TLR7/8 antagonist 2 (Compound 15) is a potent and orally active agonist of TLR7/8 with IC 50 s of 4.9 and 0.6 nM, respectively. Inappropriate activation of TLR7 and TLR8 is linked to several autoimmune diseases, such as lupus erythematosus. TLR7/8 antagonist 2 has the potential for the research of autoimmune diseases.