Despite the wide therapeutic potential of RNA interference (RNAi), clinical progress has been slow with only a few examples of successful translation. Efficient knockdown of hepatic transthyretin (87%) in patients with transthyretin amyloidosis lasted for several weeks after a single dose. Furthermore, in a phase I clinical trial, a single dose of inclisiran (small interfering RNA (siRNA) against the PCSK9 mRNA) efficiently suppressed serum cholesterol for 6 months. However, these studies suggested that siRNA delivery beyond the liver is not yet feasible in the clinic and thus limits the potential benefit of RNAi. Lipid nanoparticles (LNPs) containing ionizable cationic lipids embody the most advanced delivery platform for systemic administration of RNAi therapeutics. Our study provides a preclinical proof-of-concept that RNAi therapeutics can be exploited against leukemia cells using LNPs as a delivery tool, in a patient-derived B-cell acute lymphoblastic leukemia (ALL) xenograft mouse model.