TR antagonist 2 (Compound 10a) is a competitive inhibitor of thyroid hormone receptors (TRα/β) with an IC50 of 47 nM. It works by competitively binding to the ligand-binding domain of the receptor with triiodothyronine (T3), thereby blocking the formation of the receptor-coactivator complex, inhibiting target gene transcription, and reducing thyroid hormone-mediated metabolic effects. TR antagonist 2 holds potential for research into hyperthyroidism (such as Graves' disease) and thyrotoxicosis.