Allosteric p97 inhibitors can overcome resistance to ATP‐competitive p97 inhibitors for potential anti‐cancer therapy

A major challenge of targeted cancer therapy is the selection for drug‐resistant mutations in tumor cells leading to loss of treatment effectiveness. p97/VCP is a central regulator of protein homeostasis and a promising anti‐cancer target because of its vital role in cell growth and survival. One ATP‐competitive p97 inhibitor, CB‐5083, has entered clinical trials. Selective pressure on HCT116 cells treated with CB‐5083 identified 5 different resistant mutants. Identification of p97 inhibitors with different mechanisms of action would offer the potential to overcome this class of resistance mutations. Our results demonstrate that two CB‐5083 resistant p97 mutants, N660K and T688A, were also resistant to several other ATP‐competitive p97 inhibitors, whereas inhibition by two allosteric p97 inhibitors NMS‐873 and UPCDC‐30245 were unaffected by these mutations. We also established a CB‐5083 resistant cell line that harbors a new p97 double mutation (D649A/T688A). While CB‐5083, NMS‐873, and UPCDC‐30245 all effectively inhibited proliferation of the parental HCT116 cell line, NMS‐873 and UPCDC‐30245 were 30‐fold more potent than CB‐5083 in inhibiting the CB‐5083 resistant D649A/T688A double mutant. Our results suggest that allosteric p97 inhibitors are promising alternatives when resistance to ATP‐competitive p97 inhibitors arises during anti‐cancer treatment.