Summary

A research group led by Micheal Heuser of Hannover University have published a paper in the Annals of Hematology showing effective knockdown of a fusion oncogene in a chronic myeloid leukemia (CML) model by way of siRNA lipid nanoparticle (LNP) in vitro and in vivo.

Notably, they compared a LNP formulation produced by Precision NanoSystems Inc (PNI) to nucleofection in vitro using a human CML derived cell line and found PNI LNPs were more effective than nucleofection both in terms of knockdown of the target transcript and inhibition of leukemic cell growth.

They also tested the LNP formulation in primary human CD34+ bone marrow cells in vitro, and found the siRNA-LNP treatment significantly reduced expression of the oncogene in CML cells. They observed a significant reduction in residual colonies of CD34+ CML cells when compared to healthy CD34+ cells. 

In vivo, they tested the safety of PNI LNPs by performing 10 i.v. injections at 5 mg/kg siRNA dose each, over a 30 day period and found nearly no change in blood work compared to PBS controls, indicating a high degree of safety and tolerance to repeat dosing. In a CML xenograft model, mice treated with the LNP containing the siRNA against the fusion oncogene showed dramatically lower expression of a fluorescent reporter gene carried by the xenografted cells compared to those treated with a control siRNA-LNP.

These findings build upon prior work by the Heuser lab and others in demonstrating the effectiveness of siRNA LNPs in leukemia models. Overall, the results demonstrate a strategy for treating leukemia by targeting fusion oncogenes and knocking them down with siRNA-LNPs. The authors suggest this strategy should be further pursued to realize personalized treatments for leukemia.

Abstract

Efficient and safe delivery of siRNA in vivo is the biggest roadblock to clinical translation of RNA interference (RNAi)-based therapeutics. To date, lipid nanoparticles (LNPs) have shown efficient delivery of siRNA to the liver; however, delivery to other organs, especially hematopoietic tissues still remains a challenge. We developed DLin-MC3-DMA lipid-based LNP-siRNA formulations for systemic delivery against a driver oncogene to target human chronic myeloid leukemia (CML) cells in vivo. A microfluidic mixing technology was used to obtain reproducible ionizable cationic LNPs loaded with siRNA molecules targeting the BCR-ABL fusion oncogene found in CML. We show a highly efficient and non-toxic delivery of siRNA in vitro and in vivo with nearly 100% uptake of LNP-siRNA formulations in bone marrow of a leukemic model. By targeting the BCR-ABL fusion oncogene, we show a reduction of leukemic burden in our myeloid leukemia mouse model and demonstrate reduced disease burden in mice treated with LNP-BCR-ABL siRNA as compared with LNP-CTRL siRNA. Our study provides proof-of-principle that fusion oncogene specific RNAi therapeutics can be exploited against leukemic cells and promise novel treatment options for leukemia patients.