Yen-Chun Lee

Mutation in Enterovirus 71 Capsid Protein VP1 Confers Resistance to the Inhibitory Effects of Pyridyl Imidazolidinone

ABSTRACT Enterovirus 71 is one of the most important pathogens in the family of Picornaviridae that can cause severe complications in the postpoliovirus era, such as encephalitis, pulmonary edema, and even death. Pyridyl imidazolidinone is a novel class of potent and selective human enterovirus 71 inhibitor. Pyridyl imidazolidinone was identified by using computer-assisted drug design. This virologic investigation demonstrates that BPR0Z-194, one of the pyridyl imidazolidinones, targets enterovirus 71 capsid protein VP1. Time course experiments revealed that BPR0Z-194 effectively inhibited virus replication in the early stages, implying that the compound can inhibit viral adsorption and/or viral RNA uncoating. BPR0Z-194 was used to select and characterize the drug-resistant viruses. Sequence analysis of the VP1 region showed that the resistant variants differed consistently by seven amino acids in VP1 region from their parental drug-sensitive strains. Site-directed mutagenesis of enterovirus 71 infectious cDNA revealed that a single amino acid alteration at the position 192 of VP1 can confer resistance to the inhibitory effects of BPR0Z-194.

Isatin-β-thiosemicarbazones as potent herpes simplex virus inhibitors

A series of isatin-β-thiosemicarbazones have been designed and evaluated for antiviral activity against herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) in a plaque reduction assay. Their cytotoxicity was examined using human rhabdomyosarcoma cells (RD cells). Several derivatives of isatin-β-thiosemicarbazone exhibited significant and selective antiviral activity with low cytotoxicity. It was found that the thiourea group at thiosemicarbazone and the NH functionality at isatin were essential for their antiherpetic activity. The synthesis and structure-activity relationship studies are presented.

Design, synthesis, and anti-HCV activity of thiourea compounds

A series of thiourea derivatives were synthesized and their antiviral activity was evaluated in a cell-based HCV subgenomic replicon assay. SAR studies revealed that the chain length and the position of the alkyl linker largely influenced the in vitro anti-HCV activity of this class of potent antiviral agents. Among this series of compounds synthesized, the thiourea derivative with a six-carbon alkyl linker at the meta-position of the central phenyl ring (10) was identified as the most potent anti-HCV inhibitor (EC(50) = 0.047 microM) with a selectivity index of 596.

Synthesis, activity, and pharmacokinetic properties of a series of conformationally-restricted thiourea analogs as novel hepatitis C virus inhibitors

A series of novel conformationally-restricted thiourea analogs were designed, synthesized, and evaluated for their anti-HCV activity. Herein we report the synthesis, structure-activity relationships (SARs), and pharmacokinetic properties of this new class of thiourea compounds that showed potent inhibitory activities against HCV in the cell-based subgenomic HCV replicon assay. Among compounds tested, the fluorene compound 4b was found to possess the most potent activity (EC(50)=0.3 microM), lower cytotoxicity (CC(50)>50 microM), and significantly better pharmacokinetic properties compared to its corresponding fluorenone compound 4c.

3D‐QSAR‐Assisted Drug Design: Identification of a Potent Quinazoline‐Based Aurora Kinase Inhibitor

We describe the 3D‐QSAR‐assisted design of an Aurora kinase A inhibitor with improved physicochemical properties, in vitro activity, and in vivo pharmacokinetic profiles over those of the initial lead. Three different 3D‐QSAR models were built and validated by using a set of 66 pyrazole (Model I) and furanopyrimidine (Model II) compounds with IC50 values toward Aurora kinase A ranging from 33 nM to 10.5 μM. The best 3D‐QSAR model, Model III, constructed with 24 training set compounds from both series, showed robustness (r2CV=0.54 and 0.52 for CoMFA and CoMSIA, respectively) and superior predictive capacity for 42 test set compounds (R2pred=0.52 and 0.67, CoMFA and CoMSIA). Superimposition of CoMFA and CoMSIA Model III over the crystal structure of Aurora kinase A suggests the potential to improve the activity of the ligands by decreasing the steric clash with Val147 and Leu139 and by increasing hydrophobic contact with Leu139 and Gly216 residues in the solvent‐exposed region of the enzyme. Based on these suggestions, the rational redesign of furanopyrimidine 24 (clog P=7.41; Aurora A IC50=43 nM; HCT‐116 IC50=400 nM) led to the identification of quinazoline 67 (clog P=5.28; Aurora A IC50=25 nM; HCT‐116 IC50=23 nM). Rat in vivo pharmacokinetic studies showed that 67 has better systemic exposure after i.v. administration than 24, and holds potential for further development.

