667. Preclinical Pharmacokinetic and Pharmacodynamic Characterization of EDP-938, a Novel and Potent NonFusion Replication Inhibitor of Respiratory Syncytial Virus

BACKGROUND: Respiratory syncytial virus (RSV) infection presents a significant health challenge in young children, elderly and immunocompromised patients. To date, there are no effective treatments available. EDP-938 was designed to meet this unmet medical need and is currently in Phase 2 clinical trials. Herein we report its preclinical pharmacokinetic (PK) and pharmacodynamic (PD) properties. METHODS: The pharmacokinetics of EDP-938 following single intravenous and oral doses were determined in mice, rats, dogs, and monkeys. In vitro cellular permeability and metabolic stability were assayed using Caco-2 cells and human liver microsomes, respectively. In vivo pharmacodynamic efficacy of EDP-938 was conducted in the African green monkey model, in which animals experimentally challenged with RSV were orally dosed twice daily with 100 mg/kg EDP-938 for 6 days starting 24 hours prior to infection. RESULTS: EDP-938 was well absorbed in the preclinical species with oral bioavailability values ranging from 27.1% in dogs, 35.4% in mice, 35.7% in rats, and 39.5% in monkeys, after a single oral dose when formulated in 0.5% methylcellulose. EDP-938 showed a moderate in vitro permeability of 3.6 x 10(–6) cm/sec in Caco-2 cells. Based on the outcome of these absorption studies, EDP-938 was projected to have good oral absorption in humans. EDP-938 had low intrinsic clearance of 5 mL/minute/mg in human liver microsomes. Moreover, EDP-938 demonstrated potent antiviral efficacy in an African green monkey model of RSV infection. In untreated monkeys the RSV RNA viral load in the bronchoalveolar lavage fluid peaked at 10(6) copies/mL on day 5 post-infection, by comparison in animals treated with EDP-938 the viral load was below the limit of detection by day 3 post-infection. The PK/PD modeling suggested that plasma trough concentrations ≥10 × EC(90) led to >4-log viral load reduction in EDP-938 treated monkeys. CONCLUSION: The favorable preclinical PK and PD properties of EDP-938 support its further clinical development as a novel treatment for RSV infection. DISCLOSURES: All authors: No reported disclosures.