AZ1 is a potent and selective dual USP25 & USP28 deubiquitinase (DUBs) inhibitor (USP25/28 IC50 = 0.62/0.7 nM by Ub-Rh110 assay) th at induces HCT116 cellular c-Myc degradation (20-100 μM for 3h or 60 μM for 0.3-3h). AZ1 exhibits antiproliferation activity in cancer cultures (IC50 ≤20 μM; HCT116, HT29 and SW480) and anti-tumor efficacy in an orthotopic model of lung SCC tumours in mice in vivo (125 mg/kg or 375 mg/kg i.p. once every three days, 6 injections total).