This invention relates to certain novel tricyclic compounds of formula I as bromodomain and extra- terminal (BET) inhibitors, their synthesis and their use for treating diseases. More particularly, this invention is directed to fused heterocyclic derivatives useful as inhibitors of BET, methods for producing such compounds and methods for treating diseases and conditions wherein inhibition of one or more BET bromodomains provides a benefit.本發明關於式I所示的作為溴結構域和額外末端結構域(bromodomain and extraterminal, BET)抑制劑的某些新穎三環化合物,它們的合成及其用於治療疾病的用途。更具體地,本發明關於可用作BET抑制劑的稠合雜環衍生物,製備這些化合物的方法和治療一種或多種BET溴結構域的抑制提供益處的疾病和病症的方法。