Structural Evaluations of a Selective Human STING A230 Agonist and Its Use in Macrophage Immunotherapies.

Previously we identified a non-nucleotide agonist BDW568 that selectively activates the human STING A230 allele. Here, we further characterized the mechanism of BDW568 and highlighted its potential use for selectively controlling the activation of engineered macrophages that constitutively express STING A230 as a genetic adjuvant. We obtained the crystal structure of the C-terminal domain of STING A230 complexed with BDW-OH (active metabolite) at 1.95 Å resolution. Structure-activity relationship studies revealed that all three heterocycles in BDW568 and the S-acetate side chain are critical for retaining activity. We demonstrated that BDW568 could robustly activate type I interferon signaling in purified human primary macrophages that were transduced with lentivirus expressing STING A230 . In contrast, BDW568 could not stimulate innate immune responses in human primary peripheral blood mononuclear cells in healthy donors in the absence of a STING A230 allele. This high STING variant specificity suggested a promising application of STING A230 agonists in macrophage-based therapeutic approaches.