From Functional Group and Metabolite Analysis to Rational Design: Discovery of BXY-14 as a Highly Potent TLR2 Agonist with Enhanced Vaccine Adjuvants and Cancer Immunotherapy

TLR2 bridges innate and adaptive immunity, with agonists showing promise in vaccines and cancer therapy. In this study, we found natural product CaLGL-1, which functions as a "quiescent agonist" of TLR2, with its immunostimulatory potential masked by a labile acetal group. In an oxidative environment, CaLGL-1 is converted into potent TLR2 agonist. Inspired by this phenomenon, we rationally designed BXY-14, a derivative exhibiting cross-species TLR2 agonist activity. This compound demonstrates exceptional potency (THP-1 cells, EC₅₀ = 2.2 nM; mBMDCs, EC₅₀ = 1.8 nM), and functions as a superior vaccine adjuvant, eliciting stronger antibody responses than Diprovocim. Additionally, in murine models, BXY-14 markedly downregulated intratumoral PD-L1 expression and demonstrated synergistic efficacy with the anti-PD-L1 monoclonal antibody atezolizumab, resulting in significantly prolonged overall survival. Together, this work establishes metabolically gated immunity and delivers a translational TLR2 agonist bridging bacterial metabolite chemistry with immunotherapy.