Quantitative high-throughput gene expression profiling of human striatal development to screen stem cell-derived medium spiny neurons.

A systematic characterization of the spatio-temporal gene expression during human neurodevelopment is essential to understand brain function in both physiological and pathological conditions. In recent years, stem cell technology has provided an in vitro tool to recapitulate human development, permitting also the generation of human models for many diseases. The correct differentiation of human pluripotent stem cell (hPSC) into specific cell types should be evaluated by comparison with specific cells/tissue profiles from the equivalent adult in vivo organ. Here, we define by a quantitative high-throughput gene expression analysis the subset of specific genes of the whole ganglionic eminence (WGE) and adult human striatum. Our results demonstrate that not only the number of specific genes is crucial but also their relative expression levels between brain areas. We next used these gene profiles to characterize the differentiation of hPSCs. Our findings demonstrate a temporal progression of gene expression during striatal differentiation of hPSCs from a WGE toward an adult striatum identity. Present results establish a gene expression profile to qualitatively and quantitatively evaluate the telencephalic hPSC-derived progenitors eventually used for transplantation and mature striatal neurons for disease modeling and drug-screening.

Polyglutamine- and temperature-dependent conformational rigidity in mutant huntingtin revealed by immunoassays and circular dichroism spectroscopy.

BACKGROUND: In Huntington's disease, expansion of a CAG triplet repeat occurs in exon 1 of the huntingtin gene (HTT), resulting in a protein bearing>35 polyglutamine residues whose N-terminal fragments display a high propensity to misfold and aggregate. Recent data demonstrate that polyglutamine expansion results in conformational changes in the huntingtin protein (HTT), which likely influence its biological and biophysical properties. Developing assays to characterize and measure these conformational changes in isolated proteins and biological samples would advance the testing of novel therapeutic approaches aimed at correcting mutant HTT misfolding. Time-resolved Förster energy transfer (TR-FRET)-based assays represent high-throughput, homogeneous, sensitive immunoassays widely employed for the quantification of proteins of interest. TR-FRET is extremely sensitive to small distances and can therefore provide conformational information based on detection of exposure and relative position of epitopes present on the target protein as recognized by selective antibodies. We have previously reported TR-FRET assays to quantify HTT proteins based on the use of antibodies specific for different amino-terminal HTT epitopes. Here, we investigate the possibility of interrogating HTT protein conformation using these assays. METHODOLOGY/PRINCIPAL FINDINGS: By performing TR-FRET measurements on the same samples (purified recombinant proteins or lysates from cells expressing HTT fragments or full length protein) at different temperatures, we have discovered a temperature-dependent, reversible, polyglutamine-dependent conformational change of wild type and expanded mutant HTT proteins. Circular dichroism spectroscopy confirms the temperature and polyglutamine-dependent change in HTT structure, revealing an effect of polyglutamine length and of temperature on the alpha-helical content of the protein. CONCLUSIONS/SIGNIFICANCE: The temperature- and polyglutamine-dependent effects observed with TR-FRET on HTT proteins represent a simple, scalable, quantitative and sensitive assay to identify genetic and pharmacological modulators of mutant HTT conformation, and potentially to assess the relevance of conformational changes during onset and progression of Huntington's disease.

Discovery of novel non-carboxylic acid 5-amino-4-cyanopyrazole derivatives as potent and highly selective LPA1R antagonists.

High throughput screening (HTS) of our chemical library identified 3-alkylamino-2-aryl-5H-imidazo[1,2,b]pyrazol-7-carbonitrile 1 as a potent antagonist of the LPA1 receptor (LPA1R). Further evaluation of this class of compounds indicated that LPA1R antagonist activity originated from the degradation of the parent molecule in DMSO during the assay conditions. Here, we describe the isolation and characterization of the degradation products and their LPA1R antagonist activity. We further profiled these novel non-carboxylic acid LPA1R antagonists and demonstrated their inhibition of LPA-induced proliferation and contraction of normal human lung fibroblasts (NHLF).

