Dual small-molecule targeting of procaspase-3 dramatically enhances zymogen activation and anticancer activity.

Combination anticancer therapy typically consists of drugs that target different biochemical pathways or those that act on different targets in the same pathway. Here we demonstrate a new concept in combination therapy, that of enzyme activation with two compounds that hit the same biological target, but through different mechanisms. Combinations of procaspase-3 activators PAC-1 and 1541B show considerable synergy in activating procaspase-3 in vitro, stimulate rapid and dramatic maturation of procaspase-3 in multiple cancer cell lines, and powerfully induce caspase-dependent apoptotic death to a degree well exceeding the additive effect. In addition, the combination of PAC-1 and 1541B effectively reduces tumor burden in a murine lymphoma model at dosages for which the compounds alone have minimal or no effect. These data suggest the potential of PAC-1/1541B combinations for the treatment of cancer and, more broadly, demonstrate that differentially acting enzyme activators can potently synergize to give a significantly heightened biological effect.

Identification of a novel protein synthesis inhibitor active against gram-positive bacteria.

In an effort to identify novel antibacterial chemotypes, we performed a whole-cell screen for inhibitors of Staphylococcus aureus growth and pursued those compounds with previously uncharacterized antibacterial activity. This process resulted in the identification of a benzothiazolium salt, ABTZ-1, that displayed potent antibacterial activity against Gram-positive pathogens. Several clinically desirable qualities were demonstrated for ABTZ-1 including potent activity against multidrug-resistant clinical isolates of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant enterococci (VRE), retention of this activity in human serum, and low hemolytic activity. The antibacterial activity of ABTZ-1 was attributed to its inhibition of bacterial translation, as this compound prevented the incorporation of [³5S]methionine into S. aureus proteins, and ABTZ-1-resistant strains were cross-resistant to known inhibitors of bacterial translation. ABTZ-1 represents a promising new class of antibacterial agents.

Structure-activity relationships of heteroaromatic esters as human rhinovirus 3C protease inhibitors.

Human rhinovirus 3C protease (HRV 3C(pro)) is known to be a promising target for development of therapeutic agents against the common cold because of the importance of the protease in viral replication as well as its expression in a large number of serotypes. To explore non-peptidic inhibitors of HRV 3C(pro), a series of novel heteroaromatic esters was synthesized and evaluated for inhibitory activity against HRV 3C(pro), to determine the structure-activity relationships. The most potent inhibitor, 7, with a 5-bromopyridinyl group, had an IC(50) value of 80nM. In addition, the binding mode of a novel analog, 19, with the 4-hydroxyquinolinone moiety, was explored by molecular docking, suggesting a new interaction in the S1 pocket.

Combinatorial synthesis and biological evaluation of peptide-binding GPCR-targeted library.

As an effective strategy of the drug discovery for peptide-binding GPCRs based on the natural ligands, beta-turn peptidomimetic compound library with benzodiazepine skeleton was constructed using solid and solution phase parallel synthesis with four different scaffolds containing Phe, Lys, Ser and Glu, respectively. The usefulness of 162 library compounds was evaluated by the cell based screening at melanocortin 4 receptor in CHO-k1 cells, to find hit compounds showing agonistic effect at the receptor. The screening of library afforded three hit compounds including the most effective analog, (S)-3-benzyl-7-(4-fluorobenzyloxy)-4-(4-methoxyphenethyl)-4,5-dihydro-1H-benzo[e][1,4]diazepin-2(3H)-one, 13aiE, of which EC(50) was determined as 13 microM.

25-hydroxycholesterol contributes to cerebral inflammation of X-linked adrenoleukodystrophy through activation of the NLRP3 inflammasome.

X-linked adrenoleukodystrophy (X-ALD), caused by an ABCD1 mutation, is a progressive neurodegenerative disorder associated with the accumulation of very long-chain fatty acids (VLCFA). Cerebral inflammatory demyelination is the major feature of childhood cerebral ALD (CCALD), the most severe form of ALD, but its underlying mechanism remains poorly understood. Here, we identify the aberrant production of cholesterol 25-hydroxylase (CH25H) and 25-hydroxycholesterol (25-HC) in the cellular context of CCALD based on the analysis of ALD patient-derived induced pluripotent stem cells and ex vivo fibroblasts. Intriguingly, 25-HC, but not VLCFA, promotes robust NLRP3 inflammasome assembly and activation via potassium efflux-, mitochondrial reactive oxygen species (ROS)- and liver X receptor (LXR)-mediated pathways. Furthermore, stereotaxic injection of 25-HC into the corpus callosum of mouse brains induces microglial recruitment, interleukin-1ß production, and oligodendrocyte cell death in an NLRP3 inflammasome-dependent manner. Collectively, our results indicate that 25-HC mediates the neuroinflammation of X-ALD via activation of the NLRP3 inflammasome.

