A compound of formula (I): ** Formula ** in which R1 and R2 independently represent each other hydrogen, (C1-C4) alkyl, (C1-C4) alkoxy, halogen, trifluoromethoxy or trifluoromethyl； R3 represents hydrogen, (C1-C4) alkyl, (C1-C2) alkoxy-(C2-C3) alkyl, (C1-C4) fluoroalkyl (C3-C6) cycloalkyl-(C1-C2) alkyl； and R4 represents a heteroaryl group that is unsubstituted or mono-, di- or tri-substituted, in which the substituents are independently selected from the group consisting of halogen, (C1-C4) alkyl, cycloalkyl (C3-C6), (C1-C4) alkoxy, (C1-C4) fluoroalkyl and phenyl； or a pharmaceutically acceptable salt of said compound.Un compuesto de fórmula (I): **Fórmula** en la que R1 y R2 representan independientemente entre sí hidrógeno, alquilo (C1-C4), alcoxi (C1-C4), halógeno, trifluorometoxi o trifluorometilo； R3 representa hidrógeno, alquilo (C1-C4), alcoxi (C1-C2)-alquilo (C2-C3), fluoroalquilo (C1-C4) o cicloalquil (C3-C6)- alquilo (C1-C2)； y R4 representa un grupo heteroarilo que está no sustituido o mono-, di- o tri-sustituido, en el que los sustituyentes se seleccionan independientemente del grupo que consiste en halógeno, alquilo (C1-C4), cicloalquilo (C3-C6), alcoxi (C1-C4), fluoroalquilo (C1-C4) y fenilo； o una sal farmacéuticamente aceptable de dicho compuesto.
