Phase 2b trial results of padeliporfin (WST11 or Tookad) vascular-targeted photodynamic therapy for partial gland ablation in men with intermediate-risk prostate cancer.
Authors: Jonathan Coleman, Daniel D. Sjoberg, Quinlan Demac, Catriona ODea, Marlena McGill, Andrew Tracey, Lucas Nogueira, Andrew Vickers, Connie Estes, Samson Fine, Oguz Akin, John Mulhall, Jaspreet Sandhu, Brett Stewart Carver, Vincent Paul Laudone, Behfar Ehdaie, Avigdor Joshua Scherz, Peter T. Scardino, James Andrew Eastham
Journal: Journal of Clinical Oncology (2021)

e17006 Background: Padeliporfin (WST11) vascular-targeted photodynamic therapy (VTP) has shown significant clinical benefit as a localized partial gland ablation (PGA) therapy when compared to active surveillance for low-risk prostate cancer, by curbing progression and the need for radical treatment, leading to its regulatory approval in Europe. This phase 2b trial prospectively investigated WST11-VTP for intermediate-risk cancers. Methods: Men with unilateral Grade Group 2 (GG2) cancers (Gleason 3+4), evaluated with MRI and ultrasound-guided (TRUS) biopsy, underwent up to two WST11-VTP PGA sessions. Eligibility criteria included &lt;cT2b, PSA &lt; 10, and fusion biopsy for PIRADS 3+ lesions on pretreatment MRI. Contralateral very low–risk disease was observed. The primary endpoint was prevalence of any Gleason Grade 4 or 5 (≥GG2) cancer, determined by MRI and systematic, 14-core TRUS biopsy of the entire gland (+/- fusion) at 3 and 12 months after treatment. Treatment safety and patient-reported quality of life for sexual and urinary function were assessed with validated questionnaires (IIEF-15 and IPSS, respectively). The study was powered using β = 0.2 to reject the null hypothesis (r≤70%), using a one-sided exact binomial test with 5% alpha risk. To be valid, 44 evaluable patients were required for the 12-month primary endpoint assessment. Results: Of the 50 men treated, 46 were evaluable for the 12-month primary endpoint. Before 12 months, 1 man proceeded to prostatectomy (treatment failure), 2 men refused 12-month biopsy, and 1 man died of COVID-19. At 3 months, 12/49 (24%) men underwent per protocol second WST11-VTP PGA session for GG2 tumor: 9 for residual cancer and 4 for newly identified contralateral GG2 tumors (1 bilateral). The 12-month biopsy was performed in 45 men; 38 (83%) had no Gleason grade 4 or 5 cancer, including 11/12 (92%) patients who underwent 2 PGA sessions. By 3 months, median decline in erectile function score (IIEF-5) from baseline was -1.0 (IQR -7,0). Median improvement in urinary function score (IPSS) was -1.0 (IQR -1,5), with pad-free continence observed in all patients. Median change in IIEF score by 12-months was -1.0 (IQR -5,0). Grade 3 treatment-related adverse events occurred in 6 (12%) patients. All procedure-related prostate/pelvic pain resolved by 3 weeks. Conclusions: The positive results from this trial show that WST11-VTP is effective for PGA of intermediate-risk prostate cancer, with minimal toxicity or impact on urinary and sexual function, consistent with the phase 3 trial results in low-risk disease. Based on these data, this therapy bears consideration for approval as a conservative therapeutic option for selected cases of intermediate-risk disease. Clinical trial information: NCT03315754.