Phase 1 and 2 Studies Demonstrate the Safety and Efficacy of Intraprostatic Injection of PRX302 for the Targeted Treatment of Lower Urinary Tract Symptoms Secondary to Benign Prostatic Hyperplasia

Abstract

Background

PRX302 is a prostate specific antigen (PSA)–activated pore-forming protein toxin under development as a targeted approach for improving lower urinary tract symptoms (LUTS) caused by benign prostatic hyperplasia (BPH) without affecting sexual function.

Objective

To evaluate the safety and efficacy of PRX302 in men with moderate to severe BPH.

Design, setting, and participants

Eligible subjects were refractory, intolerant, or unwilling to undergo medical therapies for BPH and had International Prostate Symptom Score (IPSS) ≥12, a quality of life (QoL) score ≥3, and prostate volumes between 30 and 80 g. Fifteen patients were enrolled in phase 1 studies, and 18 patients entered phase 2 studies.

Interventions

Subjects received intraprostatic injection of PRX302 into the right and left transition zone via a transperineal approach in an office-based setting. Phase 1 subjects received increasing concentrations of PRX302 at a fixed volume; phase 2 subjects received increasing volumes per deposit at a fixed concentration.

Measurements

IPSS, QoL, prostate volume, maximum flow rate (Qmax), International Index of Erectile Function, serum PSA levels, pharmacokinetics, and adverse events were recorded at 30, 60, 90, 180, 270, and 360 d after treatment with PRX302.

Results and limitations

Sixty percent of men in the phase 1 study and 64% of men in the phase 2 study treated with PRX302 had ≥30% improvement compared to baseline in IPSS out to day 360. Patients also experienced improvement in QoL and reduction in prostate volume out to day 360. Patients receiving ≥1 ml of PRX302 per deposit had the best response overall. PRX302 had no deleterious effect on erectile function. Adverse events were mild to moderate and transient in nature. The major study limitation was the small sample size.

Conclusions

The promising safety profile and evidence of efficacy in the majority of treated subjects in these phase 1 and 2 studies supports further development of PRX302 as a minimally invasive, targeted treatment for BPH.