PROPEL aims to develop highly specific precision medicines by discovering and engineering riboswitches that function in human cells, enabling therapies to be activated only when and where needed. Riboswitches are RNA regulatory elements that change gene expression in response to chemical signals; while known in bacteria, fungi, and plants, they have not been validated in humans. The PROPEL project will leverage advanced AI models, high-throughput RNA structural analyses, and large-scale screening to identify or engineer riboswitches responsive to diverse chemical signals. This approach promises a new therapeutic modality that is disease-agnostic and can improve treatment specificity for cancer, autoimmune diseases, rare genetic disorders, and more. Success would enable personalized mRNA therapies that produce proteins only in desired cell types, reducing side effects and improving efficacy.