The present invention concerns compounds of formula (I): wherein R1 is selected from the group consisting of H, and optionally substituted C1-6 alkyl, C3-7 cycloalkyl, C3-7 cycloalkyl-C1-4 alkyl, and phenyl-C1-4 alkyl; R2 and R3 are either: (i) independently selected from H, R, R′, SO2R, C(═O)R, (CH2)nNR5R6, where n is from 1 to 4 and R5 and R6 are independently selected from H and R, where R is optionally substituted C1-4 alkyl group, and R′ is an optionally substituted phenyl-C1-4 alkyl group, or (ii) together with the nitrogen atom to which they are attached, form an optionally substituted C5-7 heterocyclic group; R4 is an optionally substituted C9-14 aryl group; their use as pharmaceuticals, in particular for treating conditions alleviated by antagonism of a 5-HT2B receptor.