APX001 and Other Gwt1 inhibitor Prodrugs are Effective in Experimental Coccidioides immitis Pneumonia [Experimental Therapeutics]

Coccidioidomycosis is a systemic fungal infection caused by the inhalation of the arthroconidia of either of two closely related dimorphic fungi, Coccidioides immitis, and C. posadasii that are endemic in the southwestern US and other areas in the Western Hemisphere. Chronic cavitary pulmonary infections and extra-pulmonary sites of infection are very difficult to treat and often require life-long azole therapy. APX001A is the first in a new class of broad spectrum antifungal agents which inhibit Gwt1, an enzyme which is required for localization of glycosylphosphatidyl inositol (GPI)-anchored mannoproteins in fungi. APX001A and several analogs were highly active against clinical isolates of Coccidioides, inhibiting hyphal growth at low nanogram/ml concentrations. APX001 is the N-phosphonooxymethyl prodrug of APX001A, currently in clinical trials for the treatment of invasive fungal infections. Mice were treated orally once-daily with 26 mg/kg/day of APX001 and the prodrug analog APX2097, two hours after administration of the pan-cytochrome P450 inhibitor 1-aminobenzotriazole, which was used to enhance drug half-life and exposures to more closely mimic human pharmacokinetics of APX001A. Five days of treatment reduced lung colony counts by nearly 3 logs and prevented dissemination, similar to the efficacy of fluconazole dosed orally at 25 mg/kg twice daily. In a survival experiment, both APX001 and APX2097-treated mice survived significantly longer than control and fluconazole treated mice. APX001 and other members of this new class of antifungal agents may offer great promise as effective therapies for coccidioidomycosis.

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