1,4-Naphthoquinones as inhibitors of Itch, a HECT domain-E3 ligase, and tumor growth suppressors in multiple myeloma.

A series of 1,4-naphthoquinones (10a-10q) were synthesized and evaluated for anticancer activity. Compound 10e was identified as an inhibitor of Itch, a HECT domain-E3 ligase. In an evaluation of in vivo efficacy, 10e exhibited remarkable anticancer activity with TGI values of 98.3% and 100% at 25 mg/kg and 50 mg/kg orally daily, respectively, against human RPMI-8226 multiple myeloma xenograft. Treatment with 10e also showed a decrease of Itch level in human RPMI-8226 multiple myeloma cells. Thus 10e is a lead compound for further development of inhibitors targeting E3 ligase for treatment of multiple myeloma.