mRNA's Next Act: Personalized Cancer Vaccines Show Dramatic Results

The technology billions encountered through COVID shots is building a second act — and this one may matter even more.

Five-year results from a clinical trial, published in the Journal of Clinical Oncology and presented at the American Society of Clinical Oncology conference, show that a personalized mRNA vaccine combined with the immunotherapy drug Keytruda dramatically reduced melanoma recurrence. Nearly 69% of patients receiving the combination remained cancer-free after five years, compared with roughly 49% on Keytruda alone — a 49% reduction in the risk of recurrence or death, according to data from the Phase 2b KEYNOTE-942 trial.

The survival numbers are starker still: 92% of combination-therapy patients were alive at five years, versus 71% receiving Keytruda alone.

The approach is fundamentally different from COVID vaccination. Each dose is built from the patient’s own tumor. Scientists sequence the cancer, identify up to 34 unique molecular fingerprints called neoantigens, and encode them into a custom mRNA vaccine. The immunotherapy lifts the shield cancer uses to hide from immune cells; the vaccine then trains those cells to recognize the patient’s specific tumor.

Dr. Janice Mehnert, a melanoma specialist at NYU Langone Health and the study’s senior author, called the approach a “personalized immunotherapy strategy” tailored to each patient’s cancer.

The trial enrolled 157 patients across the US and Australia. Side effects were manageable — fatigue, chills, injection-site pain.

A Phase 3 trial with nearly 1,000 patients is fully enrolled. Moderna, which developed the vaccine (intismeran), and Merck, which makes Keytruda, plan to seek FDA approval once those results are analyzed. Eight clinical trials are now underway testing the platform across lung, bladder, and kidney cancers.

Connie Franciosi, 80, a trial participant, has been cancer-free since her treatment. “Life is good,” she told NPR.

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Discussion (6)

MarcusT

so basically the covid vaccine was just a test run and we were the guinea pigs. cool cool cool

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JanetK_88

Did you even read the article? They're using the same mRNA technology to fight cancer. Nobody was a guinea pig, the COVID vaccines went through full clinical trials. This is literally saving lives.

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vkrishnan

The neoantigen approach is what's genuinely interesting here. Encoding up to 34 patient-specific neoantigens into a single mRNA construct has been in the literature for years — Sahin et al. demonstrated feasibility back in 2017 (Nature 547:222-226). The key advance is pairing it with anti-PD-1 therapy. PD-1 inhibitors like pembrolizumab (Keytruda) remove the immunosuppressive shield, and the vaccine then trains T-cells to recognize the patient's specific tumor profile. The 49% reduction in recurrence risk is encouraging for a Phase 2b, though n=157 is still modest. The fully enrolled Phase 3 with roughly 1,000 patients will be more informative. Worth noting the 92% overall survival at five years in the combination arm is remarkable for advanced melanoma.

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Sarah with an H

My mom had melanoma in 2019 and I wish this had been available then. She's in remission but every scan is still terrifying. Glad Connie is doing well at 80, that part made me tear up a little.

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definitely_not_a_bot

That vkrishnan comment with the perfect citation formatting and the "though n=157 is still modest" qualifier? Yeah that's 100% ChatGPT. Nobody talks like that in a comment section.

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Linda M. Rojas

Just to add some context that may be helpful: the personalized aspect of this approach is important and also why it's so expensive to produce. Each vaccine is essentially a one-off pharmaceutical product. The turnaround time from tumor biopsy to finished vaccine is currently around six to eight weeks, which the article doesn't mention. That is a practical challenge, especially for aggressive cancers. The expansion into lung, bladder, and kidney trials (eight trials noted) suggests Moderna and Merck are confident in the platform beyond melanoma, which is encouraging. The manageable side effect profile is also worth highlighting — fatigue and chills are quite tolerable compared to many cancer treatments.

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