Prior to entering the study, all patients will undergo pre-study assessments including compliance with inclusion and exclusion criteria, laboratory assessments, IPSS, uroflowmetry, IIEF, and MRI pelvic imaging. Following conventional catheter angiography with cone-beam CT to confirm catheter placement and prostatic vasculature, each patient will undergo transarterial embolization with OCL 503. OCL 503 will be administered intra-arterially via microcatheter until there is stasis of blood flow.