Piperidin-2,6-dione derivatives of formula (I) are new. Z = (a) -C(R1)(R2)CH2- or (b) -C(R1)=CH-;R1 = phthalimide when Z = (a) or phthalimide mono- or disubstituted by OH, CH3O or NH2 when Z = (b);R2 = H or 1-6C alkyl;R3 = H, 1-6C alkyl or heteroaromatic ring;and R4 = 1-6C alkyl or (hetero)aromatic ring.

Thalidomide prodrugs of the formula I:in which R is -CHR1-NHR2 or -(CH2)nCOOH

Compositions containing a thalidomide compound and a phosphodiesterase IV (PDE IV) inhibitor are new. Compositions containing a thalidomide compound and a phosphodiesterase IV (PDE IV) inhibitor are new. The thalidomide compound is selected from thalidomide itself (I), EM12 and their alpha -methyl compounds.

The invention relates to a combination therapy for the treatment of diseases caused by the formation of the inflammation promoting cytokine iL-12, whereby a thalidomide compound and an antiinflammatory cytokine are applied.

Illnesses caused by the formation of interleukin (IL)-12 are treated and prevented by the simultaneous administration of a thalidomide alpha -methyl-thalidomide (EM 987) or 3-(1-oxo-1,3-dihydro-isoindol-2-yl)-piperidine-2,6-dione (EM 12) antiinflammatory cytokine. The thalidomide compound is thalidomide,