Antiparasitic agent emodepside exerts cytotoxicity in human corneal stromal cells by blocking the interaction between mini-chromosome maintenance 6 protein (MCM6) and chromatin licensing and DNA replication factor 1 (CDT1)

Emodepside, a novel antiparasitic agent, exhibits remarkable efficacy against nematodes. Recent research from a phase 2b clinical trial has demonstrated that the most frequent adverse event in the emodepside treatment group is blurred vision, but the mechanism of blurred vision remains largely unexplored. To provide references for secure medication and prospective therapeutic interventions of emodepside, we conducted an investigation into the cytotoxic effects of emodepside on the corneal stroma and its underlying mechanisms using an in vitro model of human corneal stromal (HCS) cells. The loading of the mini-chromosome maintenance 6 protein (MCM6) onto chromatin at replication origins by chromatin licensing and DNA replication factor 1 (CDT1) constitutes a crucial step in licensing DNA for replication. This study demonstrates that emodepside directly binds to the CDT1-binding domain (CBD) of MCM6, competitively blocking the MCM6-CDT1 interaction as confirmed by modified enzyme-linked immunosorbent assay and drug affinity responsive target stability assays. Molecular docking reveals that emodepside binds to CBD through hydrogen bonds with Lys754, Ile760, and Lys770. In HCS cells, this blockade results in the inhibition of DNA replication licensing and a decrease in DNA synthesis, as evidenced by the ethynyl-deoxyuridine incorporation assay, leading to cell cycle arrest at the G 0 /G 1 phase. Moreover, emodepside-induced cell cycle arrest in HCS cells leads to dose-dependent apoptosis and proliferation inhibition with the IC 50 value being 32.3 μM. In conclusion, this study not only provides new insights into the mechanism of emodepside-induced vision blur but also offers a valuable molecular tool for the research of MCM6-CDT1 interaction.