Systematic co-delivery of dual agonists to enhance cancer immunotherapy

In the tumor immunosuppressive microenvironment (TIME), antigen presenting cells (APCs) usually exhibit a tumor suppressor phenotype. Toll-like receptors (TLRs) agonists could reprogram M2-type macrophages to M1-type and stimulate dendritic cells (DCs) maturation. The combination of TLR7/8 and TLR9 agonists seems to have synergistic therapeutic efficacy. Here, we designed a lipid-coated mesoporous silica nanoparticle (MSNs@Lipo) for the co-delivery of TLR7/8 agonist resiquimod (R848) and TLR9 agonist CpG oligodeoxynucleotides (ODNs) (CpG@MSNs-R@L-M). R848 was firstly conjugated onto the nanoparticle via silane chemistry, which is acidic responsive drug release. Then, CpG was loaded onto the nanoparticle through the positive charge mainly from TLR7/8 agonist R848. Our in vitro experiments further indicated that both drugs have acid-responsive release properties and could be taken up by DCs and located on the endosomes of APCs. More importantly, CpG@MSNs-R@L-M could significantly improve the antitumor efficacy in B16F10 melanoma model. The mechanistic study demonstrated that CpG@MSNs-R@L-M could remarkably modulate the TIME by promoting the maturation of DCs and repolarizing macrophages from M2 to M1 phenotype and facilitating the infiltration of tumor cytotoxic T cells. It was concluded that in comparison to single agonist, the co-delivery of dual agonists, CpG and R848, can improve anti-tumor immune responses for cancer immunotherapy.