Discovery of Anti-Amoebic Inhibitors from Screening the MMV Pandemic Response Box on Balamuthia mandrillaris, Naegleria fowleri, and Acanthamoeba castellanii

Abstract

Pathogenic free-living amoebae, Balamuthia mandrillaris, Naegleria fowleri, and several Acanthamoeba species are the etiological agents of severe brain diseases, with case mortality rates > 90%. A number of constraints including misdiagnosis and partially effective treatments lead to these high fatality rates. The unmet medical need is for rapidly acting, highly potent new drugs to reduce these alarming mortality rates. Herein, we report the discovery of new drugs as potential anti-amoebic agents. We used the CellTiter-Glo 2.0 high-throughput screening methods to screen the Medicines for Malaria Ventures (MMV) Pandemic Response Box in a search for new active chemical scaffolds. Initially, we screened the library as a single-point assay at 10 and 1 µM. From these data, we reconfirmed hits by conducting quantitative dose–response assays and identified 12 hits against B. mandrillaris, 29 against N. fowleri, and 14 against A. castellanii ranging from nanomolar to low micromolar potency. We further describe 11 novel molecules with activity against B. mandrillaris, 22 against N. fowleri, and 9 against A. castellanii. These structures serve as a starting point for medicinal chemistry studies and demonstrate the utility of phenotypic screening for drug discovery to treat diseases caused by free-living amoebae.

Evaluation of Amebicidal and Cysticidal Activities of Antifungal Drug Isavuconazonium Sulfate against Acanthamoeba T4 Strains

“…Isavuconazonium had mean EC 50 values against trophozoites ranging from 0.001 µM (strain Ma) to 0.037 µM (strain CDC:V240) (Table 1). Our reported values are lower than those reported by Rice et al against Acanthamoeba strain Ma (EC 50 of 0.09 ± 0.02 µM [14]. This could be due to the differences in experimental conditions.…”

Actives from MMV Open Access Boxes? A suggested way forward

“…In order to catalyze research in the area of infectious diseases and engage groups working on establishing novel screening systems, MMV provides open access boxes containing physical samples of up to 400 compounds to researchers all over the world, free of cost [20]. Since 2013, it has launched 4 open access boxes: the Malaria Box (2013 to 2015; [21,22]), the Pathogen Box (2016 to 2020; [23]), the Pandemic Response Box (2019 to present; [24]) in collaboration with DNDi, and the COVID Box (2020 to present; mmv.org). The availability of these compound sets for screening not only enables scientists to identify new starting points for drug discovery programs or chemical biology tools but also helps in capacity building of groups in low-and middle-income countries.…”

Balamuthia mandrillaris infection in China: a retrospective report of 28 cases

“…However, currently, there are no reports of cases treated with this drug. Other potential drugs have also been screened in vitro; however, the clinical efficacy and side effects of these drugs need to be verified clinically [39,40].…”