A class of phosphorus containing polycyclic compounds of general formula I, of general formula I′； or of general formula I″；, wherein B1, B2, R1, R2, R1′；, X1, X2, Y1, Y2, BL1, BL2, Z1, and Z2 are defined herein, that may be useful as modulators of type I interferon production, specifically as STING modulating agents, are provided. Also, provided are use of such compounds.
