This is a prospective, pilot, open-label, uncontrolled, non-randomized safety and effectiveness study of OCL 503 in men with BPH.

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.

Patient assessments include blood work, IPSS, uroflowmetry, IIEF, MRI and patient interviews conducted at 3 months, 6 months, and 12 months post embolization.

Inclusion Criteria:

• Patient has received a diagnosis of BPH with moderate to severe LUTS, as determined by IPSS
• Patient is greater than 50 years of age
• Patient has had a pelvic examination within the past 6 months
• Patient has been refractory to medical therapy for the last 6 months, or has refused medical therapy
• Patient has a Qmax below 15 mL/s or acute urinary retention
• Prostate is larger than 40 cubic centimetres
• Patient is willing and able to provide written, informed consent

Exclusion Criteria:

• Known malignancy
• Serum PSA > 10 ng/mL at screening
• Advanced atherosclerosis and tortuosity of the iliac arteries
• Prior transurethral resection of the prostate (TURP)
• Post void retention (PVR) > 250 mL
• Chronic use of metronidizole
• Phytotherapy for BPH within last two weeks of screening visit
• Secondary renal insufficiency due to prostatic obstruction
• Chronic renal failure (GSR < 60)
• Large bladder diverticula or bladder stones
• Claustrophobia or other contraindications related to performing MRI
• Compromised hematopoietic function
• Anaphylactic reaction to drug or anesthetic, allergic reaction to iodine or contrast media
• Investigational drug or experimental therapy in the past 4 weeks
• Abnormal coagulation profile
• Allergy to bovine collagen