Safety, Tolerability, and Pharmacokinetics of the Novel Anti-influenza Agent Baloxavir Marboxil in Healthy Adults: Phase I Study Findings.
Abstract
Background and objective: Baloxavir marboxil, a prodrug that is metabolized to baloxavir acid, suppresses viral replication by inhibiting cap-dependent endonuclease. This first-in-human phase I study evaluated the safety, tolerability, and pharmacokinetics of baloxavir marboxil/baloxavir acid in healthy Japanese volunteers (Study 1), while food effects were evaluated in a separate phase I, crossover study in healthy Japanese volunteers (Study 2).
Methods: Study 1 participants were randomized to single-dose oral baloxavir marboxil (6, 20, 40, 60, or 80?mg; n?=?6 per dose) or placebo (n?=?10), while Study 2 participants (n?=?15) received single-dose oral baloxavir marboxil 20?mg in fasted, fed, and before-meal states.
Results: Baloxavir marboxil was well tolerated; there were few treatment-emergent adverse events and no serious adverse events/deaths. The mean plasma baloxavir acid concentration 24?h after single-dose (C24) oral baloxavir marboxil 6?mg was 6.92?ng/mL, exceeding the target C24 (6.85?ng/mL) estimated in nonclinical studies. In Study 1, baloxavir acid exposure demonstrated dose-proportional increases in the fasted state, with maximum plasma concentration generally attained within 3.5?h. Terminal elimination half-life ranged from 49 to 91?h. In Study 2, exposure was decreased and apparent clearance increased in the fed and before-meal states versus the fasted state; however, exposure exceeded the target C24 in all states.
Conclusion: Single-dose oral baloxavir marboxil was well tolerated, had a favorable safety profile, and had favorable pharmacokinetic characteristics, including a long half-life, supporting single oral dosing. The baloxavir acid area under the plasma concentration-time curve decreased with food intake by approximately 40%.