Abstract 6759: <i>In vivo</i> tumor growth control by general control nonderepressible 2 targeting agents results from kinase activation

Abstract General Control Nonderepressible 2 (GCN2; EIF2AK4) is a serine-threonine kinase in the integrated stress response (ISR) signaling pathway that initiates adaptive responses during nutrient stress conditions. While pharmacological inhibition of GCN2 under nutrient stress conditions induces apoptosis and inhibits tumor growth, GCN2 inhibition without nutrient stress has been reported to have no effect on tumor growth. By exploring an array of GCN2 inhibitors, we demonstrate that multiple agents in fact activate GCN2 in biochemical and cell-based assays at low concentrations and inhibit GCN2 at higher concentrations. Unexpectedly, it is this activation, and not inhibition, of the GCN2 pathway that is associated with decreased viability in vitro and tumor growth inhibition in vivo across multiple models. Knockdown and knockout experiments show that activation of the ISR by GCN2-targeting agents is dependent on GCN2. We also uncover that Type 1 GCN2-targeting agents do not activate GCN2 whereas non-Type 1 agents activate GCN2 in the absence of stress. We demonstrate that a Type 1 GCN2-targeting agent does not have the same viability effects as the non-Type 1 GCN2-targeting agents. These results provide a clearer understanding of the challenges and opportunities for the clinical development of compounds targeting GCN2. Citation Format: Feven Tameire, Paulina Wojnarowicz, Crissy Dudgeon, Sho Fujisawa, Savi Ramurthy, Owen Reilly, Christopher G. Thomson, Bradley Sherborne, Simon Taylor, Fang He, Pengwei Pan, Baozhong Li, Earl May, Alan C. Rigby, Mark J. Mulvihill, Nandita Bose, David Surguladze, Eric Scott Lightcap. In vivo tumor growth control by general control nonderepressible 2 targeting agents results from kinase activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6759.