Suppressing t(4;11) Acute Leukemia by Lipopolymer Nanoparticle Delivery of siRNA Targeting KMT2A::AFF1 with Enhanced Extrahepatic Delivery.

Effective siRNA delivery in acute lymphoblastic leukemia (ALL) is limited by preferential hepatic accumulation. To address this, a lipopolymer (PEI-C) is developed by conjugating lipid to polyethylenimine and formulated lipopolymer nanoparticles (LPNPs) via complexation with siRNA. The siRNA delivery efficiency of LPNPs is evaluated in vitro in t(4;11)-positive ALL cells (RS4;11 and SEM) as well as "normal" peripheral blood mononuclear cells (PBMCs) from human donors and bone marrow stromal cells (BMSCs) from mice. Molecular effects are assessed by quantifying target mRNA silencing and downstream apoptosis. In vivo biodistribution and therapeutic efficacy are examined in mouse models. LPNPs demonstrated significantly higher siRNA uptake than commercial reagents in PBMCs and BMSCs, reaching siRNA uptakes of 87.2% and 93.0% in RS4;11 and SEM cells, respectively. Molecular analyses revealed effective silencing of KMT2A::AFF1 mRNA (≈80% in RS4;11), accompanied by BCL2 downregulation and increased apoptosis. In vivo, LPNPs showed efficient siRNA biodistribution to leukemia-associated organs (spleen and bone marrow) and significantly reduced leukemia burden in a systemic RS4;11 xenograft mouse model and improved survival. These findings suggest that PEI-C-formulated LPNPs present a promising avenue for therapeutic siRNA delivery in ALL, effectively targeting leukemia-associated organs, and warrant further exploration in clinical studies.