Enhanced Antileukemic Efficacy of Venetoclax-Loaded PEG-PLGA Nanoparticles Against THP-1 Acute Monocytic Leukemia Cells via Suppression of BCL-2 and Pro-Survival Signaling Pathways

Background: Acute myeloid leukemia (AML) presents a significant therapeutic challenge due to the systemic toxicity associated with traditional chemotherapy. Venetoclax, a selective BCL-2 inhibitor, has shown promising antileukemic activity; however, limited pharmacokinetic properties impair its clinical use. Polymeric nanocarriers composed of PEG-PLGA provide a biocompatible delivery system that enhances drug stability, controls drug release kinetics, and increases intracellular drug concentration. Methods: The physicochemical characteristics of VEN-PEG-PLGA nanoparticles were assessed using dynamic light scattering (DLS), scanning electron microscopy (SEM), drug loading analysis, and in vitro drug release studies. The antileukemic potential was evaluated in THP-1 cells using the CCK-8 viability assay, cell cycle profiling, Annexin V-FITC/PI apoptosis quantification, and Western blot analysis of Bcl-2, cleaved caspase-3, cleaved caspase-9, ERK1/2, phospho-ERK1/2 (p-ERK1/2), NF-kB, and phospho-NF-kB (p-NF-kB). Results: The VEN-PEG-PLGA nanoparticles displayed an average particle size of 186 ± 4 nm, polydispersity index of 0.195 ± 0.005 with loading efficiency of 89%, and loading capacity of 6.26%. These nanoparticles exhibited a pH-sensitive drug release profile, with approximately 72–74% cumulative release at pH 7.4 and 88–89% at pH 5.5 after 96 h. In THP-1 cells. Both free venetoclax and VEN-PEG-PLGA nanoparticles exhibited concentration-dependent cytotoxicity, although free venetoclax was more cytotoxic with EC50 values of 5.59 × 10⁻7 M (95% CI: 1.27 × 10⁻7–2.46 × 10⁻6 M) and 1.35 × 10⁻6 M (95% CI: 2.64 × 10⁻7–6.96 × 10⁻6 M) for the free drug and nanoparticle form, respectively. Cell cycle analysis indicated an increase in the G0/G1 cell population in the control group following treatment with VEN-PEG-PLGA nanoparticles, along with a reduction in the G2/M phase population. Annexin V-FITC/PI analysis demonstrated that VEN-PEG-PLGA nanoparticles increased the ratio of late apoptotic cells, compared with free venetoclax treatment. Western blot analysis showed decreased expression of Bcl-2, p-ERK1/2, and p-NF-kB, along with increased levels of cleaved caspase-3 and cleaved caspase-9 following treatment, with more pronounced changes observed in the group treated with VEN-loaded PEG-PLGA nanoparticles. Conclusions: VEN-PEG-PLGA nanoparticles modulate BCL-2/ERK1/2/NF-κB-related apoptotic responses, cell cycle kinetics, and signaling pathways in THP-1 AML cells, providing in vitro evidence supporting preclinical research on this nanoformulation in the context of AML.