The manufacture and use of compounds of formula (Ia) or a pharmaceutically acceptable salt thereof for preventing, inhibiting or treating cancer, AIDS and/or premature aging. The compounds of formula (Ia) being: where: R independently represents a hydrogen atom, a halogen atom, a (C1-C3)alkyl group, a —CN group, a hydroxyl group, a —COOR1 group, a (C1-C3)fluoroalkyl group, a —NO2 group, a —NR1R2 group, or a (C1-C3)alkoxy group; R′ is a hydrogen atom, a halogen atom, a (C1-C3)alkyl group, a —NO2 group, a (C1-C3)alkoxy group, or a —NR1R2 group; and R1 and R2 are a hydrogen atom or a (C1-C3) alkyl group.