GSK-923295: Potent Small-Molecule CENP-E Inhibitor for Mitotic Arrest

Executive Summary: GSK-923295 is a nanomolar inhibitor of CENP-E, a mitotic kinesin essential for chromosome alignment and metaphase-anaphase transition in eukaryotic cells (APExBIO). The compound acts by suppressing the microtubule-stimulated ATPase activity of CENP-E, causing mitotic arrest and cell cycle delay in vitro and in vivo (GSK-923295 review). GSK-923295 demonstrates potent inhibition of tumor cell proliferation, with a median GI50 of 32 nM across 237 cancer cell lines. In mouse Colo205 colon tumor xenografts, intraperitoneal dosing at 125 mg/kg yields dose-dependent tumor regression and increased apoptosis. The compound is insoluble in water but dissolves at ≥29.6 mg/mL in DMSO and ≥14.87 mg/mL in ethanol with ultrasonic assistance, and requires storage at -20°C to maintain stability (APExBIO).

Biological Rationale

Centromere-associated protein E (CENP-E) is a kinesin motor protein that plays a central role in chromosome congression and alignment during mitosis. CENP-E functions at the kinetochore-microtubule interface, facilitating proper biorientation and tension sensing required for metaphase plate formation (Walsh et al., 2026). Correct chromosome alignment ensures faithful genome segregation; errors in this process contribute to aneuploidy and are implicated in cancer progression. Inhibition of CENP-E disrupts chromosome alignment, activates the mitotic checkpoint, and can lead to apoptosis in dividing cells. Targeting mitotic kinesins like CENP-E is therefore a validated strategy for modulating cell cycle dynamics in cancer research and therapy (see mechanistic insights).

Mechanism of Action of GSK-923295

GSK-923295 is a small-molecule inhibitor with a Ki of 3.2 nM for CENP-E ATPase activity (APExBIO). The compound binds to CENP-E and stabilizes its ATP-bound conformation, thereby suppressing microtubule-stimulated ATP hydrolysis. This results in slowed ADP and inorganic phosphate release, preventing the normal progression from metaphase to anaphase. As a result, cells experience mitotic arrest characterized by condensed chromosomes and a disorganized metaphase plate, closely recapitulating phenotypes observed with RNAi-mediated CENP-E knockdown (see detailed mechanism).

Evidence & Benchmarks

• GSK-923295 inhibits the microtubule-stimulated ATPase activity of purified human CENP-E with a Ki of 3.2 nM (in vitro, ATPase assay, 25°C, pH 7.0) (APExBIO).
• In a panel of 237 tumor cell lines, the compound achieves an average GI50 of 253 nM and a median GI50 of 32 nM (cell proliferation assays, 72 h, RPMI/DMEM media) (benchmark study).
• In vivo, 125 mg/kg intraperitoneal dosing in mice bearing Colo205 colon cancer xenografts results in partial and complete tumor regressions, with increased apoptosis verified by TUNEL staining (n=8 per group, 21-day study) (xenograft data).
• GSK-923295-induced mitotic arrest is accompanied by chromosomal misalignment phenotypes similar to CENP-E RNAi knockdown, supporting target specificity (immunofluorescence, HCT116 cells) (Walsh et al., 2026).
• The compound is insoluble in water but dissolves at ≥29.6 mg/mL in DMSO and ≥14.87 mg/mL in ethanol (ultrasonic assistance, RT) (APExBIO).

This article extends previous reviews by integrating solubility and workflow parameters, and clarifies target selectivity using updated centromere biology (workflow optimization).

Applications, Limits & Misconceptions

GSK-923295 is widely used in cancer research for dissecting mitotic checkpoint signaling, studying chromosome alignment, and evaluating cell cycle arrest in mitosis. Its nanomolar potency and robust in vivo efficacy make it a preferred agent for preclinical antitumor studies, particularly in colon cancer xenograft models. The compound also serves as a tool for probing the microtubule motor protein pathway and ATPase activity inhibition in mitotic cells.

Common Pitfalls or Misconceptions

• Not a general microtubule poison: GSK-923295 does not disrupt microtubule polymerization directly; it specifically inhibits CENP-E ATPase.
• Limited solubility: The compound is insoluble in water; improper solvent choice can impair assay reproducibility.
• Not suitable for diagnostic or therapeutic use: GSK-923295 is supplied by APExBIO for research applications only.
• Mitotic arrest is CENP-E dependent: In cells lacking CENP-E expression, GSK-923295 will not induce mitotic arrest.
• Storage conditions matter: Degradation may occur at room temperature; always store at -20°C and use solutions promptly for reliable results.

Workflow Integration & Parameters

For in vitro studies, GSK-923295 can be reconstituted to ≥29.6 mg/mL in DMSO or ≥14.87 mg/mL in ethanol (with ultrasonication), then diluted into culture media immediately before use (APExBIO). Working solutions should be freshly prepared and kept at -20°C until use. For in vivo xenograft studies, 125 mg/kg intraperitoneal dosing is validated for robust anti-tumor activity in colon cancer models. The compound's effects on CENP-E function and chromosome alignment can be monitored via immunofluorescence microscopy and flow cytometry. For best practices and troubleshooting in cell viability and cytotoxicity assays, see this scenario-driven guide (this article clarifies solvent handling and benchmarking relative to vendor practices).

Conclusion & Outlook

GSK-923295 is a validated, potent small-molecule CENP-E inhibitor that provides high specificity for studies of mitotic checkpoint signaling and chromosome alignment regulation. Its robust in vitro and in vivo activity, combined with precise workflow parameters, enables advanced mechanistic and translational research in cancer biology. This article updates prior guides by integrating new evidence on centromere maintenance and CENP-E function. For more on recent mechanistic advances, see this review (here, new centromere and CTCF context is included beyond earlier analyses). Always use GSK-923295 from APExBIO under recommended storage and handling guidelines for reproducible results in cancer research.