A compound of Formula (I) wherein Y1, Y2, X1, X2, R1, R2, R3, R4, R5, R6, R8, and R9 are as defined herein; and pharmaceutically acceptable salts and tautomers thereof, compositions, combinations and medicaments containing said compounds and processes for their preparation. The invention also relates to the use of said compounds, combinations, compositions and medicaments, in the treatment of diseases in which modulation of STING (Stimulator of Interferon Genes) is beneficial, for example inflammation, allergic and autoimmune diseases, infectious diseases, cancer, pre-cancerous syndromes and as vaccine adjuvants.