A COMPARATIVE-ANALYSIS OF SILICON PHTHALOCYANINE PHOTOSENSITIZER FOR IN-VIVO PHOTODYNAMIC THERAPY OF RIF-1 TUMORS IN C3H MICE

Photofrin(R) photodynamic therapy (PDT) has recently received FDA appr oval for the palliative treatment of totally and partially obstructing esophageal malignancies. However, there is a need for new PDT photose nsitizers because Photofrin has a number of undesirable features, The purpose Of this study was to evaluate the efficacy of four amine-beari ng silicon phthalocyanines-Pc4, Pc10, Pc12 and Pc18-as potential PDT p hotosensitizers. Equimolar concentrations of these Pc were found to be highly effective at causing the regression of RIF-1 tumors transplant ed to C3H/HeN mice. The amount of Pc4 necessary to cause an equivalent amount of tumor regression in this model system was substantially les s than the amount of Photofrin. The cutaneous phototoxicity of the sil icon PC photosensitizer was assessed by the utilization of the murine ear-swelling model, When C3H mice were exposed to 167 J/cm(2) of polyc hromatic visible light from a UVB-filtered solar simulator, which emit ted UV radiation and visible light above 320 nm, the Pc produced littl e, if any, cutaneous photosensitivity. These results indicate that Pc4 , Pc10, Pc12 and Pc18 are at lease as effective as Photofrirn in PDT p rotocols, while at the same time addressing many of the drawbacks of P hotofrin.