A compound of Formula I: ** Formula ** or a pharmaceutically acceptable salt thereof, wherein X is NH or O； Each R1 is independently halo, CF3, C1-C6 alkyl, C3-C10 cycloalkyl or OR, wherein said alkyl and cycloalkyl are optionally substituted with one to three groups selected from halo, OR, CF3 or CN； Each R is independently H, C1-C6 alkyl, C3-C10 cycloalkyl or CF3 wherein said alkyl and cycloalkyl are optionally substituted with one to three groups selected from halo, OH, C1-C6 alkoxy, CF3 or CN； Each Ra is independently H, C1-C6 alkyl, C3-C10 cycloalkyl or CF3 wherein said alkyl, cycloalkyl and aryl are optionally substituted with one to three groups selected from halo, OR, CF3 or CN； Each Rb is independently H, C1-C6 alkyl, C3-C10 cycloalkyl, CF3 or aryl, wherein said alkyl, cycloalkyl and aryl are optionally substituted with one to three groups selected from halo, OR, CF3 or CN； R2 is triazolyl, oxadiazolyl, imidazolyl, thiazolyl, pyrazolyl, isoxazolyl, thiadiazolyl or oxazolyl, where triazolyl, oxadiazolyl, imidazolyl, thiazolyl, pyrazolyl, isoxazolyl, thiadiazolyl or oxazolyl are optionally substituted with one to two groups of R5； R4 is H, C1-C6 alkyl, aryl or C3-C10 cycloalkyl, wherein said alkyl, aryl or cycloalkyl are optionally substituted with one to four groups selected from halo or OR； Each R5 is independently OR, (CRc 2) 0-3-CF3, C1-C6 alkyl, (CRc 2) 0-3-C3-C10 cycloalkyl, (CRc 2) 0-3-aryl, (CRc 2) 0- 3-heteroaryl or (CRc 2) 0-3-halo, wherein said alkyl, cycloalkyl, aryl or heteroaryl are optionally substituted with one to three groups selected from optionally substituted aryl, optionally substituted heteroaryl, optionally substituted heterocyclyl, OR, halo, CF3 or NH2； and wherein said optionally substituted aryl, optionally substituted heteroaryl or optionally substituted heterocyclyl are optionally substituted one to four times with halo, CF3, NH2 or OR. Each Rc is independently H, C1-C6 alkyl or C3-C10 cycloalkyl, wherein said alkyl and cycloalkyl
