This invention discloses novel gamma secretase inhibitors of the formula: R<2 >and R<3>, or R<2> and R<4>, or R<3> and R<4>, together with the atoms to which they are bound, can form a fused cycloalkyl or fused heterocycloalkyl ring. The cycloalkyl ring or the heterocycloalkyl ring can be optionally substituted with one or more substituents. One or more compounds of formula (I), or formulations comprising such compounds, may be useful, e.g. in treating Alzheimer's Disease.