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  • Phase I animal safety study of new second generation porphyrin based photosensitizers in the Syrian Golden hamster
    (2007) Wittmann, Johannes
    Thesis
    Pancreatic cancer kills over 1700 people each year in Australia. In 2000, there were 1908 new cases diagnosed and it remains one of the least treatable malignancies. In the USA, it was the fourth leading cause of cancer death in 2004, with 31,860 new cases and 31,270 recorded deaths. Photodynamic therapy (PDT) is a novel, potentially useful treatment for locally advanced pancreatic cancer with only limited research and clinical work addressing this until now. PDT induces non-thermal, cytotoxic and ischaemic injury to a targeted volume of tissue. During PDT, a photosensitizer is activated by non-thermal light in the presence of oxygen, generating cytotoxic oxygen species and inducing cellular injury and microvascular occlusion. The aim of this thesis was to conduct an animal safety study using two second generation photosensitizers, talaporfin sodium and verteporfin, to assess the risks of pancreatic PDT by looking at injury to organs adjacent to the pancreas and assessing recovery from PDT treatment of the pancreas. The Syrian Golden hamster animal model was used to compare the results of this research to previous work by other authors. The study design incorporated a number of additional experiments, including quantitative tissue fluorescence techniques, plasma level analysis and histopathology techniques. The methods for the animal safety study were similar to the approach used in the clinical setting and provided vital data on the likely risks and side effects of phototherapy in humans. The first study, looking at talaporfin sodium, found likely risks of duodenal injury, gastric injury and death with a limited effect on normal pancreas at photosensitizer doses likely to be employed for pancreatic cancer PDT. The second study, using verteporfin, found similar results with a more potent effect on the normal pancreas at studied drug doses. Both agents had short drug-light intervals, ranging from 15 minutes to 2 hours, reducing the need for pre-treatment hospitalization and short photosensitivity periods of about one to two weeks. Some animals suffered minor cutaneous photosensitivity injuries. A human pancreatic cancer PDT pilot study is feasible and the risks and complications should be acceptable.