1. Laboratory for Molecular Pharmacology, University of Copenhagen, The Panum Institute, Copenhagen, Denmark, Department of Theoretical Chemistry, Lund University, P.O. Box 124, S-22100 Lund, Sweden, AnorMED Inc., Langley, British Columbia V2Y 1N5, Canada, and 7TM Pharma A/S, Fremtidsvej 3, DK-2970, Hørsholm, Denmark