FcγRIIb mediates amyloid-ß neurotoxicity and memory impairment in Alzheimer's disease.

Amyloid-ß (Aß) induces neuronal loss and cognitive deficits and is believed to be a prominent cause of Alzheimer's disease (AD); however, the cellular pathology of the disease is not fully understood. Here, we report that IgG Fcγ receptor II-b (FcγRIIb) mediates Aß neurotoxicity and neurodegeneration. We found that FcγRIIb is significantly upregulated in the hippocampus of AD brains and neuronal cells exposed to synthetic Aß. Neuronal FcγRIIb activated ER stress and caspase-12, and Fcgr2b KO primary neurons were resistant to synthetic Aß-induced cell death in vitro. Fcgr2b deficiency ameliorated Aß-induced inhibition of long-term potentiation and inhibited the reduction of synaptic density by naturally secreted Aß. Moreover, genetic depletion of Fcgr2b rescued memory impairments in an AD mouse model. To determine the mechanism of action of FcγRIIb in Aß neurotoxicity, we demonstrated that soluble Aß oligomers interact with FcγRIIb in vitro and in AD brains, and that inhibition of their interaction blocks synthetic Aß neurotoxicity. We conclude that FcγRIIb has an aberrant, but essential, role in Aß-mediated neuronal dysfunction.

Design, synthesis and X-ray crystallographic study of NAmPRTase inhibitors as anti-cancer agents.

NAmPRTase (PBEF/Visfatin) plays a pivotal role in the salvage pathway of NAD(+) biosynthesis. NAmPRTase has been an attractive target for anti-cancer agents that induce apoptosis of tumor cells via a declining plasma NAD(+) level. In this report, a series of structural analogs of FK866 (1), a known NAmPRTase inhibitor, was synthesized and tested for inhibitory activities against the proliferation of cancer cells and human NAmPRTase. Among them, compound 7 showed similar anti-cancer and enzyme inhibitory activities to compound 1. Further investigation of compound 7 with X-ray analysis revealed a co-crystal structure in complex with human NAmPRTase, suggesting that Asp219 in the active site of the enzyme could contribute to an additional interaction with the pyrrole nitrogen of compound 7.

Design and synthesis of 1,4-dihydropyridine derivatives as BACE-1 inhibitors.

BACE-1 has been shown to be an attractive therapeutic target in Alzheimer's disease (AD). Using a 1,4-dihydropyridine (DHP) scaffold, we synthesized new inhibitors of BACE-1 by modifying the known BACE inhibitor 2 containing a hydroxyethylamine (HEA) motif. Using structure-based drug design based on computer-aided molecular docking, the isophthalamide ring of 2 was replaced with a 1,4-dihydropyridine ring as a brain-targeting strategy. Several of the new dihydropyridine derivatives were synthesized and their BACE-1-inhibitory activities were evaluated using a cell-based, reporter gene assay system that measures the cleavage of alkaline phosphatase (AP)-APP fusion protein by BACE-1. Most of the 1,4-DHP analogs showed BACE-1-inhibitory activities with IC50 values in the range 8-30 microM, suggesting that the 1,4-DHP skeleton may be utilized to develop brain-targeting BACE-1 inhibitors.

5,5'-substituted indirubin-3'-oxime derivatives as potent cyclin-dependent kinase inhibitors with anticancer activity.

