Cyclic dinucleotides (cDNs) have been emerging as a promising class of immunotherapeutics targeting STING (Stimulator of Interferon Gene). However, the enzymatic instability and transmembrane barriers hinder cDNs from extensive clinical applications. In this study, we encapsulate cDNs with a neutral cytidinyl lipid DNCA and a cationic lipid CLD(Mix) via H-bonding, pi-stacking and electrostatic interaction. The optimal formulation, c-di-GMP(cdG)/Mix (500 nM), could induce 50-fold IFN-Ⅰ release compared with soluble cdG. In addition, its RP stereoisomer of monothiophosphate analogue showed much more potency for IFN-Ⅰ induction, while SP stereoisomer could hardly elicit the induction of IFN-Ⅰ. It has been confirmed that cDNs/Mix resulted in stronger anti-tumor efficacy and tumor growth inhibition in two murine tumor models. The mice with melanoma administered 5 μg cdG/Mix intratumorally showed 42.9% long-term survival, and 83% rechallenge mice obtained resistance to specific tumor and established memory immunity. Besides, 1 μg cdG/Mix i.t. administration could significantly inhibit tumor growth in breast cancer murine model, showing almost equal anti-tumor efficacy relative to 10 μg group. Importantly, cdG/Mix intravenously administration could also significantly inhibit tumor growth and result in a 11% long-term survival, which offering a treatment opportunity to patients with non-accessible cancer.
Cyclic dinucleotides; DNCA; CLD; Tumor immunotherapy; STING nanoparticle