Efficacy of PLD-118, a novel inhibitor of Candida isoleucyl-tRNA synthetase, against experimental oropharyngeal and esophageal candidiasis caused by fluconazole-resistant C. albicans
PLD-118, formerly BAY 10-8888, is a synthetic antifungal derivative of the naturally occurring beta-amino acid cispentacin. We studied the activity of PLD-118 in escalating dosages against experimental oropharyngeal and esophageal candidiasis (OPEC) caused by fluconazole (FLC)-resistant Candida albicans in immunocompromised rabbits. Infection was established by fluconazole-resistant (MIC > 64 microg/ml) clinical isolates from patients with refractory esophageal candidiasis. Antifungal therapy was administered for 7 days. Study groups consisted of untreated controls; animals receiving PLD-118 at 4, 10, 25, or 50 mg/kg of body weight/day via intravenous (i.v.) twice daily (BID) injections; animals receiving FLC at 2 mg/kg/day via i.v. BID injections; and animals receiving desoxycholate amphotericin B (DAMB) i.v. at 0.5 mg/kg/day. PLD-118- and DAMB-treated animals showed a significant dosage-dependent clearance of C. albicans from the tongue, oropharynx, and esophagus in comparison to untreated controls (P = 0.05, P = 0.01, P = 0.001, respectively), while FLC had no significant activity. PLD-118 demonstrated nonlinear plasma pharmacokinetics across the investigated dosage range, as was evident from a dose-dependent increase in plasma clearance and a dose-dependent decrease in the area under the plasma concentration-time curve. The biochemical safety profile was similar to that of FLC. In summary, PLD-118 demonstrated dosage-dependent antifungal activity and nonlinear plasma pharmacokinetics in treatment of experimental FLC-resistant oropharyngeal and esophageal candidiasis.