Nanoparticle-Mediated Delivery of Micheliolide Analogs to Eliminate Leukemic Stem Cells in the Bone Marrow

Micheliolide (MCL) is a naturally occurring sesquiterpene lactone that selectively targets leukemic stem cells (LSCs), which persist after conventional chemotherapy for myeloid leukemias, leading to disease relapse. To overcome modest MCL cytotoxicity, analogs with ≈two-threefold greater cytotoxicity against LSCs are synthesized via late-stage chemoenzymatic C-H functionalization. To enhance bone marrow delivery, MCL analogs are entrapped within bone-targeted polymeric nanoparticles (NPs). Robust drug loading capacities of up to 20% (mg drug mg^-1 NP) are obtained, with release dominated by analog hydrophobicity. NPs loaded with a hydrolytically stable analog are tested in a leukemic mouse model. Median survival improved by 13% and bone marrow LSCs are decreased 34-fold following NP_MCL treatments versus controls. Additionally, selective leukemic cell and LSC cytotoxicity of the treatment versus normal hematopoietic cells is observed. Overall, these studies demonstrate that MCL-based antileukemic agents combined with bone-targeted NPs offer a promising strategy for eradicating LSCs.