ETI41 is an orally active selective TLR inhibitor that targets the nucleoside-binding site I of TLR7 (IC50= 0.63 μM) and TLR9 (IC50= 0.16 μM), without affecting surface TLRs (including TLR1/TLR2, TLR2/TLR6, TLR4, and TLR5). It demonstrates nanomolar activity in cell-based, biophysical, and in vivo studies, effectively inhibiting endosomal TLR-mediated pro-inflammatory signaling. ETI41 suppresses the expression of inflammation-related genes and significantly improves symptoms in mouse models of psoriasis and systemic lupus erythematosus (SLE). ETI41 is applicable in research related to autoimmune and inflammatory diseases.

TLR9:0.16 μM

ETI41 effectively inhibits TNF-α production in mouse macrophages (RAW 264.7) and human B lymphoblastoid (Daudi) cell lines when induced by TLR agonists like Imiquimod (IMQ) for TLR7 and ODN2395 for TLR9, in a dose-dependent manner without causing cytotoxic effects (0-200 μM, 4-24 hours). ETI41 suppresses the activity of endosomal TLRs with an IC50 between 100 and 1,000 nM and inhibits TLR3, TLR7, and TLR8 activities in a concentration-dependent manner at 31.2 nM to 10 μM (24 hours). In RAW 264.7 cells, ETI41 (5-10 μM, 20 minutes-8 hours) inhibits IMQ or ODN2395-induced MAPKs phosphorylation (p-ERK, p-JNK, p-p38), NF-κB p65 nuclear translocation, Iκ-Bα degradation, and IRF7 expression. In ODN2395-stimulated primary bone marrow-derived dendritic cells (BMDCs), ETI41 (0.2-1 μM, 30 minutes) significantly suppresses the production of IL-12p40, IFN-β, and CD40. ETI41 (10 μM, 2-4 hours) also reduces the upregulation of multiple inflammation-related genes induced by IMQ, including IL1-β, CXCL2, IL18RAP, TNF, PDCD1, NLRP3, NFKBIZ, CCL3, CCL4, KDM6B, ZC3H12A, and PTGS2.

ETI41, administered orally at 60 mg/kg once daily from day 2 to day 5, can improve psoriasis in mice induced by IMQ. At the same dosage from day 2 to day 9, ETI41 ameliorates IL-23 induced psoriasis in mice. Administering ETI41 at 30 mg/kg orally once daily for 39 days effectively improves symptoms in a mouse model of systemic lupus erythematosus (SLE).