First clinical trials of the inhaled ENaC inhibitor BI 1265162 in healthy volunteers

Background Inhibition of the epithelial sodium channel (ENaC) represents a mutation-agnostic therapeutic approach to restore airway surface liquid hydration and mucociliary clearance in patients with cystic fibrosis. BI 1265162 is an inhaled ENaC inhibitor with demonstrated preclinical efficacy. Methods Three phase I trials of BI 1265162 in healthy male subjects are presented: NCT03349723 (single-rising-dose trial evaluating safety, tolerability and pharmacokinetics (PK)); NCT03576144 (multiple-rising-dose trial evaluating safety, tolerability and PK); and NCT03907280 (absolute bioavailability trial). Results BI 1265162 single doses ≤1200 µg and multiple doses of 600 µg were well tolerated. Adverse events were balanced across treatment groups, were of mainly mild or moderate intensity and resolved by trial-end. One subject discontinued from trial medication on day 7 (asymptomatic hyperkalaemia adverse event; recovered day 8). One subject experienced a serious adverse event (neuropathia vestibularis) leading to hospitalisation and missed one of the four dosing periods. Both events were not considered to be drug-related and subjects recovered. BI 1265162 displayed dose-proportional, time-independent PK; maximum accumulation was 1.6-fold; calculated effective elimination half-life was 3.6–8.7 h over the dose ranges tested. Renal excretion was not a major drug elimination route. Oral and inhaled dosing (±activated oral charcoal) absolute bioavailability was 0.50% and ∼40%, respectively. Conclusion BI 1265162 single or multiple doses up to 6.5 days were well tolerated. Systemic exposures mainly represent drug absorbed through the lungs and not the gastrointestinal tract, with ∼40% of the inhaled dose reaching the systemic circulation. Accumulation was minimal. Twice-daily dosing is supported for future development.