First experience of photodithazine clinical application for photodynamic therapy of malignant tumors

In 1998 a new second-generation photosensitizer was introduced in Russia - a chlorin e 6 derivative named Photodithazine - water-soluble preparation with absorption peak at 668 nm. This novel preparation has passed pre-clinical in vitro and in vivo studies. In 1999 a limited series of clinical testing of photodynamic therapy with photodithazine has been performed in the State Research Center for Laser Medicine of Russian Ministry of Public Health. In comparison to hematoporphyrin derivative (Photofrin, Photosan, Photoheme etc.) and aluminum phthalocyanine (Photosense) used in clinical practice, Photodithazine has a number of special properties. Most significant of them is rapid tissue accumulation and clearance from the organism within 48 - 72 hours. Photodithazine was used as a photosensitizer for treatment of 44 patients with malignant tumors of skin, oral cavity, larynx, bronchi, esophagus, stomach, vulva and other locations. The dose of photodithazine ranged from 0,8 to 1,2 mg/kg of body weight. Laser irradiation has been performed on a solid-state laser device Poljus-2 with wavelength 670 nm and output power 1000 mW. Energy density ranged from 100 to 400 J/cm 2 . Laser irradiation of the inner organ was performed via flexible endoscope. PDT with Photodithazine was not accompanied with systemic and local complications. The treatment was well-tolerated by the patients, including those with severe accompanying diseases, There were no complications associated with possible high skin photosensitivity in all treated group. Therapeutic effect took place in all cases, including complete tumor regression in 22 cases (53,7%) and partial regression in 19 cases (46,3%). By present time clinical PDT with Photodithazine is in the initial state. Photodithazine-based PDT appears to be a very promising technique, but analysis of long-term follow-up results is necessary to confirm its therapeutic efficacy. Further research is required to estimate adequate doses of drug and light for various types of tumors.