1. Dipartimento di Studi Farmaceutici, Università di Roma “La Sapienza”, Piazzale Aldo Moro 5, I-00185 Roma, Italy, Welsh School of Pharmacy, Cardiff University, King Edward VII Avenue, Cardiff, CF10 3XF, U.K., and Screening Technologies Branch, Developmental Therapeutics Program, Division of Cancer Treatment and Diagnosis, National Cancer Institute at Frederick, National Institutes of Health, Frederick, Maryland 21702