Abstract: The present invention relates to compositions for the treatment of a malignant disease and in particular to compositions comprising an NF-?B inhibitor and a ?-glutamyltransferase (?-GT) inhibitor and therapeutic uses thereof. The invention further relates to in vitro methods of testing putative anti-tumour agents for their potential to act as therapeutically effective anti-tumour agents in vivo. Embodiments of the invention have been particularly developed for bringing NF-?B inhibitors to the clinic such as to provide alternative therapeutic options in the treatment of malignant diseases and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.