PROVIDED ARE COMPOUNDS OF FORMULA I: OR A PHARMACEUTICALLY ACCEPTABLE SALT THEREOF, WHEREIN R1, R2, R3, R4, R5, R6, R7, R8, R9, X AND M ARE AS DEFINED HEREIN. ALSO PROVIDED IS A PHARMACEUTICALLY ACCEPTABLE COMPOSITION COMPRISING A COMPOUND OF FORMULA I, OR A PHARMACEUTICALLY ACCEPTABLE SALT THEREOF. ALSO PROVIDED ARE METHODS OF USING A COMPOUND OF FORMULA I, OR A PHARMACEUTICALLY ACCEPTABLE SALT THEREOF.