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Photodynamic therapy (PDT) involves the light activation of a drug within a tumor causing selective tumor cell death. Unfortunately, some photosensitizing drugs have been associated with adverse reactions in veterinary patients. Zinc phthalocyanine tetrasulfonate (ZnPcS₄) is a promising second-generation photosensitizer for use in veterinary medicine, however, it cannot be applied clinically until safety and efficacy data are available. ZnPcS₄ was given to Swiss Webster mice to assess acute toxicity. Doses >100 mg/kg were associated with acute toxicity and mortality, and doses >100 mg/kg resulted in renal tubular nephrosis, suggesting that the minimum toxic dose is approximately 100 mg/kg. Based on these data, a Phase I clinical trial of ZnPcS4-based PDT in tumor-bearing dogs is underway, with ZnPcS₄ doses up to 2 mg/kg producing no apparent toxicity. Tumor response has been observed after ZnPcS₄-based PDT using doses as low as 0.25 mg/kg, suggesting that conventional phase I clinical trials may not be appropriate for PDT protocols.

©2005 COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.