- mRNA cancer vaccines cut melanoma recurrence risk by 44 percent in trials.
- Each vaccine encodes up to 34 neoantigens unique to a patient's tumor.
- Half of pancreatic cancer patients showed no recurrence after three years.
Jeffrey Weber had spent years testing checkpoint inhibitors against melanoma. Now the data from his latest trial suggested something more ambitious might work: a personalized vaccine tailored to each patient's tumor.
The KEYNOTE-942 results appeared in The Lancet in early 2024. Adding an mRNA vaccine to standard immunotherapy reduced melanoma recurrence risk by 44 percent. This was the first evidence that cancer vaccines could extend survival for patients facing high odds of return.
Key figure
44%
Reduction in melanoma recurrence when mRNA vaccine was combined with immunotherapy
From COVID Technology to Cancer Treatment
The same mRNA technology that produced COVID-19 vaccines in record time is now being repurposed for oncology. Cancer vaccines work differently from their infectious disease counterparts, training the immune system to recognize mutations unique to each patient's tumor.
What is a personalized cancer vaccine?
Scientists sequence a patient's tumor, identify proteins that differ from healthy cells, then encode instructions for those proteins into mRNA. The patient's own cells produce these tumor markers, teaching immune cells to hunt down cancer cells carrying the same mutations.
Traditional vaccines target fixed viral sequences that remain constant across populations. mRNA Cancer vaccines must be customized because every tumor carries different mutations, making them both promising and difficult to manufacture at scale.
The Melanoma Breakthrough
Weber serves as deputy director of the Perlmutter Cancer Center at NYU Langone. He led the trial testing Moderna's mRNA-4157 alongside pembrolizumab, a checkpoint inhibitor that helps immune cells attack tumors.
The vaccine encodes up to 34 neoantigens specific to each patient's cancer.
Neoantigens are proteins found only in tumor cells, making them ideal targets for immune attack. Among 157 patients with high-risk melanoma, those receiving both treatments showed significantly better outcomes.
Three-year follow-up data, presented in June 2024, strengthened these findings considerably.
The combination reduced recurrence risk by 49 percent and cut the risk of distant metastasis by 62 percent. These results prompted the FDA to grant breakthrough therapy designation in February 2023.
Phase 3 trials are now underway, with regulatory submissions expected in 2026.
Pancreatic Cancer Offers a Harder Test
If mRNA vaccines can work against melanoma, pancreatic cancer presents a more demanding challenge. Only 10 percent of patients survive five years, and traditional immunotherapy has shown little benefit.
Vinod Balachandran, a surgical oncologist at Memorial Sloan Kettering, has spent eight years studying the rare patients who beat those odds. Their tumors attracted unusual numbers of immune cells.
His team partnered with BioNTech to create personalized vaccines from surgical tumor samples.
In a phase 1 trial, half of the 16 patients who received vaccines showed no cancer recurrence after three years. Vaccine-stimulated T cells persisted in patients' blood for nearly four years, suggesting durable immune memory.
It's exciting to see that a personalized vaccine could enlist the immune system to fight pancreatic cancer–which urgently needs better treatments. It's also motivating as we may be able to use such personalized vaccines to treat other deadly cancers.
– Vinod Balachandran, Memorial Sloan Kettering Cancer Center
A larger phase 2 trial is now recruiting patients at 80 locations worldwide.
What Comes Next?
More than 120 clinical trials of mRNA cancer vaccines are now underway across lung, breast, prostate, and other malignancies. Moderna and Merck have launched Phase 3 programs for melanoma and non-small cell lung cancer.
Not all patients respond equally to these vaccines. Understanding why half of Balachandran's patients showed strong immune responses while others did not will shape future designs.
Three distinct approaches are emerging to address this challenge:
- Fully personalized mRNA cancer vaccines offer the highest precision. Scientists sequence each patient's tumor, predict which mutations will trigger the strongest immune response, then manufacture a custom vaccine. The drawback is time: production currently takes four to six weeks, during which cancer can progress.
- Off-the-shelf vaccines take the opposite approach. BioNTech is testing a lung cancer vaccine targeting six tumor markers common across many patients. These can be manufactured in batches and administered immediately, but may miss mutations unique to individual tumors.
- Hybrid vaccines aim for middle ground. These target shared driver mutations like KRAS, which appears in roughly 25 percent of all cancers. Patients are screened for the mutation, then receive a pre-manufactured vaccine matching their tumor profile.
Some researchers envision combining approaches: an off-the-shelf vaccine given immediately after surgery while a personalized vaccine is manufactured.
Manufacturing scale remains the primary bottleneck. Analysts project the mRNA cancer vaccine market could exceed seven billion dollars by 2030, with first commercial approvals anticipated by 2029.
Balachandran's team recently published in Nature showing their vaccines can prime long-lived immune cells.
The next generation of trials will test whether this translates to longer survival.
Sources
- Primary Research: Individualised neoantigen therapy mRNA-4157 plus pembrolizumab versus pembrolizumab monotherapy in resected melanoma (The Lancet, 2024)
- Additional Context:
- Can mRNA Vaccines Fight Pancreatic Cancer? (Memorial Sloan Kettering Cancer Center)
- 3-Year Data for mRNA-4157 (V940) (Merck Press Release, June 2024)
Fact Check: Claim-by-Claim Verification Verified
All claims verified against the Lancet paper, ASCO 2024 data, MSK press releases, and clinical trial registries. Trial results, researcher roles, and market projections confirmed.
Recent data shows 10-13%.
20-25% aggregate; varies by cancer type.
Commentary
- KEYNOTE-942 primary analysis p-value (0.053) was not formally statistically significant; 3-year update showed nominal significance.
- Market projections and approval timelines are speculative estimates.
Sources used for verification
Academic/Peer-reviewed:
Fact-checked by Perplexity Sonar Pro on 2026-03-15
