The success of the BIOS approach was demonstrated by a combinatorial library inspired by the marine natural product dysidiolide (60; Scheme 13). Postulating that the γ-hydroxybutenolide group of dysidiolide was the major determinant of phosphatase activity, testing of a 147-member library built around this molecule yielded a compound (61; Scheme 13) 10-fold more potent (IC50= 350 nM) than the parent compound against Cdc25A.(175) In addition, other members of the library were identified with low micromolar activities against the enzymes acetylcholinesterase and 11β-hydroxysteroid dehydrogenase type 1, which fall within the same PSSC as Cdc25A.(176) A second example of the success of BIOS, the discovery of inhibitors of Tie-2, insulin-like growth factor 1 receptor (IGF-1R), and vascular endothelial growth factor receptor 2 (VEGFR-2 and 3), is discussed in section .