The present invention provides a compound of formula I; or a pharmaceutically acceptable salt thereof, wherein R1, R2, R3, R4, R5, and A-B are as defined herein, which are non-immunosuppressive, cyclophilin-binding, mPTP blockers and are therefore useful for the prevention or treatment of diseases or disorders such as HCV infection, stroke, multiple sclerosis, HBV infection, HPV infection, asthma, cancer, muscular dystrophy, sepsis, ischemia/reperfusion injury, and heart failure.