Chlorin E6 (CE6) is a second-generation photosensitizer with antitumor activity when used in combination with irradiation. In a mouse model of implanted fibrosarcoma, Chlorin E6 (2.5-10 mg/kg, i.v., 50-200 J/cm2 irradiation) resulted in complete tumor disappearance after varying degrees of irradiation. Agents including Chlorin E6 were tested in a Phase I clinical study in patients with early superficial squamous cell carcinoma of bronchial origin with favorable results (40 mg/m2, IV, 100 J/cm2 laser irradiation). In a Phase II clinical trial in patients with early stage lung cancer, the same mode of administration resulted in a complete response in 82.9% of patients. Chlorin E6 has been investigated as a nanotechnology drug delivery tool.