Substituted purinyl-pyrazol derivatives and their use as potassium channel modulators

A compound of formula (I)

• any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof, wherein
• R1 represents hydrogen or alkyl;
• and
• one of R2, R3 and R4 represents alkyl, hydroxy-alkyl, alkoxy-alkyl, halo, trifluoromethyl, trifluoromethoxy, hydroxy or alkoxy;
• and the other two of R2, R3 and R4, independently of each other, represent hydrogen, alkyl, hydroxy-alkyl, alkoxy-alkyl, halo, trifluoromethyl, trifluoromethoxy, hydroxy or alkoxy.