Most vaccines are made in bulk and sent to millions of people who all get the same product. An individualized neoantigen mRNA cancer vaccine works the other way round. Each dose is built for one patient, from that patient’s own tumor. The furthest-along example is intismeran autogene, also called mRNA-4157 or V940, from Moderna and Merck.
From tumor to mutation list
It starts after surgery. Tumor tissue and matched normal tissue from the same patient go through whole-exome sequencing, and the tumor is sequenced for RNA as well. Comparing the two sets of data reveals the somatic mutations, the changes found only in the cancer.
Those mutations produce neoantigens, mutated proteins that appear only in tumor cells and not in healthy tissue. The immune system has never learned to tolerate them, so a vaccine that presents them can in principle prime T cells to hit the tumor with less risk to normal tissue. Because they come from one person’s cancer, they are not shared from patient to patient.
Picking up to 34 targets
Not every mutation is worth targeting. A bioinformatics pipeline ranks candidates by variant allele frequency, RNA expression level and predicted binding affinity to MHC molecules, using prediction tools such as NetMHCpan alongside HLA typing. An automated algorithm then picks up to 34 neoantigens and encodes them as a single concatenated mRNA sequence.
Manufacturing follows. The mRNA is synthesized, wrapped in a lipid nanoparticle, quality-controlled and released as a single-patient dose. Every lot is unique, so there is no leaning on the fact that a previous batch passed QC. Each one needs its own antigen-expression check before release. The reported biopsy-to-dose timeline is roughly six to eight weeks.
Why it is paired with Keytruda
These therapies are almost always given alongside a checkpoint inhibitor such as pembrolizumab, sold as Keytruda. The vaccine primes tumor-specific T cells. The checkpoint inhibitor removes the PD-1/PD-L1 brake so those cells can act. Reading trial data on either component alone misses how the combination is meant to work.
The Phase 3 readout
On August 19, 2026, Moderna and Merck announced results from INTerpath-001 (NCT05933577), a randomized, double-blind, active-comparator trial in 1,137 patients with resected stage IIB to IV cutaneous melanoma who had had no earlier systemic therapy. Patients were randomized 2:1. One group received intismeran every three weeks for up to nine doses plus pembrolizumab, the other pembrolizumab alone.
At a pre-specified interim analysis, the combination significantly improved both recurrence-free survival, the primary endpoint, and distant metastasis-free survival, a key secondary endpoint. No new safety signals appeared. It is the first positive Phase 3 result for an individualized neoantigen therapy and for any mRNA-based cancer treatment. Markets noticed: Moderna shares closed up 176.97% that day, its largest one-day gain on record, while Merck rose more than 12% to a new high.
What is still unknown
The companies did not release hazard ratios or effect sizes with the topline announcement, which is the biggest open question. Overall survival data are not yet mature and the study continues. The earlier Phase 2b trial, KEYNOTE-942, offers a benchmark: at five years it showed a 49% reduction in the risk of recurrence or death (hazard ratio 0.51) and a 59% reduction in the risk of distant metastasis or death (0.41). Those are Phase 2b figures, not Phase 3 results.
Analysts see manufacturing scalability as central to whether this class of therapy can reach the patients who need it, since each dose runs as its own sequencing, synthesis and testing workflow rather than one large campaign. BioNTech and Genentech’s autogene cevumeran is another individualized program built on the same per-patient model.
