1. Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K., INSERM U-524 et Laboratoire de Pharmacologie Antitumorale du Centre Oscar Lambret, IRCL, Place de Verdun, 59045 Lille, France, Département de Pharmacochimie Moléculaire et Structurale, INSERM U266-CNRS UMR 8600, Faculté de Pharmacie, 4, Avenue de l'Observatoire, 75270 Paris, France, and Department of Chemistry, Box 90346, Duke University, Durham, North Carolina 27708-0346