SMU-R39 is a TLR7 and TLR8 antagonist with IC50 values of 3.22 μM and 0.24 μM, respectively. It binds to recombinant mTLR7 protein (KD= 2.36 μM) and recombinant hTLR8 protein (KD= 105 nM). SMU-R39 inhibits downstream NF-κB and MAPK signaling pathways, reducing the secretion and transcription of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) in PBMCs and THP-1 cells. In an Imiquimod (IMQ)-induced psoriasis mouse model, SMU-R39 exhibits anti-inflammatory activity and may be used for researching autoimmune diseases such as psoriasis.

TLR7:2.36 μM (Kd)

SMU-R39 demonstrates significant inhibitory activity against R848-induced SEAP signaling in HEK-Blue hTLR8 cells (IC50 = 0.24 μM) and moderate inhibition in HEK-Blue hTLR7 cells (IC50 = 3.22 μM). This compound, at concentrations of 0.01-10 μM over 24 hours, notably blocks SEAP signal elevation induced by Resiquimod (R848) in THP1-Dual cells, with an IC50 of 0.18 μM, indicative of its ability to inhibit NF-κB activation via TLR7/8 signaling. SMU-R39 shows a dose-dependent inhibition of R848-activated TLR7/8 activity in both HEK-Blue hTLR7/8 and THP1-Dual cells over 24 hours. At concentrations of 5-10 μM for 0.5 hours, it downregulates the expression levels of phosphorylated IKKα/β, p65, and p38 proteins in R848-stimulated THP-1 macrophages, thus suppressing downstream NF-κB and MAPK pathways. Furthermore, SMU-R39 (0.1-20 μM, 24 h) significantly reduces TNF-α secretion in R848-stimulated THP-1 macrophages, Raw 264.7 cells, and PBMCs in a concentration-dependent manner. Additionally, it effectively lowers the gene expression levels of TNF-α, IL-1β, IL-8, IL-6, and IFN-β in R848-stimulated THP-1 macrophages and PBMCs within 6 hours.

SMU-R39 (in a 0.5%-1.0% ointment, applied topically once daily for 7 days) significantly alleviates psoriasis-like skin inflammation induced by Imiquimod (IMQ) in female BALB/c mice.