Hematoporphyrin-derived soluble porphyrin-platinum conjugates with combined cytotoxic and phototoxic antitumor activity

To combine the cytotoxic activity of cisplatin and the phototoxicicity of hematoporphyrin derivatives in the same molecule, hematoporphyrin was derivatized at the two secondary alcohol positions by etherification with oligo- and poly(ethylene glycol) units. The two carboxylic acid groups of the propionate side chains were used to bind platinum fragments, The antiproliferative activity of 35 platinum complexes (0.5, 1, and 5 muM) differing in solubility and type of the platinum fragment and the corresponding porphyrin ligands were studied in tests with TCC-SUP and J82 transitional bladder cancer cells in the dark and after irradiation (lambda = 600-730 nm, 24 J/cm(2)). The most active compounds were found among the porphyrin-platinum conjugates bearing the diammine and (RR/SS)-trans-1,2-diaminocyclohexane ligand. These porphyrin-platinum conjugates, especially the water-soluble species, such as diammine{7,12-bis[1-(poly(ethylene glycol)-750-monomethyl ether-1-yl)ethyl]-3,8,13,17-tetramethylporphyrin-2,18-dipropionato}platinum(II), are promising candidates for the development of a novel type of photosensitizers with intrinsic cytotoxicity, which due to the porphyrin constituent may selectively enrich in tumor tissues.