1. Medicinal Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, U.K.
2. Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, Villigen PSI CH-5232, Switzerland
3. Screening Technologies Branch, Developmental Therapeutics Program, Division of Cancer Treatment and Diagnosis, National Cancer Institute, Frederick National Laboratory for Cancer Research, Frederick 21702, Maryland, United States
4. University of Basel, Biozentrum, Basel CH-4056, Switzerland