Enanta Pharmaceuticals has reported positive topline data from a first-in-human Phase I study of EDP-323 for the treatment of respiratory syncytial virus (RSV).

The placebo-controlled, double-blind, randomised study has assessed the pharmacokinetics, tolerability, and safety of oral EDP-323 in healthy volunteers for seven days.

It enrolled a total of 82 subjects in the single-ascending dose (SAD) and multiple-ascending dose (MAD) cohorts in fasted and fed conditions.

Both cohorts enrolled eight participants who were randomised in a 3:1 ratio to receive EDP-323 or placebo.

Six dose cohorts of the SAD phase, including 50 patients received doses varying from 50mg to 800mg in which one was a two-part food effect (FE) cohort.

In the MAD phase, 32 patients were divided into four dose cohorts that received doses ranging from 200mg to 800mg. Ten subjects in the 200mg SAD/FE cohort were randomised in a 4:1 ratio.

Enanta Pharmaceuticals senior vice-president and chief medical officer Scott Rottinghaus said: “These data demonstrate that EDP-323 was generally safe and well-tolerated up to 800mg, with a PK profile supportive of once-daily dosing and strong exposure multiples across both RSV A and B strains.”

“EDP-323 is an inhibitor of the L-protein, a distinct mechanism of action from EDP-938, our potent N-protein inhibitor, which allows the potential for each compound to be used alone or in combination therapy.

“With these positive results, we are advancing EDP-323 into a human challenge study by the early fourth quarter of 2023 and we look forward to continuing to build upon our leadership in the RSV field.”

Enanta is also engaged in developing therapeutics for hepatitis B virus and SARS-CoV-2 and conducting research on a single agent, which targets both human metapneumovirus and RSV.