Glutathione-Sensitive 6-Mercaptopurine Nanomedicine For Targeted Acute Myeloid Leukemia Therapy

Leukemia is a malignant blood cancer that causes hundreds of thousands death per year.Most leukemia patients are treated with chemotherapy,among which the antimetabolite,6-mercaptopurine（6-MP）,is one of the longest and most used antileukemic drugs in the clinics.6-MP has been classified by the World Health Organization as an essential medicine.It takes effect through interfering synthesis of adenine and guanine ribonucleotide,which are important precursors of DNA and RNA.6-MP suffers,however,from poor water solubility,short plasma half-life,low bioavailability and several off-target side effects including bone marrow and liver toxicity.In this thesis,we designed and synthesized two types of tumor-specific,glutathione-sensitive 6-MP nanomedicines for targeted acute myeloid leukemia therapy.In chapter 1,we present a literature overview to give a brief introduction on 6-MP nanomedicines,the current status and obstacles,as well as recent development of multifunctional polymeric nanomedicines.Notably cytoplasm is reductive with glutathione concentration of 2-10 mM as contrast to that in extracellular matrix and body fluid（GSH:2-20μM）.In chapter 2,we designed CD44-targeted glutathione-sensitive hyaluronic acid-mercaptopurine prodrug（HA-GS-MP）linked via carbonyl vinyl sulfide for safe and high efficient treatment of acute myeloid leukemia（AML）.HA-GS-MP obtained with 50 kDa HA and 6-MP conjugation content of6.9 wt.%showed excellent water solubility with a hydrodynamic size of ca.15 nm.Intriguingly,HA-GS-MP was extremely stable,without any drug leakage,under physiological environment while rapidly released 6-MP in response to 10 mM glutathione.HA-GS-MP exhibited obvious targetability and markedly enhanced antitumor effect to OCI/AML-2 human acute myeloid leukemia cells(IC₅₀=16.9μg 6-MP equiv./mL).The pharmacokinetic studies displayed that Cy5-labeled HA-GS-MP prodrug had a long circulation time in mice（elimination half-life=4.37 h）.The in vivo fluorescence images demonstrated strong and persistent accumulation of Cy5-labeled HA-GS-MP from 4 to 48h post injection in the subcutaneous OCI/AML-2 tumor in nude mice.Notably,HA-GS-MP while causing little side effects induced significantly enhanced growth inhibition of OCI/AML-2 tumor and better survival rate of OCI/AML-2 tumor-bearing mice as compared to free 6-MP.Carbonyl vinyl sulfide-linked hyaluronic acid-mercaptopurine prodrug has appeared to be a simple and smart nanomedicine for targeted treatment of acute myeloid leukemia.Disulfide-crosslinked chimeric polymersomes,which can efficiently load and delivery drugs into the tumor cells,have drawn much attention in drug delivery area.In chapter 3,we designed and developed CPP44-functionalized,reduction-sensitive,reversibly crosslinked chimeric polymersome（PTA-XCPP44-PS,external hydrophilic block is PEG and internal hydrophilic block is PEI）which are based on methoxy-poly（ethylene glycol）-b-poly（DTC-co-trimethylene）-polyethyleneimide（MeO-PEG-P（DTC-co-TMC）-PEI）and acute myeloid leukemia-targeting CPP44 coupled CPP44-PEG-P（DTC-co-TMC）for efficiently loading negatively charged 6-MP prodrug（PTA）.PTA-10%CPP44-PS had a high drug loading content（7.5 6-MP wt.%）and small size（103 nm,PDI 0.17）.Flow cytometry results demonstrated efficient dynamin-mediated uptake of PTA-XCPP44-PS in OCI/AML-2 cells.MTT results revealed that PTA-XCPP44-PS showed significantly enhanced antitumor effect compared with free 6-MP.At the drug concentration of 25μg6-MP/mL.the inhibition rate of 6-MP and PTA-10%CPP44-PS was 31%and 79%,respectively.PTA-loaded and CPP44-decorated reduction-sensitive,reversibly crosslinked chimeric polymersome（PTA-XCPP44-PS）offers great potential in acute myeloid leukemia therapy.Finally,chapter 4 presents a brief summary of this thesis,and gives a future perspective in the field.