The mechanism by which cholesteryl ester transfer protein (CETP) activity affects HDL metabolism was investigated using agents that selectively target CETP (dalcetrapib, torcetrapib, anacetrapib). In contrast with torcetrapib and anacetrapib, dalcetrapib requires cysteine 13 to decrease CETP activity, measured as transfer of cholesteryl ester (CE) from HDL to LDL, and does not affect transfer of CE from HDL3 to HDL2. Only dalcetrapib induced a conformational change in CETP, when added to human plasma in vitro, also observed in vivo and correlated with CETP activity. CETP-induced pre-β-HDL formation in vitro in human plasma was unchanged by dalcetrapib ≤3 µM and increased at 10 µM. A dose-dependent inhibition of pre-β-HDL formation by torcetrapib and anacetrapib (0.1 to 10 µM) suggested that dalcetrapib modulates CETP activity. In hamsters injected with [3H]cholesterol-labeled autologous macrophages, and given dalcetrapib (100 mg twice daily), torcetrapib [30 mg once daily (QD)], or anacetrapib (30 mg QD), only dalcetrapib significantly increased fecal elimination of both [3H]neutral sterols and [3H]bile acids, whereas all compounds increased plasma HDL-[3H]cholesterol. These data suggest that modulation of CETP activity by dalcetrapib does not inhibit CETP-induced pre-β-HDL formation, which may be required to increase reverse cholesterol transport.

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A new class of nonpeptidic inhibitors of the Zn II -dependent metalloprotease neprilysin with IC 50 values in the nanomolar activity range (0.034 ± 0.30 mm) were developed based on structure-based de novo design (Figs. 1 and 2). The inhibitors feature benzimidazole and imidazo [4,5-c]pyridine moieties as central scaffolds to undergo H-bonding to Asn542 and Arg717 and to engage in favorable p-p stacking interactions with the imidazole ring of His711. The platform is decorated with a thiol vector to coordinate to the Zn II ion and an aryl residue to occupy the hydrophobic S1' pocket, but lack a substituent for binding in the S2' pocket, which remains closed by the side chains of Phe106 and Arg110 when not occupied. The enantioselective syntheses of the active compounds ()-1, ()-2, ()-25, and ()-26 were accomplished using Evans auxiliaries (Schemes 2, 4, and 5). The inhibitors ()-2 and ()-26 with an imidazo[4,5-c]pyridine core are ca. 8 times more active than those with a benzimidazole core (()-1 and ()-25) ( Table 1). The predicted binding mode was established by X-ray analysis of the complex of neprilysin with ()-2 at 2.25-resolution (Fig. 4 and Table 2). The ligand coordinates with its sulfanyl residue to the Zn II ion, and the benzyl residue occupies the S1' pocket. The 1H-imidazole moiety of the central scaffold forms the required H-bonds to the side chains of Asn542 and Arg717. The heterobicyclic platform additionally undergoes p-p stacking with the side chain of His711 as well as edge-to-face-type interactions with the side chain of Trp693. According to the X-ray analysis, the substantial advantage in biological activity of the imidazopyridine inhibitors over the benzimidazole ligands arises from favorable interactions of the pyridine N-atom in the former with the side chain of Arg102. Unexpectedly, replacement of the phenyl group pointing into the deep S1' pocket by a biphenyl group does not enhance the binding affinity for this class of inhibitors.1. Introduction. ± In the preceding paper [1], we described a new class of inhibitors of the metalloprotease neprilysin with a central 1H-imidazole platform, featuring IC 50 values (IC 50 : concentration of inhibitor at which 50% V max is observed) in the low micromolar range. The de novo design of these compounds was based on the X-ray crystal structure of NEP complexed with phosphoramidon (Protein Data Bank (PDB) file name 1DMT) [2]. For the design of the second-generation inhibitors, we reverted to an unpublished X-ray crystal structure [3] of NEP complexed with the inhibitor thiorphan [4]. During the analysis, we carefully compared the active sites of the two

Endothelin-1 (ET-1) is mitogenic and/or antiapoptotic in human cancers, and antagonists to ET-1 receptors are under evaluation for cancer treatment. Inhibition of ET-1 activation by the endothelin-converting enzymes 1(a)(-)(d) (ECE-1(a)(-)(d); EC 3.4.24.71) represents another approach to block the ET-1 effect in cancer. To evaluate this potential, we synthesized and characterized a series of low nanomolar nonpeptidic thiol-containing ECE-1 inhibitors, and evaluated their effect, as well as the effect of inhibitors for the related metalloproteases neprilysin (NEP; EC 3.4.24.11) and angiotensin-converting enzyme (ACE; EC 3.4.15.1), on human glioblastoma cell growth. Only ECE-1 inhibitors inhibited DNA synthesis by human glioblastoma cells. Exogenous addition of ET-1 or bigET-1 to glioblastoma cells did not counterbalance the growth inhibition elicited by ECE-1 inhibitors, suggesting that ECE-1 inhibitors block the proliferation of human glioblastoma cells most likely via a mechanism not involving extracellular production of ET-1. This class of molecules may thus represent novel therapeutic agents for the potential treatment of human cancer.