To enhance the ability of indirubin derivatives to inhibit CDK2/cyclin E, a target of anticancer agents, we designed and synthesized a new series of indirubin-3'-oxime derivatives with combined substitutions at the 5 and 5' positions. A molecular docking study predicted the binding of derivatives with OH or halogen substitutions at the 5' position to the ATP binding site of CDK2, revealing the critical interactions that may explain the improved CDK2 inhibitory activity of these derivatives. Among the synthesized derivatives, the 5-nitro-5'-hydroxy analogue 3a and the 5-nitro-5'-fluoro analogue 5a displayed potent inhibitory activity against CDK2, with IC(50) values of 1.9 and 1.7 nM, respectively. These derivatives also showed antiproliferative activity against several human cancer cell lines, with IC(50) values of 0.2-3.3 microM. A representative analogue, 3a, showed greater than 500-fold selectivity for CDK relative to selected kinase panel and potent in vivo anticancer activity.

Crystal structure of Rattus norvegicus Visfatin/PBEF/Nampt in complex with an FK866-based inhibitor.

Visfatin (Nampt/PBEF) plays a pivotal role in the salvage pathway for NAD(+) biosynthesis. Its potent inhibitor, FK866, causes cellular NAD(+) levels to decline, thereby inducing apoptosis in tumor cells. In an effort to improve the solubility and binding interactions of FK866, we designed and synthesized IS001, in which a ribose group is attached to the FK866 pyridyl ring. Here, we report the crystal structure of rat visfatin in complex with IS001. Like FK866, IS001 is positioned at the dimer interface, and all of the residues that interact with IS001 are involved in hydrophobic or pi-pi-stacking interactions. However, we were unable to detect any strong interactions between the added ribose ring of IS001 and visfatin, which implies that a bulkier modifying group is necessary for a tight interaction. This study provides additional structure-based information needed to optimize the design of visfatin inhibitors.

Development of potent inhibitors of the coxsackievirus 3C protease.

Coxsackievirus B3 (CVB3) 3C protease (3CP) plays essential roles in the viral replication cycle, and therefore, provides an attractive therapeutic target for treatment of human diseases caused by CVB3 infection. CVB3 3CP and human rhinovirus (HRV) 3CP have a high degree of amino acid sequence similarity. Comparative modeling of these two 3CPs revealed one prominent distinction; an Asn residue delineating the S2' pocket in HRV 3CP is replaced by a Tyr residue in CVB3 3CP. AG7088, a potent inhibitor of HRV 3CP, was modified by substitution of the ethyl group at the P2' position with various hydrophobic aromatic rings that are predicted to interact preferentially with the Tyr residue in the S2' pocket of CVB3 3CP. The resulting derivatives showed dramatically increased inhibitory activities against CVB3 3CP. In addition, one of the derivatives effectively inhibited the CVB3 proliferation in vitro.

Solid-phase synthesis of tetrahydro-1,4-benzodiazepine-2-one derivatives as a beta-turn peptidomimetic library.

The beta-turn has been implicated as an important conformation for biological recognition of peptides or proteins. We adapted the concept of general Calpha atom positioning from the cluster analysis and recombination of each ideal beta-turn conformation pattern by Garland and Dean (J. Comput.-Aided Mol. Des. 1999, 13, 469) as one strategy of designing non-peptide beta-turn scaffolds. Herein, the Calpha positions of tetrahydro-1,4-benzodiazepin-2-one scaffold were analyzed after the calculation of the low-energy conformer using a semiempirical protocol. Three points of corresponding Calpha carbons for diverse substitutions in the scaffold were designated, and an efficient solid-phase synthesis of the peptidomimetic library was developed. The scaffold itself was synthesized in solution phase starting from 5-hydroxy-2-nitrobenzaldehyde and loaded to the 4-formyl-3,5-dimethoxyphenoxy (PL-FDMP) resin with high efficiency of reductive amination. Various building blocks for the derivatization of the 7-hydroxyl and N-1 amide nitrogen could be introduced via selective alkylation. Cleavage, parallel column chromatography, and NMR analysis of 62 final compounds confirmed the feasibility of this peptidomimetic library synthesis.

Structure-based virtual screening and biological evaluation of potent and selective ADAM12 inhibitors.

We describe a series of potent and selective inhibitors of ADAM12 that were discovered using computational screening of a focused virtual library. The initial structure-based virtual screening selected 64 compounds from a 3D database of 67,062 molecules. Being evaluated by a cell-based ADAM12 activity assay, compounds 5, 11, 14, 16 were further identified as the potent and selective inhibitors of ADAM12 with low nanomolar IC50 values. The mechanism underlying the potency and selectivity of a representative compound, 5, was investigated through molecular docking studies.