Abstract 14024: Results of a Phase I / II Multicenter Investigation of Udenafil in Adolescents After Fontan Palliation

Abstract

Introduction: Many pediatric clinical trials fail due to use of sub-therapeutic dosing. This phase I / II clinical trial was designed to evaluate the short-term safety, pharmacokinetics (PK), and preliminary efficacy of udenafil, a phosphodiesterase type 5 inhibitor, in adolescents following Fontan palliation to inform dose selection for a phase III clinical trial. Methods: This was a dose escalation trial with 5 dosing cohorts of 6 subjects each at 37.5 mg, 87.5 mg, and 125 mg daily, as well as 37.5 mg and 87.5 mg twice daily (bid) for 5 days. Efficacy testing (echocardiography, exercise stress test, endothelial function assessment) was performed at baseline and on day 5. A control cohort of 6 subjects underwent exercise testing without drug administration. Serum samples for PK analysis were collected on days 6-8. Adverse events (AE) were recorded throughout the 8-day study period and for 3 months thereafter. Comparison between baseline and day 5 testing was performed using ANOVA and visual trend lines. PK analysis was performed using a non-linear mixed effects model. Results: The trial enrolled 36 subjects at a mean age of 15.8 years (58.3% male). Subject characteristics were similar between cohorts. No drug-related serious AEs were reported during the study period, while 24 subjects had non-serious AEs possibly or probably related to study drug. Headache was the most common, occurring in 20 of the 30 subjects. Other possibly or probably medication related side effects occurring in more than one subject included: facial flushing (10 subjects), nasal congestion (7), spontaneous penile erection (6), nausea (3), and abdominal discomfort (2). The 87.5 mg bid cohort achieved the highest steady state serum concentration (172 ng/mL, range 117-202), the highest maximal concentration (506 +/- 188 ng/mL), and the greatest area under the curve for 24 hours (6701 +/- 1591 ng*hr/mL). Efficacy test results did not change significantly in any cohort. Conclusion: Udenafil was safe and well tolerated at all dosing levels while the 87.5 mg bid cohort achieved the highest serum drug level. With a 5-day treatment period and small sample size no significant clinical changes were observed. These data suggest that the 87.5 mg bid regimen may be most appropriate for a Phase III clinical trial.