r-848

CU-115 is a selective and potent TLR8 antagonist with IC50 of 1.04 µM and =>50 µM for TLR8 and TLR7, respectively. CU-115 decreases production of TNF-α and IL-1β activated by R-848 in THP-1 cells.

Resiquimod (R848) is an imidazoquinoline amine and Toll-like receptor (TLR) agonist with potential immune response modifying activity. Resiquimod exerts its effect through the TLR signaling pathway by binding to and activating TLR7 and 8 mainly on dendritic cells, macrophages, and B-lymphocytes. This induces the nuclear translocation of the transcription activator NF-kB as well as activation of other transcription factors. This may lead to an increase in mRNA levels and subsequent production of cytokines, especially interferon-alpha (INF-a) and other cytokines, thereby enhancing T-helper 1 (Th1) immune responses. In addition, topical application of resiquimod appears to activate Langerhans' cells, leading to an enhanced activation of T-lymphocytes.

CU-CPT9b (TLR8-specific antagonist 1) is an antagonist of toll-like receptor 8 (TLR8; Kd = 21 nM). It inhibits activation of NF- B induced by the TLR8 agonist R-848 in TLR8-overexpressing HEK-Blue cells with an IC50 value of 0.7 nM.

ODN 1982, an unmethylated oligodeoxyribonucleotide (ODN) lacking a CpG motif, serves as a key component in the preparation of DNA vaccines. This compound effectively inhibits R-848 signaling. Its sequence is denoted as 5'-tccaggacttctctcaggtt-3' [1] [2].

NCI 126224, a toll-like receptor 4 (TLR4) antagonist, demonstrates selective inhibition of nitric oxide (NO) production in RAW 264.7 macrophages, triggered by the TLR4 agonist LPS (IC50 = 0.31 µM), as opposed to minimal effects on NO production induced by agonists for TLR7/8 (R-848), TLR1/2 (Pam3CSK4), and TLR3 (poly(I:C)). Nevertheless, it also effectively inhibits NO production initiated by the TLR2/6 agonist FSL-1 at an IC50 of 0.6 µM in the same cell line. Moreover, NCI 126224 suppresses LPS-induced NF-κB activity in BV-2 microglial cells and reduces LPS-triggered increases in IL-1β and TNF-α levels in RAW 264.7 macrophages with IC50 values of 5.92, 0.42, and 1.54 µM, respectively.