Disclosed are compounds of formula (I), their tautomeric forms, stereoisomers, and pharmaceutically acceptable salts thereof, wherein ring Ar, ring B, R1-R5, X, Y, p, q, r, and s are as defined in the specification, pharmaceutical compositions including a compound, tautomer, stereoisomer, or salt thereof, and methods of treating or preventing diseases or disorders, for example, cancer, that are amenable to treatment or prevention by inhibiting the PARP enzyme of a subject.