Mezzion Pharma Co. Ltd. announced that the Food and Drug Administration (FDA) recently completed a special protocol assessment (SPA) review of two Phase 3 clinical protocols directed to the use of Mezzion Pharma's extended half-life phosphodiesterase type 5 inhibitor (PDE5i) udenafil in adolescents with single ventricle congenital heart disease with Fontan physiology. As this disease affects fewer than 200,000 people in the USA, udenafil was designated as an orphan drug by FDA in 2015.

The udenafil protocols were developed by a subcommittee made up of representatives of the Pediatric Heart Network (PHN), a multi-center clinical research network funded by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH.) These studies are designed to assess the improvement in certain acute and chronic symptoms associated with single ventricle congenital heart disease with Fontan physiology. The studies will be led by PHN, under an IND filed by Mezzion Pharma Co. Ltd. FDA confirmed that the design and planned analysis of the proposed studies adequately address the objectives necessary to support a regulatory submission.

The Fontan procedure is the final surgery in a series of palliative surgical operations in children born with single ventricle congenital heart disease. Fontan patients have a significantly shortened life span, often not surviving past the third or fourth decade of life, due to deteriorating ventricular performance, increasing pulmonary vascular resistance and associated secondary pathologies. Mezzion Pharma calculates that there are approximately 29,000 persons alive in the US with this disease.

PDE5 inhibitors have demonstrated utility in reducing pulmonary vascular resistance and in improving ventricular performance in other types of patients. Those characteristics make PDE5 inhibitors, especially a long-acting compound such as udenafil, potentially attractive as a long-term interventional therapy in that segment of the Fontan population that is still relatively unimpaired by the disease.