Studies of a Novel Photosensitizer Palladium-Bacteriopheophorbide (Tookad) for the Treatment of Prostate Cancer

In this study, photodynamic therapy (PDT) mediated with a novel, second generation photosensitizer Tookad (palladium-bacteriopheophorbide, WST09, STEBA Biotech, France), is investigated as an alternative modality in the treatment of prostate cancer. In vivo normal canine prostate and spontaneous advanced prostate cancer are used as the animal model. PDT was performed by irradiating the surgically exposed prostates with a diode laser (763 n m, 150 mW/cm) to activate the i.v. infused photosensitizer. The effects of drug concentration, drug-light interval, and light fluence rate on the PDT efficacy were studied. The prostates and adjacent tissues (bladder and underlying colon) were harvested and subjected to histopathological examination. During the one-week to 3-month period post PDT treatment, the dogs recovered well with little or no urethral complications. Prostatic urethra and prostate adjacent tissues (bladder and underlying colon) were well preserved. Light irradiation delivered during drug infusion or within 15 min post drug infusion induced the similar extend of damages. PDT induced prostate lesions in both normal and cancerous prostate were characterized by marked hemorrhagic necrosis and atrophy. Maximum lesion size of over 3 cm in dimension could be achieved with a single 1-cm interstitial treatment, suggesting the therapy is very effective in ablating cancerous prostatic tissue. In conclusion, the second generation photosensitizer Tookad mediated PDT may provide an effective alternative to treat prostate cancer.