Using Antibody-conjugated Extracellular Vesicles to Deliver Antisense Oligonucleotides for Specific Treatment of Acute Myeloid Leukemia


Student thesis: Doctoral Thesis

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Award date9 Dec 2022


Introduction: Acute Myeloid Leukemia (AML) is the most common blood cancer in adults. Although 2 out of 3 AML patients go into total remission after chemotherapies and targeted therapies, the disease recurs in 60%–65% of younger adult patients within 3 years after diagnosis with a dramatically decreased survival rate. Therapeutic oligonucleotides are promising treatments under development for AML as they can be designed to silence oncogenes with high specificity and flexibility. However, there are not many well validated approaches for safely and efficiently delivering oligonucleotide drugs. This issue could be resolved by utilizing a new generation of delivery vehicles such as extracellular vesicles (EVs).

Methods: In this study, we harness red blood cell-derived EVs (RBCEVs) and engineer them via exogenous drug loading and surface functionalization to develop an efficient drug delivery system for AML. Particularly, EVs are designed to target CD33 or CXCR4, two common surface markers with elevated expression in AML cells via the conjugation of a CD33/CXCR4-binding monoclonal antibody onto the EV surface. RBCEVs loaded with antisense oligonucleotides (ASOs) were used to study the cellular uptake of exogenous cargos loaded RBCEVs and the intracellular fate of cargos from RBCEVs.

Results: The conjugation of RBCEVs with the CD33/CXCR4-binding antibody significantly increases the uptake of RBCEVs by CD33/CXCR4-positive AML cells, but not by CD33/CXCR4-negative cells. We also load CD33-targeting RBCEVs with ASOs targeting FLT3-ITD or miR-125b, 2 common oncogenes in AML, and demonstrate that the engineered EVs improve leukemia suppression in vitro and in vivo models of AML. Furthermore, leukemia cells took up the exogenous cargos loaded RBCEVs mainly through macropinocytosis and phagocytosis pathway, and cargos carried by RBCEVs were capable of escaping from the endosome or lysosome confinement thus entering the cytoplasm for function. Notably, surface functionalization of RBCEVs with an anti-human CXCR4 antibody facilitated their specific uptake by CXCR4-positive leukemic cells, leading to enhanced BCL2 gene silencing efficiency.

Conclusion: Targeted RBCEVs represent an innovative, efficient, and versatile delivery platform for therapeutic ASOs and can expedite the clinical translation of oligonucleotide drugs for AML treatments by overcoming current obstacles in oligonucleotide delivery.