TLR9 antagonist 1 (Compound 38) is a selective TLR9 antagonist with an IC50 of 0.1 nM for hTLR9 over hTLR2/4/5/7/8. TLR9 antagonist 1 exacerbates disease symptoms with increased anti-dsDNA and anti-Sm levels in systemic lupus erythematosus (SLE) mouse models. TLR9 antagonist 1 can be used for inflammatory and immune diseases like lupus and arthritis research[1].