Design and efficient synthesis of novel arylthiourea derivatives as potent hepatitis C virus inhibitors

A novel class of arylthiourea HCV inhibitors bearing various functionalities, such as cyclic urea, cyclic thiourea, urea, and thiourea, on the alkyl linker were designed and synthesized. Herein we report the synthesis and structure-activity relationships (SARs) of this novel class of arylthiourea derivatives that showed potent inhibitory activities against HCV in the cell-based subgenomic HCV replicon assay. Among compounds tested, the new carbazole derivative 64, which has an eight-carbon linkage between the phenyl and carbazole rings and a tolyl group at the N-9 position of carbazole, was found to possess strong anti-HCV activity (EC50=0.031 microM), lower cytotoxicity (CC50 >50 microM), and higher selectivity index (SI >1612) compared to its derivatives.

Design and synthesis of indole, 2,3-dihydro-indole, and 3,4-dihydro-2H-quinoline-1-carbothioic acid amide derivatives as novel HCV inhibitors

An efficient synthetic methodology to provide indole, 2,3-dihydro-indole, and 3,4-dihydro-2H-quinoline-1-carbothioic acid amide derivatives is described. These conformationally restricted heterobicyclic scaffolds were evaluated as a novel class of HCV inhibitors. Introduction of an acyl group at the NH(2) of the thiourea moiety has been found to enhance inhibitory activity. The chain length and the position of the alkyl group on the indoline aromatic ring markedly influenced anti-HCV activity. The indoline scaffold was more potent than the corresponding indole and tetrahydroquinoline scaffolds and analogue 31 displayed excellent activity (EC(50)=510nM) against HCV without significant cytotoxicity (CC(50) >50microM).

Nerve conduction block in diabetic rats using high-intensity focused ultrasound for analgesic applications

BACKGROUND Nerve conduction block using high-intensity focused ultrasound (HIFU) has been conducted with nerves of mixed fibres in normal animal models. This study tested the feasibility and safety of HIFU for sensory nerve conduction block in diabetic neuropathic nerves to determine its potential for pain relief. METHODS Diabetes was induced in Sprague-Dawley rats using streptozotocin, and HIFU at 2.68 MHz was used for the block. This study consisted of two sections, in vitro and in vivo. For the in vitro experiments, the entire contiguous sciatic-sural nerves were obtained. Compound action potentials and sensory action potentials were recorded in the sciatic and sural nerves, respectively. For the in vivo experiments, compound muscle action potentials (CMAPs) were recorded from the gastrocnemius muscles. All data were expressed as median (range). RESULTS The in vitro results showed that HIFU temporarily inhibited sensory action potentials of the control and diabetic rat nerves to 33.9 (8.2) and 14.0 (10.7)% of the baseline values, respectively, whereas the compound action potentials were suppressed to 53.6 (8.4) and 76.2 (7.5)% of baseline, respectively. The in vivo results showed that HIFU acutely blocked CMAPs to 32.9 (12.6) and 19.9 (10.9)% of baseline in control and diabetic rat nerves, respectively. Measurements of CMAPs and histological exanmination were used for indirect assessment of the safety of the HIFU technique. CONCLUSIONS High-intensity focused ultrasound safely and reversibly suppressed nerve conduction in diabetic rat nerves when the stimulation parameters were appropriate. The results suggest that HIFU may have potential to block sensory nerves reversibly and provide peripheral pain relief.

A Potent, Selective, and Orally Bioavailable HCV NS5A Inhibitor for Treatment of Hepatitis C Virus: (S)-1-((R)-2-(Cyclopropanecarboxamido)-2-phenylacetyl)-N-(4-phenylthiazol-2-yl)pyrrolidine-2-carboxamide

Starting from the initial lead 4-phenylthiazole 18, a modest HCV inhibitor (EC50 = 9440 nM), a series of structurally related thiazole derivatives has been identified as a novel chemical class of potent and selective HCV NS5A inhibitors. The introduction of a carboxamide group between the thiazole and pyrrolidine ring (42) of compound 18 resulted in a dramatic increase in activity (EC50 = 0.92 nM). However, 42 showed only moderate pharmacokinetic properties and limited oral bioavalability of 18.7% in rats. Further optimization of the substituents at the 4-position of the thiazole ring and pyrrolidine nitrogen of the lead compound 42 led to the identification of compound 57, a highly potent and selective NS5A inhibitor of HCV (EC50 = 4.6 nM), with greater therapeutic index (CC50/EC50 > 10000). Pharmacokinetic studies revealed that compound 57 had a superior oral exposure and desired bioavailability of 45% after oral administration in rats.

Anti-influenza Drug Discovery: Identification of an Orally Bioavailable Quinoline Derivative through Activity- and Property-Guided Lead Optimization

From a high-throughput screening (HTS) hit with inhibitory activity against virus-induced cytophathic in the low micromolar range, we have developed a potent anti-influenza lead through careful optimization without compromising the drug-like properties of the compound. An orally bioavailable compound was identified as a lead agent with nanomolar activity against influenza, representing a 140-fold improvement over the initial hit.