Discovery of N-[4-[6-tert-butyl-5-methoxy-8-(6-methoxy-2-oxo-1H-pyridin-3-yl)-3-quinolyl]phenyl]methanesulfonamide (RG7109), a potent inhibitor of the hepatitis C virus NS5B polymerase.

In the past few years, there have been many advances in the efforts to cure patients with hepatitis C virus (HCV). The ultimate goal of these efforts is to develop a combination therapy consisting of only direct-antiviral agents (DAAs). In this paper, we discuss our efforts that led to the identification of a bicyclic template with potent activity against the NS5B polymerase, a critical enzyme on the life cycle of HCV. In continuation of our exploration to improve the stilbene series, the 3,5,6,8-tetrasubstituted quinoline core was identified as replacement of the stilbene moiety. 6-Methoxy-2(1H)-pyridone was identified among several heterocyclic headgroups to have the best potency. Solubility of the template was improved by replacing a planar aryl linker with a saturated pyrrolidine. Profiling of the most promising compounds led to the identification of quinoline 41 (RG7109), which was selected for advancement to clinical development.

Discovery of a novel series of potent non-nucleoside inhibitors of hepatitis C virus NS5B.

Hepatitis C virus (HCV) is a major global public health problem. While the current standard of care, a direct-acting antiviral (DAA) protease inhibitor taken in combination with pegylated interferon and ribavirin, represents a major advancement in recent years, an unmet medical need still exists for treatment modalities that improve upon both efficacy and tolerability. Toward those ends, much effort has continued to focus on the discovery of new DAAs, with the ultimate goal to provide interferon-free combinations. The RNA-dependent RNA polymerase enzyme NS5B represents one such DAA therapeutic target for inhibition that has attracted much interest over the past decade. Herein, we report the discovery and optimization of a novel series of inhibitors of HCV NS5B, through the use of structure-based design applied to a fragment-derived starting point. Issues of potency, pharmacokinetics, and early safety were addressed in order to provide a clinical candidate in fluoropyridone 19.

De novo fragment design: a medicinal chemistry approach to fragment-based lead generation.

The use of fragments with low binding affinity for their targets as starting points has received much attention recently. Screening of fragment libraries has been the most common method to find attractive starting points. Herein, we describe a unique, alternative approach to generating fragment leads. A binding model was developed and a set of guidelines were then selected to use this model to design fragments, enabling our discovery of a novel fragment with high LE.

Pyrrolopyrazines as selective spleen tyrosine kinase inhibitors.

We describe the discovery of several pyrrolopyrazines as potent and selective Syk inhibitors and the efforts that eventually led to the desired improvements in physicochemical properties and human whole blood potencies. Ultimately, our mouse model revealed unexpected toxicity that precluded us from further advancing this series.

Discovery of highly selective and orally active lysophosphatidic acid receptor-1 antagonists with potent activity on human lung fibroblasts.

Lysophosphatidic acid is a class of bioactive phospholipid that mediates most of its biological effects through LPA receptors, of which six isoforms have been identified. The recent results from LPA1 knockout mice suggested that blocking LPA1 signaling could provide a potential novel approach for the treatment of idiopathic pulmonary fibrosis. Here, we report the design and synthesis of pyrazole- and triazole-derived carbamates as LPA1-selective and LPA1/3 dual antagonists. In particular, compound 2, the most selective LPA1 antagonist reported, inhibited proliferation and contraction of normal human lung fibroblasts (NHLF) following LPA stimulation. Oral dosing of compound 2 to mice resulted in a dose-dependent reduction of plasma histamine levels in a murine LPA challenge model. Furthermore, we applied our novel antagonists as chemistry probes and investigated the contribution of LPA1/2/3 in mediating the pro-fibrotic responses. Our results suggest LPA1 as the major receptor subtype mediating LPA-induced proliferation and contraction of NHLF.

Design, synthesis, and biological evaluation of new monoamine reuptake inhibitors with potential therapeutic utility in depression and pain.

