Nous-209 neoantigen vaccine for cancer prevention in Lynch syndrome carriers: a phase 1b/2 trial

Stopping Cancer Before It Starts

For families living with Lynch syndrome, cancer risk can feel like a ticking clock. These inherited gene changes raise the odds of colorectal and other cancers to as high as 80%, and current prevention mostly means frequent colonoscopies and, in some cases, major surgery. This study explores a different idea: a vaccine designed not to fight an existing tumor, but to train the immune system to seek out and destroy precancerous cells before they ever turn into cancer.

A High-Risk Group in Need of New Options

Lynch syndrome affects about 1 in 300 people. Because of a defect in the body’s DNA repair system, cells in the gut and other organs accumulate characteristic genetic errors, especially in short repetitive stretches of DNA. When these errors fall within genes, the resulting proteins are misshapen and look foreign to the immune system. Scientists realized these abnormal protein bits, called frameshift peptides, could serve as bright flags marking cells on the path to becoming cancer. Lynch syndrome therefore offers a rare opportunity: the risky mutations are predictable and shared across many patients, making them targets for a single, \

Citation: D’Alise, A.M., Willis, J., Duzagac, F. et al. Nous-209 neoantigen vaccine for cancer prevention in Lynch syndrome carriers: a phase 1b/2 trial. Nat Med 32, 1002–1011 (2026). https://doi.org/10.1038/s41591-025-04182-9

Keywords: Lynch syndrome, cancer prevention vaccine, neoantigens, immunotherapy, colorectal cancer