Development of novel RPS23 inhibitors for the treatment of leukemia

/ABSTRACT Acute myeloid leukemia (AML) remains a lethal disease despite recent therapeutic advances, including the BCL2 inhibitor venetoclax. Most patients ultimately develop relapsed or refractory disease, underscoring the urgent need for new therapies, particularly agents that synergize with venetoclax. One promising strategy is to target the integrated stress response (ISR), a conserved pathway that modulates protein synthesis through phosphorylation of eIF2á by one of four stress-sensing kinases: GCN2, PKR, PERK, or HRI. This phosphorylation reduces global cap-dependent translation while selectively increasing translation of transcripts such as ATF4, which drive adaptive or pro-apoptotic programs depending on context. Leukemia stem cells rely on chronic ISR activity to withstand metabolic stress, suggesting that further ISR activation could tip the balance toward apoptosis. Consistent with this idea, we found that venetoclax itself activates the ISR via HRI, and its efficacy in preclinical models depends on this mechanism. We discovered novel ISR modulators using our integrated platform that combines high-throughput phenotypic screening with rapid target deconvolution. Through this approach, we identified ligands of RPS23, a 40S ribosomal subunit protein, that activate the ISR through GCN2 by a mechanism distinct from venetoclax and known ribosome binders. These ligands trigger apoptosis in leukemia cells and prolong survival in aggressive AML mouse models with minimal toxicity to normal hematopoietic cells. We hypothesize that RPS23 ligands represent a novel therapeutic strategy for AML and may act synergistically with venetoclax to overcome resistance. The discovery of this ISR-inducing target, together with a bioavailable compound showing preclinical efficacy, highlights the significance and innovation of our approach and provides a strong foundation for clinical translation. To advance this therapeutic strategy, our Specific Aims will define the mechanism by which RPS23 ligands activate the ISR and evaluate their on-target toxicities and efficacy alone and in combination with venetoclax in disease-relevant models of AML. No validated in vitro or computational model currently recapitulates the integrated immune, vascular, and metabolic interactions required to evaluate therapeutic efficacy and toxicity in vivo. Project Number: 1R01CA315853-01 | Fiscal Year: 2026 | NIH Institute/Center: National Cancer Institute (NCI) | Principal Investigator: DEEPAK NIJHAWAN (+1 co-PI) | Institution: UT SOUTHWESTERN MEDICAL CENTER, DALLAS, TX | Award Amount: $688,012 | Activity Code: R01 | Study Section: Advancing Therapeutics A Study Section [ATA] View on NIH RePORTER: https://reporter.nih.gov/project-details/11428745