Targeted Therapy with CX4945 Biomimetic Nanodrug Delivery System for High-Risk B-Cell Acute Lymphoblastic Leukemia

Background B-cell acute lymphoblastic leukemia (B-ALL) is one of the common hematological malignancies, and dysfunction of the IKAROS leukemia suppressor is a hallmark of high-risk B-ALL with high relapse rates and poor outcome (N Engl J Med, 2009, 360:470; Blood 2015, 126:1813). We reported that the Casein kinase II inhibitor CX4945 showed therapeutic efficacy in high-risk B-ALL by reducing the phosphorylation of IKAROS and restoring its function (Blood 2015, 126:1813; 2020, 136:1520; Leukemia 2021, 35:1267). However, CX4945 has relatively poor bioavailability and a rapid degradation rate (Arch Pharm Res 2013, 36:840) and nanoparticle encapsulation may significantly improve the therapeutic efficacy of the drug by increasing its bioavailability and stability. On the other hand, the homing of ALL cells to the bone marrow relies on the regulation of the C-X-C chemokine receptor 4 (CXCR4), which specifically binds to CXCL12 ligand secreted by bone marrow stromal cells (Blood 2015, 126:1297). Thus, the biomimetic nanodrugs coated with stromal cell membranes can facilitate the drugs to leukemia niches in the bone marrow. This study aims to develop a biomimetic Nanodrug Delivery System to improve biocompatibility and enhance the specific targeting of the CX4945 on high-risk B-ALL in vivo.

Methods The morphology, elemental composition, size, surface charge, and polymer dispersity index of the biomimetic nanodrug CX4945@PLGA-PEG@CM NPs were analyzed by transmission electron microscopy, scanning electron microscopy, and dynamic light scattering to characterize the nanoparticles (Bioact Mater 2022, 18:526 ). The encapsulation efficiency, drug loading, and drug release behavior of nanoparticles were tested by UV-visible absorption spectroscopy (Drug Deliv 2021, 28:2480). The blood compatibility of CX4945@PLGA-PEG@CM NPs was determined by a microplate reader. Cell Counting Kit-8 (CCK-8) to assess cell viability.

Results The results showed that all nanoparticles were spherical under transmission electron microscopy, and there was a clear cell membrane shell on the surface of CX4945@PLGA-PEG@CM NPs. The elemental analysis of scanning electron microscopy contained Cl, P, and S elements, confirming the successful preparation of CX4945@PLGA-PEG@CM NPs. The encapsulation rate was about 74% and the drug loading capacity was about 3.5%. Furthermore, CX4945@PLGA-PEG@CM NPs could prolong the drug circulation time. The stability of the drug delivery system was related to the safety and effectiveness of the drug delivery process. When CX4945@ PLGA-PEG@ CM NPs were immersed in distilled water for 7 days or incubated under physiological conditions for 72 hours, the biomimetic nanomedicine exhibited significant stability. The safety of nanomedicines determines whether they can be widely used in the clinic. Both CX4945@PLGA-PEG NPs or CX4945@PLGA-PEG@CM NPs showed no obvious hemolysis and good biocompatibility. We explore the cytotoxicity of the nanodrugs on the NALM6 B-ALL cells with high expression of CXCR4. Results showed both CX4945@PLGA-PEG@CM Nps and CX4945@PLGA-PEG NPs showed dose-dependent cytotoxicity on the cells, and their effect is significantly enhanced compared to CX4945 only control. CX4945@PLGA-PEG@CM NPs showed significantly higher cytotoxicity compared with CX4945@PLGA-PEG NPs and free CX4945 drug in the cells. The strongness of the cytotoxic effect is in order of CX4945@ PLGA-PEG@ CM > CX4945@PLGA-PEG > free CX4945 drug.

Conclusions We successfully generated two new nanodrugs, CX4945@PLGA-PEG@CM NPs and CX4945@PLGA-PEG NPs with strong cytotoxicity effects on B-ALL cells. CX4945@PLGA-PEG@CM NPs is a biomimetic nanodrug with a core-shell structure, which has high stability and biocompatibility to delay the release of CX4945 drug and improve the bioavailability of the drug. Our study not only provides the evidence to get a better CK2 inhibitor for the therapy of B-ALL but also provides a theoretical basis using a biomimetic nano-delivery system to optimize drug treatment and even a new possibility for hematological drug research.