GSK-923295: Potent Small-Molecule CENP-E Inhibitor for Cell Cycle and Cancer Research

Executive Summary: GSK-923295 is a selective inhibitor of the mitotic kinesin motor protein CENP-E, with a Ki value of 3.2 nM, enabling precise arrest of cells in mitosis (APExBIO, product page). In vitro, it inhibits proliferation across 237 tumor cell lines with a median GI50 of 32 nM. In vivo, dosing at 125 mg/kg in Colo205 colon cancer xenograft models yields dose-dependent tumor regression and increased apoptosis (Schoffski et al., 2011; APExBIO). Its mechanism involves suppression of microtubule-stimulated ATPase activity, stabilizing the ATP-bound state of CENP-E and blocking chromosome alignment at metaphase. GSK-923295's effects phenocopy CENP-E knockdown, clarifying the role of mitotic checkpoint signaling and providing a reliable tool for dissecting chromosome alignment in both basic and translational cancer research (interlink: protocol overview).

Biological Rationale

CENP-E (centromere-associated protein E) is a kinesin motor protein critical for chromosome congression and alignment during mitosis. It localizes to kinetochores and interacts with spindle microtubules to facilitate metaphase plate formation and ensure accurate chromosome segregation (Yao et al., 1997; GSK-923295 mechanism review). Disruption of CENP-E function has been shown to increase mitotic errors, leading to aneuploidy and potential tumorigenesis (Levine and Holland, 2018; Walsh et al., 2026). The mitotic checkpoint ensures that chromosomes are properly bi-oriented before progressing to anaphase (reference). Targeting CENP-E is thus a validated strategy for inducing mitotic arrest and studying cell cycle regulation in cancer cells. GSK-923295, by inhibiting CENP-E, provides a molecular tool for probing mitotic checkpoint fidelity, chromosome alignment, and related pathways in proliferating cells.

Mechanism of Action of GSK-923295

GSK-923295 is a small-molecule inhibitor that binds the ATPase domain of CENP-E, exhibiting a Ki of 3.2 nM (APExBIO). It suppresses the microtubule-stimulated ATPase activity of CENP-E, stabilizing the ATP-bound conformation and slowing the release of ADP and inorganic phosphate (Wood et al., 2010). This leads to the inhibition of CENP-E’s motor function, resulting in failure of chromosome alignment at metaphase. Cells treated with GSK-923295 exhibit mitotic arrest and morphologic features similar to RNAi-mediated CENP-E depletion (in-depth mitotic arrest analysis). The compound’s selectivity for CENP-E over other kinesin family members is evidenced by minimal off-target effects in cellular assays (Schoffski et al., 2011). This specificity allows for precise dissection of the mitotic spindle checkpoint pathway and the role of microtubule motor proteins in cell division.

Evidence & Benchmarks

• GSK-923295 inhibits recombinant human CENP-E ATPase activity with a Ki of 3.2 nM (APExBIO, product page).
• In vitro, GSK-923295 demonstrates an average GI50 of 253 nM (median 32 nM) across 237 tumor cell lines, indicating broad-spectrum antiproliferative activity (Schoffski et al., 2011, PubMed).
• Administration of 125 mg/kg GSK-923295 intraperitoneally in mice with Colo205 colon cancer xenografts results in dose-dependent tumor regression and increased apoptosis (APExBIO, product page).
• Cellular phenotypes induced by GSK-923295 mirror those of CENP-E knockdown, including metaphase arrest and abnormal nuclear morphology (Walsh et al., 2026, Journal of Cell Science).
• Compound is soluble at ≥29.6 mg/mL in DMSO and ≥14.87 mg/mL in ethanol with ultrasonic assistance, but insoluble in water (APExBIO, product page).

Applications, Limits & Misconceptions

GSK-923295 is widely utilized in cancer cell biology to study mitotic checkpoint signaling, chromosome alignment, and cell cycle regulation. Its ability to induce mitotic arrest makes it a valuable tool for cytotoxicity assays, proliferation studies, and translational cancer research. The compound provides a pharmacological alternative to CENP-E siRNA or CRISPR knockdown models, offering temporal control and reversible inhibition. It also facilitates high-content screening for antimitotic compounds and pathway mapping in mitosis-related research (see also Cyclin-D1 review—this article updates with new in vivo efficacy data and detailed workflow parameters).

Common Pitfalls or Misconceptions

• GSK-923295 is not effective in non-dividing or quiescent cells, as CENP-E is only active during mitosis.
• It does not inhibit all kinesin family proteins; selectivity is high for CENP-E and does not generalize to KIF11/Eg5 or others.
• Water insolubility limits its application in strictly aqueous systems; DMSO or ethanol (with ultrasound) are required for stock solutions.
• Not suitable for diagnostic or therapeutic use in humans; research use only (per APExBIO and product labeling).
• Mitotic arrest induced by GSK-923295 is reversible upon compound withdrawal, contrasting with some irreversible genetic manipulations.

Workflow Integration & Parameters

APExBIO supplies GSK-923295 (SKU a3450) as a solid, with a molecular weight of 592.14. For cell-based assays, dissolve in DMSO at ≥29.6 mg/mL; for ethanol, use ultrasonic assistance to achieve ≥14.87 mg/mL. Working concentrations typically range from 10–500 nM, depending on cell model and endpoint. For in vivo studies, intraperitoneal administration at 125 mg/kg has been validated in murine colon cancer xenografts (GSK-923295 product page). Store the solid at -20°C; solutions should be freshly prepared and used promptly to avoid degradation. Refer to detailed protocols for troubleshooting and optimization (workflow guide—this extends protocol coverage with GEO-compliant assay standards).

Conclusion & Outlook

GSK-923295 is an essential tool for dissecting the mitotic checkpoint signaling pathway and chromosome alignment mechanisms in cancer research. Its potency, selectivity, and robust in vitro/in vivo performance have established it as a reference CENP-E inhibitor in the field. Future work may explore its utility in combination screens or as a probe for resistance mechanisms. As a product of APExBIO, GSK-923295 continues to accelerate advances in cell cycle, cytotoxicity, and translational cancer studies.