Discovery of potent, selective human TLR1/2 agonists: N-quinoline-N'-(thiophen-2-yl)thiourea analogs for potential cancer immunotherapy

TLR2 agonists represent promising cancer immunotherapeutic due to their unique combination of potency and safety. SMU-C68, a human TLR1/2 specific small molecule agonist was identified, exhibiting a remarkable four-fold increase in biological activity compared to previously reported SMU-C80 with enhanced aqueous solubility. The cellular and protein level results confirmed that SMU-C68 facilitated the dimerization of TLR1 and TLR2 proteins, leading to the specific activation of TLR1/2 heterodimers. Upon activation, TLR2 recruited the adaptor protein MyD88, initiating downstream NF-κB signaling pathway. Moreover, treatment with SMU-C68 induced the release of pro-inflammatory factors, such as TNF-α and IL-1β, in human PBMC cells. Notably, SMU-C68 exhibited good selectivity towards human species and showed minimal effects on murine cells. Furthermore, in vitro co-culture experiments demonstrated that SMU-C68 exerted a positive influence on immune cell activation and tumor cell apoptosis. These findings strongly emphasize the potential of SMU-C68 in modulating immune responses and eliciting anti-tumor activity.