No Dose Adjustments for Cyp3a4 Substrates When Coadministered with Bemnifosbuvir

ABSTRACT

Background: Bemnifosbuvir (BEM, AT-527) is a guanosine nucleotide prodrug in development for the treatment of COVID-19 and chronic HCV. BEM was identified in vitro as an inhibitor [competitive and time-dependent inhibition (TDI)] and inducer of CYP3A4, prompting evaluation of the clinical relevance of these results in a Ph 1 drug-drug interaction (DDI) study in healthy participants using midazolam (MDZ), a sensitive CYP3A4 substrate as an index drug. Method(s) Two groups of 12 healthy participants were enrolled and received a single dose of 2mg MDZ alone on Day 1. Between Days 3 and 7 inclusive, all participants received oral BEM 550mg twice daily (BID). On day 3 and day 7, Group A received a single dose of 2mg MDZ simultaneously with BEM;Group B on these two days received 2mg MDZ 2h after BEM. Serial plasma samples were obtained and measured for MDZ and 1-OH-MDZ levels. Result(s) A single dose (simultaneous or staggered) of BEM slightly increased the plasma exposure of MDZ (14%-26%). Staggered BEM had less impact (8%-17%) on 1-OH-MDZ than simultaneous dosing (22%-31%). Inhibitory effect of BEM was more pronounced with repeat dosing, consistent with in vitro data showing TDI on CYP3A4. After repeat dosing, simultaneously administered BEM increased plasma MDZ exposure by 83%-98%, without affecting the exposure of 1-OH-MDZ. With repeat dosing, staggered BEM showed less effect on both MDZ and 1-OH-MDZ. There was no effect on vital signs, ECG, and no SAEs or drug discontinuations. Conclusion(s) BEM is a weak inhibitor (ratio between 1.25 and 2) of CYP3A4. No dose adjustment is needed for drugs that are substrates of CYP3A4 when co-administered with BEM.