Abstract 5334: Targeting the KIF15-TPX2 PPI to overcome KIF11 inhibitor resistance in epithelial ovarian cancer
Authors: Gibbs Benjamin K. , Douglas Justin T. , Wates Rebecca J. , McDonald Peter R. , Whitaker Amy M. , Ndi Cornelius N. , Pathak Harsh B. , Harned Laurie A. , Neuenswander Sarah A. , Broward Melinda A. , Freudenthal Bret D. , Roy Anuradha , Schoenen Frank J. , Godwin Andrew K. 
Published: April 2023

Abstract
Most cases of epithelial ovarian cancer (EOC) exhibit extensive molecular heterogeneity, presenting challenges in developing targeted therapies. Despite extensive efforts and incremental successes in developing targeted drugs and immunotherapies for other cancers, chemotherapies continue to be the most used treatment of ovarian cancer. Although seemingly simplistic, identification of drugs targeting cellular machinery independent of genomic and genetic status continues to be a strong clinical need. Previously, we performed an RNAi-based screen of the druggable genome across a diverse histological panel of EOC cell line representing both platinum-sensitive and -resistant tumors (PMID: 23056589). This screen elucidated KIF11 as essential in maintaining EOC cell viability. KIF11, a mitotic spindle assembly motor protein, has been targeted clinically. Although drugs are well tolerated, potent, and specific, the objective response rates to KIF11 inhibitors in clinical trials were commonly less than 10%. The efficacy of KIF11 inhibitors is blunted via a compensatory motor kinesin, KIF15. The overexpression of KIF15 has been shown to compensate for absent KIF11 in the formation of the bipolar spindle apparatus during mitosis. Silencing KIF15 significantly sensitizes cells to KIF11 inhibitors and resensitizes resistant cells to KIF11 inhibitors. We developed a high throughput screening approach using Alpha technology to identify compounds that inhibit the protein-protein interaction (PPI) between KIF15 and TPX2, a unique approach to inhibiting KIF15 from previous efforts. Of the nearly 200,000 compounds screened, 177 compounds were selected to be further characterized based on assay performance and chemical properties. These compounds were screened for TPX2 or KIF15 binding by STD-NMR and waterLOGSY. Three compounds across two chemotypes were confirmed to bind KIF15. No compounds were found to bind TPX2. Additionally, 168 of the 177 compounds were screened for drug synergism in vitro. The synergism assay yielded 32 strongly and 8 weakly synergistic hits. The lead compound in each of the two chemotypes revealed by NMR were classified as strongly synergistic (max. bliss score of 8.0 and 29.9). To expand the potential lead compounds identified for further development, an antibody-free cellular thermal shift assay (CETSA) is being completed with 168 compounds. Preliminarily, CETSA has shown that the two lead compounds significantly stabilize KIF15 (ΔTm = 5.6 °C and 9.6 °C). These two lead compounds behaved in a dose-dependent manner in the AlphaScreen (IC50= 2 µM and 6 µM), a favorable characteristic for further development. To date, two chemotypes have been identified as KIF15 inhibitors uniquely targeting the KIF15-TPX2 PPI. The data indicates KIF15 inhibition in combination with KIF11 inhibition is synergistic, thus demonstrating a potential novel treatment approach for people with EOCs.
Citation Format: Benjamin K. Gibbs, Justin T. Douglas, Rebecca J. Wates, Peter R. McDonald, Amy M. Whitaker, Cornelius N. Ndi, Harsh B. Pathak, Laurie A. Harned, Sarah A. Neuenswander, Melinda A. Broward, Bret D. Freudenthal, Anuradha Roy, Frank J. Schoenen, Andrew K. Godwin. Targeting the KIF15-TPX2 PPI to overcome KIF11 inhibitor resistance in epithelial ovarian cancer. [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 5334.