P5091

P5091 is a trisubstituted thiophene with dichlorophenylthio, nitro, and acetyl substituents mediating anti-USP7 activity. P5091 exhibits potent, specific, and selective deubiquitylating activity against USP7. In contrast, P5091 does not inhibit other DUBs or other families of cysteine proteases tested (EC50 > 100 mM). P5091 inhibits the labeling of USP7 with HA-UbVME in a concentration-dependent manner. USP7-mediated cleavage of high molecular weight polyubiquitin chains is inhibited in a dose-dependent manner by P5091. Moreover, P5091 inhibits USP7- but not USP2- or USP8-mediated cleavage of poly K48-linked ubiquitin chains. USP7 inhibition by P5091 induces HDM2 polyubiquitylation and accelerates degradation of HDM2. P5091 inhibits USP7 deubiquitylating activity, without blocking proteasome activity in MM Cells.  P5091 induces a dose-dependent decrease in viability of various MM cell lines. P5091 overcomes bone marrow stromal cell-induced growth of MM Cells. P5091 decreased HDM2 and HDMX, as well as upregulated p53 and p21 levels. Overall, P5091-induced cytotoxicity is mediated in part via HDM2-p21 signaling axis and although p53 is upregulated in response to P5091 treatment, the cytotoxic activity of P5091 is not dependent on p53. ^[1]

In animal tumor model studies, P5091 is well tolerated, inhibits tumor growth, and prolongs survival. Combining P5091 with HDAC inhibitor SAHA triggers synergistic anti-MM activity. ^[1]

• Ubiquitin Protease Assays

  Recombinant enzymes in 20 mM Tris-HCl (pH 8.0), 2 mM CaCl₂, and 2 mM β-mercaptoethanol are incubated with dose ranges of P5091 for 30 min in a 96-well plate before the addition of Ub-PLA2 and NBD C6-HPC or Ub-EKL and EKL substrate. The liberation of a fluorescent product within the linear range of the assay is monitored using a Perkin Elmer Envision fluorescence plate reader. Vehicle (2% [v/v] DMSO) and 10 mM N-ethylmaleimide (NEM) are included as controls.

• Cell lines

  293T cells

• Concentrations

  10 μM

• Incubation Time

  24 h

• Method

  Cells were treated with indicated concentration of drug for 24 h.

• Animal Models

  CB-17 SCID-mice

• Dosages

  10 mg/kg

• Administration

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