TLR1/2 Specific Small‐Molecule Agonist Suppresses Leukemia Cancer Cell Growth by Stimulating Cytotoxic T Lymphocytes

Toll‐like receptor 2 (TLR2) expressed on antigen presenting cells evokes a series of critical cytokines, which favor the development of tumor‐specific cytotoxic T lymphocytes (CTLs). Therefore, TLR2 represents an attractive cancer immunotherapeutic target. Here, a synthetic library of 14 000 compounds together with a series of newly developed compounds for NF‐κB activation using HEK‐Blue hTLR2 cells is initially screened. Following further screening in a variety of cells including HEK‐Blue hTLRs reporter cells, murine, and human macrophage cell lines, a potent small molecule agonist 23 (SMU‐Z1) is identified, which specifically activates TLR2 through its association with TLR1, with a EC(50) of 4.88 ± 0.79 × 10(−9) m. Toxicology studies, proinflammatory cytokines (e.g., TNF‐α, IL‐1β, IL‐6, and nitric oxide) and target‐protein based biophysical assays demonstrate the pharmacologically relevant characteristics of SMU‐Z1. In addition, SMU‐Z1 promotes murine splenocyte proliferation and upregulates the expression of CD8(+) T cells, NK cells and DCs, which results in a significant antitumor effect in a murine leukemia model. Finally, the induced tumors in three out of seven mice disappear after administration of SMU‐Z1. Our studies thus identify a novel and potent TLR1/2 small molecule agonist, which displays promising immune adjuvant properties and antitumor immunity.