Safety, tolerability and pharmacokinetics of the phosphodiesterase 2 inhibitor BI 474121: An overview of phase I randomized trials in healthy volunteers

Background: Cognitive impairment associated with schizophrenia predicts poor functional outcomes, but currently no efficacious pharmacotherapies are available.Aims: Four phase I trials examined the safety, tolerability and pharmacokinetics of the phosphodiesterase 2 inhibitor BI 474121, along with potential drug-drug interactions.Methods: Trial 1 evaluated single rising doses (SRDs) of BI 474121 versus placebo in healthy males. The influence of drug formulation and food on drug bioavailability was also examined. Trial 2 evaluated SRD of BI 474121 versus placebo in healthy Japanese males. Trial 3 evaluated multiple rising doses of BI 474121 in healthy young (with/without midazolam) and elderly (without midazolam) participants versus placebo. Trial 4 investigated interactions between itraconazole and single-dose BI 474121 in healthy males.Results/Outcomes: No deaths, serious adverse events (AEs), severe AEs or protocol-specified AEs of special interest were observed. BI 474121 absorbed rapidly during fasting, achieved maximum concentration of analyte in plasma and dose proportionality via tablet formulation, and decreased in a multiphasic manner. BI 474121 steady state occurred within 11 days of multiple oral administration. Multiple doses increased BI 474121 plasma concentrations, but did not alter the time course of plasma concentrations. Urinary excretion of unchanged BI 474121 was negligible. No clinically relevant inhibition or induction of CYP3A4 by BI 474121 was observed. Itraconazole co-administration produced higher exposures of BI 474121 versus BI 474121 alone.Conclusions/Interpretation: BI 474121 demonstrated favourable safety and pharmacokinetic profiles in healthy Caucasian and Japanese individuals, supporting further clinical development.