Discovery of Amoebicidal Compounds by Combining Computational and Experimental Approaches

Pathogenic and opportunistic free-living amoebae such as Acanthamoeba spp. can cause keratitis (AK), which may ultimately lead to permanent visual impairment or blindness. Acanthamoeba can also cause a rare but usually fatal granulomatous amoebic encephalitis (GAE). Current therapeutic options for AK require a lengthy treatment with nonspecific drugs that often are associated with adverse effects. Recent developments in the field led us to target cAMP pathways, specifically phosphodiesterase. Guided by computational tools we targeted the Acanthamoeba phosphodiesterase, RegA. Computational studies led to the construction and validation of a homology model followed by a virtual screening protocol guided by induced-fit docking and chemical scaffold analysis using our MBC chemical library. Subsequently, 18 virtual screening hits were prioritized for further testing in vitro against A. castellanii, identifying amoebicidal hits containing piperidine and urea imidazole cores. Promising activities were confirmed in the resistant cyst form of the amoeba and in additional clinical Acanthamoeba strains, increasing their therapeutic potential. Mechanism of action studies revealed that these compounds produce apoptosis through ROS-mediated mitochondrial damage. These chemical families show promise for further optimization to produce effective anti-Acanthamoebal drugs.