Synthesis and Characterization of Water Soluble Phosphazene Trimer-Taxol Ion Pair Adducts and Conjugates

Abstract

Paclitaxel (Taxol) is a diterpenoid isolated from Taxus brevifolia, used clinically for treatment of ovarian and breast cancer. Due to its aqueous insolubility it is administered dissolved in ethanol and Cremophore EL(polyethoxylated caster oil), which has serious side effects. Water soluble cyclotriphosphazene derivatives have been studied in order to improve water solubility and the chemotherapeutical potency of paclitaxel. Cyclotriphosphazene derivatives were synthesized by stepwise nucleophilic substitutions of hexachlorocyclotriphosphazene with a hydrophilic poly(ethylene glycol) as a solubilizing group and lysine as a spacer group. They were found to form a micelle in the presence of 2′-succinyl taxol. It is presumed that the cyclic trimer may form an ion pair adduct with carboxylic acid of 2′-succinyl taxol through the alpha-amine group of lysine. We also synthesized water soluble cyclotriphosphazene taxol conjugates. The in vitro cytotoxic activities of IPA and conjugate are very low.