## 4 Preclinical Studies
### In Vivo Studies
As expected, the final temperature was proportional to the total energy given [136]. Seven dogs were given 2 mg/kg HPD intravenously. After 24 h, 450 J/cm of 630 nm wavelength laser light was delivered interstitially to the prostate. Interstitial PDT in the canine prostate using HPD produced modest volumes of tissue necrosis [137]. 5-ALA was used in nine healthy dogs to model the transitional cell carcinoma of the lower urinary tract [95]. Vomiting was reported in 70% of dogs after administration of the compound, and submucosal bladder wall oedema was detected by ultrasound. However, no hematological or biochemical alterations were observed [95]. 5-ALA and disulfonated aluminum phthalocyanine (\(\text{AlS}_{2}\text{Pc}\)) were studied in the normal canine prostate. PDT was performed by applying red light interstitially at 100 mW (100 J) through fibers placed under transrectal ultrasound guidance. Peak levels of \(\text{AlS}_{2}\text{Pc}\) appeared at 5-24 h and 3 h for ALA. Macroscopic PDT lesions were up to 12 mm in diameter using \(\text{AlS}_{2}\text{Pc}\), but only 1-2 mm with ALA. Light at 300 mW (1080 J) caused thermal damage. At 28 days, the damaged glands remained atrophic, but the interlobular supporting stroma was well-preserved. The urethral lesions healed in 28 days without functional impairment [138]. The biological responses of the dog's prostate submitted to mTHPC and \(\text{AlS}_{2}\text{Pc}\)-based PDT were investigated as a preparatory step for clinical trials. PDT with mTHPC and \(\text{AlS}_{2}\text{Pc}\) is safe and promising for necrosing a substantial amount of prostate tissue. Note that prostate PDT was well-tolerated by the experimental animals [139]. mTHPC was administered to dogs to investigate light dosimetry. A light energy dose-response relationship was estimated, and the threshold that induced prostate gland necrosis was 20 to 30 J/cm2 [140]. BPD-MA was administered to 24 healthy dogs to uncover the amount of light needed to ablate the canine esophageal mucosa effectively. Desirable results were obtained at a light dose of 60, 80, 145, and 200 J/cm when delivered 15, 30, 60, and 120 min after drug injection, respectively [141]. The safety of combining PDT with cetuximab, an epidermal growth factor receptor (EGFR) inhibitor, was evaluated in a canine model. The dogs were subjected to different dose levels of intraperitoneal PDT based on BPD-MA, small bowel resection, and cetuximab. The results showed that dogs had acute or severe adverse events, demonstrating acceptable safety and toxicity associated with the light dose experienced, with or without bowel resection and cetuximab. The highest photosensitizer concentration was found in the small bowel, which may explain the anastomotic failure observed [142]. The esophageal region was the target of talaporfin sodium in a study aiming to evaluate the damage to dogs' normal tissue. Areas of 5 cm were irradiated at doses of 25, 50, and 100 J/cm\({}^{2}\). Tissue injury was seen at the muscle layer or even deeper and became more severe as the radiation increased. Histological examination revealed necrosis and inflammation extra-adventitious at a dose of 100 J/cm\({}^{2}\). Nevertheless, irradiation at a dose of 25 J/cm\({}^{2}\) seemed safe with minor tissue lesions [143]. Motexafin lutetium was studied in six dogs preoperatively. The dogs underwent irradiation of the rectum at 730 nm with 0.5 to 10 J/cm\({}^{2}\). All dogs recovered uneventfully. Significant light penetration into the rectum and sidewall of the pelvis was revealed without generating significant toxicity or histological sequelae [144]. This photosensitizer was also used as an experimental treatment in 11 dogs for intraperitoneal motexafin lutetium-based PDT, assessing the toxicity of normal tissues and targeting applications for treating peritoneal carcinomas and sarcomatosis. Mild transient abnormalities were observed on liver function tests, and no renal function abnormalities were found.