Two new series of monoamine triple reuptake inhibitors (TRIs) have been discovered through scaffold homologation of our recently reported series of 3,3-disubstituted pyrrolidine TRIs. The regioisomeric 2- and 3-ketopyrrolidines demonstrated high levels of potency against all three monoamine transporters as well as good human in vitro stability, low drug-drug interaction potential and a decreased propensity for hERG channel binding. Representative compounds from these series displayed good in vivo pharmacokinetics and high monoamine receptor occupancies which are indicators of good brain penetration.

2-Substituted N-aryl piperazines as novel triple reuptake inhibitors for the treatment of depression.

Recently a class of compounds known as triple reuptake inhibitors has emerged as a new strategy for the treatment of depression. These compounds work by simultaneously inhibiting the synaptic reuptake of serotonin, norepinephrine and dopamine. In this Letter we describe the optimization of a novel series of 2-substituted N-aryl piperazine based triple reuptake inhibitors.

Novel, achiral aminoheterocycles as selective monoamine reuptake inhibitors.

A variety of novel aminoheterocycle scaffolds as selective monoamine reuptake inhibitors have been prepared and one of these scaffolds is achiral. The main elements responsible for hERG channel, CYP2D6 and CYP3A4 inhibition were identified.

Novel 3,3-disubstituted pyrrolidines as selective triple serotonin/norepinephrine/dopamine reuptake inhibitors.

A series of 3,3-disubstituted pyrrolidine monoamine triple reuptake inhibitors were discovered. Analogues with low nanomolar potency, good human in vitro microsomal stability and in vitro permeability, and low drug-drug interaction potential are described. One example showed in vivo anti-depressant-like effects in the mouse tail suspension assay with a minimum effective dose of 30 mg/kg i.p.

Reversing the action of noncompetitive inhibitors (MK-801 and cocaine) on a protein (nicotinic acetylcholine receptor)-mediated reaction.

The nicotinic acetylcholine receptor (nAChR) is one of five structurally related membrane proteins required for communication between approximately 10(12) cells of the mammalian nervous system. The receptor is inhibited by both therapeutic agents and abused drugs. Understanding the mechanism of noncompetitive allosteric inhibitors of the nicotinic acetylcholine receptor is a long-standing and intensely investigated problem. During the past two decades, many attempts have been made to find drugs that prevent cocaine inhibition, including the synthesis of hundreds of cocaine analogues and derivatives, so far without success. The use of newly developed transient kinetic techniques in investigations of the inhibition of the receptor by the anticonvulsant MK-801 [(+)-dizocilpine] and the abused drug cocaine led to an inhibition mechanism not previously proposed. This mechanism indicates the properties of compounds that would prevent allosteric inhibition of the receptor and how to test for such compounds. Here we present the first evidence that small organic compounds (cocaine derivatives) exist that prevent cocaine and MK-801 inhibition of this receptor. These compounds are RTI-4229-70, a previously synthesized cocaine derivative, and based on its structure four newly synthesized cocaine derivatives, RCS-III-143, RCS-III-140A, RCS-III-218, and RCS-III-202A. Because the nAChR desensitizes rapidly, to make the required measurements a cell-flow technique with a time resolution of 10 ms was used to equilibrate BCH(3) cells containing the fetal mouse muscle-type nAChR with carbamoylcholine. The resulting whole-cell current pertaining to the nondesensitized nAChR was determined. Inhibitors and compounds that alleviate inhibition were tested by their effect on the whole-cell current.

Cytotoxic, antifouling bromotyramines: a synthetic study on simple marine natural products and Their analogues.

Synthesis and biological evaluation of two naturally-occurring bromotyramines, moloka'iamine 1 and 3,5-dibromo-4-methoxy-beta-phenethylamine 2, together with several analogues, have been completed. Bromotyramine 2 is cytotoxic, and was found to be a potent antifoulant. Analogues 15 and 16 also displayed significant cytotoxic and antifouling activities.