Chemical structure and characteristics of early generation active small molecule XIAP antagonistic compound (1396-34) and new generation active (1540-14) and inactive (1540-20) structural analog. The chemical structures of polyphenylurea compounds are provided. The 2 compounds that can inhibit XIAP (namely 1396-34 and 1540-14) are labeled as “Active,” while the third compound (1540-20) has no inhibitory activity and is labeled as “Inactive” at the top of the figure. Below each chemical structure is the name of the compound, the molecular weight (MW), the solubility (MLogP), the μM EC₅₀ (± SE) observed in the XIAP derepression assay, and the μM IC₅₀ (± SE) defined in the JURKAT cytotoxicity assay, as labeled at the bottom left-hand corner of the figure. For 1540-20, no activity in the XIAP derepression assay could be detected at the maximum concentration used (eg, 194 μM).