Assessment of Cutaneous Photosensitivity of TOOKAD (WST09) in Preclinical Animal Models and in Patients

Abstract TOOKAD (WST09) is a new, long-wavelength palladium bacteriopheophorbide photosensitizer that targets tissue vasculature. The cutaneous phototoxicity of TOOKAD was assessed in normal rat and pig animal models and in patients in a Phase-I trial of TOOKAD-mediated photodynamic therapy (PDT) for recurrent prostate cancer. Controlled skin exposures were administered using solar-simulated light at various times after drug administration. Two different spectral ranges were used. In the first, the UV portion of the spectrum was removed (UV−) because UV irradiation in nondrugged control animals produced an erythema response at incident energy densities (J/cm2) lower than those required to induce a PDT response. In the second, the full solar spectrum (UV+) was used, and the potentiation by the photosensitizer of the UV-mediated minimum erythema dose was assessed. Results showed that the PDT skin response was negligible at clinical drug doses of 2 mg/kg for any period after administration at light doses of ...