Use of Inhibitors of the Degradation of P27, in Particular Argyrin and Derivatives Thereof, for the Treatment of Proliferative Diseases

A method of treating a proliferative disorder in a subject in need of such treatment, wherein said method comprising administering to the subject an effective amount of a compound of the formula I

• wherein
• R1 and R2 independently are hydrogen, C1-C4 alkyl which is unsubstituted or substituted by OH, or C1-C4 alkoxy;
• R3 is hydrogen, C1-C8 alkyl which is unsubstituted or substituted by OH or OR, wherein R is selected from hydrogen, C1-C4 alkyl, aryl or acetyl,
• R4 is hydrogen, halogen, C1-C4 alkyl which is unsubstituted or substituted by OH, or C1-C4 alkoxy;
• R5 is hydrogen or halogen;
• R6 is hydrogen or C1-C4 alkyl;
• and
• X is C═CH2 or CHR7 wherein R7 is C1-C4 alkyl which is unsubstituted or substituted by —S—C1-C4 alkyl, and pharmaceutically acceptable salts thereof.