Compounds of general formula (I), and their pharmaceutically acceptable salts, wherein R1, R2, R3, R5, R6, R8, R9, A, X1, X2, and X3 are defined herein, that may be useful as inductors of type I interferon production, specifically as STING active agents, are provided. Also provided are compositions comprising such compounds, processes for the synthesis of such compounds, and to uses of such compounds, including administration of such compounds to induce immune response, to induce STING-dependent type I interferon production, and/or to treat a cell proliferation disorder, such as cancer.