Intra-prostatic injection of PRX302 to focally ablate clinically significant prostate cancer: An open label, phase 2a study

A polymeric paste-drug formulation for intratumoral treatment of prostate cancer

OBJECTIVE

Focal therapy has emerged as a treatment option for low- to intermediate-risk localized prostate cancer (PCa) patients, to balance the risks for urinary and sexual morbidity of radical treatment with the psychological burden of active surveillance. In this context, we developed ST-4PC, an injectable, polymeric paste formulation containing docetaxel (dtx) and bicalutamide (bic) for image-guided focal therapy of PCa. The objective of this work was to evaluate the in vitro characteristics and in vivo toxicity and efficacy of ST-4PC.

MATERIAL AND METHODS

In vitro drug release was evaluated using high-performance liquid chromatography. In vivo toxicity of blank- and drug-loaded ST-4PC was assessed in mice and rats. Tumor growth inhibition was evaluated in LNCaP subcutaneous (s.c.) and LNCaP-luc orthotopic xenograft models. Using the s.c. model, mice were monitored weekly for weight loss, tumor volume (TV) and serum PSA. For the orthotopic model, mice were additionally monitored for bioluminescence as measure of tumor growth.

RESULTS

ST-4PC demonstrated a sustained and steady release of incorporated drugs with 50% dtx and 20% bic being released after 14 days. While no systemic toxicity was observed, dose-dependent local side effects from dtx developed in the s.c. but not in the orthotopic model, illustrating the limitations of s.c. models for evaluating local cytotoxic therapy. In the s.c. model, 0.1%/4% and 0.25%/4% dtx/bic ST-4PC paste significantly reduced PSA progression, but did not have a significant inhibitory effect on TV. ST-4PC loaded with 1%/4% dtx/bic significantly reduced TV, serum PSA, and bioluminescence in the orthotopic xenograft model. Compared with drugs dissolved in DMSO, ST-4PC significantly delayed tumor growth.

CONCLUSION

Image-guided focal therapy using ST-4PC demonstrated promising inhibition of PSA progression and orthotopic tumor growth in vivo without significant toxicity, and warrants further clinical evaluation.

New advances in focal therapy for early stage prostate cancer

INTRODUCTION

Prostate focal therapy offers men the opportunity to achieve oncological control while preserving sexual and urinary function. The prerequisites for successful focal therapy are to accurately identify, localize and completely ablate the clinically significant cancer(s) within the prostate. We aim to evaluate the evidence for current and upcoming technologies that could shape the future of prostate cancer focal therapy in the next five years. Areas covered: Current literature on advances in patient selection using imaging, biopsy and biomarkers, ablation techniques and adjuvant treatments for focal therapy are summarized. A literature search of major databases was performed using the search terms 'focal therapy', 'focal ablation', 'partial ablation', 'targeted ablation', 'image guided therapy' and 'prostate cancer'. Expert commentary: Advanced radiological tools such as multiparametric magnetic resonance imaging (mpMRI), multiparametric ultrasound (mpUS), prostate-specific-membrane-antigen positron emission tomography (PSMA-PET) represent a revolution in the ability to understand cancer function and biology. Advances in ablative technologies now provide a menu of modalities that can be rationalized based on lesion location, size and perhaps in the near future, pre-determined resistance to therapy. However, these need to be carefully studied to establish their safety and efficacy parameters. Adjuvant strategies to enhance focal ablation are under development.