Discovery of iodo-phenanthroimidazole derivatives as potential HDAC1 inhibitors inducing mitophagy to suppress glioblastoma progression.

Glioblastoma, the most prevalent and highly aggressive primary brain tumor, is characterized by high clinical recurrence rates and significant resistance to conventional therapies, highlighting the need for innovative targeted agents to address current treatment limitations. This study employed an integrated computational and experimental strategy to identify novel iodo-phenanthroimidazole derivatives (compounds 1-3). Compound 3 was identified as a lead candidate that inhibits HDAC1 and may trigger autophagy, thereby suppressing glioblastoma progression. Molecular docking and molecular dynamics simulations indicated stable interactions between compound 3 and the HDAC1 catalytic site (estimated binding energies of -7.75 and - 7.74 kcal/mol), with a notable halogen bond between the iodine atom and Asp104. The phenanthroimidazole scaffold was proposed as a potential zinc-binding group (ZBG) for HDAC1 inhibition. Biophysical validation using isothermal titration calorimetry (ITC) confirmed submicromolar binding affinity (Kd = 1.04 × 10-7 M, ΔH = -91.24 kJ·mol-1). In vitro evaluation demonstrated potent inhibition of U87-MG glioblastoma cell proliferation (IC50 = 0.23 μM), and flow cytometric analysis indicated concomitant cell cycle arrest at both G2/M and S phases. Transmission electron microscopy revealed autophagic vacuoles containing damaged mitochondria, and immunofluorescence showed an increased LC3-II/LC3-I ratio. Together with the observed loss of mitochondrial membrane potential and ATP depletion, these findings are consistent with the induction of a mitophagy-like process. Using an in vivo zebrafish orthotopic glioblastoma model, the lead compound demonstrated blood-brain barrier penetration and effectively suppressed tumor growth and U87-MG cell metastasis. This work highlights the potential of iodo-phenanthroimidazole derivatives as a novel therapeutic strategy for glioblastoma. The data support a model in which HDAC1 inhibition is associated with mitochondrial dysfunction and mitophagy, contributing to tumor suppression.