N-benzylpiperidinol derivatives as novel USP7 inhibitors: Structure–activity relationships and X-ray crystallographic studies

USP7 as a deubiquitinase plays important roles in regulating the stability of some oncoproteins including MDM2 and DNMT1, and thus represents a potential anticancer target. Through comparative analysis of USP7 co-crystal structures in complex with the reported piperidinol inhibitors, we noticed that the USP7 Phe409 sub-site might have good adaptability to the ligands. Based on this observation, 55 N-aromatic and N-benzyl piperidinol derivatives were designed, synthesized and biologically evaluated, among which compound L55 was identified as a highly selective and potent USP7 inhibitor (IC50 = 40.8 nM, KD = 78.3 nM). X-ray crystallographic studies revealed that L55 bound to USP7 with a new pose that was very different from the previously reported inhibitors. The results of cellular assays showed that L55 had strong antitumor activity against LNCaP (IC50 = 29.6 nM) and RS4; 11 (IC50 = 41.6 nM) cells, probably through inducing cell death and restricting G0/G1 and S phases. Moreover, L55 dose-dependently reduced the protein levels of MDM2 and DNMT1 and increased the protein levels of p53 and p21. These findings could have valuable implications for designing novel structural classes of USP7 inhibitors.