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A brain-penetrant CDK4/6 inhibitor - AU3-14 shows robust anti-tumor efficacy against glioblastoma
Laychiluh B Mekonnen1, Theodosia Teo1, Benjamin Noll1
1Drug Discovery and Development, Clinical and Health Sciences, University of South Australia, Adelaide, SA 5000, Australia.
Abstract:
The cyclin D-CDK4/6-INK4-Rb pathway is frequently dysregulated in glioblastoma (GBM), the most aggressive and poorly prognosed brain malignancy. Despite extensive research, advances in GBM treatment have seen limited progress, with current therapy largely reliant on temozolomide (TMZ), underscoring the need for novel therapeutic strategies. This study explores the therapeutic potential of AU3-14, a potent and selective CDK4/6 inhibitor, for GBM. In CDK4-amplified GBM cell lines, AU3-14 significantly reduced phosphorylation of Rb and levels of cell cycle-related proteins, resulting in G1/G0 cell cycle arrest and senescence. Biopharmaceutical analysis indicated that AU3-14 has high membrane permeability and low P-glycoprotein substrate potential. More extensive pharmacokinetic studies revealed that AU3-14 efficiently crosses the blood-brain barrier, with an unbound brain-to-plasma concentration ratios (Kp,uu) of 1.2 and 0.63 at single oral doses of 10 and 30 mg/kg, respectively, which were 2-4 times higher than those of abemaciclib. In subcutaneous and orthotopic GBM mouse models, AU3-14 demonstrated substantial anti-tumor efficacy and safety. Further toxicokinetic studies in rats and cynomolgus monkeys following 28-day repeated doses demonstrated that AU3-14 is well-tolerated, with a low risk of hematological toxicities, such as neutropenia, which are commonly associated with other CDK4/6 inhibitors. Moreover, AU3-14 enhances TMZ's anti-tumor efficacy and delays the onset of TMZ resistance. These findings support the clinical phase I/IIa investigation of AU3-14 for the treatment of GBM (ACTRN12621000479808).
Insights
A new drug, AU3-14, shows promise for treating glioblastoma (GBM) by inhibiting CDK4/6. This drug effectively crosses the blood-brain barrier and demonstrates anti-tumor activity with good safety, potentially improving temozolomide treatment.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Glioblastoma (GBM) is an aggressive brain cancer with limited treatment options.
- The cyclin D-CDK4/6-INK4-Rb pathway is often dysregulated in GBM.
- Current GBM therapy relies heavily on temozolomide (TMZ), necessitating novel therapeutic strategies.
Purpose of the Study:
- To investigate the therapeutic potential of AU3-14, a selective CDK4/6 inhibitor, for GBM treatment.
- To evaluate AU3-14's pharmacokinetic properties, including blood-brain barrier penetration.
- To assess AU3-14's anti-tumor efficacy, safety, and potential to overcome TMZ resistance in GBM models.
Main Methods:
- In vitro studies using CDK4-amplified GBM cell lines to assess cell cycle arrest and senescence.
- Biopharmaceutical and pharmacokinetic analyses to determine membrane permeability, P-glycoprotein interaction, and blood-brain barrier penetration.
- In vivo studies using subcutaneous and orthotopic GBM mouse models to evaluate anti-tumor efficacy and safety.
- Toxicokinetic studies in rats and cynomolgus monkeys to assess tolerability and potential toxicities.
- Combination studies with temozolomide (TMZ) to evaluate synergistic effects and resistance delay.
Main Results:
- AU3-14 induced G1/G0 cell cycle arrest and senescence in GBM cells by reducing Rb phosphorylation.
- AU3-14 exhibits high membrane permeability, low P-glycoprotein substrate potential, and efficient blood-brain barrier penetration.
- Significant anti-tumor efficacy and favorable safety profile were observed in GBM mouse models.
- AU3-14 was well-tolerated in preclinical toxicology studies, with a low risk of neutropenia.
- AU3-14 enhanced TMZ's anti-tumor effects and delayed the onset of TMZ resistance.
Conclusions:
- AU3-14 is a potent and selective CDK4/6 inhibitor with promising therapeutic potential for GBM.
- Its favorable pharmacokinetic profile, including blood-brain barrier penetration, supports its use in brain tumors.
- AU3-14 demonstrates significant anti-tumor activity and safety, offering a potential new treatment strategy for GBM, including combination therapy with TMZ.
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