Efficacy and Safety of Udenafil for the Treatment of Pulmonary Arterial Hypertension: a Placebo-controlled, Double-blind, Phase IIb Clinical Trial

Purpose: Udenafil is an oral phosphodiesterase-5 inhibitor approved for the treatment of erectile dysfunction. In a multicenter, placebo-controlled, randomized Phase IIa study, the reduction of pulmonary vascular resistance index was greater with a 50-mg baseline dose of udenafil than with the 100-mg dose, the cardiac index did not decrease at most points, and the safety was excellent, suggesting that 50-mg udenafil could be used in a Phase IIb trial. Methods: In this 16-week, double-blind, placebo-controlled study, 63 patients with pulmonary arterial hypertension were randomized to receive 50-mg udenafil or a placebo BID. The primary efficacy end point was the 6-min walking distance. The secondary efficacy end points were the Borg dyspnea score and time to clinical worsening. Patients who completed the 16-week study could participate in a long-term extension study. Findings:: In terms of the difference between the baseline and 16-week 6-min walking distance in both groups, the mean placebo-corrected treatment effect was 25 (58) m (P = 0.0873). Among the patients with a history of endothelin receptor antagonist therapy, the treatment effect at week 16 between the udenafil and placebo groups was 34 (60) m (P = 0.0460). However, there were no significant differences in the Borg dyspnea score and time to clinical worsening between groups. The safety profile and adverse effects of udenafil were similar to those of typical phosphodiesterase-5 inhibitors seen in previous studies. Implications: Udenafil has a favorable safety profile and improves exercise capacity in patients with pulmonary arterial hypertension. ClinicalTrials.gov identifier: NCT01553721.