Abstract Body (Do not enter title and authors here): Background
DDCI-01, a novel, highly selective long-acting phosphodiesterase type 5 inhibitor, shows promise as a treatment for pulmonary arterial hypertension (PAH).

Methods
Seventy-two PAH patients were equally randomized to group receiving DDCI-01 (2.5, 10, or 20 mg qd) or tadalafil (0—4 weeks 20mg qd, 5—12weeks 40mg qd) for 12 weeks. The primary efficacy endpoints were changes from baseline to week 12 in hemodynamics by right heart catheterization. The key secondary efficacy endpoints included changes from baseline to week 12 in cardiac function by cardiac magnetic resonance. Treatment-emergent adverse events were evaluated.

Results
Baseline characteristics were well-balanced across groups. The mean age of participants was 41.9 years, and 78.9% were female. At week 12, DDCI-01 produced reduction in pulmonary vascular resistance (-4.3 Wood U in 10 mg group; -3.0 Wood U in 20 mg group), increase in mixed venous oxygen saturation (5.1% in 10 mg group), and cardiac index (0.8 L/min/m² in 10 mg group). The increase in cardiac index was significantly greater in DDCI-01 10 mg group versus the tadalafil group (least squares mean difference [LSMD], 0.6 L/min/m²; 95% CI, 0.2 to 1.0; P = .007). Also, DDCI-01 10 mg significantly improved right ventricular ejection fraction (8.5%), with a greater increase versus tadalafil (LSMD, 6.0%; 95% CI, 0.4 to 11.6; P = .038). No treatment-emergent severe adverse events occurred in DDCI-01 2.5 mg group and 10 mg group, whereas 3 (16.7%) in both DDCI-01 20 mg group and tadalafil group.

Conclusion
DDCI-01 10 mg tented to improve hemodynamics and cardiac function in PAH and was well tolerated, supporting further development in phase 3 trials.