Small molecule agonists of Toll-like receptors 7 and 8: an updated patent review 2021 – 2025

INTRODUCTION: Toll-like receptors 7 (TLR7) and 8 (TLR8) are endosomal receptors that sense single‑stranded RNA and activate MyD88‑dependent inflammatory signaling, linking innate immune detection to adaptive immune responses. Translational and clinical studies across therapeutic areas have underscored both the therapeutic potential and safety challenges of modulating TLR7/8 activity, driving growing interest in small‑molecule agonists and delivery strategies that enable precise control of receptor engagement. AREAS COVERED: This review highlights recent patent activity on small-molecule TLR7/8 agonists, as well as derived conjugates and alternative modalities. This review covers patents published between January 2021 and August 2025 found using Scifinder-n and Cortellis database searches. We report relevant chemical scaffolds, key trends in structure-activity relationships, innovative conjugation strategies, and, where disclosed, insights from preclinical animal models and clinical data. EXPERT OPINION: Recent patent activity reflects a marked expansion in small‑molecule TLR7/8 agonist development, with increasing emphasis on delivery‑gated strategies. Although systemic agonists and early antibody conjugates have shown preclinical efficacy and tolerability, limited clinical translatability suggests that future progress will depend on integrating agonist design with optimized delivery, linker chemistry, antigen selection, and translational assessment to better balance efficacy and tolerability.