Novel in vitro approaches for screening anti-parasitic drugs against the brain-eating amoeba Naegleria fowleri

Naegleria fowleri is both a pathogenic and free-living microbial eukaryote, responsible for the development of primary amoebic meningoencephalitis (PAM) in humans. PAM is a rapid, severe and fatal underestimated infectious disease which has been reported worldwide. The major drawback with PAM is the lack of effective therapies. The current frontline treatment presents a low rate of recovery (5%) and severe adverse effects. For example, many drug candidates lack efficacy, because they do not effectively cross the blood-brain-barrier. Consequently, more effective drugs are urgently needed. Herein, we report a new in vitro method suitable for medium- and high-throughput drug discovery assays, using the closely related Naegleria gruberi as a model. We have subsequently used this method to screen a library of 1,175 Food and Drug Administration-approved drugs. As a result, we present three new drugs (Camptothecin, Pyrimethamine, and Terbinafine) that are anticipated to readily cross the blood-brain-barrier with activity against Naegleria species in therapeutically achievable concentrations. Successively, we integrated several in vitro assays that resulted in identifying fast-acting and high amoebicidal drugs. In conclusion, we present a new approach for the identification of anti-Naegleria drugs along with three novel drug candidates for further development for the treatment of PAM.