Design and Synthesis of Novel TLR2 Agonists for Regulating Tumor Microenvironment in Immunotherapy of Lung Cancer.

Toll-like receptor 2 (TLR2) agonists hold great promise for cancer immunotherapy. Our previously identified TLR2 agonist SMU-Z1 contains a nitro group associated with potential metabolic toxicity. Herein, 47 analogs were designed and synthesized to mitigate toxicity, and SMU-H1 emerged as a potent, selective TLR2 agonist (EC50 = 5.14 ± 0.7 nM) with superior safety relative to SMU-Z1. Mechanistically, SMU-H1 binds TLR2 to recruit MyD88, activates the MAPK/NF-κB pathways, and induces proinflammatory cytokines. TLR2 dependence was confirmed for the first time using TLR2-knockout mice. SMU-H1 also drives M1 macrophage polarization and dendritic cell activation via TLR2. In vivo, SMU-H1 enhanced immune cell activation and improved antitumor efficacy when combined with conventional anticancer drugs. Overall, SMU-H1 retains robust TLR2 agonistic activity with reduced toxicity, representing a promising candidate for cancer immunotherapy development.