Ivermectin Identified Using a High-Throughput Screening System Exhibits Anti-Clonorchis sinensis Activity in Rats

Background: Clonorchiasis, caused by the parasite Clonorchis sinensis, remains a public health concern in East Asian countries. Methods: In this study, high-throughput screening was used to analyze 320 compounds for potential inhibitory activity against Clonorchis sinensis. To ensure the selection of high-confidence hits, a stringent inhibition threshold of 80% was applied, leading to the identification of three active compounds: moxifloxacin, hexachlorophene, and ivermectin (IVM). Ivermectin emerged as a hit compound and was assessed for its anti-C. sinensis efficacy. Results: Ivermectin demonstrated dose-dependent trematocidal activity against C. sinensis metacercariae (CsMC) and newly excysted juveniles (CsNEJs), showing superior efficacy against CsMC and CsNEJs compared to praziquantel. To assess in vivo efficacy, rats were infected with CsMC and treated with ivermectin at 1 and 4 weeks post-infection (wpi) to target larval and adult stages, respectively. A significant worm burden reduction was observed compared to untreated control when treatment was administered at 1 wpi, showing an antiparasitic effect against larvae. Parasite-specific IgG levels and ALT/AST responses were comparable to those of the infection control group. Conclusions: These findings suggest that ivermectin may serve as a potential alternative drug targeting C. sinensis larvae.