Characterization of cutaneous photosensitivity in healthy volunteers receiving talaporfin sodium

Purpose: Historically, cutaneous photosensitivity has been the most common side effect of treatment with light‐activated drugs. Talaporfin sodium is a water soluble photosensitizer in commercial use and clinical development that is cleared from the body relatively rapidly. This trial was conducted to determine the period of skin photosensitivity in healthy subjects given talaporfin sodium and to determine the correlation between photosensitivity and plasma levels of talaporfin sodium. Methods: Twenty healthy volunteers were dosed with 0.25–1.0 mg/kg talaporfin sodium and exposed at successive timepoints to a solar simulator applied to a small patch of skin on the back. Photosensitivity was assessed at these sites 24 h later. Duration of photosensitivity and correlation with plasma drug concentration were analyzed. Results: Skin reactions were generally mild and were classified most commonly as asymptomatic erythema. Photosensitivity subsided in each subject between 1 and 3 weeks after dosing. Subjects no longer exhibited photosensitivity at plasma drug levels between 600 and 2900 ng/ml in each subject. Two subjects in the lowest dose group did not exhibit photosensitivity despite plasma drug levels as high as 4000 ng/ml. Conclusions: These results indicate that a clinically effective dose of talaporfin sodium was well‐tolerated and that cutaneous photosensitivity was mild and resolved relatively rapidly.