The present disclosure provides compounds represented by Formula I: I, and the pharmaceutically acceptable salts, hydrates, and solvates thereof, wherein R1, R2a, R2b, R3, R4, Ar, L, X, Y, and B are as defined as set forth in the specification. The present disclosure also provides compounds of Formula I for use to treat a condition or disorder responsive to degradation of BET bromodomains such as cancer.
