The present invention is directed to compounds of the formulae I, II and III as shown belowwherein all substituents are defined herein, as well as pharmaceutically acceptable compositions comprising compounds of the invention and methods of using said compositions in the treatment of various disorders.本發明係有關如下所示之式I化合物、式II化合物及式III化合物其中所有取代基在本文中定義,並有關包含本發明化合物之醫藥學上可接受之組合物及使用該等組合物治療各種病症之方法。