Abstract 5726: The potential anti-cancer activity of dual TTK/PLK1 inhibitor, BAL0891, in bladder cancer
Authors: Park Jee Soo , Lee Ji-eun , Lee Myung Eun , Kim Jongchan , Jang Won Sik , Lee Jae Jung , Lee Jun Seung , Kang Minkyung , Ham Won Sik 
Published: March 2024

Background: BAL0891 is a novel dual inhibitor of threonine tyrosine kinase (TTK) and polo-like kinase 1 (PLK1) which affects mitotic spindle assembly checkpoint integrity resulting in aberrant mitotic progression of cancer cells. Since unlike other organs, bladder urothelium is highly regenerative in certain circumstances, there are high chances of cell cycle inhibitors to have anti-cancer activity over bladder cancer. In this study, we investigated the therapeutic potential of BAL0891 in bladder cancer compared to single TTK or PLK1 inhibitor and discovered the best therapeutic combination partner for BAL0891.

Methods: We performed meta-analysis of the mRNA expression levels of bladder cancer using Gene Expression Profiling Interactive Analysis 2 (GEPIA2). Representative bladder cancer cell lines (253J, 253J-BV, J82, RT4, T24, J82, HT1197, and HT1376) were treated with the dual protein kinase inhibitors, BAL0891, in comparison with TTK inhibitor (BAY1217389) or PLK1 inhibitor (onvansertib). BAL0891 was combined with CDK4/6 inhibitor, another cell cycle inhibitor working at different point from BAL0891. Cell viability was assessed using CCK-8 assay during 72 hours after treatment. Expression levels of TTK and PLK1 were measured by immunoblotting. Cell cycle analysis and cell apoptosis detection were performed on T24 cell.

Results: The mRNA expression levels of both TTK (16.7 times) and PLK1 (10.0 times) were significantly upregulated only in bladder cancers compared to normal bladder tissues (P&lt;0.05). Compared to TTK or PLK1 inhibitor, BAL0891 was sensitive in 75% of bladder cancer cell lines (IC50 &lt;0.1 uM) and significantly reduced proliferation of bladder cancer cell lines depending on the dosage. TTK and PLK1 expression levels of cancer cells were associated with the sensitivity to BAL0891. BAL0891 significantly induced necrosis and increased in polyploidy and G2/M arrest in T24 cell. The anti-cancer activity of BAL0891 was further enhanced in certain cell lines (RT4, and J82) by combination of CDK4/6 inhibitor.

Conclusion: This is the first study to suggest the potent anti-cancer activity of BAL0891 in bladder cancer. BAL0891 effectively worked on bladder cancer by two tracks which not only induced G2/M arrest but also increased in polyploidy. Furthermore, BAL0891 in combination with CDK4/6 inhibitor promoted anti-cancer effects. Lastly, this study suggests the use of TTK and PLK1 as the predictive biomarker for BAL0891. These data support further investigation of BAL0891 for the treatment of bladder cancer patients.

Citation Format: Jee Soo Park, Ji-eun Lee, Myung Eun Lee, Jongchan Kim, Won Sik Jang, Jae Jung Lee, Jun Seung Lee, Minkyung Kang, Won Sik Ham. The potential anti-cancer activity of dual TTK/PLK1 inhibitor, BAL0891, in bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5726.