## 4 Preclinical Studies
### In Vivo Studies
No severe PDT-related abnormalities were observed on laparoscopy or necropsy; however, thickening of the glomerular capillary wall and mesanguium was observed microscopically in the kidneys of seven dogs [145]. To determine the viability of canine prostate treatment and toxicity of the motexafin lutetium, 25 dogs were administered intravenously (2 or 6 mg/kg) and irradiated with a 732 nm laser light (75-150 J/cm). The light was delivered intersitially transurethrally to the prostate via cylindrical diffusing fibers. Interstitial PDT results in minor toxicity, with initial inflammation and necrosis, followed by fibrosis and glandular epithelial atrophy [146]. In another study, isotropic interstitial detectors used in normal canine prostate observed no significant changes before, during, and after motexafin lutetium-based PDT within a single treatment site, suggesting real-time dosimetric measurement and system feedback to monitor light fluences during treatment [147]. Motexafin lutetium-based PDT was explored in another group of canine prostate models. The feasibility of the interstitial photodynamic treatment for prostate cancer was explored in dogs. The dogs were treated with 6 mg/kg of motexafin lutetium and irradiated with different light doses (75-150 J/cm). The study demonstrates a safe and comprehensive treatment of the prostate. However, there is significant variability in the dose distribution and the subsequent tissue necrosis throughout the prostate [148]. To determine the conversion of 5-ALA into protoporphyrin IX (PpIX), four healthy cats were administered intravenously at 100, 200, or 400 mg/kg. Blood and skin biopsies were performed 24 h after administration. PpIX was detected in the tissues analyzed, with the greatest intensity in the epithelia. Due to hepatotoxicity, doses greater than 100 mg/kg were not considered safe [149]. The normal canine prostate was used as a model to study the compound WST09 (Tookad). All animals recovered well, without urethral complications. Histopathological exams showed necrosis, hemorrhage, and glandular tissue atrophy [150]. PDT based on WST09 has been shown to destroy normal prostate tissue, even with a lower photosensitizer concentration and low light energies [126]. However, treatment with WST09 and 100 J/cm\({}^{2}\) resulted in localized nerve injury and decreases in nerve conduction velocities. Treatment with 200 J/cm\({}^{2}\) severely damaged the saphenous nerve [151]. The safety and efficacy of soluble (WST11) vs. unsoluble (WST09) Tookad to target prostate vascular tissue were compared. Vascular PDT with WST11 was advantageous. Mild urinary clinical signs that resolved within 24 to 48 h were observed. All dogs evolved well, except one animal that developed intestinal intussusception [152]. ZnPcP\({}_{2}\)S\({}_{2}\) (Di-sulfo-di-phthalimidomethyl phthalocyanine zinc)-based PDT was developed as a new anticancer method to eliminate residual leukemic cells in normal mononuclear cells. The toxicity of ZnPcP\({}_{2}\)S\({}_{2}\) was evaluated in 24 dogs in doses of 0.5, 1.5, and 4.5 mg/kg. The injection sites of all animals were irradiated with a laser at 670 nm. Irradiations were performed in 48 and 72 h, once every four days, successively for ten times. The observations reported were dysphoria and mild oedema. No adverse effects were observed in the ophthalmoscopy, electrocardiography, hematology, blood biochemistry, or urinalysis [153]. The technical feasibility of destroying prostate tissue using SnET2 was also evaluated in 15 dogs. Absorption and biodistribution were evaluated in the prostate and adjacent tissues. SnET2 was administered intravenously at a concentration of 0.5 or 1.0 mg/kg, the tissue was irradiated with 100-200 J/cm, and destruction of prostatic tissue was achieved [154]. Canine prostate was also subjected to experiments to determine the effects of transperineal interstitial PDT with SnET2. The treated areas showed extensive hemorrhagic necrosis and replacement by fibrous connective tissue [155].