Disclosed herein are novel compounds that are Ras inhibitors. Also disclosed are compositions comprising the compounds and methods of using the compounds in treating various diseases. In another aspect, provided is an antibody-drug-conjugate comprising an antibody conjugated with a compound described herein. In still another aspect, provided is a pharmaceutical composition comprising a compound or antibody-drug-conjugate described herein. In a further aspect, provided is method of treating a cancer comprising administering a therapeutically effective amount of a compound or antibody-drug-conjugate described herein to a patient in need thereof.