Adult male patients, age 25 to 65 years, Type 1 or Type 2 diabetes, history of diabetes ≥5 years, HbA1c ≤10%, history of chronic ED for at least six months, body mass index between 20 and 30, and a baseline International Index of Erectile Function (IIEF-15) score of <26. Only patients with proven unresponsiveness to previous medical therapies such as PDE5 inhibitors and prostaglandin E1 were considered. The gene discussed is PDE5A; the disease is diabetes mellitus.