Design, Synthesis, and Structure–Activity Relationship of <i>N</i>-Aryl-<i>N</i>′-(thiophen-2-yl)thiourea Derivatives as Novel and Specific Human TLR1/2 Agonists for Potential Cancer Immunotherapy
Zhipeng Chen, Lina Zhang, Junjie Yang, Lu Zheng, Fanjie Hu, Siqin Duan, Kutty Selva Nandakumar, Shuwen Liu, Hang Yin, Kui Cheng
Abstract
The previous virtual screening of ten million compounds yielded two novel nonlipopeptide-like chemotypes as TLR2 agonists. Herein, we present the chemical optimization of our initial hit, 1-phenyl-3-(thiophen-2-yl)urea, which resulted in the identification of SMU-C80 (EC50 = 31.02 ± 1.01 nM) as a TLR2-specific agonist with a 370-fold improvement in bioactivity. Mechanistic studies revealed that SMU-C80, through TLR1/2, recruits the adaptor protein MyD88 and triggers the NF-κB pathway to release cytokines such as TNF-α and IL-1β from human, but not murine, cells. To the best of our knowledge, it is the first species-specific TLR1/2 agonist reported until now. Moreover, SMU-C80 increased the percentage of T, B, and NK cells ex vivo and activated the immune cells, which suppressed cancer cell growth in vitro. In summary, we obtained a highly efficient and specific human TLR1/2 agonist that acts through the MyD88 and NF-κB pathway, facilitating cytokine release and the simultaneous activation of immune cells that in turn affects the apoptosis of cancer cells.