CASTING: A Potent Supramolecular Strategy to Cytosolically Deliver STING Agonist for Cancer Immunotherapy and SARS-CoV-2 Vaccination

ABSTRACT

Stimulator of interferon genes, namely STING, an adaptor protein located in the endoplasmic reticulum, has been recognized as a shining target for cancer and infection research. However, STING agonists cyclic dinucleotides (CDNs) have shown almost zero efficacy in phase I clinical trials as a monotherapy, likely due to poor cellular permeability and rapid diffusion despite intratumoral injection. These deficiencies further affect other applications of CDNs, such as pandemic SARS-CoV-2 prevention and therapy. Here, we rationally design a supramolecular cytosolic delivery system based on controllable recognition of calixarene, namely CASTING (CAlixarene-STING), to improve CDN druggability, including degradation stability, cellular permeability, and tissue retention. CASTING efficiently enhances the immunostimulatory potency of CDG(SF) [a chemically modified cyclic di-GMP (CDG)] to generate an immunogenic microenvironment for melanoma regression, anti-PD-1 response rate increase, and durable memory formation against tumor recurrence. More importantly, CASTING displays a superior adjuvant activity on SARS-CoV-2 recombinant spike/receptor binding domain vaccines, inducing robust and coordinated T-cell and antibody responses against SARS-CoV-2 infection in vivo. Collectively, the CASTING design represents an innovative advancement to facilitate the clinical translational capability of STING agonists. [GRAPHICS] .