Fimaporfin, also known as TPCS2a, is a potent chlorin-based photosensitizer, Fimaporfin is consisted of a mixture of three isomers A, B and C (25%,50%,25%). Fimaporfin has been developed by di-imide reduction of disulfonated tetraphenyl porphine (TPPS(2a)). The synthesized TPCS(2a) contains 3 isomers as shown by HPLC with low (<4%) inter-batch variation with respect to isomer formation, less than 0.5% (w/w) of the starting material TPPS(2a) and absorbs light at 652 nm. TPCS(2a) was found to be a clinically suitable PCI photosensitizer for photochemical activation of molecules that do not readily penetrate the cellular plasma membrane.