Engineering polymeric RNA scaffolds as programmable combinatorial innate immune agonists.

Sentinel cells in the innate immune system decode combinations of pathogen-associated molecular patterns to shape immune responses, presenting an exploitable feature for vaccine adjuvants and cancer immunotherapies. Delivering innate immune agonists can direct responses toward patient-specific tumour antigens and enhance checkpoint blockade therapies. However, few adjuvants have been clinically approved, largely due to limited potencies or high toxicities. Key barriers remain in adjuvant design and translation: (i) reliance on single agonists, which poorly recapitulate complex pathogen sensing; (ii) poor understanding and control of synergistic effects among combined innate immune agonists; and (iii) a lack of scalable platforms for assembling diverse agonists. To address these issues, we developed polymeric RNAs (polyRNAs) as modular scaffolds that mimic pathogen structures and present multiple agonists. Synthesized by rolling circle transcription, polyRNAs achieve strong TLR3, TLR7, and RIG-I activation and can enable multivalent patterning of CpG-DNA for further engagement of TLR9 signalling. These polyRNA scaffolds are efficiently delivered with lipid nanoparticles and eliminate tumours in a syngeneic mouse model of colorectal cancer with comparable efficacies to clinical benchmarks. Our results establish polyRNAs as a programmable platform for combinatorial innate immune activation, with strong translational potential in cancer immunotherapy.