- Transport of the investigational anti-cancer drug 5,6-dimethylxanthenone-4-acetic acid and its acyl glucuronide by human intestinal Caco-2 cells. Zhou, S., Feng, X., Kestell, P., Paxton, J.W., Baguley, B.C., Chan, E. European journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences. (2005)