CHLORIN E6

Chlorin E6 is a natural molecule and a promising photosensitizer. Chlorin E6 is isolated from renewable natural sources. Chlorin E6 is an attractive photodynamic therapy (PDT) drug candidate because of (1) its high absorption in the red spectral region, and (2) its low cost to make compared to other porphyrin-based PDT drugs. Chlorin E6 exhibits advantageous photophysical properties for PDT such as having long lifetimes in their photoexcited triplet states and high molar absorption in the red region of the visible spectrum. Moreover, a 664-nm laser light can penetrate tissue deeper that the 630-nm laser light used for other PDT drugs. Chlorin E6 is an important starting material for making PDT drug Talaporfin sodium (mono-L-aspartyl chlorin e6 or NPe6).
PDT is currently being used as an alternative therapeutic modality for a variety of malignant tumors. Studies have examined antitumor activity of Ce6-induced PDT (Ce6-PDT) both in vitro and in vivo using a rat tumor models. In one study three-week-old male Sprague-Dawley (SD) rats were inoculated s.c. on the right flank with 5x106 RK3E-ras cells. The animals were administered i.v. with Ce6 (10 mg/kg) and 24 h later, PDT was performed using a laser diode at a light dose of 100 J/cm2. Ce6-PDT generated reactive oxygen species and led to significant growth inhibition in RK3E-ras cell. In addition, Ce6-PDT induced apoptosis through the activation of caspase-3 and its downstream target, PARP cleavage. The protein level of anti-apoptotic bcl-2 was also reduced by Ce6-PDT in RK3E-ras cells. In in vivo experiments, application of Ce6- PDT led to a significant reduction of tumor size. PCNA immunostaining and TUNEL assay revealed that Ce6-PDT inhibited tumor cell proliferation and increased apoptosis. (source: Oncology Reports, 2009, 22(5). 1085-1091.)