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Published on: November 30, 2021
Pharmaceutical-Grade Rigosertib Is a Microtubule-Destabilizing Agent.
Marco Jost1, Yuwen Chen2, Luke A Gilbert3
1Department of Cellular & Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA; Center for RNA Systems Biology, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA.
Rigosertib, an anti-cancer drug, kills cancer cells by destabilizing microtubules. This microtubule-destabilizing activity is inherent to rigosertib itself, not a contaminant, supporting its efficacy in clinical trials.
Area of Science:
- Oncology
- Cell Biology
- Biochemistry
Background:
- Rigosertib is an anti-cancer agent undergoing Phase III clinical trials.
- A recent study suggested a contaminant in rigosertib formulations, not the drug itself, caused microtubule destabilization.
Purpose of the Study:
- To investigate the mechanism of action of rigosertib.
- To determine if rigosertib or a contaminant is responsible for microtubule destabilization.
Main Methods:
- CRISPRi/a-based chemical-genetic screens
- Cellular and biochemical assays
- Structural assays
- Analysis of pharmaceutical-grade vs. commercial rigosertib
- Use of a rationally designed tubulin mutant (L240F TUBB)
Main Results:
- Pharmaceutical-grade and commercial rigosertib produced indistinguishable cellular phenotypes.
- Both rigosertib formulations destabilized microtubules in vitro and in cells.
- Expression of the L240F TUBB mutant conferred resistance to rigosertib's effects.
- The L240F TUBB mutant's specificity for microtubule-destabilizing agents was independently confirmed.
Conclusions:
- Rigosertib directly destabilizes microtubules, leading to cancer cell death.
- The microtubule-destabilizing activity is an intrinsic property of rigosertib.
- These findings reaffirm the original mechanism of action for rigosertib.
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