Novel Drug Delivery Platforms for Small Molecule and miRNA-Based Therapies in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is an aggressive and heterogeneous hematologic malignancy that largely affects older adults (≥ 60 years). Despite available treatment options, many AML patients experience drug resistance and non-responsiveness, leading to relapses and a dismal 5-year survival rate. Therefore, novel therapies are urgently required. MicroRNA (miRNA)-based treatments remain an untapped strategy in AML. Using patient-derived specimens, we found increased inflammatory cytokines, including interleukin-6 (IL-6) in the serum of older adults with AML, and decreased miR-497-5p in CD34+ leukemic blasts. Target prediction revealed that miR-497-5p could directly target mitogen-activated protein kinase-1 (MAP2K1) mRNA to indirectly target cytokines and the JAK/STAT signaling pathway through the p38-MAPK signaling pathway, potentially inhibiting leukemic growth and overcoming chemoresistance from venetoclax. To improve miRNA delivery and minimize off-target effects, which represent key barriers to clinical translation, we developed liposomes for co-delivery of miR-497-5p and venetoclax. We decorated our liposomes with a peptide targeting C-type lectin-like molecule-1 (CLL1), which is present on 92% of leukemia blasts while being absent in normal hematopoietic cells. This targeted approach demonstrated high efficacy in inhibiting AML growth in mice with minimal toxicity, as well as reduced exposure to chemoresistance. Our findings suggested that anti-CLL1-decorated, miR-497-5p, and venetoclax-loaded liposomes represent a promising novel miRNA-based therapeutic, which should be investigated further as a strategy to reduce venetoclax resistance in AML. In addition, mutations in the tumor suppressor gene TP53 are strongly associated with poor outcomes, making treatment especially challenging for these patients. Thus, we developed a new BRD4/PI3K dual-inhibitor, MDP5, to combine with azacitidine (AZA), as a novel treatment strategy for AML. As AZA and MDP5 demonstrated synergistic inhibitory effects in both TP53 wide-type and TP53-mutant AML cells, we further sought to improve delivery efficacy by developing a novel AZA-conjugated polymer, m-PEG[113]-p-[Asp-BLA]-p-[Asp-AZA]-p-g[Asp-DA], which self-assembles into nanoparticles for the co-delivery of AZA and MDP5. Our results showed that the AZA and MDP5-containing nanoparticles significantly enhanced antileukemic efficacy with limited system toxicity. To further improve targeting accuracy and minimize off-target effects, we also modified the nanoparticles with CLL1-targeted peptide. The targeted nanoparticle system effectively suppressed AML progression with minimal toxicity, particularly in TP53-mutant models. This approach holds strong potential to improve outcomes in AML patients, especially those who are unresponsive to standard therapies.