TLR9 and neoplasm: Preclinical research indicates that in situ administration of the TLR9 agonist CpG significantly enhances tumor suppression, whereas intravenous and subcutaneous administration (at distant sites) is markedly less effective, possibly due to differences in drug distribution.633 Localized injections are advantageous as they allow immune cells infiltrating near the tumor antigen to be effectively stimulated under the high concentration of CpG, thereby eliciting a robust immune response.