A synthetic cyclic dinucleotide (CDN) and agonist of stimulator of interferon genes protein (STING), with potential immunoactivating and antineoplastic activities. Upon intratumoral (IT) administration,ulevostinag binds to STING and activates the STING pathway, which promotes IKK-related kinase TANK-binding kinase 1 (TBK1) signaling and activates nuclear factor-kappa B (NF-kB) and interferon regulatory factor 3 (IRF3) in immune cells in the tumor microenvironment; this leads to the production of pro-inflammatory cytokines, including interferons (IFNs). Specifically, expression of IFN-beta (IFNb) enhances the cross-presentation of tumor-associated antigens by CD8alpha-positive and CD103-positive dendritic cells (DCs) to cytotoxic T-lymphocytes (CTLs). This results in a CTL-mediated immune response against tumor cells and causes tumor cell lysis.