A gold(III) complex of formula (I) or formula (II)






wherein R1 and R2 are each independently a hydrogen, an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted arylalkyl, or an optionally substituted aryl; R3 and R4 are each independently a hydrogen, an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted arylalkyl, an optionally substituted aryl, an optionally substituted heterocyclyl, an optionally substituted alkoxy, a hydroxyl, a halo, a nitro, a cyano, a N-monosubstituted amino group, or a N,N-disubstituted amino group; and X is Cl, Br, or I. A pharmaceutical composition containing the gold(III) complex of formula (I) or (II), and a method of treating cancer are included.