TL8-506 is a novel and selective TLR8 agonist (EC50 = 30 nM) with the potential to be used for the treatment of tuberculosis and autoimmune diseases.

TL8-506 is a novel, highly selective and potent Toll-like receptor 8 (TLR8) agonist with an EC50 of 30 nM. It induces the production of pro-inflammatory cytokines and chemokines, exhibiting immunomodulatory activity. TL8-506 has potential applications in tuberculosis treatment, cancer immunotherapy, and autoimmune disease research. Target: TLR8 (Toll-like receptor 8, EC50 = 30 nM). TL8-506 selectively binds to TLR8, a pattern recognition receptor expressed primarily on monocytes, macrophages, and dendritic cells. TLR8 activation recruits MyD88 adaptor protein, leading to NF-kappaB and IRF signaling pathway activation, culminating in the production of cytokines (TNF-alpha, IL-12, IL-18) and type I interferons. In vitro, TL8-506 (EC50 = 30 nM) potently activates TLR8 signaling in human TLR8-expressing cell lines and primary human monocytes. It induces dose-dependent production of TNF-alpha, IL-12p40, IL-18, and MCP-1 in human PBMCs. TL8-506 also enhances the anti-mycobacterial activity of macrophages by activating the TLR8-MyD88-IRF5 pathway. No in vivo efficacy data have been published specifically for TL8-506 in animal models. Based on its TLR8 agonist mechanism, it is expected to activate innate immunity against Mycobacterium tuberculosis, promote Th1-polarized adaptive immunity, and potentially reduce tumor burden in murine cancer models via enhanced NK cell and CD8+ T cell activation. For cell-free TLR8 binding assays: recombinant human TLR8 protein (e.g., TLR8 ectodomain) is immobilized on a sensor chip. TL8-506 at various concentrations (0-10 uM) is passed over the chip. Binding affinity (KD) is measured by surface plasmon resonance (SPR) and EC50 is derived. Alternatively, HEK-Blue hTLR8 cells are used in a reporter gene assay (see below). For cell-based TLR8 activity assays: HEK-Blue hTLR8 cells (HEK293 cells stably expressing human TLR8 and an NF-kappaB/AP-1-inducible SEAP reporter gene) are seeded in 96-well plates. TL8-506 is added at varying concentrations (0-1000 nM) and incubated for 18-24 h. Supernatant SEAP activity is measured by QUANTI-Blue colorimetric reagent. Absorbance is read at 620 nm, and EC50 (30 nM) is calculated. For animal studies: potential in vivo protocol using a mouse model of tuberculosis. Mice are infected with M. tuberculosis via aerosol, then treated with TL8-506 (oral or IV, 1-10 mg/kg) daily for 4-8 weeks. Bacterial load in lungs is quantified by CFU. Lung cytokine levels and TLR8 expression are analyzed. Survival and immune cell infiltration are assessed. No PK data are available for TL8-506. For small molecule TLR8 agonists (MW 331.37), predicted PK in rodents: moderate oral bioavailability (~30-50%), Tmax 1-2 h, plasma half-life 4-8 h, moderate volume of distribution, and primarily liver metabolism. No toxicity data have been reported for TL8-506. TLR8 agonists can induce cytokine release syndrome (CRS) if over-activated, leading to systemic inflammation, fever, hypotension, and organ dysfunction. The therapeutic window is likely narrow. No preclinical toxicology studies have been published. TL8-506 is a research compound not yet approved for clinical use. It serves as a valuable tool for studying TLR8 biology in infectious diseases, cancer immunology, and autoimmunity. It has potential as a vaccine adjuvant and for combination therapy with anti-PD-1/PD-L1 checkpoint inhibitors in cancer.

*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.