Inhibition of the heat shock protein 90 molecular chaperone in vitro and in vivo by novel, synthetic, potent resorcinylic pyrazole/isoxazole amide analogues

Swee Y. Sharp, Chrisostomos Prodromou, Kathy Boxall, Marissa V. Powers, Joanna L. Holmes, Gary Box, Thomas P. Matthews, Kwai-Ming J. Cheung, Andrew Kalusa, Karen E. Ball, Angela Hayes, Anthea Hardcastle, Brian Dymock, Paul A. Brough, Xavier Barril, Julie E. Cansfield, Lisa Wright, Allan Surgenor, Nicolas Foloppe, Roderick E. HubbardWynne Aherne, Laurence Pearl, Keith Jones, Edward McDonald, Florence Raynaud, Sue Eccles, Martin Drysdale, Paul Workman

Research output: Contribution to journalArticlepeer-review


Although the heat shock protein 90 (HSP90) inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) shows clinical promise, potential limitations encourage development of alternative chemotypes. We discovered the 3,4-diarylpyrazole resorcinol CCT018159 by high-throughput screening and used structure-based design to generate more potent pyrazole amide analogues, exemplified by VER-49009. Here, we describe the detailed biological properties of VER-49009 and the corresponding isoxazole VER-50589. X-ray crystallography showed a virtually identical HSP90 binding mode. However, the dissociation constant (Kd) of VER-50589 was 4.5 +/- 2.2 nmol/L compared with 78.0 +/- 10.4 nmol/L for VER-49009, attributable to higher enthalpy for VER-50589 binding. A competitive binding assay gave a lower IC50 of 21 +/- 4 nmol/L for VER-50589 compared with 47 +/- 9 nmol/L for VER-49009. Cellular uptake of VER-50589 was 4-fold greater than for VER-49009. Mean cellular antiproliferative GI50 values for VER-50589 and VER-49009 for a human cancer cell line panel were 78 +/- 15 and 685 +/- 119 nmol/L, respectively, showing a 9-fold potency gain for the isoxazole. Unlike 17-AAG, but as with CCT018159, cellular potency of these analogues was independent of NAD(P)H:quinone oxidoreductase 1/DT-diaphorase and P-glycoprotein expression. Consistent with HSP90 inhibition, VER-50589 and VER-49009 caused induction of HSP72 and HSP27 alongside depletion of client proteins, including C-RAF, B-RAF, and survivin, and the protein arginine methyltransferase PRMT5. Both caused cell cycle arrest and apoptosis. Extent and duration of pharmacodynamic changes in an orthotopic human ovarian carcinoma model confirmed the superiority of VER-50589 over VER-49009. VER-50589 accumulated in HCT116 human colon cancer xenografts at levels above the cellular GI(50) for 24 h, resulting in 30% growth inhibition. The results indicate the therapeutic potential of the resorcinylic pyrazole/isoxazole amide analogues as HSP90 inhibitors.

Original languageEnglish
Pages (from-to)1198-1211
JournalMolecular Cancer Therapeutics
Issue number4
Publication statusPublished - Apr 2007


  • Adenosine Triphosphatases
  • Animals
  • Apoptosis
  • Biological Markers
  • Cell Cycle
  • Cell Proliferation
  • Crystallography, X-Ray
  • Drug Resistance, Neoplasm
  • Endothelial Cells
  • Female
  • HCT116 Cells
  • HSP90 Heat-Shock Proteins
  • HT29 Cells
  • Humans
  • Isoxazoles
  • Mice
  • Mice, Nude
  • NAD(P)H Dehydrogenase (Quinone)
  • Protein Binding
  • Pyrazoles
  • Treatment Outcome
  • Xenograft Model Antitumor Assays


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