ML240 is a ATP-competitive inhibitor of p97 ATPase (IC50 = 110 nM). p97 is a homohexamer with each protomer containing a protein−protein interaction domain at the N-terminus, a D1 ATPase/hexamerization domain, and the catalytic D2 ATPase domain. p97 inhibitors could have improved therapeutic potential in tumor types currently treated by proteasome inhibitors.