Heterocyclic compound

A method for treating Niemann-Pick disease in a mammal, comprising administering an effective amount of a compound or a salt thereof to the mammal, wherein the compound is represented by a formula:

• wherein
• ring Ar represents an optionally further substituted aromatic heterocycle or an optionally further substituted C6-14 aromatic hydrocarbon ring;
• ring A represents an optionally further substituted C6-14 aromatic hydrocarbon ring or an optionally further substituted heterocycle;
• R1 represents an optionally substituted C6-14 aryl group, an optionally substituted C3-10 cycloalkyl group or an optionally substituted heterocyclic group
• except that when R1 is an optionally substituted heterocyclic group, R1 is represented by a formula:
• wherein ring B represents an optionally further substituted heterocycle, and
• represents a single bond or a double bond, or a formula:
• wherein ring D represents an optionally further substituted nitrogen-containing heterocycle,
• R2 represents a hydrogen atom, or
• R1 and R2 are bonded to each other to form an optionally substituted 5- or 6-membered aromatic heterocycle or an optionally substituted benzene ring.