Enhanced FTase activity achieved via piperazine interaction with catalytic zinc

Halogen-enriched fragment libraries as chemical probes for harnessing halogen bonding in fragment-based lead discovery

Halogen bonding has recently experienced a renaissance, gaining increased recognition as a useful molecular interaction in the life sciences. Halogen bonds are favorable, fairly directional interactions between an electropositive region on the halogen (the σ-hole) and a number of different nucleophilic interaction partners. Some aspects of halogen bonding are not yet understood well enough to take full advantage of its potential in drug discovery. We describe and present the concept of halogen-enriched fragment libraries. These libraries consist of unique chemical probes, facilitating the identification of favorable halogen bonds by sharing the advantages of classical fragment-based screening. Besides providing insights into the nature and applicability of halogen bonding, halogen-enriched fragment libraries provide smart starting points for hit-to-lead evolution.

Discovery of novel inhibitors of a disintegrin and metalloprotease 17 (ADAM17) using glycosylated and non-glycosylated substrates

A disintegrin and metalloprotease (ADAM) proteases are implicated in multiple diseases, but no drugs based on ADAM inhibition exist. Most of the ADAM inhibitors developed to date feature zinc-binding moieties that target the active site zinc, which leads to a lack of selectivity and off-target toxicity. We hypothesized that secondary binding site (exosite) inhibitors should provide a viable alternative to active site inhibitors. Potential exosites in ADAM structures have been reported, but no studies describing substrate features necessary for exosite interactions exist. Analysis of ADAM cognate substrates revealed that glycosylation is often present in the vicinity of the scissile bond. To study whether glycosylation plays a role in modulating ADAM activity, a tumor necrosis factor α (TNFα) substrate with and without a glycan moiety attached was synthesized and characterized. Glycosylation enhanced ADAM8 and -17 activities and decreased ADAM10 activity. Metalloprotease (MMP) activity was unaffected by TNFα substrate glycosylation. High throughput screening assays were developed using glycosylated and non-glycosylated substrate, and positional scanning was conducted. A novel chemotype of ADAM17-selective probes was discovered from the TPIMS library (Houghten, R. A., Pinilla, C., Giulianotti, M. A., Appel, J. R., Dooley, C. T., Nefzi, A., Ostresh, J. M., Yu, Y., Maggiora, G. M., Medina-Franco, J. L., Brunner, D., and Schneider, J. (2008) Strategies for the use of mixture-based synthetic combinatorial libraries. Scaffold ranking, direct testing in vivo, and enhanced deconvolution by computational methods. J. Comb. Chem. 10, 3-19; Pinilla, C., Appel, J. R., Borràs, E., and Houghten, R. A. (2003) Advances in the use of synthetic combinatorial chemistry. Mixture-based libraries. Nat. Med. 9, 118-122) that preferentially inhibited glycosylated substrate hydrolysis and spared ADAM10, MMP-8, and MMP-14. Kinetic studies revealed that ADAM17 inhibition occurred via a non-zinc-binding mechanism. Thus, modulation of proteolysis via glycosylation may be used for identifying novel, potentially exosite binding compounds. The newly described ADAM17 inhibitors represent research tools to investigate the role of ADAM17 in the progression of various diseases.

Design, synthesis and biological evaluation of substituted dioxodibenzothiazepines and dibenzocycloheptanes as farnesyltransferase inhibitors

A new series of FTase inhibitors containing a tricyclic moiety--dioxodibenzothiazepine or dibenzocycloheptane--has been designed and synthesized. Among them, dioxodibenzothiazepine 18d displayed significant inhibitory FTase activity (IC(50)=17.3 nM) and antiproliferative properties.