Abstract 7121: The novel WEE1i, APR-1051, is a potentially well tolerated and effective treatment for cyclin E-overexpressing cancers

Abstract Previous studies have demonstrated that WEE1 inhibitors (WEE1i) are a promising cancer therapeutic through synthetic lethality with Cyclin E overexpression. One challenge for two of the leading WEE1i, AZD1775 and ZN-c3, has been the observed off-targeting of PLK family members, namely, PLK1, PLK2 and PLK3. In addition, the therapeutic application of these inhibitors in clinical trials has been limited by adverse hematological effects, including anemia. Herein, we describe the testing of a novel WEE1i (APR-1051) that, based on preclinical studies: 1) demonstrates reduced off-targeting of PLK1, PLK2 and PLK3, and 2) has the ability to suppress the growth of CCNE1-overexpressing xenografted tumors while causing little impact on red blood cell and reticulocyte levels. APR-1051 has an IC50 of 2. 2 nM for WEE1 in vitro and has shown the ability to limit the proliferation of various cancer cell lines in culture. Interestingly, the genotoxicity of APR-1051 is suppressed by increasing concentrations of PLK1 inhibitors, suggesting that off-targeting of PLK1 by other WEE1i may compromise efficacy of this targeted cancer treatment in addition to the risk of producing PLK1i-associated adverse effects. APR-1051 demonstrated effectiveness in suppressing the growth of Cyclin E-overexpressing breast and ovarian cancer cells lines, thus pinpointing Cyclin E as a potential biomarker for APR-1051 treatment. Importantly, dose and scheduling of APR-1051 that causes significant suppression of CCNE1-amplified high-grade serious ovarian cancer tumors in mice is well tolerated, with red blood cell and platelet counts remaining within non-pathogenic ranges after a 28-day treatment period. In addition, inhibition WEE1 by APR-1051 occurs at an IC50 that is 200-fold lower on average than the IC50 of hERG potassium channel inhibition, implying that APR-1051 will potentially exhibit low cardiotoxicity. APR-1051 is now progressing through IND-enabling studies. Together, these findings underscore the potential of APR-1051 as a novel WEE1i for the treatment of Cyclin E-overexpressing cancers. Citation Format: Molly M. Hansbarger, Stephen J. Rocca, Sonia Ritzmann, Joseph Vacca, Bridget Tokiwa, Jonathan Weinstein, Henry Zabierek, Justin Frye, Michael Carleton, Eric J. Brown, Oren Gilad. The novel WEE1i, APR-1051, is a potentially well tolerated and effective treatment for cyclin E-overexpressing cancers 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 (6Suppl): Abstract nr 7121.