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.