Related Experiment Video
Updated: Sep 16, 2025
Malachite Green Assay for the Discovery of Heat-Shock Protein 90 Inhibitors
Published on: January 20, 2023
Optimization of an Hsp90β-selective inhibitor via exploration of the Hsp90 N-terminal ATP-binding pocket
Michael A Serwetnyk1, Taddäus Strunden1, Ian Mersich1
1Department of Chemistry and Biochemistry, Warren Family Research Center for Drug Discovery and Development, The University of Notre Dame, Notre Dame, IN, 46556, United States of America.
Abstract:
The 90-kDa heat shock protein (Hsp90) promotes the maturation of >400 client protein substrates, many of which are implicated in the development/progression of cancer. Although 22 Hsp90 N-terminal inhibitors have undergone clinical evaluation, the toxicities that arose from pan-inhibition have hindered their development as chemotherapeutic agents. Hence, Hsp90 isoform-selective inhibition represents a promising alternative to overcome these detriments. We recently described the structure-based design of an isoquinolin-1(2H)-one-containing scaffold and produced several highly potent Hsp90β-selective inhibitors, such as KUNB106. But there are limitations to these compounds that require further optimization. Herein, we describe structure-activity relationship (SAR) studies on the KUNB106 indazolone ring system to assess the structural limits of Hsp90β binding. Among the alterations explored in this work, alkyl chain homologation, fluorination, and spirocyclization were most effective at retaining high affinity and selectivity towards Hsp90β. Subsequent biological characterization revealed these derivatives to promote the degradation of Hsp90β-dependent clients while avoiding the induction of Hsp90 levels, which is consistent with prior studies. Altogether, the work presented in this study supports the therapeutic advantages of Hsp90β-selective inhibition over Hsp90 pan-inhibition.
Insights
Targeting heat shock protein beta (Hsp90β) with novel inhibitors offers a safer alternative to broad Hsp90 inhibition for cancer therapy. Structure-activity studies refined Hsp90β-selective compounds, enhancing their therapeutic potential.
Area of Science:
- Biochemistry
- Molecular Biology
- Medicinal Chemistry
Background:
- Heat shock protein 90 (Hsp90) is crucial for cancer progression, with over 400 client proteins.
- Existing Hsp90 inhibitors cause toxicities due to pan-inhibition, limiting their clinical use.
- Hsp90 isoform-selective inhibition presents a promising strategy to mitigate toxicity.
Purpose of the Study:
- To explore structure-activity relationships (SAR) of Hsp90β-selective inhibitors based on the KUNB106 scaffold.
- To identify modifications that maintain or improve Hsp90β binding affinity and selectivity.
- To evaluate the biological activity of optimized Hsp90β inhibitors.
Main Methods:
- Structure-based design and synthesis of novel isoquinolin-1(2H)-one derivatives.
- Structure-activity relationship (SAR) studies focusing on the indazolone ring system.
- Biological assays to assess Hsp90β binding, client protein degradation, and Hsp90 level induction.
Main Results:
- Alkyl chain homologation, fluorination, and spirocyclization of the indazolone ring were effective modifications.
- Optimized derivatives maintained high affinity and selectivity for Hsp90β.
- New compounds promoted degradation of Hsp90β-dependent clients without increasing overall Hsp90 levels.
Conclusions:
- Hsp90β-selective inhibitors demonstrate therapeutic advantages over pan-Hsp90 inhibitors.
- Optimized derivatives show potential as targeted cancer therapeutics.
- Further development of Hsp90β-selective agents is warranted to overcome limitations of current therapies.
More Related Videos
06:51Studies of Chaperone-Cochaperone Interactions using Homogenous Bead-Based Assay
Published on: July 21, 2021
09:39Exploring Biomolecular Interaction Between the Molecular Chaperone Hsp90 and Its Client Protein Kinase Cdc37 using Field-Effect Biosensing Technology
Published on: March 31, 2022
