Fexapotide Triflutate Induces Selective Prostate Glandular Pharmaco-Ablation in the Rat

INTRODUCTION: A clinical challenge for interventional prostate treatments for localized prostate cancer has been to elicit cancer tissue eradication which can avoid undesirable toxicities and irreparable damage to adjacent structures. Fexapotide triflutate (FT) has been shown in human clinical trials to be a well-tolerated pharmaco-ablative agent with therapeutic benefit in patients with prostate enlargement and low-grade prostate cancer. METHODS: Studies were undertaken in vitro and in the normal male rat to characterize and quantify selective ablation of prostate glandular cells exposed to fexapotide triflutate (FT) injections. N=371 2-month-old Sprague Dawley rats received direct intraprostatic injections under ether anesthesia with laparotomy (n=268 given 0.3 mL FT 0.1–2.0 mg/mL at varied schedules, and n=103 controls), and were sacrificed at intervals of 24 hr-12 months, with measurements of prostate volume, assessments of apoptosis, prostatic nerve structures, connective tissue stroma, and vasculature. In vitro prostate cell lines treated with FT were studied by electron microscopy and RNA quantification. RESULTS: Evidence shows that FT leads to prostate glandular cell loss not found in controls, by apoptosis within 24–72 hrs that is highly selective for achieving near-total loss of glandular epithelium at 6 to 12 months, without any adverse microscopic effects to adjacent periprostatic nerves, vascular elements, and stroma. CONCLUSION: Histological studies in the rat demonstrate that FT ablative effect is selective for prostate glandular epithelium, sparing adjacent tissues and structures in the prostate including nerves, vasculature, and stroma.