Targeting NHE1-Mediated Ion Homeostasis to Eradicate Relapse-Driving Leukemia Initiating Cells

Abstract: Relapse is the leading cause of treatment failure in T-cell acute lymphoblastic leukemia (T-ALL), particularly in adolescents and young adults. Relapse is driven by leukemia-initiating cells (LICs), which are rare, self-renewing cells that can survive frontline chemotherapy and regenerate the disease. Eliminating LICs is a major unmet need in T-ALL and other blood cancers. We found that the Na?/H? exchanger NHE1 plays a central role in LIC persistence by sustaining mitochondrial function and supporting bone marrow niche retention. These programs are essential for LICs to withstand cytotoxic therapy and reseed leukemia. We also discovered that amiloride, an FDA-approved, oral, and inexpensive inhibitor of NHE1, disrupts these pathways and reduces LIC frequency in zebrafish and human T-ALL models. These results raise the exciting possibility of repurposing a safe, well-characterized drug to directly target LICs. This DoD Impact Award project will build on our findings to deliver a preclinical translational package for amiloride in T-ALL. Specifically, we will: (1) define a clinically relevant continuous dosing regimen, (2) develop a simple pharmacodynamic (PD) assay to confirm target engagement in marrow, and (3) test efficacy and safety in zebrafish and patient-derived xenograft (PDX) models. Together, these studies will position amiloride for early-phase clinical testing as a novel adjunct to standard therapy in high-risk T-ALL. Because mitochondrial and niche-retention programs are conserved across leukemias, this approach may also be relevant to B-ALL and other blood cancers where relapse remains a critical barrier to cure.