Final Results of a Phase I/II Multicenter Trial of WST11 (TOOKAD ® Soluble) Vascular-Targeted Photodynamic Therapy (VTP) for Hemiablation of the Prostate in Men with Unilateral Low Risk Prostate Cancer Conducted in the United States

Introduction— Vascular targeted photodynamic therapy (VTP) with WST11 (TOOKAD ® Soluble; STEBA Biotech, Luxembourg) is a form of tissue ablation that may be used therapeutically for localized prostate cancer (PCa). To study dosing parameters and associated treatment effects we undertook a prospective multicenter phase I/II trial of WST11 VTP for treatment of PCa Methods— 30 men with unilateral, low volume, Gleason 3+3 PCa were enrolled at 5 centers following local IRB approval. Light energy, fiber number, and WST11 dose were escalated to identify optimal dosing parameters for VTP hemiablation. Men were treated by VTP and evaluated by post-treatment MRI and biopsy. PSA, light dose index (LDI-defined as sum of fiber length/ desired treatment volume), toxicity, and quality of life parameters were recorded. Results— Following dose escalation, 21 men received optimized dosing of 4 mg/kg WST11 200 J energy. On post-treatment biopsy, residual PCa was found in the treated lobe in 10 men, untreated lobe in 4, and both lobes in 1. When LDI ≥ 1, at optimal dosing, (n=15), 73.3% had a negative biopsy in the treated lobe. Six men undergoing retreatment, with optimal dose and LDI ≥ 1, had negative post-treatment biopsy. Minimal effects on urinary, sexual function, and overall quality of life, were observed. Conclusions— Hemiablation of the prostate with WST11 VTP was well-tolerated and resulted in negative biopsy in the treated lobe for the majority of men. Dosing parameters and LDI appear related to tissue response as determined by MRI and biopsy. These parameters may serve as the basis for further prospective studies. ,