EXOTLR1/2-STING: A Dual-Mechanism Stimulator of Interferon Genes Activator for Cancer Immunotherapy

As natural agonists of the stimulator of interferon genes (STING) protein, cyclic dinucleotides (CDNs) can activate the STING pathway, leading to the expression of type I interferons and various cytokines. Efficient activation of the STING pathway in antigen-presenting cells (APCs) and tumor cells is crucial for antitumor immune response. Tumor-derived exosomes can be effectively internalized by APCs and tumor cells and have excellent potential to deliver CDNs to the cytoplasm of APCs and tumor cells. Here, we leverage tumor exosomes as a delivery platform, designing an EXOTLR1/2-STING loaded with CDNs. To achieve efficient loading of CDNs onto exosomes, we chemically conjugated CDNs with Pam3CSK4, a compound featuring multiple fatty acid chains, resulting in Pam3CSK4-CDGSF. Utilizing the high lipophilicity of Pam3CSK4, Pam3CSK4-CDGSF could be efficiently loaded onto the exosomes through simple incubation. Moreover, as an agonist for Toll-like receptor 1/2, Pam3CSK4 also exhibits robust immunological synergistic effects in conjunction with CDNs. EXOTLR1/2-STING effectively induced the activation of APCs and triggered tumor cell death, producing a favorable antitumor therapeutic effect. It also demonstrated significant synergistic effects with immune checkpoint therapies.