SMU-C409 is a TLR1/2 agonist with an EC50 of 65 nM in HEK-Blue hTLR2 cells. It activates the TLR1/2–MyD88–NF-κB pathway, inducing TNF-α/IL-1β secretion and strongly activating immune cells, resulting in antitumor immunomodulatory effects. Exhibiting low toxicity in vitro, SMU-C409 is useful for cancer immunology research.

SMU-C409 selectively activates the hTLR2 signaling pathway in HEK-Blue hTLR2 cells without significant activity on other TLR subtypes (hTLR3/4/7/8). It specifically targets TLR1/2 in these cells with an EC50 value of 65 nM. At concentrations of 0-100 μM for 24 hours, SMU-C409 exhibits low toxicity in HEK-Blue hTLR2 cells, PBMC, B16-F10, and MCF-7 cells. It binds to hTLR2 protein with an affinity (K d) of 72.4 nM and specifically activates TLR2 in both HEK-Blue hTLR2 and THP-1 cells. SMU-C409 activates the TLR1/2 heterodimer, promoting MyD88-NF-κB pathway phosphorylation and the dissociation of inhibitory proteins in THP-1 cells (differentiated with PMA). Additionally, it stimulates the production of downstream cytokines via the NF-κB pathway, playing a critical role in inflammatory signaling across various immune cells, including THP-1 (PMA differentiated), PBMC, mouse peritoneal macrophages, and mouse RAW264.7 cells, with conserved species-specific signal effects. In CD3+, CD4+, CD8+, monocytes, B cells, and NK cells, SMU-C409 shows immune activation activity. It enhances immune cell-mediated apoptosis induction in SJSA-1 cells, indicating potential antitumor immune activity. Finally, SMU-C409 demonstrates significantly improved plasma stability in rat plasma, with a degradation rate constant (k) of 0.0003 min⁻¹.