Triazole derivative and use thereof

A compound represented by the formula (I′)

• wherein R1a and R1b are each independently a hydrogen atom, an optionally substituted hydrocarbon group, an optionally substituted heterocyclic group, or an optionally substituted alkoxy,
• R2 is a hydrogen atom, an optionally substituted hydrocarbon group, an optionally substituted heterocyclic group, or an optionally substituted alkoxy,
• R3 is a group represented by the formula —NHCOR4, —NHSO2R5, —NHCON(R6a)(R6b), —NHCOOR7 or —CONHR8
• wherein R4 and R7 are each independently a hydrogen atom, an optionally substituted hydrocarbon group, or an optionally substituted heterocyclic group,
• R5, R6a, R6b and R8 are each independently a hydrogen atom, an optionally substituted hydrocarbon group, an optionally substituted heterocyclic group, or an optionally substituted alkoxy,
• R6a and R6b are optionally bonded to each other to form an optionally substituted nitrogen-containing non-aromatic heterocycle,
• ring A′ is a benzene ring optionally further having substituent(s) or a 6-membered nitrogen-containing aromatic heterocycle optionally further having substituent(s),
• R2 and the substituent on ring A′ other than R3 are optionally bonded to each other to form an optionally substituted ring,
• R8 and the substituent on ring A′ are optionally bonded to each other to form an optionally substituted ring,
• R1a and R2 are optionally bonded to each other to form an optionally substituted ring,
• R1a and R1b are optionally bonded to each other to form an optionally substituted nitrogen-containing non-aromatic heterocycle,
• provided that when ring A′ is a benzene ring optionally further having substituent(s), R4 is not methyl,
• or a salt thereof.