Abstract 4965: Targeting the mitotic kinesin, KIF18A, in chromosomally unstable cancers

Abstract Background: Chromosome instability (CIN), characterized by frequent and ongoing loss or gain of chromosome number, is commonly observed in tumor cells. Although long recognized as a vulnerability of cancer cells, potential CIN-selective therapeutic targets have only recently been discovered. Genetic studies from multiple groups have identified the mitotic kinesin, KIF18A, as selectively essential for the proliferation of CIN and aneuploid cells. By targeting KIF18A genetically and with novel small molecule inhibitors here we present data supporting KIF18A as therapeutic target in CIN tumors. Methods and Materials: To explore the therapeutic potential of KIF18A, we evaluated the effects of KIF18A genetic depletion and small molecule inhibition in both CIN-positive and CIN-negative cell lines. Biochemical, cell proliferation and phenotypic assays were used to characterize the potency and cellular activity of reference and novel KIF18A small molecule inhibitors. Anti-tumor activity of KIF18A inhibitors was assessed in CIN-positive cell line xenograft models. Results: In triple negative breast and colorectal CIN positive cancer cell lines siRNA mediated KIF18A knockdown and small molecule inhibition of the KIF18A ATPase activity both lead to a reduction in proliferation associated with an increase in mitotic index and multi-polar spindles. Consistent with KIF18A knockdown, KIF18A inhibition results in increased spindle length and chromosome alignment defects. Importantly, these effects are not observed with KIF18A knockdown or KIF18A inhibition in non-transformed, near diploid cells. In vivo, treatment of CIN-positive xenograft tumors with potent, novel KIF18A inhibitors results in robust anti-tumor activity with minimal impact on body weight. Conclusions: Collectively our data support KIF18A as a therapeutic target and provide rationale for the continued development of potent selective small molecule KIF18A inhibitors for the treatment of CIN positive cancers. Citation Format: James D. Joseph, Katherine Schutt, Kira Fisher, Katelyn Queen, Olivia Budington, Weifeng Mao, Wei Liu, Zhengqing Zhu, Xiangping Zhang, Yisong Xiao, Kunmin Lai, Xiaohui Gu, Jason Stumpff, Fred Aswad. Targeting the mitotic kinesin, KIF18A, in chromosomally unstable cancers. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4965.