vaccinated group, melanoma recurred in just 22 percent of patients within two years, compared to 40 percent in the control group. Most side effects were mild, and immune-related adverse effects (such as endocrine problems) were similar in both groups, suggesting that most came from the drug, not the shot.
More study will be needed to confirm the vaccine’s efficacy, and a larger phase 3 trial is now underway. “I’m getting flooded by patients saying, ‘How can I get this?'” says M.D. Anderson Cancer Center oncologist Rodabe Amaria. “It’s not ready for prime-time, but the initial data looks very encouraging.”
A close-up look at pancreatic cancer cells, which often first spread within the abdomen and to the liver. (Credit:; Anne Weston, Francis Crick Institute/Science Photo Library)
What are Other Breakthroughs for Cancer Treatment?
That wasn’t the only success story for new cancer vaccines this year. In May, researchers at the Memorial Sloan Kettering Cancer Center in New York reported a similar breakthrough with pancreatic ductal adenocarcinoma, the most common pancreatic cancer,
