Abstract 87: Asparagine synthetase (ASNS) expression predicts response to the GLS1 inhibitor IPN60090 in ovarian cancer through selective modulation of redox homeostasis

Inhibitors of tumor metabolism have shown promise in the pre-clinical and clinical settings, however success is likely dependent upon identification of responsive patient populations to drive maximum benefit. We have previously disclosed the development of the GLS1 inhibitor, IPN60090, which is currently progressing through Phase 1 studies (NCT03894540). Current efforts are focused on developing additional patient stratification biomarkers to define those patients who will most benefit from IPN60090 single-agent treatment or combination strategies. Here we demonstrate that IPN60090 elicited a specific set of metabolic alterations and selectively inhibited the growth of high grade serous ovarian cancer (HGSOC) models in vitro and in vivo. In IPN60090-sensitive OvCa cell lines, GLS1 inhibition induced glutathione (GSH) depletion, inhibited glutamine anapleurosis (GLN), and altered cell cycle kinetics resulting from depletion of intracellular nucleotide pools and accumulation of DNA damage. Untargeted metabolic profiling of IPN60090-sensitive and -insensitive cell lines revealed that the differential response was driven by the ability of insensitive cell lines to maintain intracellular pools of glutamate (GLU), and consequently GSH, through consumption of aspartate and alanine. We examined two transaminases whose activity may result in aspartate or alanine depletion in cells, asparagine synthetase (ASNS) and glutamate pyruvate transaminase 2 (GPT2), and found that ASNS expression predicted response to IPN60090. In vivo, growth of both subcutaneous and orthotopic ASNSlow OvCa tumors was inhibited by IPN60090, while ASNShigh tumors were resistant to IPN60090. Leveraging tissue microarrays from tumor biopsies collected at MD Anderson Cancer Center, we developed an IHC assay for ASNS to determine the percentage of ASNS null or low patients that would benefit from IPN60090 treatment. Upon validation and CLIA certification, this assay was deployed across archival patient biopsies collected in the Department of Investigational Cancer Therapeutics at MD Anderson Cancer Center, and identified patients who showed no ASNS staining (ASNSnull) in their tumors, suggesting that they may benefit from treatment with IPN60090. Taken together, through a comprehensive translational effort we have identified ASNS as a predictive biomarker of response to GLS1 inhibitor-based therapeutic regimens. Citation Format: Nakia D. Spencer, Christopher A. Bristow, Virginia Giulani, Meredith A. Miller, Alessandro Carugo, Angela L. Harris, Rosalba Minelli, Ningpeng Feng, Qing Chang, Michael J. Soth, Kang Le, John N. Weinstein, Philip L. Lorenzi, Jinsong Liu, Wei-Lien Wang, Timothy A. Yap, Giulio Draetta, Philip Jones, Timothy P. Heffernan, Jeffrey J. Kovacs. Asparagine synthetase (ASNS) expression predicts response to the GLS1 inhibitor IPN60090 in ovarian cancer through selective modulation of redox homeostasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 87.