Corifungin, a New Drug Lead against Naegleria, Identified from a High-Throughput Screen

Abstract

c Primary amebic meningoencephalitis (PAM) is a rapidly fatal infection caused by the free-living ameba Naegleria fowleri. The drug of choice in treating PAM is the antifungal antibiotic amphotericin B, but its use is associated with severe adverse effects. Moreover, few patients treated with amphotericin B have survived PAM. Therefore, fast-acting and efficient drugs are urgently needed for the treatment of PAM. To facilitate drug screening for this pathogen, an automated, high-throughput screening methodology was developed and validated for the closely related species Naegleria gruberi. Five kinase inhibitors and an NFkappaB inhibitor were hits identified in primary screens of three compound libraries. Most importantly for a preclinical drug discovery pipeline, we identified corifungin, a water-soluble polyene macrolide with a higher activity against Naegleria than that of amphotericin B. Transmission electron microscopy of N. fowleri trophozoites incubated with different concentrations of corifungin showed disruption of cytoplasmic and plasma membranes and alterations in mitochondria, followed by complete lysis of amebae. In vivo efficacy of corifungin in a mouse model of PAM was confirmed by an absence of detectable amebae in the brain and 100% survival of mice for 17 days postinfection for a single daily intraperitoneal dose of 9 mg/kg of body weight given for 10 days. The same dose of amphotericin B did not reduce ameba growth, and mouse survival was compromised. Based on these results, the U.S. FDA has approved orphan drug status for corifungin for the treatment of PAM.

In Vitro Efficacy of Corifungin against Acanthamoeba castellanii Trophozoites and Cysts

“…Therefore, a drug that would be amebicidal and cysticidal and that could cross the blood-brain barrier would be optimal for the treatment of Acanthamoeba infection. We evaluated the polyene macrolide corifungin versus Acanthamoeba because an earlier study showed that it effectively killed another free-living ameba, Naegleria fowleri, with better efficacy than amphotericin B (24). Previous studies reported that a combination of amphotericin B and a second drug was effective in eradicating a skin infection and GAE caused by Acanthamoeba (25,26).…”

“…Trophozoites were harvested in logarithmic growth phase, usually 48 h after subculture, by chilling at 4°C and concentrated by centrifugation for 5 min at 300 ϫ g. In vitro studies of corifungin against A. castellanii trophozoites. To determine the effect of corifungin on the growth of A. castellanii trophozoites, 5 ϫ 10 5 amebae were incubated with 25 M, 100 M, and 200 M corifungin for 24, 48, 72, 96, and 120 h. Control trophozoites were incubated with fresh medium only. Cell numbers were calculated by hemocytometer at the end of incubation.…”

Naegleria fowleri: Pathogenesis, Diagnosis, and Treatment Options

“…Initial reports for the in vivo efficacy of corifungin in a mouse model of PAM showed activity superior to that of amphotericin B at equivalent dosing (18). Chemically, corifungin is the sodium salt of amphotericin B with excellent aqueous solubility (Ͼ100 mg/ml) (18). The increased solubility of corifungin is likely to account for the described increase in activity.…”

“…Many of the problems with amphotericin B can be linked to its lack of aqueous solubility, which affects dissolution, compartmental concentration, and clearance. Recently, corifungin, which is described as a new drug entity, was granted orphan drug status for the treatment of PAM (18). Initial reports for the in vivo efficacy of corifungin in a mouse model of PAM showed activity superior to that of amphotericin B at equivalent dosing (18).…”

“…Recently, corifungin, which is described as a new drug entity, was granted orphan drug status for the treatment of PAM (18). Initial reports for the in vivo efficacy of corifungin in a mouse model of PAM showed activity superior to that of amphotericin B at equivalent dosing (18). Chemically, corifungin is the sodium salt of amphotericin B with excellent aqueous solubility (Ͼ100 mg/ml) (18).…”