Dynamin GTPase activity increases when it oligomerizes either into helices in the presence of lipid templates or into rings in the presence of SH3 domain proteins. Dynasore is a dynamin inhibitor of moderate potency (IC₅₀ ˜ 15 μM in vitro). We show that dynasore binds stoichiometrically to detergents used for in vitro drug screening, drastically reducing its potency (IC₅₀ = 479 μM) and research tool utility. We synthesized a focused set of dihydroxyl and trihydroxyl dynasore analogs called the Dyngo™ compounds, five of which had improved potency, reduced detergent binding and reduced cytotoxicity, conferred by changes in the position and/or number of hydroxyl substituents. The Dyngo compound 4a was the most potent compound, exhibiting a 37‐fold improvement in potency over dynasore for liposome‐stimulated helical dynamin activity. In contrast, while dynasore about equally inhibited dynamin assembled in its helical or ring states, 4a and 6a exhibited >36‐fold reduced activity against rings, suggesting that they can discriminate between helical or ring oligomerization states. 4a and 6a inhibited dynamin‐dependent endocytosis of transferrin in multiple cell types (IC₅₀ of 5.7 and 5.8 μM, respectively), at least sixfold more potently than dynasore, but had no effect on dynamin‐independent endocytosis of cholera toxin. 4a also reduced synaptic vesicle endocytosis and activity‐dependent bulk endocytosis in cultured neurons and synaptosomes. Overall, 4a and 6a are improved and versatile helical dynamin and endocytosis inhibitors in terms of potency, non‐specific binding and cytotoxicity. The data further suggest that the ring oligomerization state of dynamin is not required for clathrin‐mediated endocytosis.

In our efforts to prevent highly toxic compounds progressing through our anti-parasitic drug development program, we serendipitously discovered a family of 2-phenylacrylonitriles with excellent growth inhibition of a panel of ten human cancer cell lines. Focused library approaches facilitated the identification of a simple pharmacophore, comprising two terminal aromatic moieties linked via a conjugated cyano (acrylonitrile) moiety. Efforts that perturbed this pharmacophore resulted in a significant drop in growth inhibition. Multiple libraries led to the discovery of two key lead compounds. The first, (Z)-2-(3,4-dichlorophenyl)-3-(4-methoxyphenyl)acrylonitrile (31) exhibits broad spectrum growth inhibition with GI₅₀ values of 0.52–3 μM (HT29 and BE2-C cancer cell lines respectively; average = 1.6 μM). Of greater note is (Z)-2-(3,4-dichlorophenyl)-3-(4-nitrophenyl)acrylonitrile (28), a 0.127 ± 0.043 μM growth inhibitor of the estrogen receptor positive (ER+ve) human breast cancer cell line, MCF-7. Analogue 28 displays up to 543 fold selectivity towards MCF-7 cells compared with nine other non-breast derived cancer cell lines. Further screening of 28 against one human, ER−ve breast cancer cell line (MDA-MB231) and one normal non-tumourigenic breast epithelial cell line (MCF-10A) returned poor growth inhibition values of 34 ± 2 and 16 ± 4μM, demonstrating ca. ∼268 and∼126 fold preference for the MCF-7 estrogen dependent breast cancer cells.