Glutathione-Sensitive Hyaluronic Acid-Mercaptopurine Prodrug Linked via Carbonyl Vinyl Sulfide: A Robust and CD44-Targeted Nanomedicine for Leukemia

6-Mercaptopurine (6-MP) is an essential medicine used for treating leukemia in the clinics. 6-MP suffers, however, from poor water solubility, low bioavailability, and significant side effects. Here, we designed CD44-targeted glutathione-sensitive hyaluronic acid-mercaptopurine prodrug (HA-GS-MP) linked via carbonyl vinyl sulfide for safer and enhanced treatment of acute myeloid leukemia (AML). HA-GS-MP obtained with 50 kDa HA and 6-MP conjugation content of 6.9 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 releasing 6-MP in response to 10 mM glutathione. HA-GS-MP exhibited obvious targetability and markedly enhanced antitumor effect to OCI/AML-2 human AML cells (IC50 = 16.9 mu g 6-MP equiv./mL). The pharmacokinetic studies displayed that Cy5-labeled HA-GS-MP 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 48 h 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 AML.