A novel STING agonist for cancer immunotherapy and a SARS-CoV-2 vaccine adjuvant.

A novel STING agonist, CDG, ipsilaterally modified with phosphorothioate and fluorine, was synthesized. The phosphorothioate in CDG might be a site for covalent conjugation. Injection of CDG generated an immunogenic ("hot") tumor microenvironment to suppress melanoma, more efficiently than dithio CDG. In particular, immunization with SARS-CoV-2 spike protein using CDG as an adjuvant elicited an exceptionally high antibody titer and a robust T cell response, overcoming the drawbacks of aluminum hydroxide. These results highlighted the therapeutic potential of CDG for cancer immunotherapy and the adjuvant potential of the STING agonist in the SARS-CoV-2 vaccine for the first time.