Enanta Pharmaceuticals, Inc. announced positive topline data from a Phase 1 study assessing the safety, tolerability, and pharmacokinetics (PK) of orally administered single ascending doses (SAD) and multiple ascending doses (MAD) of EDP-323 in healthy adult subjects. EDP-323, which received Fast Track designation from the U.S. Food and Drug Administration (FDA), is a novel L-protein inhibitor in development as a once-daily oral treatment for respiratory syncytial virus (RSV). Data from the Phase 1 study demonstrated favorable safety, tolerability, and PK supportive of once-daily dosing, with good exposure multiples, thereby supporting further clinical advancement of EDP-323.

This first-in-human, randomized, double-blind, placebo-controlled, Phase 1 study enrolled healthy volunteers to evaluate the safety, tolerability,and PK of oral EDP-323 for seven days.lThe study evaluated a range of single and multiple doses in fasted and fed states. The SAD phase enrolled a total of six dose cohorts (doses ranging from 50 to 800 mg), one of which was a two-part food effect (FE) cohort. The MAD phase enrolled four dose cohorts (doses ranging from 200 to 800 mg).

All SAD and MAD cohorts enrolled eight participants who were randomized to receive EDP-323 or placebo in a 3:1 ratio. The 200 mg SAD/FE cohort enrolled ten subjects randomized in a 4:1 ratio. A total of 82 subjects (n=50 in SAD; n=32 in MAD) received at least one dose of EDP-323 or placebo.

Overall, EDP-323 was generally safe and well-tolerated in healthy subjects up to 800 mg for up to seven days. Among participants receiving EDP-323, most adverse events (AEs) were mild, and there were no serious or severe AEs. There was one study discontinuation due to syncope, in the SAD/FE group, which was deemed unlikely to be related to EDP-323.

In the MAD phase, three AEs deemed possibly related to EDP-323 were mild, with two headaches and one gastrointestinal event. There were no discontinuations due to AEs in the MAD phase. EDP-323 exposure increased with increasing single and multiple dosing up to 600 mg with a half-life ranging from 11-17 hours, supporting once daily dosing.

No food effect was observed with a high fat meal during the 200 mg SAD FE cohort, suggesting that EDP-323 can be administered without regard to food. EDP-323 doses ranging from 200 to 800 mg once-daily resulted in strong EC90 multiples against both RSV A and B strains. Specifically, EDP-323 administered once daily for seven days resulted in C24 (Ctrough) concentrations at steady state of 11- to 44-fold over the protein adjusted EC90 (0.3 nM) against both RSV A and B strains.