TSHR-targeting nucleic acid aptamer treats Graves' ophthalmopathy via novel allosteric inhibition

Abstract

Abnormal thyrotropin receptor (TSHR) signaling drives a spectrum of diseases affecting hundreds of millions globally, including Graves disease (GD), Graves ophthalmopathy (GO), hyperthyroidism, and thyroid cancers. Therefore, TSHR is considered an attractive therapeutic target with immense drug discovery potential. Currently, there are no clinically available TSHR inhibitors. To address this unmet medical need, we developed YC3, a functional nucleic acid aptamer targeting TSHR, via an innovative approach combining protein-targeting cell-SELEX and functional selection. YC3 exhibited nanomolar affinity with potent TSHR inhibition. Its therapeutic potential was comprehensively evaluated both in vitro and in vivo for GO. In GO patient-derived orbital fibroblasts (OFs), YC3 reversed thyroid-stimulating antibodies (TSAbs)-induced cell activation, suppressing inflammatory cytokines and extracellular matrix (ECM) secretion. In a GO mouse model, YC3 treatment markedly attenuated orbital inflammation, ECM deposition, and fibrosis, ameliorating the pathological remodeling of orbital tissue. Mechanistically, YC3 bound to a previously unidentified allosteric site within the leucine-rich repeat domain of TSHR, thereby inhibiting receptor activation. This study identifies YC3 as a promising TSHR-targeted therapy and unveils a new druggable site for inhibitor design. It also provides the first preclinical evidence supporting pharmacological TSHR inhibition for GO treatment, advancing therapeutic development for TSHR-related diseases.