Background:

CU-CPT-9b is a specific TLR8 antagonist, with an IC50 of 0.7 nM.

CU-CPT-9b is a specific TLR8 antagonist, with an IC50 of 0.7±0.2 nM. ITC experiments have confirmed the strong binding of CU-CPT-9b with a Kd of 21 nM. It is shown that CU-CPT-9b binds to the inactive TLR8 dimer in a similar way to CU-CPT8m. CU-CPT9b utilizes hydrogen bonds with G351 and V520*, which are conserved among TLR8/antagonist structures. Additionally, CU-CPT-9b forms water-mediated contacts with S516* and Q519*, which are not observed in TLR8/CU-CPT8m structure, suggesting that the enhanced potency of CU-CPT-9b derives from the new interactions with these polar residues. The orientation of Y567* also changes to facilitate van der Waals interactions with CU-CPT-9b as compared to TLR8/CU-CPT8m[1].

[1]. Zhang S, et al. Small-molecule inhibition of TLR8 through stabilization of its resting state. Nat Chem Biol. 2018 Jan;14(1):58-64.