wherein X1 is H or F X2 is H or F at least one among X1 and X2 is a fluorine atom Z is OH, OR1, SH or SR1, wherein: R1 is Na or NH4, or R1 is an enzyme-labile group which provides OH or SH in vivo such as pivaloyloxymethyl B1 and B2 are bases chosen from Adenine, Hypoxanthine or Guanine, and B1 is a different base than B2 and a pharmaceutically acceptable salt thereof. Pharmaceutical compositions including the cyclic dinucleotide, as well as their use in the treatment of a bacterial infection, a viral infection or a cancer are also described.
